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 — deviates toward the side of the lesion in LMN lesion). Motor examination evaluates strength (MRC 0-5 scale), tone (spasticity indicates UMN lesion; flaccidity indicates LMN), and bulk (atrophy suggests LMN or disuse). Deep tendon reflexes are graded 0-4+: hyperreflexia with clonus and upgoing plantar response (Babinski sign) localizes to UMN pathology (corticospinal tract); hyporeflexia or areflexia indicates LMN, peripheral nerve, or neuromuscular junction pathology. Sensory examination tests the two major ascending systems: light touch and proprioception (dorsal column-medial lemniscus pathway) and pain/temperature (spinothalamic tract) — dissociated sensory loss (one modality preserved while another is lost) localizes lesions precisely (e.g., Brown-Séquard syndrome in hemisection of the spinal cord produces ipsilateral loss of proprioception and vibration with contralateral loss of pain and temperature below the lesion). Cerebellar testing (finger-to-nose, heel-to-shin, rapid alternating movements, Romberg test, gait assessment) evaluates coordination and balance — cerebellar lesions produce ipsilateral ataxia, dysmetria, intention tremor, and dysdiadochokinesia.