Egyptian Board Neurosurgery cheat sheet

Corticospinal fibres arise from layer V pyramidal cells; 85-90% decussate at the medullary pyramid (lateral corticospinal tract), the rest form the anterior corticospinal tract.

Broca area = pars triangularis + pars opercularis of the inferior frontal gyrus (dominant hemisphere); Wernicke area = posterior superior temporal gyrus.

MCA territory supplies the lateral convexity including Broca and Wernicke areas; ACA supplies medial frontal/parietal cortex and leg motor area.

Internal capsule: anterior limb (thalamocortical), genu (corticobulbar), posterior limb (corticospinal, somatosensory); lenticulostriate arteries supply its posterior limb and basal ganglia.

Vertebral arteries unite at the lower pontine border to form the basilar artery; PICA arises from the vertebral, AICA from the lower basilar, SCA from the upper basilar.

Cranial nerve nuclei: III/IV in midbrain, V-XII in pons and medulla; CN VI nucleus lies in the dorsal pons, its fibres loop over the facial nucleus (facial colliculus).

Conus medullaris terminates at L1-L2 in adults (L3 in neonates); the dural sac ends at S2; lumbar puncture is performed at L3-L4 or L4-L5.

Circle of Willis components: A1 and A2 segments, anterior communicating artery, M1 segment, internal carotid, posterior communicating, P1 segment and basilar tip.

Cerebral blood flow is ~50 mL/100 g/min; electrical failure occurs below ~18-20 mL/100 g/min and membrane failure/infarction below ~10 mL/100 g/min.

Monro-Kellie doctrine: intracranial volume = brain + blood + CSF; an increase in one compartment must be offset by a decrease in another or ICP rises.

Cerebral perfusion pressure = mean arterial pressure − intracranial pressure; normal CPP is 60-70 mmHg in adults.

Cerebral autoregulation holds CBF constant between MAP ~50-150 mmHg; it is impaired in severe TBI and ischaemia.

Cerebral oedema types: cytotoxic (ischaemia, failure of Na/K ATPase), vasogenic (tumour, trauma; BBB breakdown), interstitial (hydrocephalus) and osmotic.

CO2 is the most potent CBF modulator: hyperventilation to PaCO2 30-35 mmHg reduces CBF ~3% per mmHg; hypocapnia below 25 mmHg risks ischaemia.

Cerebral metabolism: brain consumes ~20% of body oxygen and ~25% of glucose; it has minimal substrate storage and depends on continuous perfusion.

Glioblastoma (WHO grade 4) shows necrosis and microvascular proliferation; IDH-wildtype status and MGMT promoter methylation guide prognosis and temozolomide response.

Glasgow Coma Scale: eye 1-4, verbal 1-5, motor 1-6; total 3-15; motor score is the strongest prognostic component in TBI.

Pupillary light reflex: afferent CN II, efferent CN III; a fixed dilated pupil suggests ipsilateral uncal herniation with CN III compression.

Upper motor neuron signs: spasticity, hyperreflexia, extensor plantar (Babinski), loss of superficial abdominal reflexes; lower motor neuron: flaccidity, atrophy, fasciculations, areflexia.

Cerebellar signs: dysdiadochokinesia, intention tremor, ataxia, nystagmus, hypotonia; vermis lesions cause truncal ataxia, hemisphere lesions cause ipsilateral limb ataxia.

Cushing triad = hypertension with widened pulse pressure, bradycardia and irregular respiration - a late sign of raised ICP.

Decorticate posturing (flexor arms) indicates lesions above the red nucleus; decerebrate (extensor) indicates lesions at or below the red nucleus/midbrain.

Romberg test is positive with dorsal column/proprioceptive loss; it is not a test of cerebellar function alone.

Cranial nerve palsy localisation: CN III palsy with spared pupil suggests diabetes/ischaemia; pupil-involving CN III palsy suggests compressive aneurysm (posterior communicating).

Non-contrast CT is first-line in acute trauma and suspected haemorrhage; it detects acute blood immediately (hyperdense, ~50-70 HU).

MRI sequences: T1 (anatomy, fat bright), T2 (pathology bright, CSF bright), FLAIR (CSF suppressed, oedema bright), DWI/ADC (restricted diffusion = acute infarct, abscess, highly cellular tumour).

CT angiography detects aneurysms >2-3 mm and vascular malformations; digital subtraction angiography remains the reference standard.

Acute ischaemic stroke: CT excludes haemorrhage; ASPECTS score ≤6 or large core on perfusion imaging predicts poor outcome and influences thrombectomy decisions.

Hydrocephalus on imaging: temporal horn dilatation, ballooning of frontal horns, periventricular lucency (transependymal oedema), Evans index >0.3.

Gadolinium enhancement reflects blood-brain barrier breakdown; ring enhancement with central necrosis suggests high-grade glioma, abscess or metastasis.

MR spectroscopy: choline rise and N-acetylaspartate fall indicate tumour; lactate/lipid peak suggests necrosis or anaerobic metabolism.

Cervical spine clearance in trauma: NEXUS or Canadian C-spine rules can defer imaging in low-risk patients; CT is the modality of choice for bony injury.

Epidural haematoma: middle meningeal artery, biconvex/lens shape, does not cross sutures; can cross the midline; lucid interval is classic.

Subdural haematoma: bridging cortical veins, crescent shape, crosses sutures, does not cross the midline; common in elderly and alcoholics.

Traumatic subarachnoid haemorrhage and diffuse axonal injury (grey-white junction, corpus callosum, brainstem) are common in high-energy trauma; DAI often shows no CT abnormality.

Basal skull fracture signs: Battle sign, raccoon eyes, CSF rhinorrhoea/otorrhoea, haemotympanum; avoid nasogastric tube placement.

TBI management: avoid hypoxia (SpO2 <90%) and hypotension (systolic <90-100 mmHg); maintain CPP 60-70 mmHg and ICP <22 mmHg.

Hyperosmolar therapy: mannitol 0.25-1 g/kg or hypertonic saline; monitor osmolality (target <320 mOsm/kg) and renal function.

Spinal shock (flaccid paralysis, areflexia, hypotension/bradycardia from loss of sympathetic tone) differs from neurogenic shock; both follow high cervical injury.

Spinal cord injury: methylprednisolone is not routinely recommended; early decompression (<24 h) for incomplete cervical injury is supported by current evidence.

WHO 2021 classification integrates histology with molecular markers (IDH, 1p/19q codeletion, H3K27M, TERT promoter).

Glioblastoma: IDH-wildtype, grade 4; standard of care is maximal safe resection followed by radiotherapy with concurrent and adjuvant temozolomide (Stupp protocol).

Oligodendroglioma: IDH-mutant with 1p/19q codeletion, grade 2-3; typically calcified and frontal, better prognosis.

Meningioma: extra-axial, dural tail, hyperostosis; WHO grade 1 (benign) in most; grade 2/3 show brain invasion, high mitotic index or atypia.

Metastases: most common adult brain tumour; grey-white junction, multiple, ring-enhancing; lung, breast, melanoma, renal and colorectal are common primaries.

Pituitary adenoma: bitemporal hemianopia from optic chiasm compression; prolactinoma is treated first-line with dopamine agonists (cabergoline).

Vestibular schwannoma: CN VIII, cerebellopontine angle, widened internal acoustic meatus; sensorineural hearing loss and tinnitus are typical.

Spinal tumours: extradural (metastasis most common), intradural extramedullary (meningioma, schwannoma), intramedullary (ependymoma, astrocytoma).

Subarachnoid haemorrhage: thunderclap headache; CT within 6 h is highly sensitive; if CT negative and suspicion persists, LP for xanthochromia after 12 h.

Aneurysm treatment: clipping (surgical) versus coiling/flow diversion (endovascular); anterior circulation and MCA aneurysms favour clipping, posterior circulation favours endovascular.

SAH complications: rebleeding (peak 24 h), vasospasm (days 3-14, peak 7), hydrocephalus, hyponatraemia (SIADH or cerebral salt wasting).

Nimodipine 60 mg every 4 h for 21 days reduces delayed cerebral ischaemia and poor outcome after aneurysmal SAH.

Arteriovenous malformation: Spetzler-Martin grading uses size (<3, 3-6, >6 cm), eloquent location and deep venous drainage; grade 1-2 low risk, 4-5 high risk.

Intracerebral haemorrhage: haematoma expansion within 6 h; BP control (systolic target ~140 mmHg), reversal of anticoagulation, and surgery for cerebellar haemorrhage >3 cm or with brainstem compression.

Ischaemic stroke: IV thrombolysis within 4.5 h of onset; mechanical thrombectomy up to 24 h in selected large-vessel occlusion with favourable imaging.

Moyamoya disease: progressive stenosis of distal ICA and proximal circle of Willis with collateral network; revascularisation (direct/indirect bypass) reduces stroke risk.

Cauda equina syndrome: bilateral leg pain, saddle anaesthesia, bladder/bowel dysfunction, reduced anal tone; requires urgent MRI and decompression, ideally within 24-48 h.

Lumbar disc herniation: posterolateral herniation compresses the traversing nerve root (L4-L5 disc affects L5); far lateral herniation affects the exiting root.

Cervical spondylotic myelopathy: gait disturbance, hyperreflexia, Hoffmann sign, hand clumsiness; MRI shows cord compression with T2 hyperintensity.

Degenerative lumbar stenosis: neurogenic claudication relieved by flexion (shopping cart sign), unlike vascular claudication relieved by standing still.

Spondylolisthesis: Meyerding grading I-V by percentage slip; grade I-II usually managed conservatively unless instability or neurologic deficit.

Spinal metastasis: Tokuhashi and Tomita scores guide prognosis and surgical decision; unstable spine (SINS score) may need instrumentation.

Spinal epidural abscess: fever, back pain, neurologic deficit; MRI with contrast is diagnostic; urgent surgical decompression plus antibiotics.

Vertebral osteomyelitis: Staphylococcus aureus most common; MRI is sensitive; biopsy for culture when possible; duration of antibiotics 6-12 weeks.

Myelomeningocele: failure of neural tube closure; associated Chiari II malformation and hydrocephalus in ~80%; repair within 24-48 h and cover with sterile dressing.

Chiari I malformation: cerebellar tonsillar herniation >5 mm below the foramen magnum; often asymptomatic or presents with cough headache and syringomyelia.

Hydrocephalus in children: congenital aqueductal stenosis, post-haemorrhagic, post-infectious; endoscopic third ventriculostomy is an option in obstructive hydrocephalus.

Dandy-Walker malformation: cystic dilatation of the fourth ventricle, cerebellar vermis hypoplasia, enlarged posterior fossa; hydrocephalus common.

Craniosynostosis: premature suture fusion; scaphocephaly (sagittal), brachycephaly (coronal), trigonocephaly (metopic); surgery before 1 year improves outcome.

Tumours of childhood: medulloblastoma (posterior fossa, drop metastases), pilocytic astrocytoma (cerebellar, cystic with mural nodule), ependymoma (fourth ventricle).

Tethered cord: low conus, thickened filum, cutaneous stigmata (hair tuft, dimple, lipoma); presents with progressive leg weakness, pain or sphincter dysfunction.

Shunt infection: most commonly Staphylococcus epidermidis; presents with fever, headache, shunt malfunction; treatment is removal and external drainage plus antibiotics.

Stereotactic frame systems (Leksell) use a Cartesian coordinate system referenced to the anterior commissure-posterior commissure line.

Deep brain stimulation targets: subthalamic nucleus or globus pallidus internus for Parkinson disease; ventral intermediate thalamus for essential tremor.

DBS programming: adjust amplitude, frequency and pulse width; monopolar versus bipolar stimulation; check impedance and battery status when effect wanes.

Trigeminal neuralgia: carbamazepine is first-line; surgical options include microvascular decompression (Jannetta), percutaneous balloon compression, glycerol rhizotomy and gamma knife.

Stereotactic radiosurgery: single high-dose radiation with sub-millimetre accuracy; used for vestibular schwannoma, meningioma, metastases and AVMs.

Radiofrequency lesioning and pallidotomy are older ablative options; DBS is preferred for bilateral disease because of lower risk of dysarthria and cognitive decline.

Spasticity: intrathecal baclofen via pump for severe generalised spasticity; selective dorsal rhizotomy for selected cerebral palsy patients.

Stereotactic biopsy is indicated for deep or inaccessible lesions; frame-based or frameless navigation; risk of haemorrhage ~1-3%.

Focal seizures arise from a localised cortical region; temporal lobe epilepsy is the most common surgically remediable form.

Mesial temporal sclerosis: hippocampal atrophy and T2 hyperintensity on MRI; anterior temporal lobectomy gives seizure freedom in ~60-70%.

Presurgical evaluation: video-EEG monitoring, high-resolution MRI, neuropsychology; invasive monitoring (SEEG/subdural grids) when non-invasive data conflict.

Status epilepticus: benzodiazepine first-line, then second-line IV antiepileptic (levetiracetam, valproate, phenytoin); refractory cases need anaesthetic coma.

Vagus nerve stimulation reduces seizure frequency by ~50% in some patients; not curative; useful in palliative cases.

Pain pathways: spinothalamic tract carries nociceptive input; dorsal root ganglion, dorsal horn, and thalamus are targets for neuromodulation.

Spinal cord stimulation is used for failed back surgery syndrome and complex regional pain syndrome; dorsal column stimulation paresthesias should cover the painful area.

Cancer pain: WHO analgesic ladder; intrathecal morphine or nerve blocks for refractory pain; cordotomy for unilateral refractory pain.

CSF production ~500 mL/day, mostly by choroid plexus; total volume ~150 mL in adults; turnover ~3-4 times/day.

Communicating hydrocephalus: obstruction outside ventricles (post-haemorrhagic, post-meningitic); non-communicating: obstruction within ventricular system (aqueductal stenosis, tumour).

Normal pressure hydrocephalus triad: gait disturbance (early), urinary incontinence, cognitive decline; large-volume LP or external lumbar drain trial predicts shunt response.

Shunt types: ventriculoperitoneal (most common), ventriculoatrial, ventriculopleural; programmable valves allow pressure adjustment.

Shunt malfunction: headache, vomiting, lethargy, slit ventricles on CT; may require shunt revision; overdrainage causes subdural haematoma.

Endoscopic third ventriculostomy: indicated in obstructive hydrocephalus (aqueductal stenosis, tectal plate tumour); success rate ~70-80% in selected patients.

Skull base approaches: pterional, subfrontal, transsphenoidal, retrosigmoid, far lateral; choose based on lesion location and neurovascular anatomy.

CSF leak after skull base surgery: suspect with clear rhinorrhoea; confirm with beta-2 transferrin; manage with head elevation, lumbar drain, or reoperation.

Brachial plexus: C5-C6 (upper trunk) injury causes Erb palsy (waiter's tip); C8-T1 (lower trunk) causes Klumpke palsy (claw hand).

Radial nerve injury at the midshaft humerus causes wrist drop; posterior interosseous nerve palsy spares wrist extension but loses finger extension.

Median nerve: carpal tunnel syndrome causes nocturnal pain, thenar wasting, positive Tinel and Phalen tests; EMG/NCS confirm.

Ulnar nerve: cubital tunnel syndrome causes clawing of ring and little fingers, Froment sign, wasting of interossei; anterior transposition for severe cases.

Peroneal nerve injury at the fibular neck causes foot drop and impaired sensation over the dorsum of the foot; common after trauma or prolonged positioning.

Nerve repair: primary end-to-end repair for clean transection; nerve graft for gaps >2-3 cm; nerve transfer for proximal injuries (e.g., spinal accessory to suprascapular).

Neuroma: painful nodule at nerve end; treatment includes excision, relocation, or coverage; prevention with tension-free repair.

Thoracic outlet syndrome: neurogenic (most common), venous, arterial; symptoms worsened by arm elevation; scalenectomy or rib resection for refractory cases.

ICP monitoring indications: GCS ≤8 with abnormal CT, or GCS ≤8 with normal CT plus risk factors (age >40, hypotension, decerebrate posturing).

ICP targets: <22 mmHg; CPP 60-70 mmHg; head elevation 30°, loose collar, avoid neck compression, maintain normocapnia.

Sedation and analgesia (propofol, fentanyl) reduce ICP; barbiturate coma for refractory intracranial hypertension; decompressive craniectomy as last resort.

Hyponatraemia after SAH: distinguish SIADH (euvolemic, treat with fluid restriction) from cerebral salt wasting (hypovolemic, treat with saline).

Postoperative complications: haematoma, oedema, seizure, infection, CSF leak, hydrocephalus; early CT for unexplained deterioration.

Venous thromboembolism prophylaxis: mechanical (compression stockings) early; pharmacologic after 24-48 h in stable neurosurgical patients.

Antibiotic prophylaxis: single dose at induction for clean neurosurgery; avoid prolonged courses; shunt surgery uses antibiotic-impregnated catheters.

Perioperative steroids: dexamethasone reduces vasogenic oedema around tumours; taper after surgery; monitor glucose and infection risk.

Wound healing phases: haemostasis, inflammation, proliferation, remodelling; collagen type III is replaced by type I over weeks.

Suture materials: absorbable (vicryl, monocryl) versus non-absorbable (nylon, prolene); monofilament reduces infection risk.

Surgical asepsis: sterile field, hand scrub, gowning and gloving; surgical site infection prevention includes chlorhexidine skin prep and normothermia.

Haemostasis: bipolar cautery for precise coagulation; monopolar for cutting and coagulation; avoid thermal injury near nerves.

Fluid and electrolyte balance: maintenance ~30-35 mL/kg/day; monitor urine output, electrolytes and osmolality in neurosurgical patients.

Blood transfusion: restrictive threshold (Hb 7-8 g/dL) in most stable patients; avoid unnecessary transfusion in neurocritical care.

Local anaesthetics: lidocaine with epinephrine prolongs effect and reduces bleeding; avoid in digits and end-arterial territories.

Evidence-based practice: randomised controlled trials, systematic reviews and meta-analyses; GRADE system rates quality of evidence and strength of recommendations.

Informed consent: patient must have capacity, be informed of risks/benefits/alternatives, and consent voluntarily; document the discussion.

Capacity assessment: patient understands, retains, weighs and communicates the decision; if lacking, use best-interest decisions and substitute decision-makers.

Research ethics: institutional review board approval, informed consent, risk minimization, confidentiality; Declaration of Helsinki governs human research.

Levels of evidence: systematic reviews/meta-analyses of RCTs (level I) down to expert opinion (level V); GRADE separates evidence quality from recommendation strength.

Publication bias: positive studies are more likely to be published; funnel plots and trial registries help detect bias.

Conflict of interest: disclose financial and non-financial interests; manage with recusal or independent oversight.

Medical error disclosure: duty to disclose harmful errors to patients; root cause analysis and incident reporting improve safety.

Resource allocation: triage and distributive justice; transparent criteria for ICU and surgical prioritization in resource-limited settings.