Nervous System and Special Senses
Localization
Upper motor neuron lesions cause spasticity, hyperreflexia, and an upgoing plantar response; lower motor neuron lesions cause flaccidity, atrophy, fasciculations, and areflexia. Broca aphasia is nonfluent with preserved comprehension; Wernicke aphasia is fluent with poor comprehension. A third-nerve palsy with a fixed dilated pupil suggests compression (for example, aneurysm), while pupil sparing suggests ischemia. Horner syndrome is ptosis, miosis, and anhidrosis.
Vascular and infectious disease
Middle cerebral artery stroke: contralateral face and arm weakness greater than leg, with aphasia if dominant. Anterior cerebral artery: leg greater than arm. Posterior cerebral artery: contralateral homonymous hemianopia. Basilar: coma, quadriparesis, pinpoint pupils. Epidural hematoma: middle meningeal artery, lucid interval, lens-shaped. Subdural: bridging veins, crescent-shaped, in the elderly. Subarachnoid hemorrhage: thunderclap headache with xanthochromia. Meningitis CSF distinguishes bacterial (neutrophils, low glucose, high protein) from viral and tuberculous or fungal patterns.
Neuromuscular and degenerative disease
Guillain-Barré: ascending symmetric weakness with areflexia and albuminocytologic dissociation; monitor respiratory capacity. Myasthenia gravis: fatigable weakness, ptosis, anti-acetylcholine receptor antibodies. Amyotrophic lateral sclerosis: combined upper and lower motor neuron signs with sensory sparing. Parkinson disease: resting tremor, rigidity, bradykinesia. Alzheimer disease: memory loss first. Multiple sclerosis: relapsing-remitting course, optic neuritis, periventricular plaques, oligoclonal bands.
Special senses
Acute angle-closure glaucoma: painful red eye, mid-dilated fixed pupil, halos, urgently lower intraocular pressure. Central retinal artery occlusion: sudden painless monocular vision loss with a pale retina and cherry-red macula. Papilledema: bilateral disc swelling from raised intracranial pressure.
Rule of thumb
Weakness worse in the leg than the arm suggests an anterior cerebral artery lesion; arm and face worse than the leg suggests middle cerebral artery.