Arab Board Neurosurgery Final Written cheat sheet

Corticospinal tract decussates at the medullary pyramids (~85% crossed); the 15% uncrossed form the anterior corticospinal tract.

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

MCA supplies lateral convexity and insula; ACA supplies medial frontal/parietal cortex; PCA supplies occipital lobe and inferomedial temporal lobe.

Internal capsule: anterior limb (thalamocortical), genu (corticobulbar), posterior limb (corticospinal); lenticulostriate arteries supply it.

CN III exits interpeduncular fossa; CN VI has the longest intracranial course and is the most commonly injured extraocular nerve in raised ICP.

Circle of Willis communicates via ACoA and paired PCoAs; PCoA aneurysms risk CN III palsy; ACoA aneurysms risk frontal lobe and hypothalamic injury.

Ulnar nerve: C8-T1; median nerve: C6-T1; radial nerve: C5-T1; axillary nerve: C5-C6 through the quadrangular space.

Cerebellar signs are ipsilateral; cortical lesions are contralateral; a unilateral cerebellar hemisphere lesion causes ipsilateral ataxia and dysmetria.

CT Hounsfield units: water 0, acute blood 50-80, bone ~1000+, air -1000; hyperacute blood may be isodense.

MRI sequences: DWI detects cytotoxic edema within minutes of ischemia; ADC maps confirm restricted diffusion; FLAIR suppresses CSF.

SAH CT sensitivity is ~100% within 6 h, ~50% at 1 week; LP xanthochromia is most reliable 12 h to 2 weeks after onset.

Gadolinium enhancement reflects blood-brain barrier breakdown; ring enhancement is nonspecific (tumor, abscess, demyelination).

MRA/CTA detect aneurysms ≥3-5 mm; DSA remains the reference standard and permits therapeutic intervention.

Perfusion imaging (CTP/MRP) identifies penumbra: Tmax >6 s with CBF <30% core; mismatch guides thrombectomy decisions.

Spine MRI is first-line for cord compression and discitis; CT is preferred for acute fracture and bony detail.

EEG is the standard for nonconvulsive status epilepticus; 10-second bursts of 3-Hz spike-wave define absence seizures.

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

TBI ICP thresholds: treat ICP >22 mmHg; CPP target 60-70 mmHg; CPP = MAP − ICP.

Rotterdam CT score uses basal cisterns, midline shift, epidural mass, and traumatic SAH to predict outcome.

Epidural hematoma: biconvex, middle meningeal artery, lucid interval; subdural: crescentic, bridging veins.

Monro-Kellie doctrine: brain + blood + CSF + mass = fixed intracranial volume; compensation is limited.

Cushing reflex = hypertension + bradycardia + irregular respiration, indicating raised ICP and impending herniation.

Spinal cord injury: MAP target 85-90 mmHg for 5-7 days; high-dose steroids are not routinely recommended.

Hypertonic saline and mannitol both reduce ICP; mannitol requires adequate renal function and serum osmolality monitoring.

WHO 2021 grading: adult diffuse gliomas are graded 2-4; IDH-mutant astrocytoma grade 4 is distinct from glioblastoma (IDH-wildtype grade 4).

Glioblastoma: IDH-wildtype, TERT promoter mutation, EGFR amplification, +7/−10; median survival ~15 months with standard therapy.

Meningioma: extra-axial, dural tail, homogeneous enhancement; WHO grade 2 if brain invasion or ≥4 mitoses/10 HPF.

Medulloblastoma: cerebellar vermis, drop metastases; molecular groups WNT (best prognosis), SHH, group 3, group 4.

Pilocytic astrocytoma: WHO grade 1, BRAF-KIAA1549 fusion, cystic with mural nodule; gross total resection is curative.

Brain metastases: most common adult intracranial tumors; lung, breast, melanoma, renal, colorectal; number and systemic status determine surgery vs SRS vs WBRT.

Spinal tumors: extradural metastases most common; intradural extramedullary = schwannoma/meningioma; intramedullary = ependymoma/astrocytoma.

Primary CNS lymphoma: periventricular enhancement, restricted diffusion, marked steroid response; biopsy before steroids is preferred.

Aneurysm SAH grading: Hunt-Hess and WFNS grade clinical status; modified Fisher grade predicts vasospasm risk.

Aneurysm rebleeding peaks within 24 h (highest in first 6 h); secure aneurysm by clipping or coiling as early as feasible.

Vasospasm peaks days 3-14; nimodipine 60 mg q4h improves outcome; euvolemia is preferred over hypervolemia.

Aneurysm locations: ACoA (most common), MCA bifurcation, PCoA, basilar tip; ACoA rupture can cause frontal disinhibition.

AVM Spetzler-Martin grade = size (1-3) + eloquence (0-1) + deep venous drainage (0-1); grades 4-5 carry high surgical risk.

ICH: basal ganglia most common site; lobar ICH in elderly suggests cerebral amyloid angiopathy; spot sign predicts expansion.

Ischemic stroke thrombolysis window 4.5 h with CT excluding hemorrhage; thrombectomy up to 24 h in selected patients with mismatch.

Moyamoya disease: distal ICA stenosis with collateral puff-of-smoke; EDAS or STA-MCA bypass for ischemic or hemorrhagic presentations.

Denis three-column model: middle column involvement predicts instability; two or more column injury = unstable.

Cervical radiculopathy: C5 = deltoid/biceps, C6 = wrist extension/brachioradialis, C7 = triceps, C8 = finger flexors.

Lumbar disc herniation: L4-L5 affects L5 (foot dorsiflexion/EHL); L5-S1 affects S1 (ankle reflex, plantarflexion).

Cauda equina syndrome is a surgical emergency: saddle anesthesia, bowel/bladder dysfunction, bilateral leg weakness; decompress urgently.

Spondylolisthesis Meyerding grades I-V by percentage slip; grade I-II often managed conservatively without instability.

Cervical myelopathy: Hoffmann sign, inverted radial reflex, gait disturbance; MRI shows cord signal change and compression.

Odontoid fractures: type II (base of dens) is most common and least likely to unite; consider anterior screw or posterior fusion.

Ankylosing spondylitis and DISH produce a fused, brittle spine; even minor trauma can create unstable hyperextension fractures.

Myelomeningocele: repair within 24-48 h, assess for hydrocephalus and Chiari II; latex precautions from birth.

Chiari II is associated with myelomeningocele; Chiari I presents in adolescence with cough headache and syrinx.

Hydrocephalus in infants: increasing head circumference, sunsetting eyes, tense fontanelle; treat with ETV/CPC or shunt.

Craniosynostosis: sagittal = scaphocephaly, coronal = plagiocephaly, metopic = trigonocephaly; surgery before 1 year improves outcomes.

Medulloblastoma and pilocytic astrocytoma are the most common pediatric posterior fossa tumors; ependymoma arises from the floor of the fourth ventricle.

Craniopharyngioma: calcified suprasellar mass in children; risks include panhypopituitarism, diabetes insipidus, and visual loss.

Tethered cord: conus below L2-L3, fatty filum, cutaneous stigmata; release if symptomatic or progressive deficit.

Pediatric TBI: hypotension is a strong predictor of poor outcome; maintain age-appropriate blood pressure and avoid hyperthermia.

Parkinson disease: STN or GPi DBS improves motor fluctuations; best candidates have levodopa-responsive symptoms without dementia.

Essential tremor: VIM thalamic DBS or thalamotomy; tremor is action/postural, unlike Parkinson rest tremor.

Epilepsy surgery: temporal lobectomy for mesial temporal sclerosis yields the highest seizure-freedom rates; workup includes video-EEG and MRI.

Trigeminal neuralgia: carbamazepine first-line; microvascular decompression is most durable for neurovascular conflict.

Stereotactic frame systems (Leksell) use Cartesian coordinates; frameless systems use surface registration and fiducials.

Dystonia: GPi DBS is effective for primary generalized and cervical dystonia; secondary dystonia responds less predictably.

Vagal nerve stimulation reduces seizure frequency by ~50% in responders; it is palliative, not curative.

Deep brain stimulation programming: monopolar review identifies thresholds for benefit and side effects; impedance checks detect lead fracture.

Seddon classification: neuropraxia (conduction block, full recovery), axonotmesis (axonal loss, wallerian degeneration, spontaneous recovery), neurotmesis (complete transection, needs surgery).

Wallerian degeneration begins within 24-48 h distal to injury; regeneration proceeds ~1 mm/day.

Tinel sign advancing distally indicates regenerating axons; a static Tinel suggests neuroma or blockage.

Carpal tunnel syndrome: median nerve, nocturnal paresthesias, thenar atrophy; EMG/NCS confirms; release of transverse carpal ligament.

Ulnar neuropathy at the elbow (cubital tunnel): ring and little finger numbness, Froment sign, clawing; consider anterior transposition.

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

Nerve repair: primary repair within 72 h for clean transection; otherwise graft with sural nerve; tension-free coaptation is essential.

Facial nerve: House-Brackmann scale I-VI; Bell palsy is idiopathic and treated with steroids within 72 h.

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

Communicating hydrocephalus: enlarged ventricles with open fourth ventricle; non-communicating: obstruction at or above the fourth ventricle.

Normal pressure hydrocephalus triad: gait apraxia, urinary incontinence, cognitive decline; large-volume tap test predicts shunt response.

Shunt valve types: fixed pressure, programmable, and flow-regulated; programmable valves require resetting before MRI.

Shunt infection: most commonly Staphylococcus epidermidis; treat with antibiotics plus removal and external drainage.

Endoscopic third ventriculostomy is preferred for aqueductal stenosis and obstructive hydrocephalus; success is lower in communicating types.

Slit ventricle syndrome and overdrainage cause postural headaches; consider anti-siphon device or programmable valve adjustment.

Pseudotumor cerebri: raised opening pressure with normal CSF and imaging; treat with weight loss, acetazolamide, or optic nerve sheath fenestration.

SRS delivers a single high dose with steep falloff; SRT uses fractionation; typical intracranial SRS doses are 12-20 Gy depending on pathology.

Radiosurgery for vestibular schwannoma: ~12-13 Gy to the margin; facial and hearing preservation are key endpoints.

Brain metastases: SRS for limited numbers and small volume; WBRT adds hippocampal avoidance and memantine to reduce cognitive decline.

Radiation tolerance: whole-brain ~30 Gy in 10 fractions; optic chiasm and brainstem are dose-limiting structures.

Radionecrosis vs tumor progression: MR perfusion, MR spectroscopy, and PET help distinguish; pseudoprogression often occurs 3-6 months post-radiation.

SRS is generally avoided for lesions >3 cm or >10-12 mL because of toxicity risk; hypofractionation or surgery is preferred.

Acute radiation effects: fatigue, edema, alopecia; late effects include leukoencephalopathy, vasculopathy, and radiation necrosis.

Spine SRS (SBRT) is used for oligometastatic disease; dose constraints include spinal cord and cauda equina.

Status epilepticus: benzodiazepines first, then levetiracetam, fosphenytoin, or valproate; refractory cases need intubation and anesthetic doses.

Targeted temperature management at 32-36 °C is used after cardiac arrest; avoid fever in all neurocritical patients.

Subarachnoid hemorrhage: monitor for hyponatremia; distinguish SIADH (euvolemic) from cerebral salt wasting (hypovolemic).

Mechanical ventilation: target normocapnia (PaCO2 35-40 mmHg); hyperventilation only as a temporary bridge for herniation.

Brain death examination requires coma, absent brainstem reflexes, apnea test, and exclusion of confounders such as sedation and hypothermia.

Delirium in neurocritical care is common; nonpharmacologic measures first; avoid benzodiazepines when possible.

Antithrombotic reversal: warfarin with vitamin K and PCC; dabigatran with idarucizumab; heparin with protamine.

Neurogenic stunned myocardium and pulmonary edema can follow SAH; monitor troponin and echocardiography.

Informed consent requires decision-making capacity, disclosure of risks/benefits/alternatives, and voluntariness.

Capacity: patient understands, appreciates, reasons, and expresses a choice; capacity is decision-specific.

Emergency exception applies when immediate treatment is needed and no surrogate is available.

Do-not-resuscitate orders apply to cardiopulmonary arrest; they do not preclude surgery or other treatments.

Wrong-site surgery prevention: pre-operative verification, marking, and time-out; the WHO surgical safety checklist reduces complications.

Conflict of interest must be disclosed; physicians should not accept gifts or incentives that influence clinical decisions.

Confidentiality may be breached when required by law (reportable diseases, imminent harm) or with patient consent.

Medical error disclosure is an ethical obligation; systems-based reporting improves patient safety more than individual blame.