Arab Board Neurosurgery Part 1 cheat sheet

Corticospinal tract fibers decussate at the medullary pyramids (~85%); lateral corticospinal tract synapses on contralateral anterior horn cells.

Broca area lies in the dominant inferior frontal gyrus (pars opercularis/triangularis); Wernicke area in posterior superior temporal gyrus.

CSF is produced mainly by choroid plexus (~500 mL/day); total volume ~150 mL in adults, with ~20-25 mL in ventricles.

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

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

Upper motor neuron lesions produce spasticity, hyperreflexia, and Babinski sign; lower motor neuron lesions produce flaccidity, atrophy, and fasciculations.

Astrocytoma grading per WHO uses mitoses, microvascular proliferation, and necrosis; IDH mutation and 1p/19q codeletion define key glioma classes.

Glioblastoma shows pseudopalisading necrosis and microvascular proliferation; median survival with standard therapy is roughly 14-16 months.

Afferent pupillary defect (Marcus Gunn) indicates optic nerve dysfunction; test with swinging flashlight.

Third nerve palsy with a fixed dilated pupil suggests compressive lesion (e.g., PCom aneurysm); pupil-sparing suggests ischemic diabetic cause.

Internuclear ophthalmoplegia = impaired adduction ipsilateral to a medial longitudinal fasciculus lesion with contralateral abducting nystagmus; consider MS in young patients.

Horner syndrome: ptosis, miosis, anhidrosis; a postganglionic lesion does not cause anhidrosis of the whole face.

Cerebellar hemisphere lesions cause ipsilateral limb ataxia; vermian lesions cause truncal/gait ataxia.

Papilledema is bilateral optic disc swelling from raised ICP; it spares visual acuity early and enlarges the blind spot.

Decerebrate posturing (extension) localizes to brainstem between red nucleus and pons; decorticate (flexion) to above the red nucleus.

Contralateral homonymous hemianopia localizes to the optic tract, lateral geniculate body, optic radiation, or occipital cortex.

CT Hounsfield units: air ~ -1000, fat ~ -100 to -50, water/CSF 0, white matter ~20-30, gray matter ~30-40, acute blood ~50-80, bone ~1000.

Acute intracranial hemorrhage is hyperdense on noncontrast CT; subacute blood becomes isodense and chronic blood hypodense.

DWI restricts in acute ischemia (cytotoxic edema) within minutes; ADC map is low in acute infarction and high in vasogenic edema.

Contrast enhancement requires an intact blood-brain barrier; ring enhancement suggests abscess, metastasis, or high-grade glioma.

Xanthochromia in CSF (spectrophotometry) supports subarachnoid hemorrhage and can persist for days to weeks.

MR spectroscopy: elevated choline and reduced N-acetylaspartate suggest neoplasm; lactate/lipid peaks suggest necrosis.

Spinal epidural abscess: enhancement of the epidural collection and adjacent vertebral body/disc helps distinguish from tumor.

Vascular imaging: CTA and MRA screen for aneurysms and stenosis; DSA remains the reference standard for vascular lesions.

Glasgow Coma Scale: eye 1-4, verbal 1-5, motor 1-6; severe ≤8, moderate 9-12, mild 13-15.

Traumatic epidural hematoma: biconvex/lens shape, often middle meningeal artery, can have a lucid interval.

Subdural hematoma: crescentic shape crossing sutures; acute blood hyperdense on CT.

Basilar skull fracture signs: hemotympanum, Battle sign, raccoon eyes, CSF rhinorrhea/otorrhea.

Cushing reflex (hypertension, bradycardia, irregular respiration) indicates raised ICP and impending herniation.

Traumatic brain injury: avoid hypotension (SBP <90 mmHg) and hypoxia (PaO2 <60 mmHg); both worsen outcome.

Diffuse axonal injury: punctate hemorrhages at gray-white junction, corpus callosum, and dorsolateral brainstem; often poor prognosis.

Cervical spine clearance follows NEXUS or Canadian C-spine rules; obtain CT when criteria are met.

Meningioma: extra-axial, dural tail, homogeneous enhancement; WHO grade based on mitoses and brain invasion.

Brain metastasis: gray-white junction, ring enhancement, extensive vasogenic edema; common primary sources are lung, breast, melanoma, renal, and colon.

Primary CNS lymphoma: periventricular, homogeneous enhancement in immunocompetent patients; responds to high-dose methotrexate.

Medulloblastoma: posterior fossa midline mass in children, often with hydrocephalus; treatment includes resection, craniospinal radiation, and chemotherapy.

Pituitary adenoma: microadenoma <10 mm; prolactinoma is treated first-line with dopamine agonists.

Vestibular schwannoma: cerebellopontine angle mass widening the internal acoustic meatus; bilateral cases suggest NF2.

Cerebellopontine angle tumors: schwannoma, meningioma, epidermoid; epidermoid restricts on DWI.

Tumor grading: Ki-67 index estimates proliferation; higher index correlates with more aggressive behavior.

Subarachnoid hemorrhage: CT sensitivity highest within 6 hours; if CT negative and suspicion high, perform LP for xanthochromia.

Aneurysm locations: anterior communicating artery most common overall; posterior communicating artery causes third nerve palsy.

Hunt and Hess and WFNS scales grade subarachnoid hemorrhage severity; Fisher/modified Fisher grade predicts vasospasm risk.

Vasospasm peaks at 4-14 days after SAH; nimodipine improves outcome (not necessarily angiographic spasm).

Intracerebral hemorrhage: hypertensive bleeds favor putamen, thalamus, pons, and cerebellum; lobar bleeds suggest amyloid angiopathy in elderly.

Arteriovenous malformation: Spetzler-Martin grade uses size, eloquence, and venous drainage; higher grade indicates higher surgical risk.

Moyamoya disease: progressive stenosis of distal ICA with collateral rete; revascularization (direct/indirect bypass) is the main treatment.

Carotid stenosis: endarterectomy benefits symptomatic high-grade stenosis; perioperative risk must be acceptable.

Spinal cord syndromes: anterior cord (bilateral motor and pain/temperature loss, preserved proprioception), posterior cord (loss of vibration/proprioception), Brown-Séquard (ipsilateral motor/proprioception loss, contralateral pain/temperature loss).

Cauda equina syndrome: saddle anesthesia, bowel/bladder dysfunction, bilateral leg weakness; urgent decompression is indicated.

Central cord syndrome: upper limbs more affected than lower limbs, often after hyperextension in a stenotic canal.

Herniated disc: posterolateral herniation compresses the traversing nerve root in the lumbar spine (e.g., L4-L5 affects L5).

Spinal stenosis: neurogenic claudication relieved by flexion and worsened by extension; degenerative changes narrow the canal.

Spinal cord injury: high-dose steroids are not routine; avoid hypotension and maintain spinal precautions.

Syringomyelia: fluid-filled cavity in the cord causing cape-like loss of pain/temperature; often associated with Chiari malformation.

Vertebral osteomyelitis/discitis: fever, focal pain, elevated ESR/CRP; MRI with contrast is the imaging modality of choice.

Chiari II malformation: caudal displacement of cerebellar vermis, myelomeningocele, hydrocephalus, tectal plate beaking.

Myelomeningocele: neural tube defect; repair within 24-48 hours reduces infection risk; assess for hydrocephalus and Chiari II.

Hydrocephalus: in infants, signs include macrocephaly, sunset sign, tense fontanelle, and irritability.

Shunt malfunction: headache, vomiting, lethargy; evaluate with CT and shunt series.

Craniosynostosis: premature suture fusion; scaphocephaly with sagittal synostosis, trigonocephaly with metopic synostosis.

Tethered cord: low-lying conus below L2, thickened filum, lipoma, or diastematomyelia; presents with progressive neurological or urologic symptoms.

Medulloblastoma and pilocytic astrocytoma are common pediatric posterior fossa tumors; pilocytic astrocytoma is WHO grade 1.

Cerebral palsy: nonprogressive motor impairment from early brain injury; spasticity management includes selective dorsal rhizotomy and intrathecal baclofen.

Stereotactic frame coordinates use a Cartesian system referenced to the anterior commissure-posterior commissure line.

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

Trigeminal neuralgia: carbamazepine is first-line; microvascular decompression relieves vascular compression of the trigeminal root.

Epilepsy surgery: temporal lobectomy is effective for medial temporal lobe epilepsy; presurgical evaluation includes video-EEG and MRI.

Vagus nerve stimulation reduces seizure frequency; it is palliative, not curative.

Radiofrequency lesioning and gamma knife radiosurgery are ablative options for movement disorders and trigeminal neuralgia.

Spasticity: intrathecal baclofen delivers drug to the spinal subarachnoid space; abrupt withdrawal can cause severe symptoms.

Stereotactic biopsy: frame-based or frameless; risk of hemorrhage is higher in deep or vascular lesions.

Median nerve entrapment at the wrist (carpal tunnel syndrome): nocturnal paresthesias in the thumb, index, and middle fingers; Tinel and Phalen signs.

Ulnar nerve entrapment at the elbow (cubital tunnel): numbness in the little and ring fingers; Froment sign indicates intrinsic hand weakness.

Common peroneal nerve palsy: foot drop, sensory loss over the dorsum of the foot; often from fibular neck compression.

Erb palsy (C5-C6): waiter's tip posture; Klumpke palsy (C8-T1): claw hand and Horner syndrome.

Nerve injury Seddon classification: neurapraxia (conduction block), axonotmesis (axon loss with intact sheath), neurotmesis (complete transection).

Peripheral nerve repair: tension-free coaptation, epineurial or fascicular repair; nerve grafting for gaps.

Brachial plexus injury: preganglionic avulsion shows pseudomeningocele and denervation; postganglionic lesions may be graftable.

Peripheral nerve tumors: schwannoma is eccentric and often separable from nerve fascicles; neurofibroma is more infiltrative.

Cerebral perfusion pressure = mean arterial pressure minus intracranial pressure; target CPP is typically 60-70 mmHg in adults.

Intracranial pressure monitoring is indicated for severe TBI (GCS ≤8) with abnormal CT or risk factors; normal ICP is ≤15-20 mmHg.

Hyperventilation lowers PaCO2, causing cerebral vasoconstriction and reduced ICP; use briefly for herniation.

Mannitol (osmotic diuretic) and hypertonic saline reduce cerebral edema; monitor osmolality and renal function.

Hyponatremia after SAH: distinguish SIADH from cerebral salt wasting; CSW requires volume replacement.

Antiepileptic prophylaxis after TBI reduces early seizures but does not prevent late posttraumatic epilepsy.

Venous thromboembolism prophylaxis: mechanical prophylaxis early; pharmacologic prophylaxis after intracranial hemorrhage risk assessment.

Postoperative neurosurgical care: monitor for hematoma, seizures, hydrocephalus, and airway compromise; avoid hypotension and hypoxia.