1996 a Novel Computer-Assisted Volumetric Stereotactic Approach for Resecting Tumors of the Posterior Parahippocampal Gyrus

7/31/2019 1996 a Novel Computer-Assisted Volumetric Stereotactic Approach for Resecting Tumors of the Posterior Parahippo

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UMORS of the posterior parahippocampal gyrus rep-resent a formidable technical challenge to neuro-surgeons. The proximity of such lesions to vital

structures surrounding the posterior mesial temporal lobein the dominant hemisphere, including the brainstem, cra-nial nerves, posterior cerebral and anterior choroidal ar-teries, basal vein of Rosenthal, as well as the vein ofLabb and the language cortex, raises the possibility ofpotentially disastrous operative morbidity. Several surgi-cal approaches to this region have been described for

resecting epileptogenic lesions in the amygdala and hip-pocampus.3,8,1214,16,17 However, these approaches requireeither resection or significant retraction of eloquent cor-tex and have been associated with several postoperativecomplications, including dysphasia and visual field de-fects. Moreover, exposure of the posterior hippocampusby means of an anterior approach is technically difficult. 8

Using both computer-assisted stereotactic and micro-surgical techniques, the senior author (P.J.K.) has imple-mented a novel approach for volumetrically resectingtumors of the mesial posterior temporal lobe and parahip-pocampal gyrus. By avoiding resection or retraction of thetemporal lobe, this approach avoids injuring surroundingneural and vascular structures. In this report, we describe

our recent experience using this lateral occipitosubtempo-ral, computer-assisted volumetric stereotactic approachin seven patients, all operated on since 1994 by a singlesurgeon.

Clinical Material and Methods

Patient Characteristics

Seven patients (six males and one female) underwent

stereotactic resection of posterior mesial temporal lobetumors via a lateral occipitosubtemporal approach. Theoperations were all performed by the senior author (P.J.K.)at New York University Medical Center between January1994 and March 1995 (a 15-month period). Clinical infor-mation pertaining to these cases is summarized in Table 1.Patient ages at presentation ranged from 15 to 67 years(mean 39 years). Five tumors were located in the domi-nant (left) posterior hippocampusparahippocampal gyrusand two were located in the nondominant (right) hemi-sphere. Three patients presented with seizures, one withvisual field loss and hemiparesis, one with visual field lossand dysphasia, and one with headache. One patient har-bored a tumor found incidentally.

J Neurosurg 85:272277, 1996

272

A novel computer-assisted volumetric stereotactic approachfor resecting tumors of the posterior parahippocampal gyrus

HOWARD L. WEINER, M.D., AND PATRICK J. KELLY, M.D.

Department of Neurosurgery, New York University Medical Center, New York, New York

The authors report their experience using a novel surgical approach for resecting tumors located in the posterior parahip-pocampal gyrus. Prior attempts to resect epileptogenic foci in this location have been limited by a significant risk of injuryto lateral temporal lobe cortical and vascular structures. To avoid these potential complications, the authors have used alateral occipitosubtemporal, computer-assisted stereotactic volumetric approach to resect radiographically defined tumorsin seven patients with intraaxial neoplasms of the posteromedial temporal lobe. This series included one female and sixmale patients, ranging in age from 15 to 67 years, who presented with seizures, visual field loss, or headache. Gross-total

resection of three high-grade gliomas, two gangliogliomas, and one mixed glioma was accomplished with no permanentmorbidity or operative mortality. The authors conclude that this approach is advantageous for resecting tumors in this loca-tion because, by avoiding unnecessary brain resection or retraction, it significantly reduces the risk of injury to lateral tem-poral lobe structures, helps maintain precise spatial and anatomical orientation for the surgeon, and, like all computer-assisted volumetric approaches, delineates the margin between the tumor and surrounding neural tissue.

KEY WORDS brain neoplasm computer hippocampus stereotaxis

temporal lobe

T

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Several patients were referred for stereotactic volumet-ric resection after previous neurosurgical interventionshad failed. One patient (Case 1) had undergone previousstereotactic biopsy and radiation therapy at another insti-tution followed by stereotactic volumetric resection of aright posterior hippocampal oligoastrocytoma 30 monthsprior to his current admission. A second patient (Case 2)

presented after undergoing stereotactic biopsy of a domi-nant-hemisphere high-grade glioma at another hospital.Another patient (Case 3) was also referred for stereotac-tic volumetric resection of a dominant-hemisphere hippo-campal glioblastoma multiforme following stereotactic bi-opsy at an outside institution. A fourth patient (Case 6)was referred for resection of a right hippocampal glioblas-toma multiforme after a stereotactic biopsy performed atour institution revealed the lesion. A fifth patient with adominant-hemisphere cystic ganglioglioma (Case 7) hadundergone multiple unsuccessful procedures over a 10-year period including: two subtotal surgical resections,three stereotactic cyst aspirations, two stereotactic implan-tations of iodine-125, fenestration of the cyst into the ven-

tricular system, and placement of an intracystic reservoir,which eventually became infected.

The preoperative computerized tomography (CT) andmagnetic resonance (MR) imaging characteristics foundin this group were as follows: three tumors (Cases 2, 3,and 5) were contrast-enhancing ring lesions with sur-rounding T

2prolongation (Type II); two (Cases 1 and 4)

showed T1

and T2

prolongation but no contrast enhance-ment (Type III); one (Case 6) had solid contrast enhance-ment with surrounding T

2prolongation (Type II); and

one (Case 7) showed homogeneous contrast enhancementwith an associated cyst (Type I).4,5

Data Acquisition and Surgical Planning

The technical aspects of the computer-assisted volu-metric stereotactic craniotomy have been described previ-ously.1,49 After local anesthesia has been induced in thepatient, a CT- and MR-compatible stereotactic headframeis attached to the head by means of four carbon-fiber pinsinserted through holes drilled into the diploe of the skull.Data acquisition is begun as the patient undergoes stereo-tactic CT and MR imaging, followed by stereoscopic dig-ital subtraction internal carotid and vertebral angiography.These data are then transferred into the operating roomcomputer system (COMPASS Stereotactic System; Ste-reotactic Medical Systems, Inc., Rochester, MN). On theimage-display console, the surgeon views each CT and

MR image that demonstrates the target lesion. A singlepoint located in the approximate center of the lesion onone of the CT or MR imaging slices is digitized and re-tained as the reference target point. The most inferior andsuperior slices that demonstrate the lesion are indicated,and the computer then reads in each intermediate slice.Using the display cursor, the surgeon digitizes successivetumor contours on contiguous CT and MR imaging slicesby tracing the outline of the lesion. The interpolated CT-and MR imagingdefined volumes are constructed aroundthe reference target point, which is placed in the focalpoint of the stereotactic arc-quadrant frame. The com-puter then reconstructs the digitized CT- and MR im-agingdefined tumor outlines into a volume within

stereotactic space with reference to the target point. Thecomputer can then slice these CT- and MR imagingdefined volumes perpendicular to any specified viewlinethat is expressed in arc and collar angles on the stereotac-tic instrument. Tumor volume slices viewed perpendicularto an intended trajectory may then be displayed with re-spect to the stereotactic trephine craniotomy (1.5- or 2-in

diameter) or the stereotactic retractor (2- or 3-cm diame-ter). The tumor volume may also be superimposed on thedigital subtraction angiographic images so that when plan-ning the operative trajectory, the surgeon can avoid im-portant arteries, veins, sulci, and gyri. The stereoscopicangiographic images of the cortical arteries and veins helpto establish the sulcal anatomy.

Data acquisition and surgery take place on separatedays. The stereotactic headholder is removed followingCT and MR imaging and angiography and is subsequent-ly reapplied at the time of surgery. Detachable microme-ters that record the distance from the end of the carbon-fiber pins to the vertical supports of the headframe are

used to ensure precise replacement of the frame for latersurgical procedures. Therefore, surgical planning can takeplace at the computer console in a relaxed environment.

Surgical Procedure

Figure 1 illustrates the operative approach to the poste-rior parahippocampal gyrus that is made using a stereo-tactic volumetric lateral occipitosubtemporal approach.Each procedure is performed after general anesthesia hasbeen induced endotracheally in the patient. The CT-com-patible stereotactic headframe is replaced using the samepin placements and micrometer settings that were used fordata acquisition. The patient is placed in the three-quarterprone position, with the head rotated to the 135 or 225position for left- or right-sided lesions, respectively. Afterinfiltrating the skin with 1% lidocaine, a pilot hole isdrilled at specified arc and collar angles, and a vertical lin-ear skin incision is made. A 2-in diameter trephine cra-niotomy is performed in line with the selected trajectory,and the dura is opened in a cruciate fashion. The trephineis positioned so that its diameter is two-thirds above andone-third below the lateral sinus, approximately half thedistance between the torcular herophili and the vein ofLabb. To avoid potential sinus laceration, extreme care istaken to ensure that the trephine axis does not depart fromits perpendicular orientation to the skull or inadvertentlyextend too deeply. This routine maneuver has resulted in

no sinus injuries. Dural tack-up sutures are used to retractthe lateral sinus inferiorly. Relaxation of the posterior tem-poral lobe is facilitated primarily with the aid of reverseTrendelenburg positioning, propofol-induced anesthesia,and hyperventilation to a PCO

2of from 25 to 28 mm Hg.

Continuous drainage of small amounts of cerebrospinalfluid from the subarachnoid space during the procedurefurther facilitates mobilization of the temporal lobe fromthe tentorium. This maneuver has not resulted in a signif-icant intraoperative shift of structures with respect to theimaging data and, therefore, has not compromised theaccuracy of the stereotactic approach in any of the cases.The vein of Labb is identified and preserved. Smallerdraining veins from the posterior temporal lobe to the


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The follow-up period for this study ranged from 4months to 18 months (median 11 months; mean 8.4

months). No patient died or experienced permanent mor-bidity. The five patients who were neurologically intactpreoperatively experienced no new neurological deficitsafter surgery. One patient (Case 7) who had a right hemi-paresis preoperatively was initially worse following sur-gery. However, she experienced progressive improvementin her power and was eventually discharged on the 7thpostoperative day neurologically unchanged. Another pa-tient (Case 5) who presented with a superior right quad-rantanopsia experienced transient postoperative visualworsening in the inferior quadrant as well, which resolved1 week after surgery. Two months after surgery, one pa-tient (Case 3) experienced a marked progression of histumor while undergoing chemotherapy; since then hehas required continual steroid administration. The patientsdiagnosed with glioblastoma multiforme and anaplasticastrocytoma were each referred for radiation therapy andchemotherapy.

Discussion

Exposure of the posteromedial temporal lobe has long

been considered technically challenging.8 The proximityof this region to the midbrain, crural and ambient cisterns,anterior choroidal and posterior cerebral arteries, and thebasal vein of Rosenthal mandates precise anatomical lo-calization and spatial orientation by the surgeon. More-over, standard approaches to this area have been unsatis-factory insofar as each has necessitated either retraction orresection of lateral temporal cortex, risking speech andvisual field disturbances or potential injury to the vein ofLabb. Neurosurgeons have gained access to the region ofthe posteromedial temporal lobe via transsylvian, trans-cortical, or subtemporal approaches. The majority of ap-proaches to this area already described have been directedat the removal of foci of seizure activity in patients withtemporal lobe epilepsy.3,8,1214,16,17

Wieser, Yasargil, and others8,16,17 developed the trans-sylvian approach for selective amygdalohippocampecto-



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FIG. 2. Case 6. Preoperative (A and C) and postoperative (B and D) axial and sagittal magnetic resonance imagesobtained in a 67-year-old man who underwent resection of a contrast-enhancing glioblastoma of the right parahippo-campal gyrus.

TABLE 1

Characteristics of seven patients undergoing lateral occipitosubtemporal computer-assisted stereotactic volumetricresection of posterior parahippocampal gyrus tumors*

Case Age (yrs), CT/MR Imaging Type of Finding at Follow Up,No. Sex Location Diagnosis Presentation Characteristics Resection Time Postop

1 19, M rt PHG mixed glioma GTC seizure; nonenhancing GT neurologically intact,neurologically intact 5 mos2 61, M lt PHG anaplastic incidental finding; ring enhancing GT neurologically intact,

astrocytoma neurologically intact 4 mos3 29, M lt PHG glioblastoma headache; ring enhancing ST recurrence, 7 mos

neurologically intact4 15, M lt PHG ganglioglioma GTC seizure; nonenhancing GT neurologically intact,

neurologically intact 12 mos5 48, M lt PHG glioblastoma VF loss; dysphasia ring enhancing GT neurologically intact,

4 mos6 67, M rt PHG glioblastoma CP seizure; contrast enhancing GT neurologically intact,

neurologically intact 9 mos7 35, F lt PHG ganglioglioma VF loss; hemiparesis cystic/contrast GT hemiparesis, 18 mos

enhancing

* CP = complex partial seizure; CT = computerized tomography; GT = gross total; GTC = generalized tonicclonic seizure; MR =magnetic resonance; PHG = parahippocampal gyrus; ST = subtotal; VF = visual field.


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my to minimize temporal neocortical resection, leavingthe lateral surface of the temporal lobe intact and sparingspeech functions of the dominant hemisphere. This ap-proach involves opening of the sylvian fissure, subtotalresection of the amygdala, and hippocampal and parahip-pocampal resection through the temporal horn.3,16,17 Find-ing this anterior approach to the mesial temporal struc-

tures to be encouraging in the control of complex partialseizures of anteromedial origin, Kelly, et al.,8 nonethelessemphasized that exposure of the posterior hippocampusby means of this anterior approach is not adequate.

Spencer and associates14 described a technique forachieving access to posterior medial temporal lobe struc-tures in patients with unilateral posterior hippocampal sei-zure foci. Their modified anteromedial temporal lobecto-my consisted ofen bloc removal of the anterior middleand inferior temporal gyri, retraction of the remaining lat-eral temporal lobe, and resection of the posterior hip-pocampus or posteromedial temporal intraaxial mass.3,14

However, this approach is not optimal because it requiresnot only an anterior temporal lobectomy but also retrac-tion of the remaining posterolateral temporal cortex witha self-retaining retractor.

Similarly, transcorticaltransventricular approaches tomesial temporal structures all require some resection ofcortical tissue, as well as disruption of white matter fibersof the temporal stem.3 The transventricular amygdalo-hippocampectomy described by Niemeyer,10 in which acortical incision was made in the middle temporal gyrus,preserves the superior temporal gyrus; however, it neces-sitates significant resection of middle and inferior tem-poral white matter to gain access to the temporal horn,amygdala, hippocampus, and parahippocampal gyrus.3,10

Olivier11 described a similar approach through the supe-

rior temporal gyrus. His technique involves resection ofthe anterosuperior temporal gyrus, followed by aspirationof the amygdala, opening of the temporal horn, and resec-tion of the hippocampus.3,11 Shimizu and colleagues12 ap-proached the mesial temporal lobe through the inferiortemporal gyrus, following removal of the zygomatic arch.

Kelly, et al.,8 have previously described a computer-assisted stereotactic resection of the amygdala and hip-pocampus via a posterolateral approach in patients withmedically intractable complex partial seizures. However,because this transcortical approach involved disruptionof the inferior optic radiations, all patients in their seriesdeveloped nondisabling visual field deficits in the imme-diate postoperative period. This posterolateraltranscorti-

cal approach, identical to that used for resection of intra-ventricular tumors located in the temporal horn or atriumof the lateral ventricle, was selected to spare the corticaltissue related to speech function.8,15 The lateral occipito-subtemporal approach, described in the present report, isessentially a modification of the posterolateraltranscorti-cal approach, designed specifically to avoid disruption ofthe optic radiations as well as of the speech cortex.

The subtemporal approach, as first described by Drake2

for use in treating basilar bifurcation aneurysms, avoidsresection of cortical tissue. However, this procedurenecessitates use of significant brain retraction to gainaccess to tumors located in the posterior parahippocampalgyrus.

Smith and Spetzler13 recently described a supratentori-alinfraoccipital approach to posteromedial temporal lobelesions, in which they used a viewing wand intraoperativenavigational system for guidance. Their technique differsfrom the one described here insofar as it is a midlineapproach, which is performed through an occipital cra-niotomy and which requires exposure of the falx, superior

sagittal sinus, torcular herophili, both transverse sinuses,the occipital pole, and the great vein of Galen and its trib-utaries. As they observed, the disadvantages of the su-pratentorialinfraoccipital approach include the need foroccipital lobe retraction as well as wide exposure of themidline dural venous sinuses, with the inherent risk ofblood loss, air embolism, and delayed sinus thrombosis.

The lateral occipitosubtemporal approach has not beenpreviously described in the neurosurgical literature. Tak-ing into consideration the limitations of previous tech-niques for gaining access to this region, we believe thatthis route offers several advantages. Because of its lateraloccipitosubtemporal trajectory, it obviates the need forboth resection and retraction of brain tissue and thereby

avoids potential damage to vital neurovascular structures,which include the optic radiations, anterior and lateraltemporal cortex, vein of Labb, the occipital pole, and themidline dural sinuses. As noted by Smith and Spetzler,13

the surgical anatomy of the medial temporooccipital junc-tion is not familiar to most neurosurgeons, particularlyas viewed from the posterolateral approach, and the sur-gical trajectory is long and narrow, limiting exploration.Therefore, some form of stereotactic guidance is essen-tial, in either the supratentorialinfraoccipital or the later-al occipitosubtemporal approach, to maintain spatial andanatomical orientation. Smith and Spetzler13 observed thatif a frameless stereotactic unit were not available, a stan-dard frame-based stereotactic instrument could be used to

place a catheter in the lesion to assure correct localization.We believe that our computer-assisted stereotactic volu-metric approach not only can accurately localize theselesions but offers the additional advantage of facilitatingcomplete removal of radiographically defined tumor vol-umes by delineating the margin between tumor tissue andthe surrounding parenchyma.1,49

References

1. Abernathey CD, Davis DH, Kelly PJ: Treatment of colloid cystsof the third ventricle by stereotaxic microsurgical laser crani-otomy. J Neurosurg 70:525529, 1989

2. Drake CG: Bleeding aneurysms of the basilar artery. Directsurgical management in four cases. J Neurosurg 18:230238,1961

3. Fried I: Anatomic temporal lobe resections for temporal lobeepilepsy. Neurosurg Clin North Am 4:233242, 1993

4. Kelly PJ: Tumor Stereotaxis. Philadelphia: WB Saunders,1991

5. Kelly PJ, Daumas-Duport C, Scheithauer BW, et al: Ste-reotactic histologic correlations of computed tomography- andmagnetic resonance imaging-defined abnormalities in patientswith glial neoplasms. Mayo Clin Proc 62:450459, 1987

6. Kelly PJ, Kall BA, Goerss S, et al: Computer-assisted stereo-taxic laser resection of intra-axial brain neoplasms. J Neu-rosurg 64:427439, 1986

7. Kelly PJ, Kall BA, Goerss SJ: Results of computed tomogra-phy-based computer-assisted stereotactic resection of metasta-tic intracranial tumors. Neurosurgery 22:717, 1988

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8. Kelly PJ, Sharbrough FW, Kall BA, et al: Magnetic resonanceimaging-based computer-assisted stereotactic resection of thehippocampus and amygdala in patients with temporal lobeepilepsy. Mayo Clin Proc 62:103108, 1987

9. Morita A, Kelly PJ: Resection of intraventricular tumors via acomputer-assisted volumetric stereotactic approach.Neurosur-gery 32:920927, 1993

10. Niemeyer P: The transventricular amygdala-hippocampectomyin temporal lobe epilepsy, in Baldwin M, Bailey P (eds): Tem-poral Lobe Epilepsy. Springfield, Ill: Charles C Thomas,1958, pp 461482

11. Olivier A: Commentary: cortical resection, in Engel J Jr (ed):Surgical Treatment of the Epilepsies. New York: RavenPress, 1987, pp 405416

12. Shimizu H, Suzuki I, Ishijima B: Zygomatic approach for re-section of mesial temporal epileptic focus. Neurosurgery 25:798801, 1989

13. Smith KA, Spetzler RF: Supratentorialinfraoccipital approachfor posteromedial temporal lobe lesions. J Neurosurg 82:940944, 1995

14. Spencer DD, Spencer SS, Mattson RH, et al: Access to the pos-terior medial temporal lobe structures in the surgical treatmentof temporal lobe epilepsy. Neurosurgery 15:667671, 1984

15. Talairach J, Bancaud J, Szikla G, et al: Approche nouvelle dela neurochirurgie de lpilepsie: mthodologie strotaxique etrsultats thrapeutiques. Neurochirurgie 20 (Suppl):1240,1974

16. Wieser HG, Yasargil MG: Selective amygdalohippocampecto-my as a surgical treatment of mediobasal limbic epilepsy. SurgNeurol 17:445457, 1982

17. Yasargil MG, Wieser HG, Valavanis A, et al: Surgery andresults of selective amygdala-hippocampectomy in one hun-dred patients with nonlesional limbic epilepsy.Neurosurg ClinNorth Am 4:243261, 1993

Manuscript received October 4, 1995.Accepted in final form March 27, 1996.

Address reprint requests to: Patrick J. Kelly, M.D., Departmentof Neurosurgery, New York University Medical Center, 550 FirstAvenue, New York, New York 10016.



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1996 a Novel Computer-Assisted Volumetric Stereotactic Approach for Resecting Tumors of the Posterior Parahippocampal Gyrus