Page 1


Contents Contributors iii Evidence based medicine iv Booking the case v Abbreviations vi 1. Neuroanesthesia 1 1.1. 1.2. 1.3. 1.4. 1.5.

General information 1 Drugs used in neuroanesthesia 1 Anesthetic requirements for intraoperative evoked potential monitoring 4 Malignant hyperthermia 5 References 6

2. Neurocritical care 7 2.1. 2.2. 2.3. 2.4. 2.5.

Fluids and Electrolytes 7 Blood pressure management 19 Sedatives & paralytics 23 Neurogenic pulmonary edema 28 References 28

3. General care 31 3.1. 3.2. 3.3. 3.4.

Endocrinology 31 Hematology 34 Pharmacology 44 References 53

4. Neurology 56 4.1. 4.2. 4.3. 4.4. 4.5. 4.6. 4.7. 4.8. 4.9.

Dementia 56 Headache 57 Parkinsonism 59 Multiple sclerosis 61 Motor neuron diseases 65 Guillain-BarrĂŠ syndrome 66 Myelitis 69 Neurosarcoidosis 71 Vascular dysautoregulatory encephalopathy 73 4.10. Vasculitis and vasculopathy 74 4.11. References 80

5. Neuroanatomy and physiology 84 5.1. 5.2. 5.3. 5.4.

Surface anatomy 84 Cranial foramina & their contents 89 Cerebellopontine angle anatomy 90 Occiptoatlantoaxial-complex anatomy 91 5.5. Spinal cord anatomy 92 5.6. Cerebrovascular anatomy 96 5.7. Internal capsule 107 5.8. Miscellaneous 108 5.9. Neurophysiology 109 5.10. References 119

6. Neuroradiology 122 6.1. 6.2. 6.3.

Contrast agents in neuroradiology 122 Radiation safety for neurosurgeons 126 CAT scan or CT scan 128

CONTENTS

6.4. 6.5. 6.6. 6.7. 6.8. 6.9.

Magnetic resonance imaging (MRI) 129 Angiography (cerebral) 134 Plain films 135 Myelography 140 Radionuclide scanning 140 References 141

7. Operations and procedures 144 7.1. 7.2. 7.3. 7.4. 7.5. 7.6. 7.7. 7.8. 7.9. 7.10. 7.11. 7.12. 7.13. 7.14. 7.15. 7.16.

Intraoperative dyes 144 Operating room equipment 144 Surgical hemostasis 146 Craniotomies 146 Cranioplasty 173 Localizing levels in spine surgery 173 Anterior approaches to the spine 174 Surgical fusion of the cervical spine 179 Surgical fusion of the thoracic spine 190 Surgical fusion of the lumbar and lumbosacral spine 191 Bone graft 197 Percutaneous access to the CSF 201 CSF diversionary procedures 207 Sural nerve biopsy 214 Nerve blocks 215 References 217

8. Developmental anomalies 222 8.1. 8.2. 8.3. 8.4. 8.5. 8.6. 8.7. 8.8. 8.9. 8.10. 8.11. 8.12. 8.13. 8.14. 8.15.

Arachnoid cysts 222 Intracranial lipomas 225 Hypothalamic hamartomas 226 Neurenteric cysts 227 Craniofacial development 228 Chiari malformation 233 Dandy Walker malformation 240 Aqueductal stenosis 241 Neural tube defects 243 Absence of the septum pellucidum 247 Klippel-Feil syndrome 253 Tethered cord syndrome 254 Split cord malformation 256 Lumbosacral nerve root anomalies 256 References 257

9. Neuroendovascular intervention 262 9.1. 9.2.

Neuroendovascular procedure basics 263 References 264

10. Electrodiagnostics 266 10.1. Electroencephalogram (EEG) 266 10.2. Evoked potentials 266 10.3. NCS/EMG 269 xi


10.4. References 271

11. Neurotoxicology 273 11.1. 11.2. 11.3. 11.4. 11.5. 11.6.

Ethanol 273 Opioids 275 Cocaine 276 Amphetamines 277 Carbon monoxide 277 References 278

12. Coma 279 12.1. 12.2. 12.3. 12.4. 12.5.

General information 279 Approach to the comatose patient 281 Herniation syndromes 284 Hypoxic coma 287 References 288

13. Brain death 289 13.1. 13.2. 13.3. 13.4.

Brain death in adults 289 Brain death in children 292 Organ and tissue donation 293 References 296

14. Cerebrospinal fluid 297 14.1. 14.2. 14.3. 14.4. 14.5. 14.6.

General information 297 CSF constituents 297 Artificial CSF 300 CSF fistula (cranial) 300 Intracranial hypotension 305 References 306

15. Hydrocephalus 307 15.1. 15.2. 15.3. 15.4. 15.5. 15.6.

Treatment of hydrocephalus 314 Shunt problems 321 Normal pressure hydrocephalus 329 Blindness from hydrocephalus 335 Hydrocephalus and pregnancy 336 References 337

16. Infections 342 16.1. Prophylactic antibiotics 342 16.2. Meningitis 343 16.3. Shunt infection 345 16.4. Wound infections 348 16.5. Osteomyelitis of the skull 349 16.6. Cerebral abscess 350 16.7. Subdural empyema 356 16.8. Viral encephalitis 358 16.9. Creutzfeldt-Jakob disease 361 16.10. Neurologic manifestations of AIDS 364 16.11. Lyme disease - neurologic manifestations 368 16.12. Parasitic infections of the CNS 369 16.13. Fungal infections of the CNS 374 16.14. Amebic infections of CNS 375 16.15. Spine infections 376 16.16. References 388

17. Seizures 394 17.1. 17.2. 17.3. 17.4. 17.5. 17.6. xii

Seizure classification 394 Special types of seizures 396 Status epilepticus 402 Antiepileptic drugs (AEDs) 407 Seizure surgery 420 References 425

18. Spine & spinal cord 428 18.1. 18.2. 18.3. 18.4. 18.5.

Low back pain and radiculopathy 428 Sagittal balance 441 Intervertebral disc herniation 442 Degenerative disc/spine disease 474 Craniocervical junction and upper cervical spine abnormalities 494 18.6. Rheumatoid arthritis 494 18.7. Atlantoaxial subluxation (AAS) in Down syndrome 498 18.8. Paget’s disease 498 18.9. Ankylosing spondylitis 502 18.10. Ossification of the posterior longitudinal ligament (OPLL) 504 18.11. Ossification of the anterior longitudinal ligament (OALL) 506 18.12. Diffuse idiopathic skeletal hyperostosis 506 18.13. Scheuermann's kyphosis 506 18.14. Spinal vascular malformations 507 18.15. Spinal meningeal cysts 509 18.16. Syringomyelia 510 18.17. Spinal cord herniation (idiopathic) 514 18.18. Spinal epidural hematoma 515 18.19. Spinal subdural hematoma 515 18.20. Spinal epidural lipomatosis (SEL) 516 18.21. Coccydynia 516 18.22. References 517

19. Functional neurosurgery 532 19.1. Deep brain stimulation 532 19.2. Surgical treatment of Parkinson’s disease 532 19.3. Dystonia 536 19.4. Spasticity 536 19.5. Torticollis 541 19.6. Neurovascular compression syndromes 542 19.7. Hyperhidrosis 544 19.8. Tremor 545 19.9. Sympathectomy 545 19.10. References 546

20. Pain 548 20.1. 20.2. 20.3. 20.4. 20.5.

Neuropathic pain syndromes 548 Craniofacial pain syndromes 549 Postherpetic neuralgia 564 Pain procedures 567 Complex regional pain syndrome (CRPS) 576 20.6. References 577

21. Tumor 582 21.1. 21.2. 21.3. 21.4. 21.5. 21.6. 21.7. 21.8.

General information 582 Primary brain tumors 590 Pediatric brain tumors 697 Skull tumors 698 Cerebral metastases 702 Carcinomatous meningitis 711 Foramen magnum tumors 711 Idiopathic intracranial hypertension (IIH) 713 CONTENTS


21.9. Empty sella syndrome 719 21.10. Tumor markers 720 21.11. Neurocutaneous disorders 722 21.12. Tumors of the spine and spinal cord 728 21.13. Neuroblastomas 748 21.14. References 749

22. Radiation therapy (XRT) 770 22.1. Conventional external beam radiation 770 22.2. Stereotactic radiosurgery & radiotherapy 773 22.3. Interstitial brachytherapy 779 22.4. References 779

23. Stereotactic surgery 782 23.1. References 783

24. Peripheral nerves 786 24.1. Some basic points about peripheral nerve injury/surgery 789 24.2. Brachial plexus 790 24.3. Peripheral neuropathies 793 24.4. Thoracic outlet syndrome 822 24.5. Miscellaneous peripheral nerve 824 24.6. References 824

25. Neurophthalmology 828 25.1. 25.2. 25.3. 25.4. 25.5.

Nystagmus 828 Papilledema 828 Visual fields 829 Pupillary diameter 829 Extraocular muscle (EOM) system 834 25.6. Miscellaneous neurophthalmologic signs 838 25.7. References 839

26. Neurotology 840 26.1. 26.2. 26.3. 26.4. 26.5.

Dizziness and vertigo 840 Meniere’s disease 842 Facial nerve palsy 844 Hearing loss 848 References 849

27. Head trauma 850 27.1. 27.2. 27.3. 27.4. 27.5.

Transfer of trauma patients 854 Management in E/R 855 Neuromonitoring 866 Skull fractures 885 Posttraumatic parenchymal injuries 892 27.6. Epidural hematoma 894 27.7. Subdural hematoma 896 27.8. Traumatic posterior fossa mass lesions 905 27.9. Posttraumatic hydrocephalus 906 27.10. Aspects of general care in severe TBI 907 27.11. Outcome from head trauma 908 27.12. Gunshot wounds to the head 912 27.13. Non-missile penetrating trauma 916 27.14. High altitude cerebral edema 916 27.15. Pediatric head injury 917 27.16. References 919 CONTENTS

28. Spine injuries 930 28.1. Whiplash-associated disorders 931 28.2. Pediatric spine injuries 932 28.3. Initial management of spinal cord injury 933 28.4. Neurological assessment 944 28.5. Spinal cord injuries 948 28.6. Cervical spine fractures 951 28.7. Blunt cerebrovascular injuries 982 28.8. Thoracic & lumbar spine fractures 986 28.9. Osteoporotic spine fractures 992 28.10. Sacral fractures 997 28.11. Gunshot wounds to the spine 998 28.12. Penetrating trauma to the neck 998 28.13. Delayed deterioration following spinal cord injuries 1000 28.14. Chronic management issues with spinal cord injuries 1000 28.15. References 1002

29. Stroke 1010 29.1. 29.2. 29.3. 29.4. 29.5. 29.6. 29.7. 29.8.

Cerebrovascular hemodynamics 1010 Strokes: general information 1011 Stroke in young adults 1024 Lacunar strokes 1026 Collateral circulation 1027 “Occlusion” syndromes 1027 Miscellaneous stroke 1029 References 1030

30. SAH and aneurysms 1034 30.1. 30.2. 30.3. 30.4. 30.5. 30.6. 30.7. 30.8.

Introduction to SAH 1034 Grading SAH 1039 Initial management of SAH 1040 Vasospasm 1045 Cerebral aneurysms 1055 Treatment options for aneurysms 1057 Timing of aneurysm surgery 1060 General technical considerations of aneurysm surgery 1061 30.9. Aneurysm recurrence after treatment 1065 30.10. Aneurysm type by location 1066 30.11. Post-op orders for aneurysm clipping 1076 30.12. Unruptured aneurysms 1077 30.13. Multiple aneurysms 1080 30.14. Familial aneurysms 1080 30.15. Traumatic aneurysms 1081 30.16. Mycotic aneurysms 1082 30.17. Giant aneurysms 1082 30.18. SAH of unknown etiology 1083 30.19. Nonaneurysmal SAH 1084 30.20. Pregnancy & intracranial hemorrhage 1086 30.21. References 1087

31. Vascular malformations 1098 31.1. Arteriovenous malformation 1098 31.2. Venous angiomas 1104 31.3. Angiographically occult vascular malformations 1105 31.4. Dural AVM 1109 xiii


31.5. Vein of Galen malformation 1112 31.6. Carotid-cavernous fistula 1113 31.7. References 1114

32. Intracerebral hemorrhage 1118 32.1. Intracerebral hemorrhage in adults 1118 32.2. ICH in young adults 1131 32.3. Intracerebral hemorrhage in the newborn 1131 32.4. References 1138

33. Occlusive cerebro-vascular disease 1144 33.1. Atherosclerotic cerebrovascular disease 1144 33.2. Cerebral arterial dissections 1160 33.3. Extracranial-intracranial (EC/IC) by-

xiv

pass 1165 33.4. Cerebrovascular venous thrombosis 1166 33.5. Moyamoya disease 1170 33.6. References 1174

34. Outcome assessment 1182 34.1. References 1184

35. Differential diagnosis 1185 35.1. Differential diagnosis (DDx) by signs and symptoms 1185 35.2. Differential diagnosis (DDx) by location 1209 35.3. References 1235

36. Index 1240 Quick reference tables 1331

CONTENTS


eye movements to the opposite direction

Medial surface

LG

(Figure 5-2) CT The cingulate sulprcs CENTRAL SULCUS cus terminates posteriPL pM orly in the pars SFG marginalis (pM) (plusps cins ins c ral: partes marginales). PCu Cin G On axial imaging, the MRI pMs: are visible on 95% callosum p us pos of CTs and 91% of cor MRIs4, are usually the most prominent of the Cu paired grooves straddling the midline, and they extend a greater pons distance into the hemispheres4. On axial CT, the pM is located slightly posterior to the widest biparietal diameter4; on the typiFigure 5-2 Medial aspect of the right hemisphere cally more horizontally “CT” & “MRI” bars depict typical axial slice orientation for CT & MRI scans. oriented MRI slices the See Table 5-1 and Table 5-2 for abbreviations 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 midline).

Pointers: • parieto-occipital sulcus (pos) (or fissure): more prominent over the medial surface, and on axial imaging is longer, more complex, and more posterior than the pars marginalis5 • post-central sulcus (pocs): usually bifurcates and forms an arc or parenthesis (“lazy-Y”) cupping the pM. The anterior limb does not enter the pM-bracket and the posterior limb curves behind the pM to enter the IHF

NEUROSURGERY

cs

CG

cs

Pre PL

See 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 posteriorly as it approaches the interhemispheric 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 often does not reach the midline).

SFG

Central sulcus on axial imaging

tCG Pos

pocs

pM

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

5.1. Surface anatomy

85


Table 5-2 Cerebral gyri and lobules (abbreviations)

Table 5-1 Cerebral sulci (abbreviations) cins cs ips-ios los pM pocn pocs pof pos prcs sfs, ifs sps sts, its tos

5.1.2.

cingulate sulcus central sulcus intraparietal-intraoccipital sulcus lateral occipital sulcus pars marginalis pre-occipital notch post-central sulcus parieto-occipital fissure parieto-occipital sulcus pre-central sulcus superior, inferior frontal sulcus superior parietal sulcus superior, inferior temporal sulcus trans occipital sulcus

AG CinG Cu LG MFG, SFG OG PCu PreCG, PostCG PL IFG POp PT POr

angular gyrus cingulate gyrus cuneus lingual gyrus middle & superior frontal gyrus orbital gyrus precuneous pre- and post-central gyrus paracentral lobule (upper SFG and PreCG and PostCG) inferior frontal gyrus pars opercularis pars triangularis pars orbitalis

STG, MTG, ITG superior, middle & inferior temporal gyrus SPL, IPL superior & inferior parietal lobule SMG supramarginal gyrus

Surface anatomy of the cranium

CRANIOMETRIC POINTS

IP IT AL

O C C

GWS

cs

See Figure 5-4. Pterion: region vertex where the following bregma bones are approximatPARIE ed: frontal, parietal, TAL AL stephanion temporal and sphenoid NT O R (greater wing). EstiF pterion mated as 2 fingerstl lambda breadths above the zyophyron sqs gomatic arch, and a glabella thumb’s breadth benasion hind the frontal proTEMPORAL rhinion ls cess of the zygomatic pms sms bone (blue circle in FigID ure 5-4). TO s G Asterion: juncNASAL ZY AS om M tion of lambdoid, occipinion prosthion itomastoid and MAXILLA parietomastoid suasterion inferior tures. Usually lies opisthion alveolar point within a few millimeE gonion IBL gnathion ters of the posterior-inD N MA or menton ferior edge of the junction of the transverse and sigmoid siFigure 5-4 Craniometric points & cranial sutures. nuses (not always Named bones appear in all upper case letters. reliable6 - may overlie Abbreviations: GWS = greater wing of sphenoid bone, NAS = nasal bone, stl = either sinus). superior temporal line, ZYG = zygomatic. Vertex: the topSutures: cs = coronal, ls = lambdoid, oms = occipitomastoid, pms = parietomasmost point of the skull. toid, sms = squamomastoid, sqs = squamosal Lambda: junction of the lambdoid and sagittal sutures. Stephanion: junction of coronal suture and superior temporal line. 86

5. Neuroanatomy and physiology

NEUROSURGERY


Glabella: the most forward projecting point of the forehead at the level of the supraorbital 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 lines

ce n tral sulc us

Taylor-Haughton (T-H) 2 cm 1/2 lines can be constructed on an angiogram, CT scout film, or skull x-ray, and can then be reconstructed on the patient in the O.R. based on visible external 3/4 landmarks9. T-H lines are shown as dashed lines in Figure 5-5. 1. Frankfurt plane, AKA re baseline: line from inferissu n fi or margin of orbit vi a l y s through the upper margin of the external auditory meatus (EAM) (as distinguished from ReEAM id’s base line: from infeFrankfurt rior orbital margin plane through the center of the EAM)10 (p 313) posterior ear line 2. the distance from the nacondylar line sion to the inion is measured across the top of the calvaria and is divided into quarters (can be Figure 5-5 Taylor-Haughton lines done simply with a piece and other localizing methods of tape which is then folded in half twice) 3. posterior ear line: perpendicular to the baseline through the mastoid process 4. condylar line: perpendicular to the baseline through the mandibular condyle 5. T-H lines can then be used to approximate the sylvian fissure (see below) and the motor cortex (also see below) ©2001 Mark S Greenberg, M.D. All rights reserved. Unauthorized use is prohibited.

Sylvian fissure AKA lateral fissure Approximated 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 gyrus Located 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 artery Located 6 cm above the EAM.

Motor cortex Numerous 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: NEUROSURGERY

5.1. Surface anatomy

87


cs

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 behind the coronal suture), to B. the point where the “condylar line” intersects the line representing the sylvian fissure method 4: a line drawn B 45° to Reid’s base line starting at the pterion D1 FM F A O points in the direction of V3 the motor strip14 (p 584-5) Aq T Twining

D2

V4

RELATIONSHIP OF VENTRICLES

D3 D4

TO SKULL

Figure 5-6 shows the relationship of non-hydrocephalic opisthion ventricles to the skull in the latbaseline eral view. Some dimensions of interest are shown in Table 5-315. sigmoid sinus In the non-hydrocephalic sella turcica adult, the lateral ventricles lie 45 cm below the outer skull surface. The center of the body of the Figure 5-6 Relationship of ventricles to skull landmarks* lateral ventricle sits in the midp* Abbreviations: (F = frontal horn, B = body, A = atrium, O = ocupillary line, and the frontal cipital horn, T = temporal horn) of lateral ventricle. FM = forahorn is intersected by a line passmen of Monro. Aq = sylvian aqueduct. V3 = third ventricle. V4 ing perpendicular to the calvaria = fourth ventricle. cs = coronal suture. Dimensions D1-4 → along this line16. The anterior see Table 5-3 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) D1 D2 D3 D4 *

88

Description

Lower limit (mm)

length of frontal horn anterior to FM distance from clivus to floor of 4th ventricle at level of fastigium* length of 4th ventricle at level of fastigium* distance from fastigium* to opisthion

Upper limit (mm)

33.3

Average (mm) 25 36.1

10.0 30.0

14.6 32.6

19.0 40.0

40.0

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

5. Neuroanatomy and physiology

NEUROSURGERY


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 highest 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.

Table 5-4 Cervical levels17 Level Landmark C1-2 angle of mandible C3-4 1 cm above thyroid cartilage (≈ hyoid bone) C4-5 level of thyroid cartilage C5-6 crico-thyroid membrane C6 carotid tubercle C6-7 cricoid cartilage

Cranial foramina & their contents Table 5-5 Cranial foramina and their contents*

Foramen nasal slits superior orbital fissure

Contents anterior ethmoidal nn., a. & v Cr. Nn. III, IV, VI, all 3 branches of V1 (ophthalmic division divides into nasociliary, frontal, 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 maxillary 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 nerves incisive 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; vertebral aa.; anterior & posterior spinal arteries foramen cecum occasional small vein cribriform plate olfactory nn. optic canal Cr. N. II (optic); ophthalmic a. foramen rotundum Cr. N. V2 (maxillary div.), a. of foramen rotundum foramen 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, XI stylomastoid foramen Cr. N. VII (facial); stylomastoid a. condyloid foramen v. from transverse sinus mastoid foramen v. to mastoid sinus; branch of occipital a. to dura mater *

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

Porus acusticus AKA 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 (conNEUROSURGERY

5.2. Cranial foramina & their contents

89


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” facial canal (Cr. N. VII with NI*) as VII is in superior portion) vertical crest (”Bill’s bar”) 2. nervus intermedisuperior vestibular area (superior us: the somatic vestibular nerve) (to utricle & sensory branch of superior & lateral semicircular canals) the facial nerve primarily innertransverse crest (crista falciformis) vating mechanoreinferior vestibular area ceptors of the hair (inferior (to saccule) follicles on the investibular foramen singulare (to ner surface of the posterior semicircular canal) nerve) pinna and deep mechanoreceptors tractus spiralis foraminosus (cochlear of nasal and buccal area) (acoustic portion of Cr. N. VIII) cavities and chemoreceptors in the taste buds on Figure 5-7 Right internal auditory canal (porus acusticus) & nerves the anterior 2/3 of * NI = nervus intermedius 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 semicircular canals 5. inferior branch of vestibular nerve: passes through inferior vestibular area to terminate in the saccule

5.3.

Cerebellopontine angle anatomy retractor on cerebellar hemisphere foramen of Luschka

foramen of Magendie cerebellar tonsil PICA

V Meckel's cave pons flocculus choroid plexus VII IAC VIII IX jugular foramen X XI XII olive medulla

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

90

5. Neuroanatomy and physiology

NEUROSURGERY


5.4.

Occiptoatlantoaxial-complex anatomy

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

Ligaments of the occipito-atlanto-axial complex

apical odontoid ligament cruciate ligament, ascending band anterior atlantooccipital membrane anterior transverse ligament longitudinal ligament cruciate ligament, descending band tectorial membrane posterior longitudinal ligament

posterior atlantooccipital membrane

C1

ligamentum flavum spinal cord

C2

C3

Figure 5-9 Sagittal view of the ligaments of the craniovertebral junction Modified with permission from “In Vitro Cervical Spine Biomechanical Testing” BNI Quarterly, Vol.9, No. 4, 1993

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 atlanto-occipiascending tal memclivus band brane: cephalright alar ad extension ligament of the anterior longitudinal ligament. accessory Extends from (deep) portion anterior marof tectorial C1 gin of foramembrane men magnum transverse (FM) to anteCRUCIATE band rior arch of C1 LIGAMENT B. posterior atdescending lanto-occipiC2 band tal membrane: connects the posFigure 5-10 Dorsal view of the cruciate and alar ligaments terior margin Viewed with tectorial membrane removed. of the FM to Modified with permission from “In Vitro Cervical Spine Biomechanical posterior arch Testing” BNI Quarterly, Vol.9, No. 4, 1993 of C1 C. the ascending band of the cruciate ligament 2. ligaments that connect the axis (viz. the odontoid) to the occiput: A. tectorial membrane: some authors distinguish 2 components 1. superficial component: cephalad continuation of the posterior longituNEUROSURGERY

5.4. Occiptoatlantoaxial-complex anatomy

91


3.

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 condyle 2. atlanto-alar portion: connects side of the dens to the lateral mass of C1 C. apical odontoid ligament: connects tip of odontoid right alar dens to the FM. Little process ligament mechanical strength transverse ligaments that connect the ligament axis to the atlas: A. transverse (atlantoaxial) ligament: the horizontal component of the cruciate ligatubercle tectorial ment. Traps the dens membrane against the anterior atlas via a strap-like mechanism (see Figure posterior arch C1 5-11). Provides the majority of the strength Figure 5-11 C1 viewed from above, showing the trans(“the strongest ligaverse and alar ligaments ment of the spine”20) Modified with permission from “In Vitro Cervical Spine BioB. atlanto-alar portion of mechanical Testing” BNI Quarterly, Vol.9, No. 4, 1993 the alar ligaments (see above) C. descending band of the cruciate ligament

The most important structures in maintaining atlanto-occipital stability are the tectorial membrane and the alar ligaments. Without these, the remaining cruciate ligament 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, ascending and descending paths coexist on both sides. Table 5-6 Descending (motor) tracts (↓) in Figure 5-12 Number (see Figure 5-12) 1 2 3 4 5 6

92

Path anterior corticospinal tract medial longitudinal fasciculus vestibulospinal tract medullary (ventrolateral) reticulospinal tract rubrospinal tract lateral corticospinal (pyramidal) tract

Function

Side of body

skilled movement ? facilitates extensor muscle tone automatic respirations? flexor muscle tone skilled movement

5. Neuroanatomy and physiology

opposite same same same same same

NEUROSURGERY


Table 5-7 Bi-directional tracts in Figure 5-12 Number (see Path Figure 5-12) 7 dorsolateral fasciculus (of Lissauer) 8 fasciculus proprius

Function

short spinospinal connections

Table 5-8 Ascending (sensory) tracts (↑) in Figure 5-12 Number (see Figure 5-12) 9 10 11 12 13 14 15

Path

Function

Side of body joint position, fine touch, same vibration

fasciculus gracilis fasciculus cuneatus posterior spinocerebellar tract lateral spinothalamic tract anterior spinocerebellar tract spinotectal tract anterior spinothalamic tract

stretch receptors pain & temperature whole limb position unknown, ? nociceptive light touch

same opposite opposite opposite opposite

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

bi-directional paths 7

8

S TC

6

SENSORY (ascending paths)

{

{

{

MOTOR (descending paths)

S = sacral T = thoracic C = cervical

I II

III

intermediolateral grey nucleus (sympathetic)

9 10

IV

5

11 12

V

STC

VI X

VII VIII

IX

IX

CTS dentate ligament

4 3

13 14

2

2.5-4

1

15

cm

anterior spinal artery

anterior motor nerve root

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

SENSATION

PAIN & TEMPERATURE: BODY Receptors: 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 geNEUROSURGERY

5.5. Spinal cord anatomy

93


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: BODY Fine 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: fasciculus gracilis; above T6: fasciculus cuneatus). Synapse: nucleus gracilis/cuneatus (respectively), just above pyramidal decussation. 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 postcentral gyrus. ANTERIOR

trigeminal nerve

{

POSTERIOR

V1 V2 V3

C2

superior clavicular

occipitals

C2

C3

INTERCOSTALS posterior lateral medial axillary RADIAL post. cutaneous dorsal cutan.

C3 C4 T3 T4 T2

T6

T8

T1

C6

T1 T1

T4

L1

C5

T6 T8

T2

T10

0

T12

musculocutan. medial cutan.

2

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

S4

C5

C4 T2

radial

T1 C6

clunials

S5 S3

C8 L2

C7

ilioinguinal lateral cutan. nerve of thigh

L3 L4

C8

median

L3

ulnar FEMORAL posterior cutaneous anterior cutaneous saphenous

L5

SCIATIC COMMON PERONEAL lat. cutan. sup. peroneal deep peroneal S1

TIBIAL sural plantars

D E R M AT O M E S (anterior)

{

L4 S1 C7

L5

L4

S1

med. lat.

C U TA N E O U S NERVES

D E R M AT O M E S (posterior)

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)

LIGHT (CRUDE) TOUCH: BODY Receptors: as fine touch (see above), also peritrichial arborizations. 94

5. Neuroanatomy and physiology

NEUROSURGERY


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 postcentral 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 basilar artery spinal cord radicular artery at C3 anterior spinal artery radicular artery at C6 right vertebral artery right common carotid

deep cervical artery

left vertebral artery

costocervical trunk

left common carotid

right subclavian brachiocephalic trunk

radicular artery at C8 left subclavian left posterior spinal artery radicular artery at T5

aorta posterior intercostal artery (dorsal branch) posterior spinal arteries radicular artery

aorta Axial view

posterior intercostal artery anterior spinal artery

}

intercostal arteries artery of Adamkiewicz (arteria radicularis anterior magna) arteria radicularis magna (posterior branch)

Figure 5-14 Schematic diagram of spinal cord arterial supply Modified from Diagnostic Neuroradiology, 2nd ed., Volume II, pp. 1181, Taveras J M, Woods EH, editors, Š 1976, the Williams and Wilkins Co., Baltimore, with permission)

Although a radicular artery from the aorta accompanies the nerve root at many levels, 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. Major contributors of blood supply to the anterior spinal cord is from 6-8 radicular arteries NEUROSURGERY

5.5. Spinal cord anatomy

95


at the following levels (“radiculomedullary arteries”, the levels listed are fairly consistent, but the side varies21 (p 1180-1)): • C3 - arises from vertebral artery ≈ 10% of population lack an an• C6 - usually arises from deep cervical artery terior radicular artery in lower • C8 - usually from costocervical trunk cervical spine22 • T4 or T5 • artery of Adamkiewicz AKA arteria radicularis anterior magna A. the main arterial supply for the spinal cord from ≈ T8 to the conus B. 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”), possessing only the above noted artery at T4 or T5. It is thus more susceptible to vascular insults.

ANATOMIC VARIANTS Arcade 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 AXIAL VIEW

CORONAL VIEW anterior cerebral artery

middle cerebral artery

RAH

MCA AChA

internal carotid

PCommA basilar artery

anterior choroidal artery

posterior cerebral artery

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

Figure 5-15 depicts approximate vascular distributions of the major cerebral arteries. There is considerable variability of the major arteries24 as well as the central distri96

5. Neuroanatomy and physiology

NEUROSURGERY


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