Neurosurgery Greenberg

CONTENTS xi

Contributors iiiEvidence based medicine ivBooking the case vAbbreviations vi

1. Neuroanesthesia 11.1. General information 11.2. Drugs used in neuroanesthesia 11.3. Anesthetic requirements for intraoper-

ative evoked potential monitoring 41.4. Malignant hyperthermia 51.5. References 6

2. Neurocritical care 72.1. Fluids and Electrolytes 72.2. Blood pressure management 192.3. Sedatives & paralytics 232.4. Neurogenic pulmonary edema 282.5. References 28

3. General care 313.1. Endocrinology 313.2. Hematology 343.3. Pharmacology 443.4. References 53

4. Neurology 564.1. Dementia 564.2. Headache 574.3. Parkinsonism 594.4. Multiple sclerosis 614.5. Motor neuron diseases 654.6. Guillain-Barré syndrome 664.7. Myelitis 694.8. Neurosarcoidosis 714.9. Vascular dysautoregulatory

encephalopathy 734.10. Vasculitis and vasculopathy 744.11. References 80

5. Neuroanatomy and physiology 845.1. Surface anatomy 845.2. Cranial foramina & their contents 895.3. Cerebellopontine angle anatomy 905.4. Occiptoatlantoaxial-complex anatomy

915.5. Spinal cord anatomy 925.6. Cerebrovascular anatomy 965.7. Internal capsule 1075.8. Miscellaneous 1085.9. Neurophysiology 1095.10. References 119

6. Neuroradiology 1226.1. Contrast agents in neuroradiology 1226.2. Radiation safety for neurosurgeons

1266.3. CAT scan or CT scan 128

6.4. Magnetic resonance imaging (MRI) 129

6.5. Angiography (cerebral) 1346.6. Plain films 1356.7. Myelography 1406.8. Radionuclide scanning 1406.9. References 141

7. Operations and procedures 1447.1. Intraoperative dyes 1447.2. Operating room equipment 1447.3. Surgical hemostasis 1467.4. Craniotomies 1467.5. Cranioplasty 1737.6. Localizing levels in spine surgery 1737.7. Anterior approaches to the spine 1747.8. Surgical fusion of the cervical spine

1797.9. Surgical fusion of the thoracic spine

1907.10. Surgical fusion of the lumbar and lum-

bosacral spine 1917.11. Bone graft 1977.12. Percutaneous access to the CSF 2017.13. CSF diversionary procedures 2077.14. Sural nerve biopsy 2147.15. Nerve blocks 2157.16. References 217

8. Developmental anomalies 2228.1. Arachnoid cysts 2228.2. Intracranial lipomas 2258.3. Hypothalamic hamartomas 2268.4. Neurenteric cysts 2278.5. Craniofacial development 2288.6. Chiari malformation 2338.7. Dandy Walker malformation 2408.8. Aqueductal stenosis 2418.9. Neural tube defects 2438.10. Absence of the septum pellucidum

2478.11. Klippel-Feil syndrome 2538.12. Tethered cord syndrome 2548.13. Split cord malformation 2568.14. Lumbosacral nerve root anomalies

2568.15. References 257

9. Neuroendovascular intervention 2629.1. Neuroendovascular procedure basics

2639.2. References 264

10. Electrodiagnostics 26610.1. Electroencephalogram (EEG) 26610.2. Evoked potentials 26610.3. NCS/EMG 269

Contents

xii CONTENTS

10.4. References 27111. Neurotoxicology 273

11.1. Ethanol 27311.2. Opioids 27511.3. Cocaine 27611.4. Amphetamines 27711.5. Carbon monoxide 27711.6. References 278

12. Coma 27912.1. General information 27912.2. Approach to the comatose patient 28112.3. Herniation syndromes 28412.4. Hypoxic coma 28712.5. References 288

13. Brain death 28913.1. Brain death in adults 28913.2. Brain death in children 29213.3. Organ and tissue donation 29313.4. References 296

14. Cerebrospinal fluid 29714.1. General information 29714.2. CSF constituents 29714.3. Artificial CSF 30014.4. CSF fistula (cranial) 30014.5. Intracranial hypotension 30514.6. References 306

15. Hydrocephalus 30715.1. Treatment of hydrocephalus 31415.2. Shunt problems 32115.3. Normal pressure hydrocephalus 32915.4. Blindness from hydrocephalus 33515.5. Hydrocephalus and pregnancy 33615.6. References 337

16. Infections 34216.1. Prophylactic antibiotics 34216.2. Meningitis 34316.3. Shunt infection 34516.4. Wound infections 34816.5. Osteomyelitis of the skull 34916.6. Cerebral abscess 35016.7. Subdural empyema 35616.8. Viral encephalitis 35816.9. Creutzfeldt-Jakob disease 36116.10. Neurologic manifestations of AIDS

36416.11. Lyme disease - neurologic manifesta-

tions 36816.12. Parasitic infections of the CNS 36916.13. Fungal infections of the CNS 37416.14. Amebic infections of CNS 37516.15. Spine infections 37616.16. References 388

17. Seizures 39417.1. Seizure classification 39417.2. Special types of seizures 39617.3. Status epilepticus 40217.4. Antiepileptic drugs (AEDs) 40717.5. Seizure surgery 42017.6. References 425

18. Spine & spinal cord 42818.1. Low back pain and radiculopathy 42818.2. Sagittal balance 44118.3. Intervertebral disc herniation 44218.4. Degenerative disc/spine disease 47418.5. Craniocervical junction and upper cer-

vical spine abnormalities 49418.6. Rheumatoid arthritis 49418.7. Atlantoaxial subluxation (AAS) in

Down syndrome 49818.8. Paget’s disease 49818.9. Ankylosing spondylitis 50218.10. Ossification of the posterior longitudi-

nal ligament (OPLL) 50418.11. Ossification of the anterior longitudi-

nal ligament (OALL) 50618.12. Diffuse idiopathic skeletal hyperosto-

sis 50618.13. Scheuermann's kyphosis 50618.14. Spinal vascular malformations 50718.15. Spinal meningeal cysts 50918.16. Syringomyelia 51018.17. Spinal cord herniation (idiopathic)

51418.18. Spinal epidural hematoma 51518.19. Spinal subdural hematoma 51518.20. Spinal epidural lipomatosis (SEL) 51618.21. Coccydynia 51618.22. References 517

19. Functional neurosurgery 53219.1. Deep brain stimulation 53219.2. Surgical treatment of Parkinson’s dis-

ease 53219.3. Dystonia 53619.4. Spasticity 53619.5. Torticollis 54119.6. Neurovascular compression syn-

dromes 54219.7. Hyperhidrosis 54419.8. Tremor 54519.9. Sympathectomy 54519.10. References 546

20. Pain 54820.1. Neuropathic pain syndromes 54820.2. Craniofacial pain syndromes 54920.3. Postherpetic neuralgia 56420.4. Pain procedures 56720.5. Complex regional pain syndrome

(CRPS) 57620.6. References 577

21. Tumor 58221.1. General information 58221.2. Primary brain tumors 59021.3. Pediatric brain tumors 69721.4. Skull tumors 69821.5. Cerebral metastases 70221.6. Carcinomatous meningitis 71121.7. Foramen magnum tumors 71121.8. Idiopathic intracranial hypertension

(IIH) 713

CONTENTS xiii

21.9. Empty sella syndrome 71921.10. Tumor markers 72021.11. Neurocutaneous disorders 72221.12. Tumors of the spine and spinal cord

72821.13. Neuroblastomas 74821.14. References 749

22. Radiation therapy (XRT) 77022.1. Conventional external beam radiation

77022.2. Stereotactic radiosurgery & radiother-

apy 77322.3. Interstitial brachytherapy 77922.4. References 779

23. Stereotactic surgery 78223.1. References 783

24. Peripheral nerves 78624.1. Some basic points about peripheral

nerve injury/surgery 78924.2. Brachial plexus 79024.3. Peripheral neuropathies 79324.4. Thoracic outlet syndrome 82224.5. Miscellaneous peripheral nerve 82424.6. References 824

25. Neurophthalmology 82825.1. Nystagmus 82825.2. Papilledema 82825.3. Visual fields 82925.4. Pupillary diameter 82925.5. Extraocular muscle (EOM) system

83425.6. Miscellaneous neurophthalmologic

signs 83825.7. References 839

26. Neurotology 84026.1. Dizziness and vertigo 84026.2. Meniere’s disease 84226.3. Facial nerve palsy 84426.4. Hearing loss 84826.5. References 849

27. Head trauma 85027.1. Transfer of trauma patients 85427.2. Management in E/R 85527.3. Neuromonitoring 86627.4. Skull fractures 88527.5. Posttraumatic parenchymal injuries

89227.6. Epidural hematoma 89427.7. Subdural hematoma 89627.8. Traumatic posterior fossa mass lesions

90527.9. Posttraumatic hydrocephalus 90627.10. Aspects of general care in severe TBI

90727.11. Outcome from head trauma 90827.12. Gunshot wounds to the head 91227.13. Non-missile penetrating trauma 91627.14. High altitude cerebral edema 91627.15. Pediatric head injury 91727.16. References 919

28. Spine injuries 93028.1. Whiplash-associated disorders 93128.2. Pediatric spine injuries 93228.3. Initial management of spinal cord in-

jury 93328.4. Neurological assessment 94428.5. Spinal cord injuries 94828.6. Cervical spine fractures 95128.7. Blunt cerebrovascular injuries 98228.8. Thoracic & lumbar spine fractures 98628.9. Osteoporotic spine fractures 99228.10. Sacral fractures 99728.11. Gunshot wounds to the spine 99828.12. Penetrating trauma to the neck 99828.13. Delayed deterioration following spi-

nal cord injuries 100028.14. Chronic management issues with spi-

nal cord injuries 100028.15. References 1002

29. Stroke 101029.1. Cerebrovascular hemodynamics 101029.2. Strokes: general information 101129.3. Stroke in young adults 102429.4. Lacunar strokes 102629.5. Collateral circulation 102729.6. “Occlusion” syndromes 102729.7. Miscellaneous stroke 102929.8. References 1030

30. SAH and aneurysms 103430.1. Introduction to SAH 103430.2. Grading SAH 103930.3. Initial management of SAH 104030.4. Vasospasm 104530.5. Cerebral aneurysms 105530.6. Treatment options for aneurysms 105730.7. Timing of aneurysm surgery 106030.8. General technical considerations

of aneurysm surgery 106130.9. Aneurysm recurrence after treatment

106530.10. Aneurysm type by location 106630.11. Post-op orders for aneurysm clipping

107630.12. Unruptured aneurysms 107730.13. Multiple aneurysms 108030.14. Familial aneurysms 108030.15. Traumatic aneurysms 108130.16. Mycotic aneurysms 108230.17. Giant aneurysms 108230.18. SAH of unknown etiology 108330.19. Nonaneurysmal SAH 108430.20. Pregnancy & intracranial hemorrhage

108630.21. References 1087

31. Vascular malformations 109831.1. Arteriovenous malformation 109831.2. Venous angiomas 110431.3. Angiographically occult

vascular malformations 110531.4. Dural AVM 1109

xiv CONTENTS

31.5. Vein of Galen malformation 111231.6. Carotid-cavernous fistula 111331.7. References 1114

32. Intracerebral hemorrhage 111832.1. Intracerebral hemorrhage in adults

111832.2. ICH in young adults 113132.3. Intracerebral hemorrhage in the new-

born 113132.4. References 1138

33. Occlusive cerebro-vascular disease 114433.1. Atherosclerotic cerebrovascular dis-

ease 114433.2. Cerebral arterial dissections 116033.3. Extracranial-intracranial (EC/IC) by-

pass 116533.4. Cerebrovascular venous thrombosis

116633.5. Moyamoya disease 117033.6. References 1174

34. Outcome assessment 118234.1. References 1184

35. Differential diagnosis 118535.1. Differential diagnosis (DDx)

by signs and symptoms 118535.2. Differential diagnosis (DDx) by loca-

tion 120935.3. References 1235

36. Index 1240Quick reference tables 1331

NEUROSURGERY 5.1. Surface anatomy 85

eye movements to the opposite direction

Medial surface(Figure 5-2)

The cingulate sul-cus terminates posteri-orly in the pars marginalis (pM) (plu-ral: partes marginales). On axial imaging, the pMs: are visible on 95% of CTs and 91% of MRIs4, are usually the most prominent of the paired grooves strad-dling the midline, and they extend a greater distance into the hemispheres4. On axial CT, the pM is located slightly posterior to the widest biparietal diameter4; on the typi-cally more horizontally oriented MRI slices the pM assumes a more posterior position. The pMs curve posteriorly in lower slices and anteriorly in higher slices (here, the paired pMs form the “pars bracket” - a characteristic “handlebar” configuration straddling the mid-line).

Central sulcus on axial imagingSee Figure 5-3. Identification is

important to localize the motor strip (contained in the PreCG). The central sulcus (CS) is visible on 93% of CTs and 100% of MRIs4. It curves posterior-ly as it approaches the interhemispher-ic fissure (IHF), and often terminates in the paracentral lobule, just anterior to the pars marginalis (pM) within the pars bracket (see above)4 (i.e. the CS of-ten does not reach the midline).

Pointers:• parieto-occipital sulcus (pos) (or

fissure): more prominent over the medial surface, and on axial imag-ing is longer, more complex, and more posterior than the pars marginalis5

• post-central sulcus (pocs): usually bifurcates and forms an arc or pa-renthesis (“lazy-Y”) cupping the pM. The anterior limb does not en-ter the pM-bracket and the posteri-or limb curves behind the pM to enter the IHF

Figure 5-2 Medial aspect of the right hemisphere “CT” & “MRI” bars depict typical axial slice orientation for CT & MRI scans.

See Table 5-1 and Table 5-2 for abbreviations

CinG

LG

SFG PL

PCu

Cu

corpus callosum

cins cins

prcs CENTRAL SULCUSCT

MRIpos

spspM

pons

Figure 5-3 CT scan (upper cut) showing gyri/sulci.See Table 5-1 and Table 5-2 for abbreviations

SFG

PL

PreCGcscs

pM

pocsPostCG

creo

86 5. Neuroanatomy and physiology NEUROSURGERY

5.1.2. Surface anatomy of the cranium

CRANIOMETRIC POINTSSee Figure 5-4.

Pterion: region where the following bones are approximat-ed: frontal, parietal, temporal and sphenoid (greater wing). Esti-mated as 2 finger-breadths above the zy-gomatic arch, and a thumb’s breadth be-hind the frontal pro-cess of the zygomatic bone (blue circle in Fig-ure 5-4).

Asterion: junc-tion of lambdoid, occip-itomastoid and parietomastoid su-tures. Usually lies within a few millime-ters of the posterior-in-ferior edge of the junction of the trans-verse and sigmoid si-nuses (not always reliable6 - may overlie either sinus).

Vertex: the top-most point of the skull.

Lambda: junc-tion of the lambdoid and sagittal sutures.

Stephanion: junction of coronal suture and superior temporal line.

Table 5-2 Cerebral gyri and lobules(abbreviations)

AG angular gyrusCinG cingulate gyrusCu cuneusLG lingual gyrusMFG, SFG middle & superior frontal gyrusOG orbital gyrusPCu precuneousPreCG, PostCG pre- and post-central gyrusPL paracentral lobule (upper SFG and PreCG

and PostCG) IFG

POpPTPOr

inferior frontal gyruspars opercularispars triangularis pars orbitalis

STG, MTG, ITG superior, middle & inferior temporal gyrusSPL, IPL superior & inferior parietal lobuleSMG supramarginal gyrus

Table 5-1 Cerebral sulci (abbreviations)

cins cingulate sulcuscs central sulcusips-ios intraparietal-intraoccip-

ital sulcuslos lateral occipital sulcuspM pars marginalispocn pre-occipital notchpocs post-central sulcuspof parieto-occipital fissurepos parieto-occipital sulcusprcs pre-central sulcussfs, ifs superior, inferior frontal

sulcussps superior parietal sulcussts, its superior, inferior tem-

poral sulcustos trans occipital sulcus

Figure 5-4 Craniometric points & cranial sutures.Named bones appear in all upper case letters. Abbreviations: GWS = greater wing of sphenoid bone, NAS = nasal bone, stl = superior temporal line, ZYG = zygomatic. Sutures: cs = coronal, ls = lambdoid, oms = occipitomastoid, pms = parietomas-toid, sms = squamomastoid, sqs = squamosal

opisthionasterion

nasionrhinion

prosthion

inferioralveolar point

glabella

gnathionor menton

gonion

inion

bregmavertex

lambdastl

sqs

pmssms

pterion

ls

oms

cs

stephanion

ophyron

MANDIBLE

MAXILLA

ZYGNASAL

TEMPORAL

PARIETAL

MASTOID

FRON

TAL

OCCIP

ITAL

GW

S

creo

NEUROSURGERY 5.1. Surface anatomy 87

Glabella: the most forward projecting point of the forehead at the level of the su-praorbital ridge in the midline.

Opisthion: the posterior margin of the foramen magnum in the midline.Bregma: the junction of the coronal and sagittal sutures.Sagittal suture: midline suture from coronal suture to lambdoid suture. Although

often assumed to overlie the superior sagittal sinus (SSS), the SSS lies to the right of the sagittal suture in the majority of specimens7 (but never by > 11 mm).

The most anterior mastoid point lies just in front of the sigmoid sinus8.

RELATION OF SKULL MARKINGS TO CEREBRAL ANATOMY

Taylor-Haughton linesTaylor-Haughton (T-H)

lines can be constructed on an angiogram, CT scout film, or skull x-ray, and can then be re-constructed on the patient in the O.R. based on visible external landmarks9. T-H lines are shown as dashed lines in Figure 5-5.

1. Frankfurt plane, AKA baseline: line from inferi-or margin of orbit through the upper mar-gin of the external audi-tory meatus (EAM) (as distinguished from Re-id’s base line: from infe-rior orbital margin through the center of the EAM)10 (p 313)

2. the distance from the na-sion to the inion is mea-sured across the top of the calvaria and is divid-ed into quarters (can be done simply with a piece of tape which is then folded in half twice)

3. posterior ear line: perpendicular to the baseline through the mastoid process4. condylar line: perpendicular to the baseline through the mandibular condyle5. T-H lines can then be used to approximate the sylvian fissure (see below) and the

motor cortex (also see below)

Sylvian fissure AKA lateral fissureApproximated by a line connecting the lateral canthus to the point 3/4 of the way

posterior along the arc running over convexity from nasion to inion (T-H lines).

Angular gyrusLocated just above the pinna, important on the dominant hemisphere as part of

Wernicke’s area. Note: there is significant individual variability in the location2.

Angular arteryLocated 6 cm above the EAM.

Motor cortexNumerous methods utilize external landmarks to locate the motor strip (pre-central

gyrus) or the central sulcus (Rolandic fissure) which separates motor strip anteriorly from primary sensory cortex posteriorly. These are just approximations since individual variability causes the motor strip to lie anywhere from 4 to 5.4 cm behind the coronal suture11. The central sulcus cannot even be reliably identified visually at surgery12.

• method 1: the superior aspect of the motor cortex is almost straight up from the EAM near the midline

• method 213: the central sulcus is approximated by connecting:

Figure 5-5 Taylor-Haughton linesand other localizing methods

©2001 Mark S Greenberg, M.D.All rights reserved.Unauthorized use is prohibited.

3/4

1/2

posterior ear line

Frankfurtplane

condylar line

syan ssure

cent

ral s

ulcu

s

2 cm

lvifi

EAMEAMEAM

creo


A. the point 2 cm posterior to the midposition of the arc extending from nasion to inion (illustrated in Figure 5-5), to

B. the point 5 cm straight up from the EAM• method 3: using T-H lines, the central sulcus is approximated by connecting:

A. the point where the “posterior ear line” intersects the circumference of the skull (see Figure 5-5) (usually about 1 cm behind the vertex, and 3-4 cm be-hind the coronal suture), to

B. the point where the “condylar line” in-tersects the line representing the sylvian fissure

• method 4: a line drawn 45° to Reid’s base line starting at the pterion points in the direction of the motor strip14 (p 584-5)

RELATIONSHIP OF VENTRICLES TO SKULL

Figure 5-6 shows the rela-tionship of non-hydrocephalic ventricles to the skull in the lat-eral view. Some dimensions of in-terest are shown in Table 5-315.

In the non-hydrocephalic adult, the lateral ventricles lie 4-5 cm below the outer skull sur-face. The center of the body of the lateral ventricle sits in the midp-upillary line, and the frontal horn is intersected by a line pass-ing perpendicular to the calvaria along this line16. The anterior horns extend 1-2 cm anterior to the coronal suture.

Average length of third ventricle ≈ 2.8 cm.

Table 5-3 Dimensions from Figure 5-6

Dimension(see Figure 5-6)

Description Lower limit(mm)

Average(mm)

Upper limit(mm)

D1 length of frontal horn anterior to FM 25D2 distance from clivus to floor of 4th ventricle at

level of fastigium*

* the fastigium is the apex of the 4th ventricle within the cerebellum

33.3 36.1 40.0

D3 length of 4th ventricle at level of fastigium* 10.0 14.6 19.0D4 distance from fastigium* to opisthion 30.0 32.6 40.0

Figure 5-6 Relationship of ventricles to skull landmarks*

* Abbreviations: (F = frontal horn, B = body, A = atrium, O = oc-cipital horn, T = temporal horn) of lateral ventricle. FM = fora-men of Monro. Aq = sylvian aqueduct. V3 = third ventricle. V4 = fourth ventricle. cs = coronal suture. Dimensions D1-4 → see Table 5-3

baseline

sella turcica

V3

V4

Aq

FM

D2 D3

opisthion

Twining

D4

D1

T

F

B

O

T

A

sigmoid sinus

cs

creo

NEUROSURGERY 5.2. Cranial foramina & their contents 89

5.1.3. Surface landmarks of spine levels

Estimates of cervical levels for anterior cervical spine surgery may be made using the landmarks shown in Table 5-4. Intra-operative C-spine x-rays are essential to verify these estimates.

The scapular spine is located at about T2-3.The inferior scapular pole is ≈ T6 posteriorly.Intercristal line: a line drawn between the high-

est point of the iliac crests across the back will cross the midline either at the interspace between the L4 and L5 spinous processes, or at the L4 spinous process itself.

5.2. Cranial foramina & their contents

Porus acusticusAKA internal auditory canal (see Figure 5-7)The filaments of the acoustic portion of VIII penetrate tiny openings of the lamina

cribrosa of the cochlear area18. Transverse crest: separates superior vestibular area and facial canal (above) from

the inferior vestibular area and cochlear area (below)18.Vertical crest (AKA Bill’s bar): separates the meatus to facial canal anteriorly (con-

Table 5-5 Cranial foramina and their contents*

* Abbreviations: a. = artery, aa. = arteries, v. = vein, vv. = veins, n. = nerve, nn. = nerves, br. = branch, Cr. N. = cranial nerve, fmn. = foramen, div. = division

Foramen Contentsnasal slits anterior ethmoidal nn., a. & vsuperior orbital fissure Cr. Nn. III, IV, VI, all 3 branches of V1 (ophthalmic division divides into nasociliary, fron-

tal, and lacrimal nerves); superior ophthalmic vv.; recurrent meningeal br. from lacrimal a.; orbital branch of middle meningeal a.; sympathetic filaments from ICA plexus

inferior orbital fissure Cr. N. V-2 (maxillary div.), zygomatic n.; filaments from pterygopalatine branch of max-illary n.; infraorbital a. & v.; v. between inferior ophthalmic v. & pterygoid venous plexus

foramen lacerum usually nothing (ICA traverses the upper portion but doesn’t enter, 30% have vidian a.)carotid canal internal carotid a., ascending sympathetic nervesincisive foramen descending septal a.; nasopalatine nn.greater palatine foramen greater palatine n., a., & v.lesser palatine foramen lesser palatine nn.internal acoustic meatus Cr. N. VII (facial); Cr. N. VIII (stato-acoustic) - (see text & Figure 5-7 below)hypoglossal canal Cr. N. XII (hypoglossal); a meningeal branch of the ascending pharyngeal a.foramen magnum spinal cord (medulla oblongata); Cr. N. XI (spinal accessory nn.) entering the skull; ver-

tebral aa.; anterior & posterior spinal arteriesforamen cecum occasional small veincribriform plate olfactory nn.optic canal Cr. N. II (optic); ophthalmic a.foramen rotundum Cr. N. V2 (maxillary div.), a. of foramen rotundumforamen ovale Cr. N. V3 (mandibular div.) + portio minor (motor for CrN V)foramen spinosum middle meningeal a. & v.jugular foramen internal jugular v. (beginning); Cr. Nn. IX, X, XIstylomastoid foramen Cr. N. VII (facial); stylomastoid a.condyloid foramen v. from transverse sinusmastoid foramen v. to mastoid sinus; branch of occipital a. to dura mater

Table 5-4 Cervical levels17

Level LandmarkC1-2 angle of mandibleC3-4 1 cm above thyroid carti-

lage (≈ hyoid bone)C4-5 level of thyroid cartilageC5-6 crico-thyroid membraneC6 carotid tubercleC6-7 cricoid cartilage


taining VII and nervus intermedius) from the vestibular area posteriorly (containing the superior division of vestibular nerve).

The “5 nerves” of the IAC: 1. facial nerve (VII)

(mnemonic: “7-up” as VII is in superi-or portion)

2. nervus intermedi-us: the somatic sensory branch of the facial nerve primarily inner-vating mechanore-ceptors of the hair follicles on the in-ner surface of the pinna and deep mechanoreceptors of nasal and buccal cavities and chemoreceptors in the taste buds on the anterior 2/3 of the tongue

3. acoustic portion of the VIII nerve (mnemonic: “Coke down” for cochlear portion)4. superior branch of vestibular nerve: passes through the superior vestibular area

to terminate in the utricle and in the ampullæ of the superior and lateral semi-circular canals

5. inferior branch of vestibular nerve: passes through inferior vestibular area to ter-minate in the saccule

5.3. Cerebellopontine angle anatomy

* NI = nervus intermediusFigure 5-7 Right internal auditory canal (porus acusticus) & nerves

facial canal (Cr. N. VII with NI*)

superior vestibular area (superior vestibular nerve) (to utricle &superior & lateral semicircular canals)

transverse crest (crista falciformis)

vertical crest (”Bill’s bar”)

inferior vestibular area (to saccule)foramen singulare (toposterior semicircular canal)

tractus spiralis foraminosus (cochleararea) (acoustic portion of Cr. N. VIII)

(inferiorvestibular nerve)

Figure 5-8 Normal anatomy of right cerebellopontine angle viewed from behind (as in a suboccipital approach)18

V

VIIIAC

VIIIIX

XXI

XII

medullaolive

ponsflocculuschoroidplexus

jugularforamen

Meckel'scave

cerebellartonsil

foramen ofMagendie

foramen ofLuschka

retractoron cerebellarhemisphere

PICA

creo

NEUROSURGERY 5.4. Occiptoatlantoaxial-complex anatomy 91

5.4. Occiptoatlantoaxial-complex anatomy

≈ 50% of head rotation occurs at the C1-2 (atlantoaxial) joint.

Ligaments of the occipito-atlanto-axial complex

Stability of this joint complex is primarily due to ligaments, with little contribution from bony articulations and joint capsules (see Figure 5-9 through Figure 5-11):

1. ligaments that connect the atlas to the occiput: A. anterior at-

lanto-occipi-tal mem-brane: cephal-ad extension of the anteri-or longitudi-nal ligament. Extends from anterior mar-gin of fora-men magnum (FM) to ante-rior arch of C1

B. posterior at-lanto-occipi-tal mem-brane: con-nects the pos-terior margin of the FM to posterior arch of C1

C. the ascending band of the cruciate ligament2. ligaments that connect the axis (viz. the odontoid) to the occiput:

A. tectorial membrane: some authors distinguish 2 components1. superficial component: cephalad continuation of the posterior longitu-

Figure 5-9 Sagittal view of the ligaments of the craniovertebral junctionModified with permission from “In Vitro Cervical Spine Biomechanical Testing” BNI Quarterly,

Vol.9, No. 4, 1993

anterioratlantooccipital

membrane

apicalodontoidligament

cruciate ligament,ascending band

cruciate ligament,descending band

tectorialmembrane

transverseligamentanterior

longitudinalligament

posteriorlongitudinal

ligament

posterioratlantooccipitalmembrane

ligamentumflavum

C3

C2spinalcord

C1

Figure 5-10 Dorsal view of the cruciate and alar ligamentsViewed with tectorial membrane removed.

Modified with permission from “In Vitro Cervical Spine Biomechanical Testing” BNI Quarterly, Vol.9, No. 4, 1993

transverse bandCRUCIATE

LIGAMENT

right alarligament

accessory(deep) portionof tectorialmembrane

descendingband

C1

clivus

C2

ascending band

creo


dinal ligament. A strong band connecting the dorsal surface of the dens to the ventral surface of the FM above, and dorsal surface of C2 & C3 bodies below

2. accessory (deep) portion: located laterally, connects C2 to occipital condyles

B. alar (“check”) ligaments19

1. occipito-alar portion: connects side of the dens to occipital condyle2. atlanto-alar portion: connects side of the dens to the lateral mass of C1

C. apical odontoid liga-ment: connects tip of dens to the FM. Little mechanical strength

3. ligaments that connect the axis to the atlas:

A. transverse (atlanto-axial) ligament: the horizontal component of the cruciate liga-ment. Traps the dens against the anterior at-las via a strap-like mechanism (see Figure 5-11). Provides the ma-jority of the strength (“the strongest liga-ment of the spine”20)

B. atlanto-alar portion of the alar ligaments (see above)

C. descending band of the cruciate ligament

The most important structures in maintaining atlanto-occipital stability are the tec-torial membrane and the alar ligaments. Without these, the remaining cruciate liga-ment and apical dentate ligament are insufficient.

5.5. Spinal cord anatomy

5.5.1. Spinal cord tracts

Figure 5-12 depicts a cross-section of a typical spinal cord segment, combining some elements from different levels (e.g. the intermediolateral grey nucleus is only present from T1 to ≈ L1 or L2 where there are sympathetic (thoracolumbar outflow) nuclei). It is schematically divided into ascending and descending halves, however, in actuality, as-cending and descending paths coexist on both sides.

Table 5-6 Descending (motor) tracts (↓) in Figure 5-12

Number (see Figure 5-12)

Path Function Side of body

1 anterior corticospinal tract skilled movement opposite2 medial longitudinal fasciculus ? same3 vestibulospinal tract facilitates extensor muscle tone same4 medullary (ventrolateral) reticulospinal tract automatic respirations? same5 rubrospinal tract flexor muscle tone same6 lateral corticospinal (pyramidal) tract skilled movement same

Figure 5-11 C1 viewed from above, showing the trans-verse and alar ligaments

Modified with permission from “In Vitro Cervical Spine Bio-mechanical Testing” BNI Quarterly, Vol.9, No. 4, 1993

tectorialmembrane

posterior arch C1

transverseligament

tubercle

right alarligament

odontoidprocess

creo

NEUROSURGERY 5.5. Spinal cord anatomy 93

Figure 5-12 also depicts some of the laminae according to the scheme of Rexed. Lam-ina II is equivalent to the substantia gelatinosa. Laminae III and IV are the nucleus pro-prius. Lamina VI is located in the base of the posterior horn.

SENSATION

PAIN & TEMPERATURE: BODYReceptors: free nerve endings (probable).1st order neuron: small, finely myelinated afferents; soma in dorsal root ganglion

(no synapse). Enter cord at dorsolateral tract (zone of Lissauer). Synapse: substantia ge-

Table 5-7 Bi-directional tracts in Figure 5-12


Path Function

7 dorsolateral fasciculus (of Lissauer)8 fasciculus proprius short spinospinal connections

Table 5-8 Ascending (sensory) tracts (↑) in Figure 5-12


Path Function Side of body

9 fasciculus gracilis joint position, fine touch, vibration

same10 fasciculus cuneatus11 posterior spinocerebellar tract stretch receptors same12 lateral spinothalamic tract pain & temperature opposite13 anterior spinocerebellar tract whole limb position opposite14 spinotectal tract unknown, ? nociceptive opposite15 anterior spinothalamic tract light touch opposite

Figure 5-12 Schematic cross-section of cervical spinal cord

2

34

5

6

7 8 910

1112

13

14

15

MOTOR(descending

paths)

bi-directionalpaths

SENSORY(ascending

paths)

S TCTC

STCSTC

S TC

STC

CTSCTSCTS

{

1

S = sacralT = thoracicC = cervical

anterior spinalartery

dentateligament

{{

anterior motornerve root

2.5-4 cm

intermediolateralgrey nucleus

(sympathetic)IIIIII

IV

V

VI

IX

IX

VII

VIIIX

creo


latinosa (Rexed II).2nd order neuron axon cross obliquely in the anterior white commissure ascending

≈ 1-3 segments while crossing to enter the lateral spinothalamic tract.Synapse: VPL thalamus. 3rd order neurons pass through IC to postcentral gyrus

(Brodmann’s areas 3, 1, 2).

FINE TOUCH, DEEP PRESSURE & PROPRIOCEPTION: BODYFine touch AKA discriminative touch. Receptors: Meissner’s & pacinian corpuscles,

Merkel’s disks, free nerve endings.1st order neuron: heavily myelinated afferents; soma in dorsal root ganglion (no

synapse). Short branches synapse in nucleus proprius (Rexed III & IV) of posterior gray; long fibers enter the ipsilateral posterior columns without synapsing (below T6: fascicu-lus gracilis; above T6: fasciculus cuneatus).

Synapse: nucleus gracilis/cuneatus (respectively), just above pyramidal decussa-tion. 2nd order neuron axons form internal arcuate fibers, decussate in lower medulla as medial lemniscus.

Synapse: VPL thalamus. 3rd order neurons pass through IC primarily to postcen-tral gyrus.

LIGHT (CRUDE) TOUCH: BODYReceptors: as fine touch (see above), also peritrichial arborizations.

Figure 5-13 Dermatomal and sensory nerve distribution(Redrawn from “Introduction to Basic Neurology”, by Harry D. Patton, John W. Sundsten, Wayne E. Crill and

Phillip D. Swanson, © 1976, pp 173, W. B. Saunders Co., Philadelphia, PA, with permission)

©2001 Mark S Greenberg, M.D.All rights reserved.Unauthorized use is prohibited.

DERMATOMESC U T A N E O U S

N E R V E S

P O S T E R I O RA N T E R I O R

trigeminalnerve {V1

V2

V3 superior clavicular

axillary

post. cutaneousdorsal cutan.

RADIAL

musculocutan.medial cutan.

radial

median

ulnar

INTERCOSTALSposterior

lateral

clunials

posteriorcutaneous

saphenous

sural

plantars {lat.med.

medial

occipitals

FEMORALanteriorcutaneous

SCIATIC

deep peroneal

DERMATOMES

(an te r io r ) (pos te r io r )

lateral cutan.nerve of thigh

ilio-inguinal

COMMON PERONEALlat. cutan.

sup. peroneal

TIBIAL

S3

S5

T12

C6

L3 L4

S1

C3

C4T2

T4

T6

T8

T10

C4T3T4

T6

T8

T10T12

L1

L2

S4

C3

C2

C5 C5

C8

T1

T2

L3

L4

L5

S1

C6

C7

C8

T1

T2

C2

S1

L5L4

C7

creo

NEUROSURGERY 5.5. Spinal cord anatomy 95

1st order neuron: large, heavily myelinated afferents (Type II); soma in dorsal root ganglion (no synapse). Some ascend uncrossed in post. columns (with fine touch); most synapse in Rexed VI & VII.

2nd order neuron axons cross in anterior white commissure (a few don’t cross); enter anterior spinothalamic tract.

Synapse: VPL thalamus. 3rd order neurons pass through IC primarily to postcen-tral gyrus.

5.5.2. Dermatomes and sensory nerves

Figure 5-13 shows anterior and posterior view, each schematically separated into sensory dermatomes (segmental) and peripheral sensory nerve distribution.

5.5.3. Spinal cord vasculature

Although a radicular artery from the aorta accompanies the nerve root at many lev-els, most of these contribute little flow to the spinal cord itself. The anterior spinal artery is formed from the junction of two branches, each from one of the vertebral arteries. Ma-jor contributors of blood supply to the anterior spinal cord is from 6-8 radicular arteries

Figure 5-14 Schematic diagram of spinal cord arterial supplyModified from Diagnostic Neuroradiology, 2nd ed., Volume II, pp. 1181, Taveras J M, Woods EH, editors, ©

1976, the Williams and Wilkins Co., Baltimore, with permission)

aorta

brachiocephalic trunk

rightsubclavian

right commoncarotid

right vertebralartery

left vertebralartery

left subclavian

costocervical trunk

anterior spinal artery

left commoncarotid

radicular artery at C3



deep cervical artery

radicular artery at T5

arteria radicularismagna(posterior branch)

artery ofAdamkiewicz(arteria radicularisanterior magna)

left posterior spinal artery

spinal cord

intercostal arteries}

basilar artery

posterior inter-costal artery(dorsal branch)

posteriorintercostalartery

aorta

radicularartery

Axial view

anteriorspinalartery

posteriorspinal arteries

creo


at the following levels (“radiculomedullary arteries”, the levels listed are fairly consis-tent, but the side varies21 (p 1180-1)):

• C3 - arises from vertebral artery

• T4 or T5• artery of Adamkiewicz AKA arteria radicularis anterior magna

A. the main arterial supply for the spinal cord from ≈ T8 to the conusB. located on the left in 80%23

C. situated between T9 & L2 in 85% (between T9 & T12 in 75%); in remaining 15% between T5 & T8 (in these latter cases, there may be a supplemental radicular artery further down)

D. usually fairly large, gives off cephalic and caudal branch (latter is usually larger) giving a characteristic hair-pin appearance on angiography

The paired posterior spinal arteries are less well defined than the anterior spinal artery, and are fed by 10-23 radicular branches.

The midthoracic region has a tenuous vascular supply (“watershed zone”), possess-ing only the above noted artery at T4 or T5. It is thus more susceptible to vascular in-sults.

ANATOMIC VARIANTSArcade of Lazorthes: normal variant where the anterior spinal artery joins with

the paired posterior spinal arteries at the conus medullaris.

5.6. Cerebrovascular anatomy

5.6.1. Cerebral vascular territories

Figure 5-15 depicts approximate vascular distributions of the major cerebral arter-ies. There is considerable variability of the major arteries24 as well as the central distri-

• C6 - usually arises from deep cervical artery• C8 - usually from costocervical trunk } ≈ 10% of population lack an an-

terior radicular artery in lower cervical spine22

RAH = recurrent artery of HeubnerFigure 5-15 Vascular territories of the cerebral hemispheres

RAH

internal carotid

basilar artery

posterior cerebralartery

middle cerebralartery

anterior choroidalartery

anterior cerebralartery

AChA

MCA

PCommA

AXIAL VIEWCORONAL VIEW

creo

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