ABNS Neurological Surgery cheat sheet

Glasgow Coma Scale: eye 1-4, verbal 1-5, motor 1-6; total 3-15; severe TBI defined as GCS ≤8 after resuscitation.

Pupillary light reflex and GCS motor score are the strongest early prognosticators in severe TBI.

Monro-Kellie doctrine: intracranial volume = brain + blood + CSF + mass; compensation fails as each compartment is exhausted.

CPP = MAP − ICP; typical ICP target <22 mmHg and CPP target 60-70 mmHg in adult severe TBI.

Epidural hematoma: biconvex, arterial (middle meningeal), often lucid interval; subdural: crescentic, venous bridging veins.

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

Cushing reflex (hypertension, bradycardia, irregular respiration) signals impending herniation.

Hypertonic saline and mannitol reduce ICP by osmotic gradient; mannitol requires adequate renal function and euvolemia.

Prophylactic phenytoin/levetiracetam reduces early (≤7 days) posttraumatic seizures but not late epilepsy.

Subarachnoid hemorrhage: CT sensitivity highest within 6 hours; xanthochromia in CSF if CT negative after 6-12 hours.

Hunt-Hess and World Federation of Neurosurgical Societies grades predict outcome after aneurysmal SAH.

Aneurysm risk factors: smoking, hypertension, ADPKD, connective tissue disease, family history; size and location drive rupture risk.

Vasospasm peaks days 4-14 after SAH; nimodipine improves outcome though it does not reverse angiographic spasm.

ACom aneurysms threaten recurrent artery of Heubner and perforators; MCA bifurcation aneurysms threaten lenticulostriate and temporal branches.

Arteriovenous malformation annual hemorrhage risk roughly 2-4%; Spetzler-Martin grade (size, eloquence, venous drainage) guides operability.

Moyamoya disease: progressive ICA stenosis with basal collaterals; direct or indirect bypass for ischemic presentations.

Carotid endarterectomy benefits symptomatic high-grade stenosis most within 2 weeks of the index event.

ICH: lobar (amyloid, elderly) versus deep (hypertensive: putamen, thalamus, pons, cerebellum).

Glioblastoma: IDH-wildtype, MGMT promoter methylation predicts temozolomide benefit; standard is resection plus radiation and temozolomide.

1p/19q codeletion with IDH mutation defines oligodendroglioma and predicts chemosensitivity and better survival.

Meningioma: extra-axial, dural tail, hyperostosis; WHO grade and Simpson grade of resection predict recurrence.

Brain metastases: gray-white junction, ring-enhancing; stereotactic radiosurgery for limited lesions, whole-brain radiation for diffuse disease.

Primary CNS lymphoma: periventricular enhancing mass, highly steroid-responsive; biopsy before steroids to avoid obscuring diagnosis.

Medulloblastoma: posterior fossa midline mass in children; drop metastases via CSF; treatment includes resection, craniospinal radiation, chemotherapy.

Pilocytic astrocytoma: cystic with mural nodule, BRAF alterations, WHO grade 1, excellent prognosis after gross total resection.

Cerebellopontine angle tumors: vestibular schwannoma (widened IAC), meningioma, epidermoid (restricted diffusion).

Pituitary adenoma: bitemporal hemianopsia from optic chiasm compression; prolactinoma treated first with dopamine agonists.

Cauda equina syndrome: saddle anesthesia, bowel/bladder dysfunction, bilateral leg pain; surgical emergency requiring urgent decompression.

Cervical spondylotic myelopathy: hand clumsiness, gait spasticity, hyperreflexia, Hoffmann sign; MRI shows cord compression.

Dermatomes: C6 thumb, C7 middle finger, L4 medial leg, L5 dorsum of foot, S1 lateral foot.

Lumbar disc herniation: L4-L5 affects L5 root, L5-S1 affects S1 root; 90% improve with conservative care.

Carpal tunnel syndrome: median nerve, nocturnal paresthesias in thumb-index-middle digits, thenar atrophy; Phalen and Tinel signs.

Ulnar neuropathy at cubital tunnel: ring and small finger numbness, interosseous wasting, claw hand.

Odontoid fracture types: I (tip), II (base, unstable, often needs fixation), III (into body, usually stable in halo).

Hangman fracture: bilateral C2 pars injury from hyperextension; Jefferson fracture: C1 ring burst from axial load.

Myelomeningocele: neural placode exposed; risk of Chiari II malformation and hydrocephalus; close within 24-48 hours.

Chiari II: small posterior fossa, tonsillar and vermian herniation, tectal beaking, associated with myelomeningocele.

Chiari I: tonsillar descent >5 mm below foramen magnum; syrinx and cough headache; posterior fossa decompression if symptomatic.

Craniosynostosis: scaphocephaly (sagittal), trigonocephaly (metopic), plagiocephaly (unicoronal), brachycephaly (bicoronal).

Dandy-Walker malformation: cystic fourth ventricle, cerebellar vermis hypoplasia, hydrocephalus.

Vein of Galen malformation: high-output heart failure and hydrocephalus in neonates; staged endovascular embolization.

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

Tethered cord: conus below L2, fatty filum or lipoma; presents with leg weakness, scoliosis, bladder dysfunction.

Shunt infection most commonly involves Staphylococcus epidermidis; presents with fever, wound erythema, and shunt malfunction signs.

Deep brain stimulation of subthalamic nucleus improves motor fluctuations in Parkinson disease; GPi targets dystonia.

DBS programming: monopolar versus bipolar stimulation, contact selection, amplitude, pulse width, and frequency titration.

Essential tremor: ventral intermediate thalamus is the preferred DBS target and radiosurgery target.

Trigeminal neuralgia: carbamazepine first-line; microvascular decompression for neurovascular conflict, percutaneous rhizotomy for elderly.

Stereotactic frames: Leksell frame with arc and ring angles; accuracy depends on fiducial registration and imaging.

Radiofrequency lesioning versus DBS: lesioning is irreversible but avoids hardware; DBS is adjustable and reversible.

Pallidotomy and thalamotomy remain options when DBS is contraindicated or unavailable.

Spasticity management: intrathecal baclofen, selective dorsal rhizotomy, and botulinum toxin for focal spasticity.

Temporal lobe epilepsy with hippocampal sclerosis: anterior temporal lobectomy yields the best seizure-freedom rates.

Presurgical evaluation: semiology, scalp EEG, MRI, neuropsychology, and video-EEG monitoring; invasive monitoring if nonlocalizing.

Wada test assesses language and memory lateralization before dominant temporal resection.

Corpus callosotomy is palliative, reducing drop attacks in Lennox-Gastaut syndrome.

Hemispherotomy for Rasmussen encephalitis, Sturge-Weber, and hemimegalencephaly in selected children.

Vagus nerve stimulation and responsive neurostimulation are palliative options for multifocal or unresectable epilepsy.

Seizure semiology: temporal lobe shows automatisms and déjà vu; frontal lobe shows brief nocturnal hypermotor events.

MRI findings: hippocampal atrophy with T2 hyperintensity, focal cortical dysplasia, cavernoma, and tumor.

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

Communicating hydrocephalus: enlarged ventricles with open fourth ventricle; noncommunicating: obstruction proximal to fourth ventricle.

CSF production ~500 mL/day by choroid plexus; total volume ~150 mL; turnover several times daily.

Shunt types: ventriculoperitoneal, ventriculoatrial, ventriculopleural; programmable valves adjust opening pressure noninvasively.

Shunt malfunction: headache, vomiting, lethargy; slit ventricles or enlarged ventricles on imaging; tap shunt to assess flow.

Endoscopic third ventriculostomy treats obstructive hydrocephalus (aqueductal stenosis, tectal tumor) by creating a stoma in the third ventricle floor.

Pseudotumor cerebri: elevated opening pressure with normal CSF and imaging; papilledema and headache; acetazolamide and weight loss.

Overdrainage causes subdural hematoma, slit ventricle syndrome, and orthostatic headache.

Vestibular schwannoma: sensorineural hearing loss, tinnitus, disequilibrium; MRI shows enhancing mass widening the internal auditory canal.

Facial nerve: upper face receives bilateral cortical innervation; lower face unilateral, so forehead sparing suggests central lesion.

Cavernous sinus contents: CN III, IV, V1, V2, VI, internal carotid artery, and sympathetic fibers; CN VI is most medial.

Jugular foramen syndrome: CN IX, X, XI deficits from glomus jugulare, schwannoma, or meningioma.

Acoustic neuroma treatment: observation, stereotactic radiosurgery for small tumors, microsurgery for large tumors or brainstem compression.

Cerebellopontine angle approach options: retrosigmoid, translabyrinthine, and middle fossa, chosen by hearing status and tumor size.

Pituitary apoplexy: sudden headache, visual loss, ophthalmoplegia, and adrenal crisis; urgent steroids and decompression.

Glossopharyngeal neuralgia: severe throat pain triggered by swallowing; microvascular decompression of CN IX.

Status epilepticus: benzodiazepine first-line, then second-line antiseizure drug; refractory requires intubation and continuous infusion.

Targeted temperature management after cardiac arrest: 32-36 °C for at least 24 hours with controlled rewarming.

Hyperventilation reduces PaCO2 and cerebral blood flow transiently; reserve for acute herniation.

Sodium target in neurocritical care: avoid hyponatremia; hypertonic saline for symptomatic hyponatremia and cerebral edema.

Cerebral salt wasting versus SIADH: both cause hyponatremia; volume status distinguishes them (hypovolemia versus euvolemia).

Propofol infusion syndrome: metabolic acidosis, rhabdomyolysis, arrhythmia; limit high-dose prolonged infusions.

Total intravenous anesthesia with propofol or dexmedetomidine supports evoked potential monitoring; volatile agents suppress signals.

Antithrombotic reversal: prothrombin complex concentrate for warfarin, idarucizumab for dabigatran, andexanet for factor Xa inhibitors.

CT hyperdensity: acute blood, calcification, bone, and contrast; hypodensity: edema, ischemia, air.

Ischemic stroke CT early signs: loss of insular ribbon, dense MCA sign, sulcal effacement; MRI diffusion is most sensitive acutely.

MR sequences: T1 dark CSF, T2 bright CSF; FLAIR suppresses CSF; DWI detects restricted diffusion; GRE/SWI detects blood.

Ring-enhancing lesion differential: abscess, glioblastoma, metastasis, toxoplasmosis, demyelination.

Angiography: digital subtraction angiography remains the reference standard for vascular lesions and vasospasm.

EEG: periodic lateralized discharges suggest herpes encephalitis or structural lesion; burst suppression guides treatment of refractory status.

Myelography and CT myelography localize CSF leaks and nerve root compression when MRI is contraindicated.

Perfusion imaging: increased CBV in tumor, reduced CBV in radiation necrosis; MR spectroscopy choline-to-NAA ratio rises in tumor.

Cerebral blood flow ~50 mL/100 g/min; EEG slows below 20 and isoelectric below 10-15 mL/100 g/min.

Autoregulation maintains constant cerebral blood flow between MAP ~60 and 150 mmHg; impaired in trauma and ischemia.

Cerebral perfusion depends on PaCO2 (potent vasodilator) and PaO2; hypoxemia increases flow, hypocapnia decreases it.

Blood-brain barrier: tight junctions at endothelial cells, astrocyte foot processes; circumventricular organs lack a barrier.

Cranial nerve nuclei: CN III-IV in midbrain, V-VIII in pons, IX-XII in medulla; lower motor neuron lesions cause ipsilateral deficits.

Dopamine pathways: nigrostriatal (motor), mesolimbic and mesocortical (reward, psychosis), tuberoinfundibular (prolactin inhibition).

Neurotransmitter glutamate is the main excitatory transmitter; excitotoxicity via NMDA receptors drives secondary injury.

Cerebral edema types: cytotoxic (intracellular, ischemia), vasogenic (blood-brain barrier breakdown, tumor), interstitial (hydrocephalus).