Pathophysiology
Clinical meaning
The comprehensive neurological examination systematically evaluates the functional integrity of the nervous system from cortex to peripheral nerve, with each component designed to localize pathology to a specific anatomical level. Mental status testing (orientation, attention, memory, language, visuospatial function) evaluates cerebral cortical function — the Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) provide standardized screening. Cranial nerve examination tests brainstem function: CN II (visual acuity, fields, pupillary light reflex testing the afferent limb via the optic nerve and efferent limb via CN III parasympathetics), CN III/IV/VI (extraocular movements — CN III palsy produces ptosis, mydriasis, and 'down and out' eye position from unopposed lateral rectus and superior oblique), CN V (facial sensation and masseter strength), CN VII (facial motor — upper motor neuron lesion spares the forehead due to bilateral cortical innervation, while lower motor neuron lesion affects the entire hemiface), CN VIII (hearing — Weber lateralizes to the affected ear in conductive loss, to the unaffected ear in sensorineural loss), CN IX/X (gag reflex, palate elevation), CN XI (trapezius and sternocleidomastoid strength), and CN XII (tongue protrusion...