The Neurologic Examination
A range of clinical conditions may necessitate a neurological examination, especially injury to the head, neck, or spine. A mental status examination (consciousness, speech, understanding commands) are part of the examination, as are tests of motor and sensory systems, the cerebellum, and muscle stretch reflexes. The olfactory nerve (CN I) is rarely tested because it may be affected by smoking, sinus disease, or trauma. The optic nerve (CN II) is tested by assessing visual acuity, visual fields (hemifields, quadrants) peripheral, and central vision. Eye movements, CNs III, IV, and VI, are evaluated by having the patient look up, down, to the right, and to the left. Shining a light into the eye also tests the pupillary light reflex. Sensation on the face and forehead, on the cornea, in the oral cavity, and movements of the muscles of mastication indicate the integrity of CN V. This includes the afferent limb of the corneal reflex (efferents via CN VII) and the jaw jerk reflex. Asking the patient to smile or wrinkle the forehead tests CN VII; this includes the efferent limb of the corneal reflex. Auditory stimuli provide a test for CN VIII and will localize laterality, degree of loss, and possible lesion location. CNs IX and X are usually tested together; the deficits seen may include dysarthria, dysphagia, loss of gag reflex, and uvular deviation. Inability to elevate the shoulder against resistance would indicate CN XI dysfunction, and deviation of the tongue on protrusion would signify damage to CN XII.