neurologic disorders
How to Assess the Cranial Nerves
3rd, 4th, and 6th Cranial nerves
For the 3rd (ocolomotor), 4th (trochlear), and 6th (abducens) cranial nerves, eyes are observed for symmetry of movement, globe position, asymmetry or droop of the eyelids (ptosis), and twitches or flutters of globes or lids. Extraocular movements controlled by these nerves are tested by asking the patient to follow a moving target (eg, examiner’s finger, penlight) to all 4 quadrants (including across the midline) and toward the tip of the nose; this test can detect nystagmus and palsies of ocular muscles. Brief fine amplitude nystagmus at end-lateral gaze is normal. Anisocoria or differences in pupillary size should be noted in a dimly lit room. The pupillary light response is tested for symmetry and briskness. 