Cranial Nerve Damage From Head Trauma

There are a total of 12 cranial nerves. These nerves exit from the base of the brain, and run through different parts of the face and head. The cranial nerves perform essential functions from providing sensation and controlling facial movements, to initiating protective reflexes.

The cranial nerves are vulnerable during head trauma because many of them run over the surface of the skull and are only protected by the muscles and tissues of the face. Penetrating, scraping and shearing injuries can stretch, rupture or cut across a cranial nerve. Broken facial and skull bones can also damage the nerves. The effects of cranial nerve injury may be temporary or permanent, depending on the nature of the injury.

Cranial Nerve Functions

Since the cranial nerves control observable activities such as moving the eyes, chewing and smiling, damage can be seen and felt when the nerve’s associated function is altered. Here is what the 12 cranial nerves do, and what might be lost if the nerve is injured:

I Olfactory: provides the sense of smell

II Optic: communicates visual information from the eye to the brain

III Oculomotor: controls numerous movements of the eyes and the eyelids; also controls the size of the pupils in response to light.

IV Trochlear: controls the movement of the eyes downward and inward toward the nose

V Trigeminal: communicates the sensation of touch to the face; also controls the chewing muscles

VI Abducens: controls the horizontal movement of the eyeball

VII Facial: moves the muscles that create facial expressions; provides the sense of taste to the front two-thirds of the tongue.

VIII Auditory-vestibular: provides the sense of hearing, and also communicates information about the body’s position in space to the brain.

IX Glossopharyngeal: controls throat muscles, salivary glands, and provides taste information from the back third of the tongue; senses changes to blood pressure and communicates that to the brain so it can respond.

X Vagus: controls the heart, lungs and abdominal organs

XI Spinal Accessory: controls throat and neck muscles.

XII Hypoglossal: moves the tongue and enables speech

It’s clear that these nerves control essential functions of the head, face, and neck. While sometimes the damage is noticeable right away, it can also take hours to days for a disability to manifest. For example, if there is a growing blood clot pressing on a cranial nerve and the nerve begins to die, this can take some time to show up. 

What Does Damage Look Like?

One of the most commonly damaged nerves during head trauma is Cranial Nerve I, the olfactory nerve. Damage to this nerve not only affects the sense of smell but also the ability to taste food since smell is an important component of taste.

If the facial nerve is damaged, cranial nerve VII, one side of the face will not be able to make expressions, and taste may be altered. Damage to this nerve is distressing because impairs one of our most relied upon forms of expression, and also affects one’s self-image.

The optic nerve, cranial nerve II, can be damaged by skull fractures. If sheared, it leads to permanent blindness in the affected eye.

These are just a few examples. Each nerve exhibits unique symptoms after injury.

Treatment

If a cranial nerve is completely cut in two, it cannot be repaired. However, if it is stretched or bruised but the nerve remains intact, it can recover. This takes time and can cause a variety of unpleasant symptoms including tingling and pain. These symptoms are a good sign that the nerve is healing.

Steroids may be used to decrease inflammation around a cranial nerve. Surgery is sometimes needed if a collection of blood, called a hematoma, is squeezing the nerve and leading to paralysis or dysfunction.

Neurologists and neurosurgeons have specialized assessments and interventions that address this type of nerve damage and should be consulted.