Neuro-ophthalmology and Neuro-otology: Anatomy of Vision and Balance
Use bedside physiology to separate central from peripheral
These items test whether you can localize with a penlight, a reflex hammer, and simple positioning maneuvers.
Pupils and vision. An afferent pupillary defect indicates optic nerve dysfunction. Horner syndrome gives ipsilateral ptosis and miosis, with anhidrosis only in first-order lesions; add neck pain and consider carotid dissection. Argyll Robertson pupils (small, irregular, light-near dissociation) suggest neurosyphilis. A painful third nerve palsy with a dilated pupil suggests a posterior communicating artery aneurysm. Papilledema from raised intracranial pressure may spare the blind spot and central vision while enlarging the blind spot and producing transient visual obscurations. Painless loss of vision with an altitudinal field defect suggests ischemic optic neuropathy rather than optic neuritis, which is painful with eye movement and shows an afferent pupillary defect.
Eye movements. Internuclear ophthalmoplegia shows impaired adduction on the affected side with nystagmus of the abducting eye, reflecting a medial longitudinal fasciculus lesion; bilateral internuclear ophthalmoplegia in a young patient suggests multiple sclerosis. Parinaud syndrome means upgaze palsy, convergence retraction nystagmus, and lid retraction from dorsal midbrain compression.
Vertigo. The HINTS examination identifies central vertigo: a normal head impulse test, direction-changing nystagmus, and skew deviation each point centrally. Benign paroxysmal positional vertigo produces brief positional vertigo with a torsional upbeating nystagmus on Dix-Hallpike testing, treated with canalith repositioning. Vestibular neuritis causes prolonged spontaneous vertigo with nausea and an abnormal head impulse test without hearing loss. Meniere disease gives episodic vertigo with fluctuating hearing loss, tinnitus, and aural fullness.
Rule of thumb: any vertical or direction-changing nystagmus, or normal head impulse in acute vertigo, means image the brain.
Child Neurology: Development as the Baseline
Everything is measured against expected milestones
Pediatric items depend on knowing what a child should be doing at each age, and on separating static injury from progressive disease.
Development. Head control by about 2 to 3 months, sitting by 6 to 8 months, walking by 12 to 15 months, two-word phrases by about 2 years. Regression in achieved milestones, especially language, demands evaluation for epilepsy syndromes, metabolic disease, and leukodystrophy.
Hypotonia. Peripheral hypotonia comes with absent or reduced reflexes and weakness, as in spinal muscular atrophy (SMN1 deletion, tongue fasciculations) or congenital myopathy. Central hypotonia comes with preserved reflexes, normal strength, and often developmental delay, as in cerebral palsy. Cerebral palsy is a static encephalopathy with motor deficits from early injury; a new deficit later in childhood is not cerebral palsy until proven otherwise.
Epilepsy syndromes. Infantile spasms with hypsarrhythmia requires urgent treatment (adrenocorticotropic hormone or vigabatrin) because delay worsens cognitive outcome. Dravet syndrome begins in infancy with prolonged febrile seizures and later cognitive decline from SCN1A mutation; sodium channel blockers such as carbamazepine worsen it. Childhood absence epilepsy responds to ethosuximide.
Neurocutaneous syndromes. Neurofibromatosis type 1 shows cafe-au-lait macules, axillary freckling, neurofibromas, optic pathway glioma, and Lisch nodules. Tuberous sclerosis shows hypopigmented macules, facial angiofibromas, cortical tubers, and subependymal giant cell astrocytoma. Sturge-Weber syndrome pairs a facial port-wine nevus with ipsilateral leptomeningeal angioma. Leukodystrophies such as metachromatic leukodystrophy and X-linked adrenoleukodystrophy are progressive white matter diseases.
Traps: simple febrile seizures last under 15 minutes and do not recur in the same illness; meningitis can present with seizure and fever and must be excluded.
Rule of thumb: hypotonia with areflexia points peripheral, hypotonia with brisk reflexes points central.
Neurotrauma: Protect the Brain Before the Brain Herniates
Physiology drives every management decision
Trauma questions test the Monro-Kellie concept and the consequences of failing to control intracranial pressure.
Assessment. The Glasgow Coma Scale scores eye, verbal, and motor responses; the motor component carries the greatest prognostic weight. Apply validated imaging decision rules for minor head injury, and never defer imaging when there is a focal deficit, seizure, vomiting, anticoagulation, or a dangerously declining level of consciousness. Cushing triad of hypertension, bradycardia, and irregular respirations signals raised intracranial pressure and impending herniation, often with an ipsilateral dilated pupil reflecting uncal herniation.
Lesion patterns. Epidural hematoma is biconvex and arterial, often from middle meningeal artery injury, with a classic lucid interval. Subdural hematoma is crescentic and venous, more common in older patients and with anticoagulation. Subarachnoid hemorrhage from trauma follows the sulci. Diffuse axonal injury produces punctate white matter lesions at gray-white junctions and the corpus callosum with immediate coma. Concussion is a functional, not structural, injury; management is graded return to activity with cognitive rest and no same-day return to play.
ICU physiology. Cerebral perfusion pressure equals mean arterial pressure minus intracranial pressure; target roughly 60 to 70 mmHg while preventing hypotension and hypoxia, both of which worsen outcome. Hyperventilation is a short-term bridge for herniation, not a maintenance therapy.
Spinal cord. Spinal shock refers to transient flaccid areflexia after injury; neurogenic shock refers to hypotension with bradycardia from sympathetic loss. Central cord syndrome affects the upper extremities more than lower.
Rule of thumb: cerebral perfusion pressure equals mean arterial pressure minus intracranial pressure, and hypotension plus hypoxia predict worse outcome than the initial CT.
Toxic, Metabolic, and Nutritional Disorders: Reversible Causes First
Search for the deficiency, the toxin, and the rate of correction
These items reward remembering that many severe encephalopathies are reversible if treated before the window closes.
Nutritional. Wernicke encephalopathy causes confusion, ophthalmoplegia, nystagmus, and ataxia; give intravenous thiamine before glucose to avoid precipitating or worsening it. Korsakoff syndrome leaves persistent amnesia with confabulation after mammillary body and thalamic injury. Vitamin B12 deficiency causes subacute combined degeneration with dorsal column and corticospinal signs plus macrocytic anemia; copper deficiency produces a similar myeloneuropathy. Vitamin E deficiency causes spinocerebellar syndrome with neuropathy.
Metabolic. Hepatic encephalopathy causes asterixis, altered sleep pattern, and elevated ammonia. Uremia produces asterixis, myoclonus, and seizures. Hypoglycemia can mimic stroke or status epilepticus. Correcting chronic hyponatremia too quickly risks osmotic demyelination with quadriparesis and pseudobulbar affect. Hyperglycemia can produce chorea and nonketotic hyperosmolar encephalopathy.
Toxins. Carbon monoxide poisoning produces bilateral globus pallidus lesions and delayed neuropsychiatric deterioration; treat with high-flow oxygen and consider hyperbaric therapy. Methanol produces putaminal necrosis and visual loss; ethylene glycol produces oxalate crystals and basal ganglia injury. Organophosphate poisoning produces cholinergic excess (salivation, lacrimation, urination, diarrhea, bronchorrhea, bradycardia, miosis) treated with atropine and pralidoxime. Lead causes encephalopathy in children and wrist drop in adults.
Drug syndromes. Serotonin syndrome shows clonus, hyperreflexia, and agitation; anticholinergic toxicity shows dry skin with flushing and delirium; opioid toxicity shows pinpoint pupils and respiratory depression.
Rule of thumb: give thiamine before dextrose in any malnourished or alcoholic patient with altered mental status.