10ournalofNeurology, Neurosurgery, and Psychiatry 1993;56:1330-1337

Proceedings of the 122nd Meeting of the Society of BritishNeurological Surgeons, Nottingham, 26-28 May 1993

REGIONAL DIFFERENCES IN MANAGING

SUBARACHNOID HAEMORRHAGE: THREE

YEARS OF AUDIT FROM NEWCASTLE ANDNOTTINGHAMDT Hope, JC Stevenson, V Orpe, IChambers, AD Mendelow. Queen'sMedical Centre, Nottingham andNewcastle General Hospital, Newcastleupon Tyne, UK

All subarachnoid haemorrhage patients(850) admitted to the neurosurgical units ofQueen's Medical Centre and NewcastleGeneral Hospital between January 1990and December 1992 have been audited.The purpose was to look at differing pat-terns of referral and presentation. Of partic-ular interest were the World Federation ofNeurosurgical Societies (WFNS) grades on

admission (and on day of surgery), theinterval from bleed to admission and fromadmission to surgery. The total length ofstay in each regional unit was audited andthe outcome as judged at discharge. Thestudy attempted to identify areas where thequality of care may be improved in themanagement of subarachnoid haemorrhage.The patients in good grades, WFNS I or II,still showed wide variations in the timing ofsurgery, possibly reflecting the availability ofbeds, angiogram facilities, and the numberof consultants. Surgeons in Newcastletended to operate earlier than those inNottingham although the overall outcomewas similar. Delayed surgery was associatedwith a higher rebleed rate in patients ingood grades. Direct comparisons of out-come between surgical units can be mis-leading unless strict criteria for comparisoncan be agreed. To measure quality of care,standards must be established and Britishneurosurgery has, as a specialty, been slowto set these.

MOBILISATION OF ZYGOMA FACILITATES

BASILAR ARTERY ANEURYSM SURGERY

ATH Casey, D Uttley, D Archer. AtkinsonMorley's Hospital and Royal MarsdenHospital, London, UK

An improved understanding of skull baseand vascular anatomy and an appreciationof the need to minimise brain retraction hasresulted in some ingenious approaches toskull-base lesions. In 1985 the advantagesthat mobilisation of the zygoma wouldafford in clipping terminal basilar arteryaneurysms were first realised.'

Since 1986 this approach has been usedin 10 patients. Their mean age was 43 years(range 23-58) with admission in WFNSgrade II (range I-V). Surgery was per-formed via a frontozygomatic approach atan average of 8-4 days (range 1-18) fromictus.2 Four patients had multiple

aneurysms whose definitive treatment was

also possible with this approach. Therewere two fatalities occurring 48 hours and72 hours postoperatively which were attrib-uted to brainstem perforator involvementand vasospasm, respectively. The survivingpatients all achieved a satisfactory final out-come with one patient having a persistentthird-nerve palsy. There were no permanentfacial nerve sequelae or significant jaw-opening difficulties. This approach istherefore encouraging and adds little tothe overall length of the operation. It istherefore recommended for the treatment ofterminal basilar artery aneurysms.

1 Fujitsu K, Kutawara T. Zygomatic approachfor lesions in the interpeduncular cistern.Neurosurg 1985;62:340-3.

2 Uttley D, Archer DJ, Bell BA. Improvedaccess to lesions of the central skull base bymobilisation of the zygoma: experience with54 cases. Neurosurgery 1991;28:99-104.

THE PREDICTION OF DELAYED CEREBRAL

ISCHAEMIA FOLLOWING SUBARACHNOIDHAEMORRHAGE BY MEASURING MIDDLE

CEREBRAL ARTERY MEAN FLOW VELOCITY

AND MEAN CEREBRAL TRANSIT TIMEFC Wong, IR Piper, JD Miller, CStevenson, M Merrick. University ofEdinburgh, Western General Hospital,Edinburgh, UK

The cause of delayed cerebral ischaemia(DCI) following subarachnoid haemorrhageis multifactorial. The measurement ofmiddle cerebral artery mean flow velocity todetect vasospasm combined with themeasurement of mean cerebral transit time(MCTT) as an index of cerebral perfusionreserve may predict the onset of DCI. Bothmethods are relatively inexpensive, can bereadily available and can be performed atthe bedside.

Middle cerebral artery mean flow velocityhas been monitored (on a daily basis ifrequired) by transcranial Doppler sonogra-phy (TCD). Vasospasm was defined whenthe mean flow velocity exceeded 120 cm/s.MCTT has been measured using a tech-nique developed in Edinburgh based on thefirst-pass transit of a radiolabelled intra-vascular tracer injected intravenously anddetected as it passes through the cerebralcirculation using a standard gamma camera.

Normal hemispheric MCTT is between 2-5and 7-7 s (95% confidence interval) andnormal interhemispheric assymmetry doesnot exceed 0-6 s.

Eighteen patients admitted with sub-arachnoid haemorrhage have had bothMCTT and TCD studies performed. Sixpatients developed DCI and all six patientshad either Doppler-defined vasospasm(n = 4) or abnormal MCTT results (n = 5)or both (n = 3). Localised or unilateral

abnormalities matched the clinical neurolog-ical deficits of the patients. The combinedapplication of both these tests may be poten-tially useful in predicting delayed cerebralischaemia.

CEREBRAL ISCHAEMIC EFFECTS OFENDOTHELIN AND INDUCED SUBARACHNOIDHAEMORRHAGEAH Huneidi, C Thiemermann, DDrincevic, F Afshar, JR Vane. StBartholomew's Hospital, London, UK

The development of cerebral ischaemiafollowing the systemic administration of thevasoconstrictor peptides endothelin-1 (ET-1; 1 nmol.kg'; n = 1 1), big-endothelin (b-ET; 3 nmol.kg-'; n = 11), or angiotensin-II(A-II; 10 rnol.kg'.min-'.30 min; n = 8) wascompared with a double subarachnoidhaemorrhage model in the NZ white rabbit.Haemorrhage was induced by an autologousarterial blood injection into the cisternamagna on day 1 (SAH-I; n = 11) and ondays 1 and 4 (SAH-II; n = 11). Brain histol-ogy showed acute neuronal and astrocyteswelling, cytoplasmic vacuolation, pyknosis,and cell loss in the hippocampus (HPC),cerebellum (CBLM) and brain stem (BS).Electron microscopy of the basilar arteryendothelium (BA-END) showed vacuola-tion, mitochondrial loss, and cellular disrup-tion. The table shows the relative incidenceas the mean (SD) percentage of ischaemiaand vascular endothelial damage in allgroups.

Group n BS HPC CBLM BA-END

SAH-I 11 38 (13) 38 (13) 38 (13) 31 (13)SAH-II 11 62 (13) 69 (13) 69 (13) 69 (13)ET-1 11 55 (15) 64 (14) 55 (15) 64 (14)B-ET 11 64 (14) 72 (14) 72 (14) 82 (12)A-II 8 22 (5) 25 (12) 20 (7) 15 (6)Control 12 8 (5) 10 (9) 10 (9) 10 (9)

It is concluded that ET-1 and b-ET pro-duced cerebral ischaemia with a similar inci-dence and pattern to ischaemia complicatingSAH. Endothelins may thus participate inthe pathogenesis of ischaemic complicationsof subarachnoid haemorrhage, but this stillneeds further elucidation.

MANAGEMENT AND OUTCOME OF PATIENTSIN POOR NEUROLOGICAL GRADE FOLLOWINGSUBARACHNOID HAEMORRHAGEMG O'Sullivan, C McIntosh, R Sellar, AJWSteers, IR Whittle, JD Miller. WesternGeneral Hospital, Edinburgh, UK

The prognosis for patients in poor neuro-logical grades (WFNS grades IV and V)following subarachnoid haemorrhage (SAH)is poor.' A favourable outcome was recentlyreported in 65% of a selected cohort of

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Outcome according to group Outcome according to CT abnormality

Group(n) D PVS + SD MD + G CT D PVS + SD MD + G

1 (16) 6 2 8 Haematoma (18) 12 2 42 (12) 1 1 10 Hydrocephalus (23) 8 0 153 (34) 19 0 15 SAH (21) 6 1 14

D = dead; PVS = persistent vegetative state; SD = severely disabled; MD = moderately disabled; G =good recovery.

patients treated intensively.2 The authors'experience with patients in poor gradesover the two-year period 1991 to 1992 isreported. The aim of the review is to identi-fy deficiencies in the management protocol.A patient was defined as being in a poor

grade if a Glasgow coma score (GCS) of< 12 was recorded within 24 hours ofhospital admission. CT scans were reviewedand the predominant abnormality classifiedas haematoma, hydrocephalus, or diffuseSAH. Outcome was assessed at threemonths using the Glasgow outcome scale.

Sixty-two patients were suitable forreview. Three groups may be definedaccording to their clinical course: GCS13-15 on admission with subsequent deteri-oration (16 patients); GCS < 12 on admis-sion with subsequent improvement (12patients); and GCS < 12 without improve-ment, or with improvement followingintervention (34 patients). The groups maybe further subdivided according to the CTfeatures. The table shows the managementand outcome.

Patients in a poor neurological gradefollowing SAH are a heterogenous group,and urgent CT scanning is required todefine the cause of the depressed level ofconsciousness. Hydrocephalus should betreated intensively. The prognosis forpatients in a poor neurological grade due tohaematoma is grave and the role ofemergency surgery has yet to be defined.

1 Ljundgren B, Soveland H, Brandt L, et al.Early operation and outcome in aneurysmalSAH. Neurosurg 1985;62:547-5 1.

2 Bailes J, Spetzler R, Hadley M, et al.Management morbidity and mortality ofpoor grade aneurysm patients. Neurosurg1 990;72:559-66.

RECOGNITION AND MANAGEMENT OFANTERIOR THORACIC SPINAL CORD HERNIAB D White, I Holland, T Jaspan, JL Firth.University Hospital, Nottingham, UK

Anterior spinal hernia is a rare cause ofmaturity onset, progressive, thoracic corddysfunction which has only recently beenrecognised, with four cases appearing inpublished reports since 1991. The patient istypically middle-aged with a history ofprogressive, mid-thoracic, anterior hemi-cord syndrome manifesting initially as

hemianalgesia below the affected segmentwith contralateral crural spasticity.Untreated this develops into an asymmetricspastic paraparesis with sparing of dorsalcolumn sensation.CT myelography demonstrates a focally

narrowed thoracic cord kinked and para-doxically drawn towards what appears to bean extradural mass. MRI shows thenarrowed, kinked cord closely applied to avertebral body, and may demonstrate thecord hemia. At operation the cord is foundto be morphologically normal but prolapsedand incarcerated in a ventrolateral dural

dehiscence. The pathogenesis of the under-lying dural defect is unknown, but severalhypotheses have been advanced. Thesyndrome is characteristic, the radiologicalfindings, though subtle, are also typical andsurgical repair is easily effected. This condi-tion is probably more common than cur-rently appreciated and should be consideredin all patients presenting with progressivethoracic cord dysfunction.

SUBOCCIPrTAL TRANSCONDYLAR APPROACHTO THE CLIVUS AND CRANIOCERVICALJUNCTIONG Neil-Dwyer, DA Lang, F Iannotti.Southampton University Hospital,Southampton, UK

Access to the anterior rim of the foramenmagnum, craniocervical junction, clivus,and front of the lower brainstem can beobtained by using an anterior, lateral orposterolateral approach. The access usedshould provide good visualisation of thepathology and the surrounding anatomicalstructures with minimal retraction of neuralstructures. Ideally the skull should beentered and anatomical routes followed insuch a way that there is a short, straight linebetween the surgeon and the lesion. Thepreferred approach to this region dependson the exact site of the lesion, the nature ofthe pathology, and the aim of the operation.Of particular importance is the superiorextent of the lesion, its relationship to theneuraxis and its position relative to the mid-line.The authors' experience of the

transcondylar suboccipital approach isreported, which has been used in 12patients to remove lesions related to theanterior rim of the forarhen magnum, thelateral clivus, the front of the lower brain-stem, and for access to the vertebrobasilarcirculation. There are limitations imposedboth by the location of the pathology andthe nature of the lesion, and there is a needfor flexibility and combined anterior andtranscondylar suboccipital approaches inselected cases.

ODONTOID FRACTURES IN ELDERLY PATIENTSR Viswanathan, MG O'Sullivan, JMcEachan, T Russell. Western GeneralHospital, Edinburgh, UK

Reports detailing cervical spinal injury inpatients > 65 years are rare.' A retrospec-tive survey is reported of patients of 65years or older with odontoid fractures man-aged in our department over the six-yearperiod to December 1992.

Fifteen patients had isolated odontoidfractures and four suffered injury at multi-ple levels including the odontoid process(these were excluded from analysis). A frac-tured odontoid process was found in 50%of patients with cervical injury in this agegroup. The median age of the patients was

78 years (range 65-86). Injury occurred as aresult of a fall in 12 cases and a road trafficaccident in three cases. Type II fractureswere seen in 10 patients. Type III in fourpatients, and Type I in one patient. Twopatients had a mild neurological deficit.Nine patients underwent internal stabilisa-tion and six patients were treated with acervical collar. One patient died and a fur-ther patient suffered a monoparesis as aresult of surgery. All patients had follow-upassessments that included flexion/extensionviews of the cervical spine. The medianduration of follow up was 38 months (range11-50 months). All surviving patients wereindependent with no evidence of instability.

It is concluded that odontoid fracturesaccount for a significant proportion of cervi-cal spinal injuries in patients aged 65 yearsor more, and surgical stabilisation is rela-tively safe. Type IIm fractures may be suc-cessfully treated with a cervical collar untilbony fusion occurs.

1 Pepin JW, Bourne RB, Hawkins RJ. Odontoidfractures, with special reference to theelderly patient. Clin Orthop 1985;193:178-83.

THE ROLE OF EMERGENCY SURGERY INMALIGNANT SPINAL EXTRADURALCOMPRESSION: ASSESSMENT OF FUNCTIONALOUTCOMEJK Harris, JC Sutcliffe, N Robinson, ESWatkins. Royal London Hospital, London,UK

Delay in reaching neurosurgical care incases of malignant spinal compression iswell known,' but the action taken subse-quently by the neurosurgeon is less clearlydocumented. In the presence of such initialdelays should emergency surgical interven-tion be considered necessary? In this retro-spective analysis of functional outcome in81 patients requiring 84 operations forcompressive, malignant, extradural lesionsbetween 1982 and 1991, an assessment ofthe role of emergency surgery was madeindependently by physiotherapists andmedical staff, with regard to maintaining orimproving continence and mobility.

Overall 70% of patients retained orregained their mobility and 80% of thesewere continent postoperatively. Emergencysurgery was performed in 65% cases, and61-5% of these experienced improvement,compared with only 25% of the electivesurgery group, pathology in the two groupsbeing similar. Even among those inconti-nent and immobile, 47% could walk post-operatively, of whom 76% had emergencysurgery.The findings suggest that despite initial

delays in referral, and even if the patient isincontinent and immobile, emergencyspinal decompression is justified.

1 Maurice-Williams RS, Richardson PL. Spinalcord compression: delay in the diagnosisand referral of a common neurosurgicalemergency. BrJ Neurosurg 1988;2:55-60.

STRESS AND HYPOTHALAMIC-PITUITARYBLOOD FLOW IN THE RATCJ Gerber, T Loughlin, EW Hillhouse,PD Lees. Wessex Neurological Centre,Southampton, and University of Newcastle,Newcastle upon Tyne, UK

Hypothalamic-pituitary portal blood flowcontrols the anterior pituitary and may

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therefore modulate neuroendocrine func-tion. To test this hypothesis, a new mathe-matical model was developed and validatedin the rat, overcoming the problems of theportal system to allow the measurement ofpituitary blood flow using '4C-iodoanti-pyrine autoradiography.' A minimallystressed rat model was also developed,using chronic arterial and venous cannula-tion with repeated handling to evaluate andovercome the effects of surgical stress whichis known to activate the hypothalamic-pituitary-adrenal axis. Results show signifi-cant elevation of plasma corticosterone andcorticotropin under anaesthesia (mean (SE)536(54) ng/ml, 822(159) pg/ml respec-tively); at one hour (585(71) ng/ml,768(97) pglml) and one day(441(116) ng/ml, 768(97)pg/ml) comparedwith control non-cannulated animals(30(3) ng/ml, 460(83) pg/ml) (p = 0-01).Both return to normal at three days(25-25(0 2) ng/ml, 572(155) pg/ml). Bloodflow was significantly higher at three daysin the hypothalamus (2 7(0 48) ml/g perminute) and anterior pituitary(1 73(0 2) ml/g per minute) compared withanaesthetised animals (1-53(0-36) ml/g perminute, 0-45(0 05) ml/g per minute)(p = 0 05).These results show that anaesthetised

rats and those in acute recovery show stresswhich resolves by three days. The stressedstate is associated with lower blood flowrates in the hypothalamus and pituitarygland than the unstressed state. This sug-gests that there is a opportunity at threedays, when stress is minimised, when theinterrelationship between neuroendocrineblood flow and function may be evaluated.

1 Lees PD, Lynch DT, Richards HK, et al.J7 Cereb Blood Flow Metab 1992;12:128-38.

CELL CULTURE OF PITUITARY ADENOMAS:ROLE IN CLINICAL MANAGEMENTS Chatterjee, R Jeffreys, P Foy, S Atkins,M White, L Hipkin, J McKenzie. Universityof Liverpool, Liverpool, UK

Human pituitary adenomas have been pre-viously classified according to histology,immunocytochemistry, S-phase fractionand their hormone production in vivo. Thisstudy looks at categorisation on the basis ofcell culture and hormnone production invitro.The clinical and laboratory details of 50

patients with pituitary adenoma presentingto the Liverpool Neurosurgical Departmentbetween 1989 and 1992 were reviewed. Allcell cultures were performed using anIsocoves-modified Delbeccos medium with10% fetal calf serum. Following successfulgrowth of the cells under special conditions,hormone analysis was performed byradioimmunoassay.

Clinically 14 patients presented withacromegaly, five had obvious features ofprolactinomas, two were Cushingoid, threepresented with features of panhypopitu-itarism, and 26 were thought to be func-tionless before any endocrine evaluation.There appeared to be a better correlation ofpreoperative hormone levels with cell-culture data rather than with immuno-histochemistry, and this was particularlyapparent in patients with acromegaly. In asignificant number of cases, the adenomathought to be producing only growth hor-mone or prolactin was found, in culture, to

be capable of producing both these hor-mones. In prolactinomas, hormone levels invitro may be an indicator of prognosis, thelarger and more extensive tumours pro-ducing higher levels.

AN AUDIT OF THE DIRECT TRANSNASALTRANSSPHENOIDAL APPROACH TO THEPITUITARY FOSSARS Cooke, RAC Jones. Hope Hospital,Salford, UK.

Several routes may be used to gain access tothe sphenoid sinus in transsphenoidalpituitary surgery. The direct transnasalapproach has been used in this unit since1987. An audit of this technique is reportedin 48 patients who have had 52 transnasalpituitary procedures performed.

Over 80% of patients presented with anendocrine syndrome. All underwent directcoronal CT. The mean tumour diameterwas 17 mm and 25 (52%) had extrasellarextension. The surgical aim (biopsy,debulking or total removal), was achieved in42 (87 5%) cases; in six cases the procedurewas aborted due to venous haemorrhage(four patients) or anatomical difficulties(two patients). In these last two cases, asuccessful re-exploration was made afterrepeat CT. The mean theatre time was 62minutes. Complications (diabetes insipidus,cerebrospinal fluid rhinorrhoea, or visualdeterioration) occurred after eight pro-cedures (15-4%) and were not directlyattributable to the transnasal route.Postoperative stay averaged three days foruncomplicated cases. No nasal complica-tions have occurred.

Other approaches to the sphenoidc sMiusinvolve difficult dissection through ethmoidair cells, or along the nasal septal submu-cous plane; the Direct Transnasal approachis straightforward, quick, and does notrequire laborious dissection of nasal mucosaor removal of septal cartilage. The compli-cation rate is similar to other transsphe-noidal series,' but the authors have notencountered any nasal, septal, or dentalcomplications, which can occur with theother approaches.

1 Black P, Zervas N, Guillermo C. Incidenceand management of complications oftranssphenoidal operation for pituitary ade-nomas. Neurosurgery 1987;20:920-4.

TRANSSPHENOIDAL SURGERY VERSUSOCTREOTIDE TREATMENT FOR ACROMEGALYF Afshar, AHS Huneidi, TPD Blackbum,JH Wass. St Bartholomew's Hospital,London, UK

Octreotide, a synthetic analogue of somato-statin, has been used recently for the treat-ment of acromegaly. This prospective studycompares octreotide with transsphenoidalsurgery in 33 patients (17 men, 16 women;mean age 45 years, range 21-64). Theywere allocated for either octreotide (n = 17;8 men) or surgery (n = 16; 8 men) treat-ment according to their visual signs. All hadpituitary tumours proven by CT, rangingfrom moderate to large size (10-30 mm intheir widest diameter). Fifteen patients hadintrasellar tumours (meso-adenomas), and18 had extrasellar extension (macro-adeno-mas). Mean (SE) growth hormone (GH)levels were 160 (70) mU.1-' and 136(25) mU.l-' for the surgery (control) and the

octreotide-treated groups respectively.Octreotide (300-600 ,ug/day) was given

subcutaneously for a period of 2-18 months(mean (SE) 11 (1)). GH levels werereduced to 28-7 (6 5) mU.1'. Seven patientsshowed a minor degree of tumour shrink-age. Subsequently, all the octreotide grouppatients, except one, underwent surgery.Octreotide reduced the GH levels by 74%,but did not produce a significant change inthe tumour size. Surgery, however, reducedGH levels by 74-5%, and the tumour size bymore than 95%.

It is concluded that surgery should be thefirst line of treatment for GH-producingpituitary adenomas; octreotide and radio-therapy can be reserved as postsurgicaladjuvant therapy.

MRI CISTERNOGRAPHY AND LOCALISATION OFCEREBROSPINAL FLUID FISTULAEMS Eljamel, CN Pidgeon, J Toland, JPhillips, A O'Dwyer. Richmond Institutefor Neurology and Neurosurgery, Dublin,Eire

Accurate localisation of cerebrospinal fluid(CSF) fistulae has always been a difficultproblem for both the neurosurgeon andneuroradiologist. Several techniques havebeen advocated over the years with variablesuccess. Precise localisation of the site ofCSF leakage not only makes planning ofsurgery easier, but it also increases thechances of successful dural repair and elimi-nates negative exploration. Plain skull radi-ography and complex motion tomographyhave been superseded by radioisotope cis-ternography (RIC) and, more recently, bymetrizamide CT cisternography (MICTC).However, both RIC and MCTC are inva-sive, carry risks to the patient and cannot beperformed in the presence of intracranialmass lesions. They are time consumingand insensitive, when the CSF leakage isinactive. Furthermore, patients have to bedetained in hospital to carry out such inves-tigations. Because CSF gives a high signalon T2-weighted MRI images and MRIcan demonstrate the cranial anatomyexquisitely, this is a potentially very valuablelocalising technique for CSF fistulae.The aim of this study was to evaluate

MRI cisternography in localising the site ofinactive CSF leakage. Ten patients withinactive traumatic CSF fistulae were studiedusing T2-weighted MRI, whose age variedfrom 11 to 60 years and the female:maleratio was 2:8. Three had Le Forte III frac-tures and two had petrous bone fractures.Half the patients had meningitis, three ofwhich were recurrent pneumonococcalmeningitis. MRI cisternography was per-formed in all cases and the site of the CSFfistula was demonstrated in the ethmoidsinus (five), frontal sinus (three), cribriformplate (two), sphenoid sinus (one) and themiddle ear complex (two). All patients wereexplored surgically, the sites of CSF fistulaewere confirmed and repaired intradurally ineach case, using fibrin glue and a pericranialgraft.

Although this series is still relativelysmall, MRI cistemography is safe, carries norisk to the patients, takes a relatively shorttime to perform and shows the site of theCSF fistula in all cases. MRI cistemographyshould be the preferred method for localis-ing CSF fistulae, particularly in the absenceof active CSF leakage.

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TRANSCRANIAL DOPPLER ULTRASONOGRAPHYAND USE OF A STANDARDISED PULSATILITYINDEX IN THE ASSESSMENT OF PATIENTSWITH HEAD INJURIESPJ Kirkpatrick, M Czosnyka, V Iyer, HWhitehouse, P Smielewski, E Guazzo, JDPickard, Cambridge University, Cambridge,UK

Measurement of middle cerebral arterymean flow velocities (FV) using non-inva-sive transcranial Doppler ultrasonographyhas yet to contribute significantly to theroutine management of patients with headinjuries. Calculation of the dimensionlesspulsatility index (PI = FV,P1lit,dYFVm,)provides a warning of reduced cerebralperfusion pressure (CPP) in these patients.'In this study, serial transcranial Dopplerultrasonography measurements of FV wereundertaken in 21 ventilated patients withdiffuse head injury in whom continuousmeasurements of arterial blood pressure(ABP) and intracranial pressure wereacquired allowing coordinated waveformanalysis at different values of CPP. Therelationship between CPP and mean FVshowed a poorly defined autoregulatorythreshold at a CPP of approximately 50 mmHg. The PI increased gradually, however,as CPP fell below 75 mmHg, and moreabruptly as CPP fell below 50 mmHg.Averaged FV amplitude and ABP ampli-tude were strongly correlated (r = 0-578;p < 0 0001), prompting the calculation ofa standardised pulsatility index (SPI =PI/ABPmpfitjde). As CPP fell below 70mmHg, the SPI increased more uniformlyand at a greater rate than the PI, andshowed a more dramatic increase at theautoregulatory threshold. Further, analysisof variance indicated a closer relationshipbetween the SPI and CPP than for the PI.It is concluded that estimation of SPI pro-vides a more accurate index of falling CPP,and may help to define a potential thera-peutic opportunity for patients with headinjuries.

1 Chan, etal.3JNeurosurg 1992;77:55-61.

AUDIT OF TRANSFER OF NEUROSURGICALPATIENTSKS El-Shunnar, L Chadwick, G Gill.Oldchurch Hospital, Romford, UK

Neurosurgical patients are often transferredout of normal working hours. Some aremechanically ventilated during transfer andothers are critically ill. Several investigatorshave shown that critically ill patients cansuffer secondary insults as a result of trans-fers both within' and between2 hospitals.Eventual mortality in critically ill patientstransported between hospitals can be ashigh as 28%.

Assessment of these patients and thedecision to transfer them is often left tojunior medical staff inexperienced in dealingwith acute neurological problems. An auditof referrals to a regional neurosurgical unitwas carried out over a period of 3-5 months.Of 136 patients referred, 26 (19%) sufferedtrauma and 42 (30n8%) suffered from sub-arachnoid or intracerebral haemorrhage. Atotal of 54 (39-7%) were referred afterhours. A senior house officer was the mostsenior doctor to assess the patient in 36(26 5%) cases. In 16 (11-8%) cases, asenior house officer was the most seniordoctor to know about the patient.

The consultant on call saw the patient in44 (32 3%) cases and knew about thepatient in 66 (48 5%) cases. These figuresclearly demonstrate the need for moresenior involvement in the management ofneurosurgical patients.

1 Andrews PJD, Piper IR, Dearden NM, et al.Secondary insults during intrahospital trans-port of head-injured patients. Lancet 1990;335:327-30.

2 Reeve WG, Runcie CJ, Reidy J, et al. Currentpractice in transferring critically ill patientsamong hospitals in the west of Scotland.BMJ 1990;300:85-7.

THE OUTCOME OF HEAD INJURIES RESCUEDBY A HELICOPTER EMERGENCY MEDICALSERVICE IN A METROPOLISJN Wilden, JC Sutcliffe, R McAvinchey,CJC Kirk, H Hetherington, SE Turvey, AWilson, IG Wylie, ES Watkins. RoyalLondon Hospital, London, UK

A total of 112 patients with head injurieswere rescued by a doctor with advancedtraining in resuscitative techniques andtransported to the Royal London Hospitalby helicopter. The service is available to apopulation of 14 million.

Before reaching the hospital, Glasgowcoma score, pulse rate, blood pressure, andpulse oximetry were recorded. In hospital,CT of the brain was performed and thetypes of injury classified according to theTraumatic Coma Data Bank.'Neurosurgical treatment was started, andoutcome categorised according to theGlasgow outcome scale.

At the accident scene, the mean GlasgowComa Scale was 7, pulse oximetry wasreduced in 35% of cases and 60% ofpatients were ventilated. Average time frominjury to helicopter arrival was 24 minutes.

Preliminary results demonstrate that90% of patients sustaining a diffuse I headinjury and 60% a diffuse II injury achieved"independence" compared with 61% and35% respectively, in the Traumatic ComaData Bank. Reasons for these significantlydifferent results (p = 0-001) were discussedin relation to the methods of measuringseverity, type, and outcome of head injury.Definitions of "rapid resuscitation" and"early definitive neurosurgical care" wereproposed.

1 Marshall 1, Bloers Marshall S, Klauber MR,et al. A new classification of head injurybased on computerized tomography. JfNeurosurg 1991;75:S14-20.

CEREBELLAR ASTROCYTOMA OF CHILDHOOD:LONG-TERM FOLLOW-UPS Sgouros, PW Fineron, AD Hockley.Queen Elizabeth Hospital, Birmingham,UK

Cerebellar astrocytoma of childhood hasalways been regarded as a benign tumour.Certain issues still remain controversial-for example, the role of radiotherapy as anadjuvant to surgery, the management of thecyst wall in cystic tumours, and what aresignificant adverse prognostic factors. Toaddress these questions, the experience inBirmingham from 1959 to 1991 wasreviewed. The records of 97 patients aged0-14 years were studied and the histologicalmaterial assessed independently.

Following clinical and statistical analysisthe following conclusions were reached:

postoperative radiotherapy does notimprove survival, but may actually predis-pose to malignant transformation; excisionof the cyst wall does not enhance survival;and brainstem involvement is the mostadverse prognostic factor. Implications onmanagement are discussed.

INTRACRANIAL TUMOURS IN THE ELDERLY:THE EFFECT OF AGE ON THE OUTCOME OFFIRST-TIME SURGERY OF MENINGIOMASRS Maurice-Williams, ND Kitchen. RoyalFree Hospital, London, UK

The effect of age is reported on the out-come of first-time surgery for intracranialmeningiomas carried out over 14 years.Patients, reviewed retrospectively, weredivided into three age groups: young (up to44 years, 38 patients); middle-aged (45-64,60 patients); and elderly (65 and over, max-imum age 86, 46 patients). There were nodifferences between the groups as regardsthe sizes or positions of the tumours, exceptthat there were no suprasellar meningiomasin the elderly group. Overall surgical mor-tality was 2-7%. Postoperative complica-tions increased with age (16, 23, 30%respectively) but most of these complica-tions had no lasting effects. Postoperativeintracranial bleeding requiring re-operationwas common in elderly patients, occurringin 20% (compared with none in theyoungest group), perhaps a reflection ofcerebral atrophy leading to a postoperativedead space. Outcome was assessed at thefirst follow-up appointment 4-6 monthsafter discharge from neurosurgical care. Bythen, all of the younger patients, 88% ofthose who were middle-aged, and 83% ofthe elderly were in Glasgow outcome scoregrade V. A total of 89% of the elderlypatients showed clear improvement com-pared with their preoperative condition, 2%were unchanged, and 9% were worse or haddied. Macroscopic total removal of thetumour had been achieved in a greater pro-portion of the elderly patients (86%) thanyounger patients. The intellectual deteriora-tion apparent in more than half of the elder-ly patients had recovered fully by the timeof first follow-up in 80%. It is concludedthat age has little effect on the prospects ofsuccess after removal of an intracranialmeningioma.

MANAGEMENT OF TUMOURS OF THE PINEALREGIONL Symon, S Tomita. The NationalHospital, London, UK

Management of tumours of the pinealregion remains, to some extent, controver-sial. Diagnosis may be made followingimaging studies, with evidence of spreadalong the habenula region, the presence ofseeding in other parts of the ventricularsystem, indicative of germinoma, or onexamination of the ventricular or lumbarcerebrospinal fluid (CSF) for exfoliatedcells. Markers of a-fetoprotein or humanchorionic gonadotrophin in the CSF andblood also may be helpful. In recent years,however, there has been a re-awakenedinterest in direct surgery for tumours of thepmeal region.

In the past 15 years, 12 of 26 pinealtumours have been radically excised by thedirect occipital transtentorial approach(four malignant teratomas, two germino-

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mas, two pineoblastomas, one astrocytictumour, two metastatic tumours, and oneependymoma of the parapineal region).Pineal tumours have been identified in threeother cases, all germinomas, by biopsy.Eleven other tumours, three of which wereclearly metastatic, were managed by CSFshunting only without positive identifica-tion. There has been no operative mortalityin radical removal, and symptom-free sur-vival over three years has been noted in thecases of germinoma and in three of the fourcases of teratoma in the current group.

HIGH-FREQUENCY EYE TREMOR IN THEASSESSMENT OF THE COMATOSE PATIENTC Bolger, D Coakley, J Philips, N Sheahan,J Malone. Beaumont Hospital, Dublin, Eire

High-frequency eye tremor or ocularmicrotremor (OMT) is a constant, physio-logical, high-frequency tremor of the eye. Itis caused by the constant tonic input tobrainstem oculomotor centres.' It has beenpostulated that OMT could be a usefulindicator of brainstem dysfunction, particu-larly in the comatose patient.The authors have developed a highly

portable and accurate method of recordingOMT.' Records are obtained at thepatient's bedside, each recording takingabout 10 minutes. Thirty comatose patientswere selected from serial admissions to theneurosurgical intensive therapy unit andcompared with 30 age-matched, normalcontrols. All records were analysed inde-pendent of clinical data. The resultsdemonstrate that OMT frequency is signifi-cantly reduced in the comatose group (p <0-001). The frequency correlates positivelywith the clinical state of the patient. Serialrecordings demonstrate that a change inclinical status is reflected in a correspondingchange in OMT frequency. A low initialfrequency, on admission to intensivetherapy, is an indicator of poor prognosis.

1 Coakley D. Minute eye movement and brainstem function, CRC Press, Florida, 1983.

2 Bolger C, Sheehan N, Coakley D, Malone J.High frequency eye tremor: reliability ofmeasurement. Clin Phys Physiol Measurement1992;13:151-9.

3-D ORBITAL RECONSTRUCTION AFTERTUMOUR ABLATIONDA Lang, G Neil-Dwyer, BT Evans.Southampton University Hospital,Southampton, UK

Benign lesions, including meningioma enplaque, producing globe displacement,visual deterioration, and facial deformityare a notoriously difficult neurosurgicalchallenge. Following radical resection ofbenign tumours in the orbit or anteriorcranial fossa, immediate orbital reconstruc-tion is mandatory. To obtain a goodcosmetic and functional reconstruction, athree-dimensional appreciation of theorbital anatomy is important so that theorbital volume, margins and bony partitionscan be accurately replaced. Rigid fixation isof paramount importance. The authorsbelieve that extensive tumour removal fromaround the orbit requires a multidisciplinaryteam and a flexible surgical approach. In 10patients, including two children with suchlesions, these concepts were illustrated.

ORBITAL SURGERY: TECHNICAL ASPECTS AND

COMPLICATION AVOIDANCEIR Whittle. Western General Hospital,Edinburgh, UK

Retrobulbar orbital fossa microsurgery isinfrequently performed by most neurosur-

geons. Indications for such surgery includedysthyroid eye disease, orbital fossa masses,

trauma, and various optic neuropathies.Many of the potential complications of suchsurgery are unique to the region. Theauthor's experience with 55 cases of orbitalsurgery is presented with particular empha-sis on surgical technique and approaches,potential pitfalls, and occurrence and avoid-ance of complications.

Indications for surgery included dysthy-roid eye disease (29) orbital masses (21including six meningioma, five haeman-gioma, two neurofibroma, and one each oflymphoma, teratoma, dermoid cyst, orbitalvarix, aesthesioneuroblastoma, pseudo-tumour, adenoid cystic carcinoma, andlacrimal lymphoepithelial hyperplasia), trau-ma (two) and optic nerve dural fenestration(three). Surgical approaches used includedlateral orbitotomy (38), low frontal cranio-tomy (13), pterional craniotomy (3) andfronto-orbito-zygomatic osteotomy in one

case. Patients with dysthyroid eye diseasehad decompressive superior, posterior, andlateral orbitotomies performed through a

small superolateral eyebrow incision.Although short-term or long-term relief ofsymptoms was unsatisfactory in six eyes,

this was unrelated to technical aspects ofthe surgery. The remaining patients experi-enced a median 5 mm globe recession, hadimproved visual actuity and visual fields,less orbital pain, improved ocular motility,and lower steroid requirements. Excision oforbital masses was generally uncomplicatedbut particular problems and dilemmasarose with optic nerve sheath meningioma(sacrifice of the optic nerve when some

vision is preserved, lateral versus subfrontalapproach), patients in whom a secondorbital operation was being performed (dueto intense scarring in the retroconal tissues)and in one case of retrobulbar lymphoma(iatrogenic monocular blindness). Althoughoptic nerve sheath fenestration is technicallysimple to perform and led to resolution ofpapilloedema in all three cases, in none didvisual acuity improve. Overall there were no

infections and morbidity was low.

TITANIUM CRANIOPLASTY: POST-OPERATlVERADIOLOGYCL Chandler, DJ Archer, D Uttley.Atkinson Morley's Hospital, London andRoyal Marsden Hospital, London, UK

Titanium cranioplasty has been used in theauthors' units since 1988 for the reconstruc-tion of a wide range of cranial defects.Titanium is still regarded by many as lesssatisfactory than acrylic for the purpose ofcranioplasty. It is biologically and chemi-cally inert, light in weight, malleable, andvery strong. Most importantly, it is a non-ferrous metal, weakly paramagnetic, and

relatively radiolucent.' 2

The lack of clinically significant imagedegradation on MRI, and CT, plain radiog-raphy, and contrast cisternography has beendemonstrated.On the basis of its strength, biocompati-

bility, and excellent handling characteristics,

allied to its suitability for all postoperativeimaging techniques, it is concluded thattitanium plate is the material of choice forcranioplasty.

1 Blake GB, Macfarlane MR, Hinton JW.Titanium in reconstructive surgery of theskull and face. Br J Plastic Surg 1990;43:528-35.

2 Gordon DS, Blair GAS. Titanium cranio-plasty. BMJ7 1974;2:478.

THE EFFECT OF EXOGENOUS CALCITONINGENE-RELATED PEPTIDE ON FOCAL CEREBRALISCHAEMIC INJURY IN RATSJP Holland, SG Sydserff, BA Bell.Atkinson Morley's Hospital, London, UK

Calcitonin gene-related peptide (CGRP) isa potent endogenous vasodilator existing asa neuropeptide in the trigeminocerebro-vascular system.' It is believed that the(nociceptive) depolarisation of these nervesin the event of a subarachnoid haemorrhageor migraine causes the antidromic release ofCGRP in an attempt to restore normalcerebrovascular tone.2The effect of intravenous CGRP was

studied in a rat model of middle cerebralartery (MCA) occlusion, observing theeffects on cerebral blood flow and ischaemicneuronal injury. The results show that aninfusion of intravenous CGRP started onehour before MCA occlusion, produces animproved cerebral blood flow in theischaemic hemisphere (control: mean (SD)13-3 (1-8) ml/100 g per minute, CGRP:32 3 (2-1) ml/100 g per minute) and reducesthe volume of ischaemic neuronal injuryby 58% (n = 10). A CGRP infusion startedone hour after MCA occlusion similarlymaintains cerebral blood flow and reducesthe volume of ischaemic neuronal injury by38% (n = 5).The results demonstrate that exogenous

CGRP improves the ischaemic microenvi-ronment and reduces the volume ofischaemic neuronal injury. The clinicalbenefit of this peptide to combat the effectsof a predicted ischaemic insult, such as mayoccur following subarachnoid haemorrhageor during carotid endarterectomy, needs tobe re-examined.

1 Edvinsson L, et al. Peptide containing nervefibres in human cerebral arteries: immuno-cytochemistry, radioimmunoassay andin-vitro pharmacology. Am Neurol 1987;21:431-41.

2 Edvinsson L, et al. Reduced levels of calci-tonin gene-related peptide-like immuno-reactivity in human brain vessels aftersubarachnoid haemorrhage. Neurosci Lett1991;121:151-4.

PULSATILITY OF CEREBRAL BLOOD FLOWVELOCITY AS A FUNCTION OFAUTOREGULATORY RESERVE: EXPERIMENTALSTUDY IN NORMAL ANAESTHETIZED RABBITSM Czosnyka, HK Richards, PJ Kirkpatrick,JD Pickard. Addenbrooke's Hospital,Cambridge, UK

The pulsatility of cerebral artery blood flowvelocity (FV) assessed by transcranialDoppler (TCD) ultrasonography is depen-dent on cerebral autoregulatory reserve.' 2Why does the pulsatile component of theFV waveform increase with inducedhypotension and how does TCD assessmentof the autoregulatory threshold relate tolaser Doppler (LDP) findings?

Eleven anaesthetized, ventilated rabbits(PaCO2: 30-38 mmHg), had arterial blood

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pressure (ABP) monitored in the commoncarotid artery (pressure monitor, CaminoLaboratories, United States), FV in thebasilar artery was measured using 8 MHztranscranial Doppler (PCDop, Scimed,UK) and LDP flux was obtained from thehemisphere contralateral to the side ofinsertion of the Camino probe (Laser BloodFlow Monitor, Moor Instruments, UK). Allwaveforms were recorded and analysed onthe authors' own computer system underresting conditions and during haemorrhage-induced hypotension. Results were thenstandardized for PaCO2 and averaged.

Both average of flux and systolic FVstarted to decrease below an ABP of 45mmHg; mean FV started to decrease gradu-ally below 70 mmHg with a more rapid fallbelow 45 mmHg. Diastolic FV fell rapidlybelow 70 mmHg. The difference betweenthese thresholds (45 and 70 mmHg) wasequal to the systolic-diastolic difference ofABP at a mean pressure of 50 mmHg.Standardised pulsatility index (SPI-defined as the Gosling pulsatility indexdivided by ABP,pli,,d,) started to increase atABP 70 mmHg, reaching a maximum atABP 30 mmHg and then fell. It was con-cluded that, in the healthy rabbit, thedecrease in diastolic FV takes place earlier(by ABP pulse peak-to-peak value) than theexhaustion of autoregulatory reserve. Thisphenomenon is responsible for the earlyincrease in SPI. Decrease in systolic FVmarks the limit of autoregulation indicatedusing LDP flux.

1 Chan KH, Miller JD, Dearden M, et al. JNeurosurg 1992;77:55-61.

2 Nelson RJ, Czosnyka M, Pickard JD, et al.Neurosurgery 1992;31:705-10.

PROLONGED DERANGED CEREBRAL OXYGENMETABOLISM WITH TEMPORARY CAROTIDCLAMPINGAHS Huneidi, A Bristow, F Afshar. StBartholomew's Hospital, London, UK

Cerebral oxygen metabolic rate (CMRO2)remains an evasive parameter of crucialimportance. It can be calculated as theproduct of cerebral blood flow (CBF) andthe arterio-jugular oxygen content differ-ence (AJDO2). This study shows a methodfor direct monitoring of CBF and cerebraltissue oxygen tension (PcerO2) andCMRO2, and its significance in potentialischaemia with temporary arterial occlusion.NZ white rabbits (mean weight (SD) 2-4(0 2) kg; n = 12) were used for temporarybilateral common carotid artery occlusion.A Clarke's electrode (1 mm), implanted inthe cerebral cortex, continuously measuredthe PcerO2 and CBF was continuouslyrecorded using a laser-Doppler shift moni-tor with an implantable dedicated cerebralfibreoptic catheter (0-5 mm). Recordingwas started 45 minutes before temporarybilateral carotid artery clamping (10 min-utes) and continued for 120 minutes there-after. Peripheral arterial (PaO2) and jugularbulb (PjO2) oxygen tensions were measuredserially at regular intervals. The PcerO2showed a good correlation with PaO2 andPjO2 (r = 0-92 and 0 94, respectively;p < 0-001) before carotid clamping. Thesecorrelations and the corresponding CMRO2were not maintained during and after thetemporary carotid artery occlusion.

It is concluded that temporary cerebralarterial occlusion can result in a prolonged

CMRO2 disorder. This technique can be abasis for cerebral blood flow and oxygentension and CMRO2 monitoring at surgeryand in the ventilated patients with cerebralvascular and traumatic lesions.

MINIMALLY EIVASIVE SURGERY FORTEMPORAL LOBE EPILEPSY: A TECHNIQUE FORHIGHLY SELECTIVE MEDIAL TEMPORALLOBECTOMY USING PEROPERATIVE IMAGEGUIDANCE AND ELECTROPHYSIOLOGYD Sandeman, J Bird, H Morgan, S Butler.Frenchay Hospital and The BurdenHospital and Institute, Bristol, UK

The authors have recently set up an adultepilepsy surgery service in Bristol. Inaddition to the standard facilities for epi-lepsy assessment, they are in the uniqueposition in Europe of having access todetailed peroperative physiology and frame-less image-directed surgery. As a result theyhave adopted a minimally invasive approachto the surgery of temporal lobe epilepsy.The initial series of 21 operative procedureson 18 patients includes seven cases of selec-tive medial temporal lobectomy. Three ofthese had a structural lesion on MRI orinterictal single photon emission CT, whilefour had no structural abnormality demon-strable radiologically. The structural lesionswere removed using the ISG viewing wandby the technique already described to thesociety. In the other cases, 2 mm axialreconstructions from a Tl-weighted volumeacquisition MRI were used to direct theviewing wand. The position of a 3 cm diam-eter temporal trephine was then determinedusing the wand. Specially constructed deepbrain electrodes that attach to the wandwere then passed across the middle tempo-ral gyrus into the amygdala and the pos-terior hippocampus. Recordings from theseand from subdural strip electrodes werethen carried out with Brietal provocation tolocalise abnormal spike activity. The extentof resection of the medial temporal struc-tures was then tailored to the electrophysio-logical findings, the wand being used toidentify the inferior hom of the lateral ven-tricle to allow orientation within the tempo-ral lobe and to determine the position of themedial surface of the temporal lobe, beforebiopsy and removal using the ultrasonicaspirator, leaving the medial temporalarachnoid intact. No complications with thetechnique have been encountered and pre-liminary results in terms of epilepsy controlare encouraging. Preoperative and postop-erative volumetric analysis is being carriedout and these results were presented. Theinteresting and controversial implications ofthis approach were discussed.

VOLUMETRIC ANALYSIS OF EPILEPSY SURGERYRESECTIONS USING HIGH RESOLUTION MRIND Kitchen, DGT Thomas, SD Shorvon,DR Fish, J Stevens. Institute of Neurology,London, UK

Epilepsy surgery is becoming increasinglyguided by preoperative imaging, particularlyMRI. Postoperative appearances, however,have not been studied to any extent. This isa significant omission as an accurate meansof defining the surgical resection is essentialto any meaningful follow-up outcome

study. The authors therefore attempted todefine the volume and anatomical site ofepilepsy resections using high resolutionMRI.MRI was performed three months after

surgery on a GE 1-5 T Signa unit.Volumetric imaging was performed in thecoronal plane using contiguous TI 1-5 mmslices. Sagittal Ti and axial T2 and protondensity series were also obtained. Accuracywas assessed using postmortem studies.Variability within and between observerswas consistently less than 5%. The tech-nique was applied to 50 patients following awide variety of operations for temporal andextratemporal lobe epilepsy. Considerablevariability in resection volume and anatomywas found which may be of considerableprognostic importance. Comparison withpreoperative MRI has enabled the cor-relation of the site of resection with thepreoperative abnormality. Postoperativevolumetric MRI provides clinically usefulinformation for individual patient manage-ment, and could prove invaluable for com-parison of different epilepsy surgerytechniques.

MULTIPLE SUBPIAL TRANSECTION: THEMAUDSLEY EXPERIENCEIJA Robertson, IMS Swahney, CD Binnie,CE Polkey. Maudsley Hospital, London,UK

Multiple subpial transection (MST) is anovel technique in epilepsy surgery forthose patients where the epileptogeniclesion cannot be resected because it is in aneloquent area. The first 14 patients toundergo MST by the authors werereviewed. Twelve patients had medicallyintractable epilepsy and two patients hadLandau-Kleffner syndrome. Their agesranged from 8-47 (mean 17) years. Theirduration of epilepsy 0-75-42 (mean 10)years. Preoperative MRI showed a focalabnormality in five cases. Detailed electro-physiological studies, including intraopera-tive electrocorticography were carried out inall cases. Most cases underwent MST ofprecentral and postcentral areas. In addi-tion, five patients had brain resected andseven patients had a biopsy. Histopathologyrevealed five cases of Rasmussen's syn-drome, four cases of cortical dysplasia andnon-specific changes in three cases. Patientshave been followed up for 6-48 months(mean 16). Eight patients have experiencedmarked reduction in seizure frequency, fourpatients have had limitation of seizure pro-pogation. The two patients with Landau-Kleffner syndrome have shown very goodrecovery of language. No patient experi-enced significant additional neurologicaldeficit.

FUNCTIONAL HEMISPHERECTOMY IN THEMANAGEMENT OF INTRACTABLE SEIZURES INCHILDHOODW Harkness. Hospitals for Sick Children,London, UK

Between April 1992 and March 1993 func-tional hemispherectomy has been per-formed in six children at the Hospitals forSick Children. Indications for surgery weresevere intractable seizures in the presence

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of an established functional neurologicaldeficit. Age of onset of seizures ranged frombefore birth to eight months before hemi-spherectomy and age at surgery was fromtwo to nine years. Preoperative investigationincluded EEG, neuropsychology, andanatomical and functional imaging. Under-lying pathology was a neuronal migrationaldefect in most cases, with one case ofRasmussen's encephalitis. Functional hemi-spherectomy was performed following intra-operative electrocorticography whichdemonstrated widely variable electricalabnormalities. The surgical technique wasdescribed and compared with otherdescribed techniques of hemispherectomy.Early results were discussed in terms offunctional and seizure outcome.

TEMPORAL LOBECTOMY FOR INTRACTABLEEPILEPSY. EXPERIENCE WITH 58 CASES OVER21 YEARSKG Davies, RD Weeks. University Hospitalof Wales, Cardiff, UK

Sixty patients with intractable complexpartial seizures underwent surgery between1969 and 1990, and 58 of these underwenta temporal resection. Of 39 patients whohad chronic subdural electrocorticography(ECoG) 37 subsequently underwent ananterior temporal lobectomy (ATL) andtwo had the electrodes removed withoutresection. Two patients had bilateral depthelectrodes placed and then had an ATL.Fourteen patients with evidence of temporalstructural lesions had temporal resectionswith intraoperative ECoG, and five hadresection without ECoG. Mean length offollow-up for all patients was six years. Atotal of 55% of cases were seizure free post-operatively, 7% almost seizure free, 21%had worthwhile improvement and 17% noimprovement. The outcome for patientswith structural lesions was particularlygood. Nine patients complained of mildmemory impairment postoperatively andone had a severe amnestic problem. Onepatient with an unsuspected tumour devel-oped a hemiparesis and dysphasia. Oneother patient had persistent dysphasia. Nomortality was attributable to the surgery.It is concluded that ATL is an excellentoperation for the treatment of intractableepilepsy arising from the temporal lobe, andchronic subdural ECoG is a safe and reli-able method for localising the seizure onset.

NEUROSTIMULATION FOR MOVEMENTDISORDERSJC Sutcliffe, TH Koeze, ES Watkins. RoyalLondon Hospital, London, UK

It has been known since the last centurythat neurostimulation, at least in animals,could be used to control muscle tone' andthis has become clinically significant.2Involuntary movement disorders are notori-ously difficult to treat, despite-an increasingvariety of drugs.A series of 31 patients in whom a neuro-

stimulator was implanted for a variety ofmovement disorders is presented and thesepatients were assessed in a simple manner,to answer the question: did the neurostimu-lator in any way improve their motor func-tions? This study revealed that all but one

patient had improved function and reducedsymptomatology after neurostimulation.Complications related to electrical failure(nine cases) and infection (six cases) werecommon, but did not prevent the patientsseeking further intervention, because of thedegree of benefit obtained.

It is suggested that neurostimulation isindicated in selected patients with involun-tary movement disorders, to control theirdebilitating symptoms, when more conven-tional methods of management have failed.

1 Lowenthal J, Horsley V. Proc R Soc Lond 1897;61:20.

2 Waltz JM, Andreesen WH, Hunt DP. PacingClin Electrophysiol 1987;10:180-204,

MAGNETIC RESONANCE ANGIOGRAPHY CANIDENTIFY FIFTH NERVE COMPRESSION INTRIGEMINAL NEURALGIAJFM Meaney, JB Miles, E Ballantyne, TENixon, GH Whitehouse. Walton Centre forNeurology and Neurosurgery, Liverpool andUniversity of Liverpool, Liverpool, UK

Magnetic resonance angiography (MRA)was performed in 16 patients with trigeminalneuralgia. The axial images were inspectedto establish the exact relationship of thetrigeminal nerve to the adjacent arteries. If avessel was seen compressing the nerve, theangiogram was inspected to identify the ves-sel and its origin.

In 12 patients compression of the trige-minal nerve on the symptomatic side wasidentified by MRA. In 10 cases this was by asingle vessel whereas, in the remaining cases,compression by two vessels was noted. Thesuperior cerebellar artery was responsible forall cases in which compression was by asingle vessel. In the two patients with doublecompression, the nerve was sandwichedbetween the anterior inferior cerebellarartery and superior cerebellar artery in onepatient; and between the anterior inferiorcerebellar artery and a persistent trigeminalartery in the other patient. Four patients hadnegative results.

In nine patients with positive MRA stud-ies the findings were confirmed at posteriorfossa exploration. Two of the patients withnegative scans had previously undergoneposterior fossa exploration which failed toreveal a cause for their continuing trigeminalneuralgia. Surgery was not offered to twopatients because of the normal findings onMRA.To date, there has been complete correla-

tion between MRA and the surgical find-ings. MRA is proposed as the preferreddiagnostic investigation in the preoperativeassessment of patients with trigeminalneuralgia. It provides an added degree ofconfidence to patients and their surgeons,and also prevents unnecessary surgery.

PITFALLS IN THE DIAGNOSIS OF BLOCKEDCEREBROSPINAL FLUID SHUNTS: APROSPECTIVE STUDY OF REFERRAL TO APAEDIATRIC NEUROSURGICAL UNITLD Watkins, U Andar, WF Harkness, RDHayward. Hospitals for Sick Children,London, UK

The diagnosis of shunt blockage can be asimple one when the patient presents withthe classic symptoms and signs of raisedintracranial pressure, and cranial scanning

reveals an increase in the size of the ven-tricular system. In children, however,headache, vomiting, drowsiness, irritability,etc may be associated with many other dis-orders (intercurrent infections, for example)and this may make the diagnosis of shuntfailure less obvious, particularly to thosenon-neurosurgical specialists whose opinionsmay be the first to be sought by the patient'sfamily.

At the Hospitals for Sick Children, GreatOrmond Street, we studied prospectively allrecent cases referred to the neurosurgicalunit with a diagnosis of shunt blockage.Such children may have been brought in bytheir parents without previous medical con-sultation, or may have been referred by gen-eral practitioners or local paediatric units.Our analysis revealed the relative accuracy ofeach of these three groups in making thediagnosis and identifies those conditionswith which shunt failure is most likely to beconfused. It also posed the question as tohow accurately neurosurgeons should expectthe diagnosis to be made in the communityif a decline in the number of "false alarms"is not to be offset by even the slightest rise inthe number of cases where failure to recog-nise the early symptoms of shunt blockagemay result in serious neurological damage oreven death.

THEORETICAL AND PRACTICAL ISSUES INFRAME-BASED AND FRAMELESS STEREOTACTICSURGERY PIANNINGL Lemieux, ND Kitchen, DGT Thomas.Institute of Neurology, London, UK

Stereotaxy is an ensemble of techniques forthe accurate localisation of structures withina body through external means. To a largeextent, stereotaxy has been synonymous with"CT stereotaxy", based on rigid framesattached to the patient's skull. Whereas orig-inally only one CT slice could be analysed ata time, recent advances in computing haveallowed complete data sets to be analysedsimultaneously. This has also allowed thedevelopment of so-called frameless (land-mark-based) stereotaxy. The fundamentaltheoretical and practical differences betweenthe two approaches are discussed. Novelmethods, based on perturbation studies, arepresented for the estimation of the effect ofstereotactic fiducial marker localisation ontarget coordinate calculation in a stereotacticsurgery planning program,' both for CT anddigitised radiography. A method is intro-duced for the evaluation of the accuracy ofstereotactic correlation of tomographic datawhich is based on the calculation of a vol-ume transformation matrix (VTM). Resultsof the perturbation studies clearly indicatethe necessity of sub-pixel registration of thefiducial markers in CT. The loss of accuracyassociated with the use of the VTM indi-cates possible limitations in the accuracy oflocalisation based on frameless stereotaxy.

1 Lemieux L, Lester S, Fish DR. Electroen-cephalogr Clin Neurophysiol 1992;82:399-407.

THE VALUE OF STEREOTACTIC BRAIN BIOPSY INPAEDIATRIC NEUROSURGERYDA Jellinek, M Vloeberghs, G Turner, KRobson, JAG Punt. Queens Medical Centre,Nottingham, UK

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A series of 26 paediatric image-guided,stereotactic brain biopsies was presented.The age range was 2-15, mean 8-8 years.Twenty-four procedures were CT guided,whereas two were MRI guided. The lesionwas hemispheric in seven cases, parasellarin one case, pineal in one, located inthe diencephalon/brainstem in 15, andcerebellar in two patients. There wasno morbidity or mortality after the proce-dures.The diagnostic confidence and correla-

tions of the preoperative clinical and radio-logical diagnoses were reviewed incomparison with the pathological diagnosis(frozen section and definitive specimenhistology). In most patients the preoperativemanagement plan was confirmed by thehistological diagnosis. In three key cases, ofcerebral lymphoma, cerebral vasculitis, andprimitive neuroectodermal tumour, however,the histological diagnosis radically alteredmanagement.

It is concluded that stereotactic biopsy inchildren is technically feasible, safe, and is amajor contributor to the management ofpaediatric neurosurgical disease.

DOES STEREOTACTIC BRAIN BIOSPY INPATIENTS WITH AIDS CONTRIBUTE TO THEIRMANAGEMENT?

R Viswanathan, J Ironside, JE Bell, RPBrettle, IR Whittle. Western GeneralHospital, Edinburgh, UK

Twelve lesions have been biopsied in ninepatients who were either HIV positive or hadAIDS. Indications for biopsy were clinicaldeterioration despite active medical manage-ment in HIV positive patients with cerebrallesions. Preoperatively most patients were

thought to have toxoplasma, CNS lym-phoma or progressive multifocal leukoen-cephalopathy (PML). Most patients hadsigns of focal CNS dysfunction and psy-chomotor slowing. Mean CD4 count was 45(normal > 500). Biopsy was performed usingCT imaging and a BRW stereotactic system.One biopsy revealed non-specific gliosis andmicrocalcification but the others showed tox-oplasmosis (four), CNS lymphoma (three),PML (three), HIV encephalitis (two) andone case of non-specific encephalitis. In 25%of the specimens, single biopsy specimensrevealed more than one pathology-for

example, contiguous CNS lymphoma andtoxoplasma, HIV encephalitis and toxoplas-ma. Complications of biopsy included onedelayed (eight days) biopsy site haematomaand one incidental subarachnoid haemor-rhage but neither required any special treat-ment. Median survival after biopsy was sevenweeks. Although the impact of tissue diagno-sis on patient survival was poor, it did enablemodification of drug treatment such as ces-sation of toxoplasma therapy, commence-ment of antiviral therapy for PML, andtreatment-limiting decisions to be made-forexample, withdrawal of treatment in patientswith CNS-lymphoma or HIV encephalitis.The conclusions of this study are firstly

that the outcome is uniformly poor, irrespec-tive of pathology, in patients who are HIVpositive and in a bad clinical and immuno-logical state at the time of biopsy. Secondlywith comprehensive neuropathological stud-ies, the diagnostic yield from stereotacticbiopsy specimens is similar to non-AIDScases. Although histological diagnosis mayfacilitate decisions affecting quality of life inthese patients, whether earlier biopsy wouldalter life expectancy is uncertain.

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