Iraqi Board Neurosurgery cheat sheet

Corticospinal tract: motor cortex layer V Betz cells -> corona radiata -> posterior limb internal capsule -> cerebral peduncle -> ventral pons -> medullary pyramid -> 85-90% decussate at cervicomedullary junction (lateral corticospinal tract, lamina IX); 10-15% remain ipsilateral (anterior corticospinal tract).

MCA territory infarction: contralateral face/arm weakness and sensory loss, homonymous hemianopia, aphasia if dominant hemisphere; ACA: contralateral leg weakness; PCA: contralateral homonymous hemianopia with macular sparing.

Cerebral perfusion pressure = mean arterial pressure - intracranial pressure; normal ICP 5-15 mmHg in adults; CPP target 60-70 mmHg after traumatic brain injury.

Monro-Kellie doctrine: intracranial volume is fixed (brain 80%, CSF 10%, blood 10%); an expanding mass is compensated first by CSF displacement, then venous blood, then arterial blood, after which ICP rises steeply.

Cerebrospinal fluid: produced mainly by choroid plexus at ~0.35 mL/min (500 mL/day); total volume ~150 mL adults, ~50 mL neonates; absorption via arachnoid granulations into superior sagittal sinus (pressure-dependent).

Circle of Willis: anterior communicating, paired anterior cerebral (A1), internal carotid, posterior communicating, posterior cerebral (P1), basilar and vertebral arteries; complete in only ~20-45% of individuals.

Herniation syndromes: uncal (dilated pupil, ipsilateral CN III palsy, contralateral hemiparesis), central transtentorial (bilateral pupillary dilation, Cheyne-Stokes), tonsillar (respiratory arrest, neck stiffness).

Neurotransmitter pharmacology: levodopa crosses blood-brain barrier via L-amino acid transporter and is decarboxylated to dopamine; carbidopa inhibits peripheral decarboxylase, increasing CNS delivery and reducing nausea.

Cerebral autoregulation maintains constant cerebral blood flow (~50 mL/100 g/min) between MAP ~50-150 mmHg; lost in severe head injury and ischemia, making perfusion pressure-dependent.

CT head: hyperdense acute hemorrhage (40-60 HU), hypodense ischemia (may be normal in first 6-12 hours), isodense subdural in chronic stage; bone windows for fractures.

MRI sequences: T1 (CSF dark, fat bright), T2 (CSF bright), FLAIR (CSF suppressed, edema bright), DWI (restricted diffusion bright, low ADC in acute infarction and abscess), SWI/GRE (susceptibility for blood, calcification).

SAH diagnosis: non-contrast CT sensitivity ~95-100% within 6 hours, declining after 24 hours; if CT negative and suspicion persists, lumbar puncture at least 6-12 hours after ictus showing xanthochromia.

Digital subtraction angiography remains gold standard for aneurysm and AVM; CTA sensitivity ~95% for aneurysms >3 mm; MRA useful for screening but lower spatial resolution.

EEG: 3 Hz spike-and-wave = absence epilepsy; temporal lobe spikes in mesial temporal sclerosis; burst suppression for refractory status epilepticus; alpha rhythm 8-13 Hz over posterior regions in wakefulness.

Evoked potentials: BAEP (waves I-V, wave V most robust) for acoustic neuroma and brainstem function; SSEP for spinal cord monitoring and outcome prediction after cardiac arrest (absent N20 poor prognosis).

ICP monitoring: ventricular catheter (also allows CSF drainage, gold standard), intraparenchymal fiberoptic/strain gauge, subdural and epidural devices; zero at foramen of Monro or tragus.

Brain death ancillary testing: four-vessel angiography (no intracranial filling), transcranial Doppler (reverberating flow), EEG (electrocerebral silence), radionuclide scan; all require core temperature >36 C and no sedatives.

Glasgow Coma Scale: eye 1-4, verbal 1-5, motor 1-6; total 3-15; severe <=8, moderate 9-12, mild 13-15; intubate if GCS <=8.

Epidural hematoma: middle meningeal artery tear with temporal bone fracture, biconvex/lentiform, lucid interval, arterial; subdural: bridging veins, crescentic, venous, common in elderly and alcoholics.

Basal skull fracture signs: Battle sign, raccoon eyes, CSF rhinorrhea/otorrhea, hemotympanum; avoid nasogastric tube and nasal intubation.

Diffuse axonal injury: gray-white junction, corpus callosum, dorsolateral brainstem; CT may be normal, MRI SWI shows petechial hemorrhage; common cause of persistent vegetative state.

Cushing triad (hypertension, bradycardia, irregular respiration) indicates raised ICP and impending herniation; hyperventilation to PaCO2 30-35 mmHg is a temporizing bridge only.

Traumatic brain injury management: avoid hypotension (systolic <90 mmHg doubles mortality), maintain PaO2 >60 mmHg, head of bed 30 degrees, normothermia, seizure prophylaxis 7 days for severe TBI.

Spinal trauma: ASIA impairment scale A-E; high-dose methylprednisolone is not recommended routinely (NASCIS results not reproduced); maintain MAP 85-90 mmHg for 5-7 days in acute cord injury.

Atlantoaxial rotatory subluxation and odontoid fractures: type II dens fracture (base) most common and most prone to nonunion; halo vest or C1-C2 fusion depending on displacement.

Peripheral nerve injury: neurapraxia (myelin, recovers weeks), axonotmesis (axon, Wallerian degeneration, regenerates 1 mm/day), neurotmesis (transection, requires repair).

Glioblastoma (WHO grade 4): IDH-wildtype, MGMT promoter methylation predicts temozolomide response; standard of care is maximal safe resection plus radiotherapy with concomitant and adjuvant temozolomide (Stupp protocol).

Meningioma: extra-axial, dural tail, homogeneous enhancement, WHO grade 1 in ~80%; grade 2 (atypical) shows brain invasion or >=4 mitoses per 10 high-power fields; grade 3 (anaplastic) >=20 mitoses.

Metastases: most common adult brain tumor; gray-white junction; lung, breast, melanoma, renal, colorectal; single lesion may be resected, multiple lesions treated with whole-brain radiotherapy or stereotactic radiosurgery.

Medulloblastoma: posterior fossa, children, drop metastases; molecular groups WNT (best prognosis), SHH, group 3, group 4; treatment resection plus craniospinal irradiation and chemotherapy.

Pilocytic astrocytoma: WHO grade 1, cerebellum in children, cystic with mural nodule, BRAF-KIAA1549 fusion; complete resection is curative.

Pituitary adenoma: prolactinoma treated first-line with dopamine agonists (cabergoline); transsphenoidal resection for nonfunctioning macroadenoma with visual field deficit; check cortisol, prolactin, IGF-1, TSH preoperatively.

Vestibular schwannoma: CN VIII, cerebellopontine angle, widened internal acoustic meatus, NF2 if bilateral; treatment observation, stereotactic radiosurgery, or microsurgical resection.

Skull base approaches: anterior (transsphenoidal, subfrontal), lateral (pterional, orbitozygomatic, middle fossa), posterior (retrosigmoid, far lateral); CSF leak risk highest with extended endoscopic endonasal approaches.

Corticosteroid (dexamethasone) reduces peritumoral edema; seizure prophylaxis is not routine for all tumors but used in cortical lesions with seizure history.

Aneurysm SAH: Hunt and Hess and World Federation of Neurosurgical Societies (WFNS) grading predict outcome; Fisher grade on CT predicts vasospasm risk (thick clot = higher risk).

Nimodipine 60 mg every 4 hours for 21 days is the only proven pharmacologic therapy for vasospasm; triple-H therapy is not supported by strong evidence.

Aneurysm treatment: clipping (middle cerebral, pericallosal) versus endovascular coiling; ISAT showed better 1-year outcome with coiling for ruptured anterior circulation aneurysms, with higher late rebleeding.

Berry aneurysm locations: anterior communicating (~30-35%), middle cerebral bifurcation (~20%), posterior communicating (~20%), basilar tip, posterior inferior cerebellar artery.

AVM: Spetzler-Martin grade 1-5 based on size (<3, 3-6, >6 cm = 1-3), eloquence (1), deep venous drainage (1); grades 4-5 have high surgical morbidity.

Cavernoma: popcorn appearance with hemosiderin ring on MRI, no intervening brain, low flow; resection for recurrent hemorrhage or epilepsy; radiosurgery has limited role.

Moyamoya: progressive stenosis of distal internal carotid and proximal circle of Willis with collateral puff of smoke; direct bypass (STA-MCA) or indirect (encephaloduroarteriosynangiosis) for ischemic presentation.

Intracerebral hemorrhage: basal ganglia most common site (hypertensive); lobar hemorrhage in elderly suggests cerebral amyloid angiopathy; surgery for cerebellar hemorrhage >3 cm with deterioration or brainstem compression.

Arteriovenous malformation rupture risk ~2-4% per year, higher after prior hemorrhage; rebleeding risk highest in first year.

Lumbar disc herniation: posterolateral (paracentral) affects traversing nerve root (L4-L5 disc -> L5 root); far lateral affects exiting root; cauda equina syndrome (saddle anesthesia, urinary retention) requires urgent decompression.

Cervical spondylotic myelopathy: anterior approach (ACDF or corpectomy) for ventral compression; laminoplasty or laminectomy with fusion for multilevel posterior compression; preserve cervical lordosis.

Degenerative spondylolisthesis: Meyerding grading I-V; fusion indicated for instability, progressive slip, or revision; decompression alone acceptable for stable grade I with leg-dominant symptoms.

Spinal epidural abscess: fever, back pain, neurologic deficit triad; MRI with contrast is the study of choice; urgent decompression plus 6-8 weeks antibiotics; Staphylococcus aureus most common organism.

Spinal metastases: most common in thoracic spine; breast, lung, prostate most frequent primaries; Tokuhashi and Tomita scores guide operative versus palliative management; cord compression needs dexamethasone and urgent decompression or radiosurgery.

Syringomyelia: fluid cavity in cord, often with Chiari I malformation; cape-like suspended sensory loss; treatment is posterior fossa decompression for Chiari-associated syrinx.

Scoliosis: Cobb angle >10 degrees defines scoliosis; >40-50 degrees in skeletally immature patients progresses and may need fusion; adolescent idiopathic most common type.

Intramedullary tumors: ependymoma (central, syrinx, cap sign) and astrocytoma; ependymoma is usually well circumscribed and resectable; astrocytoma is infiltrative.

Thoracolumbar junction (T12-L1) is the most common site of spinal fracture; Denis three-column model: two or more column injury is unstable.

Parkinson disease: deep brain stimulation of subthalamic nucleus or globus pallidus internus for motor fluctuations and dyskinesia; thalamic VIM stimulation for tremor; best candidates have levodopa-responsive symptoms and no dementia.

Essential tremor: VIM thalamotomy or thalamic DBS; bilateral DBS preferred to avoid bilateral lesion side effects.

Epilepsy surgery: anterior temporal lobectomy for mesial temporal sclerosis gives seizure freedom in ~60-70%; callosotomy for drop attacks; hemispherectomy for Rasmussen encephalitis or hemimegalencephaly.

Vagus nerve stimulation reduces seizure frequency by ~50% in a subset; responsive neurostimulation and deep brain stimulation of anterior nucleus of thalamus are alternatives for drug-resistant epilepsy.

Trigeminal neuralgia: carbamazepine first-line; microvascular decompression of superior cerebellar artery at root entry zone is most durable surgical option; percutaneous options include glycerol, balloon, and radiofrequency rhizotomy.

Stereotactic frames: Leksell and Cosman-Roberts-Wells; accuracy depends on rigid fixation and imaging registration; frame-based biopsy of deep lesions has diagnostic yield ~90%.

Spasticity: intrathecal baclofen for generalized spasticity; selective dorsal rhizotomy for spastic diplegic cerebral palsy; botulinum toxin for focal spasticity.

Movement disorder targets: subthalamic nucleus, globus pallidus internus, ventral intermediate thalamus; coordinates referenced to anterior commissure-posterior commissure line and midcommissural point.

Radiofrequency lesioning versus DBS: lesions are irreversible and may be preferable in resource-limited settings or patients unable to comply with programming.

Chiari II malformation: myelomeningocele, hindbrain herniation, tectal beaking, corpus callosum dysgenesis, hydrocephalus; prenatal repair reduces need for shunting.

Myelomeningocele: closure within 24-48 hours to reduce infection; assess for hydrocephalus, tethered cord, and latex allergy; 80-90% develop hydrocephalus requiring shunt.

Craniosynostosis: sagittal synostosis most common (scaphocephaly); coronal synostosis gives plagiocephaly (unilateral) or brachycephaly (bilateral); surgery before 12 months for remodeling.

Hydrocephalus in children: endoscopic third ventriculostomy preferred in obstructive hydrocephalus, especially aqueductal stenosis; ventriculoperitoneal shunt for communicating hydrocephalus.

Dandy-Walker malformation: cystic dilation of fourth ventricle, cerebellar vermis hypoplasia, hydrocephalus; associated with agenesis of corpus callosum.

Pediatric tumors: infratentorial tumors most common in children (medulloblastoma, pilocytic astrocytoma, ependymoma); supratentorial in infants; pilocytic astrocytoma is most common overall.

Craniopharyngioma: suprasellar, calcified, cystic, adamantinomatous in children; resection risks hypothalamic obesity, diabetes insipidus, and panhypopituitarism.

Tethered cord: conus below L2, thickened filum (>2 mm), low-lying cord; release for progressive neurologic or urologic symptoms.

Aqueductal stenosis: triventricular hydrocephalus with normal fourth ventricle; endoscopic third ventriculostomy is first-line in children over 2 years.

Normal pressure hydrocephalus triad: gait disturbance (magnetic), urinary incontinence, dementia; ventriculomegaly with normal opening pressure; high-volume lumbar tap or external drainage trial predicts shunt response.

Communicating hydrocephalus: obstruction at arachnoid granulations (post-SAH, meningitis); noncommunicating: obstruction within ventricular system (tumor, aqueductal stenosis, colloid cyst).

Shunt types: ventriculoperitoneal (most common), ventriculoatrial (if peritoneal failure or infection), lumboperitoneal, cystoperitoneal; programmable valves allow pressure adjustment noninvasively.

Shunt complications: obstruction, infection (Staphylococcus epidermidis most common, usually within 6 months), overdrainage with slit ventricles and subdural hematoma, disconnection, distal catheter migration.

Endoscopic third ventriculostomy success factors: age >2 years, obstructive hydrocephalus, no prior shunt; failure risk higher in communicating hydrocephalus.

Pseudotumor cerebri (idiopathic intracranial hypertension): obese young women, papilledema, normal CSF composition, elevated opening pressure >25 cm H2O; acetazolamide first-line, optic nerve sheath fenestration or shunt for vision loss.

CSF leak: beta-2 transferrin is confirmatory; traumatic leaks often resolve with conservative measures (head elevation, avoid straining); persistent leaks need repair or lumbar drain.

Slit ventricle syndrome: small ventricles with intermittent shunt obstruction symptoms; management includes antimigraine therapy, valve upgrade, or cranial vault expansion in severe cases.

Carpal tunnel syndrome: median nerve compression; nocturnal symptoms, thenar atrophy, positive Phalen and Tinel tests; EMG/NCS confirm; release of transverse carpal ligament after conservative failure.

Ulnar neuropathy at cubital tunnel: paresthesia in fourth and fifth digits, Froment sign, claw hand; anterior transposition for severe or recurrent cases.

Peroneal neuropathy at fibular neck: foot drop with preserved inversion (tibialis posterior); common after weight loss or leg crossing.

Nerve repair: primary repair for clean transection within days; graft for gaps >2-3 cm (sural nerve); conduits for short gaps; tension-free coaptation is essential.

Brachial plexus: Erb palsy (C5-C6, upper trunk) vs Klumpke (C8-T1, lower trunk); root avulsion shows pseudomeningocele on MRI and negative sensory nerve action potentials with intact sensory potentials.

Pituitary adenoma: transsphenoidal approach is standard; complications include CSF leak, diabetes insipidus, SIADH, hypopituitarism, and carotid injury.

Prolactinoma: dopamine agonist first-line except for resistant or intolerant cases; surgery for apoplexy, visual loss, or CSF leak.

Cushing disease: ACTH-secreting pituitary adenoma; inferior petrosal sinus sampling distinguishes pituitary from ectopic source; remission confirmed by postoperative cortisol suppression.

Acromegaly: IGF-1 and oral glucose tolerance test with GH suppression; transsphenoidal resection first-line; somatostatin analogs and pegvisomant for persistent disease.

Increased ICP management in stepwise order: head elevation, sedation, normocapnia, osmotherapy (mannitol 0.25-1 g/kg or hypertonic saline), CSF drainage, short-term hyperventilation, barbiturate coma, decompressive craniectomy.

Mannitol: osmotic diuretic, monitor osmolarity (<320 mOsm/L) and renal function; hypertonic saline 3% or 23.4% for refractory ICP with volume expansion.

Status epilepticus: benzodiazepine first-line, then phenytoin/fosphenytoin, valproate, or levetiracetam; refractory cases need intubation and continuous infusion (midazolam, propofol, pentobarbital) with EEG monitoring.

Subarachnoid hemorrhage complications: rebleeding (first 24 hours), vasospasm days 3-14, hydrocephalus, hyponatremia (SIADH or cerebral salt wasting; distinguish by volume status).

Venous thromboembolism prophylaxis: mechanical in all neurosurgical patients; pharmacologic (low-molecular-weight heparin) usually after 24-48 hours when hemostasis secure.

Perioperative steroids: dexamethasone for vasogenic edema and tumor surgery; taper promptly; stress-dose steroids for patients with known adrenal insufficiency.

Postoperative hematoma: declining consciousness, new deficit, or pupillary change requires immediate CT and return to theater; epidural hematoma after craniotomy is a surgical emergency.

Sodium disorders: diabetes insipidus (polyuria, dilute urine, hypernatremia) treated with desmopressin; SIADH (euvolemic hyponatremia) treated with fluid restriction.

Seizure prophylaxis after craniotomy: levetiracetam or phenytoin for 7 days in high-risk cases; routine long-term prophylaxis not recommended.

Pterional craniotomy: key landmarks are sylvian fissure, sphenoid wing, and anterior clinoid; approach to anterior circulation aneurysms, suprasellar tumors, and ICA bifurcation.

Sylvian fissure dissection: split from superficial to deep, identify middle cerebral artery branches and lenticulostriate arteries; preserve veins of Labbe and Trolard where possible.

Retrosigmoid approach: transverse and sigmoid sinuses define the craniotomy; access to cerebellopontine angle, CN V-VIII, and foramen magnum lesions; risk to lower cranial nerves.

Transsphenoidal approach: nasal speculum and endoscopic or microscopic; key landmarks are sphenoid ostium, sella floor, and cavernous sinus laterally; avoid carotid injury.

Suboccipital approach to fourth ventricle: midline or paramedian; landmarks include torcula, foramen magnum, and cerebellar tonsils; risk of aseptic meningitis and mutism in children.

Anterior cervical approach: between sternocleidomastoid and carotid sheath, retract trachea and esophagus medially; protect recurrent laryngeal nerve and sympathetic chain.

Prone positioning for spine surgery: free abdomen to reduce venous bleeding; pad pressure points; eyes free of compression to prevent ischemic optic neuropathy.

Hemostasis techniques: bipolar cautery, gelatin sponge, oxidized cellulose, thrombin, and bone wax (sparingly to avoid infection); maintain normotension during closure.

Wound closure: watertight dural closure is essential to prevent CSF leak; multilayer closure for posterior fossa and transsphenoidal approaches.

Informed consent requires capacity, disclosure of diagnosis, proposed treatment, alternatives, and material risks; documented before surgery; emergency exception applies when life-threatening and no surrogate available.

Brain death determination: irreversible coma with known cause, absent brainstem reflexes, apnea test with PaCO2 rise to >=60 mmHg (or 20 mmHg above baseline), no confounding drugs or hypothermia.

Confidentiality: disclose only with patient consent or legal mandate; exceptions include reportable communicable disease and imminent harm to identifiable others.

Conflict of interest: disclose financial relationships with industry; research participation requires ethics committee approval and separate consent.

Medical error disclosure: inform the patient of harmful errors; apology and explanation are ethically required and increasingly legally protected.

Capacity assessment: patient must understand, appreciate, reason, and express a choice; delirium, severe depression, and cognitive impairment may impair capacity.

End-of-life care: advance directives and surrogate decision-makers guide withdrawal of life-sustaining therapy; palliative care should be integrated early in poor-prognosis neurosurgical disease.

Resource allocation and triage: use validated prognostic scores (e.g., WFNS, GCS, APACHE) transparently; avoid discriminatory criteria; document decisions.

Research ethics: Institutional Review Board approval, equipoise, and voluntary participation; vulnerable populations require additional safeguards.