Cranial Nerves Overview

The sensation of smell. It can be tested by having the patient identify a familiar odor, such as coffee or peppermint, while one nostril is occluded.

The inability to smell. This can be caused by several factors, including head trauma, brain lesions, or blocked nasal passages.

A loss of smell on one side of the nose, possibly due to a blockage or neurological issue affecting the olfactory nerve.

A loss of smell caused by damage to the olfactory nerve itself, rather than a blockage or other issue.

The ability to see. It can be tested by measuring visual acuity and visual fields.

A test of visual fields using confrontation. The examiner compares their own visual field to that of the patient.

The normal appearance of the optic disc, as seen through an ophthalmoscope.

Swelling of the optic disc, which can be caused by increased intracranial pressure. It can be seen through an ophthalmoscope.

A degeneration of the optic nerve, which can lead to vision loss. It can be seen through an ophthalmoscope.

Drooping of the eyelid, often caused by weakness of the levator palpebrae superioris muscle, controlled by the oculomotor nerve.

A syndrome characterized by a constricted pupil, drooping eyelid (ptosis), and decreased sweating on the affected side of the face. It is often caused by damage to the sympathetic nervous system.

Dilation or widening of the pupil. It can be caused by various factors, including medications, injury, and neurological conditions.

The ability of the eyes to move in different directions. It is tested by assessing the movement of the eyes following an object or light.

The third, fourth, and sixth cranial nerves which control eye movements and pupillary reflexes.

The width of the eyelid opening. They should be equal in a normal examination.

The round opening in the center of the iris. They should be equal in size and shape.

The ability of the pupil to constrict when exposed to light. It is tested by shining a light into each eye and observing the pupil's reaction.

The ability of the pupil to constrict when focusing on a near object. It is tested by having the patient focus on a distant object and then a near object.

The seventh cranial nerve, which controls facial expressions and taste sensation. It can be tested by assessing facial mobility, symmetry, and light touch sensation.

The sense of touch. It can be tested by lightly touching different areas of the face with a cotton swab.

The ability to smile, frown, close eyes, lift eyebrows, show teeth, and puff cheeks. These actions test the motor function of the facial nerve.

Weakness or paralysis of one side of the face, which can be caused by damage to the facial nerve. It can lead to difficulty with facial movements.

The twelfth cranial nerve, which controls tongue movements and speech. It can be tested by observing the tongue for wasting, tremors, and deviation, and by assessing lingual speech.

A loss of muscle mass, which can occur in the tongue due to disuse, injury, or neurological conditions affecting the hypoglossal nerve.

Involuntary twitching of muscle fibers, which can be seen in the tongue due to neurological conditions affecting the hypoglossal nerve.

Deviation of the tongue to one side when it is protruded, which can be caused by weakness or paralysis of the hypoglossal nerve on that side.

Increased size and strength of a muscle, which can occur in the tongue due to overuse or certain medical conditions.

Diminished or absent strength in the tongue muscles, which can be caused by damage to the hypoglossal nerve. It can lead to difficulty with speech and swallowing.

The fifth cranial nerve, which controls the muscles of mastication, sensation of the face, and certain reflexes.

The muscles involved in chewing, such as the masseter and temporalis muscles.

The strength of the muscles of mastication, which can be tested by palpating the muscles while the patient clenches their teeth.

The ability to move the jaw in different directions, which can be tested by having the patient open and close their mouth and move their jaw side-to-side.