Overview of the Neurological Exam

Core Concepts

The exam as a series of pathway probes

Each component tests a specific neural pathway, and each result is meaningful only in combination with others:

• The mental status exam probes circuits of the cerebral cortex (especially association areas).
• The cranial nerve exam probes the brainstem and the nerves emerging from it — vision, eye movements, facial expression and sensation, hearing, swallowing, tongue movement.
• The sensory exam probes receptors, peripheral nerves, spinal tracts (dorsal column–medial lemniscus for touch/proprioception/vibration; spinothalamic for pain and temperature), and somatosensory cortex.
• The motor exam probes lower motor neurons (ventral horn cells and cranial nerve nuclei), the corticospinal (upper motor neuron) pathway, and cerebellar coordination.
• The coordination and gait exams probe the cerebellum, basal ganglia, proprioception, and vestibular input.

A "normal" result tells you an entire pathway is functioning — just as informative as a deficit.

Localization: the core reasoning skill

• Contralateral motor findings: the motor cortex and corticospinal tract control the opposite side (most fibers decussate in the medulla). Right-sided weakness → left hemisphere lesion.
• Cranial nerve findings: most cranial nerve innervation is ipsilateral, so a one-sided facial weakness points to the ipsilateral facial nerve or its nucleus.
• Reflex findings: a normal reflex requires an intact receptor, sensory nerve, spinal segment, motor nerve, and muscle. An absent reflex with preserved strength suggests a break in the arc; exaggerated reflexes suggest loss of descending (upper motor neuron) inhibition.
• Sensory patterns: a deficit confined to one nerve's territory points to that nerve; a "glove-and-stocking" distal numbness points to widespread peripheral neuropathy; loss of pain/temperature on one side with preserved touch suggests a spinal cord hemisection (the classic Brown-Séquard pattern taught in neurology).

The exam is a hypothesis test: each finding supports or refutes candidate localizations until a consistent picture emerges.

Symmetry: focal versus diffuse

Findings are interpreted by comparison — right versus left, and patient versus expected baseline:

• Asymmetric findings (one side weak, one reflex brisk) suggest a focal lesion — stroke, tumor, or nerve injury.
• Symmetric findings suggest a diffuse or systemic process — metabolic disturbance, generalized neuropathy, medication effect.

This is one of the first forks in clinical reasoning: focal → image the nervous system; diffuse → look for systemic causes.

Upper motor neuron versus lower motor neuron signs

• UMN signs (motor cortex or corticospinal tract lesion): weakness, increased tone (spasticity), exaggerated reflexes (hyperreflexia), and the Babinski sign — a commonly taught finding in which stroking the sole produces extension (fanning) of the toes instead of normal curling. These reflect loss of descending inhibition.
• LMN signs (ventral horn cell or axon lesion): weakness, decreased tone (flaccidity), decreased or absent reflexes (hyporeflexia), and muscle atrophy.

These are standard teaching concepts; in practice, findings vary with lesion location, timing, and examiner technique, and interpretation is the clinician's responsibility.

Tools and technique

The exam needs little equipment: a reflex hammer, tuning fork (vibration), penlight, cotton wisp and pin (light touch and sharp sensation), and an ophthalmoscope for the cranial nerve exam. A quiet room, clear instructions, and patient cooperation matter. The exam is safe and repeatable, and findings are documented descriptively (e.g., "5/5 strength on the right, 3/5 on the left" using commonly taught grading scales) so trends can be tracked.

Common Confusions