Trigeminal Palsy

Definition

The trigeminal nerve is one of the most important nerves in the human body. It is counted among the so-called brain nerves. These are characterized by the fact that they all originate directly from the brain stem.

The main task of the trigeminal nerve is, in addition to the nervous supply (innervation) of the masticatory muscles, above all the perception of sensations in the facial region (sensitivity). These functions can be lost due to paralysis (paresis) of the nerve, as may be the case with trigeminal paresis. The causes for such a functional failure can be very different.

Causes

There are various causes that can lead to paralysis of the trigeminal nerve. These include inflammation, a mass or pressure increase in the brain, and injury to the nerve as a result of an accident. In this context, a distinction must be made between a central and a peripheral lesion.

Depending on the location of the injury, different failures are the result. Since the trigeminal nerve is counted among the cranial nerves, it has its origin in the brain stem. Here it originates from so-called cranial nerve nuclei, which are responsible for the various functions of the nerve, such as sensitivity or motor functions.

If one of these nuclei fails due to an injury or because it is displaced, for example by a tumor, specific failures can occur. This can lead to a loss of sensitivity in the face without the movement of the masticatory muscles being restricted. Peripheral injuries of the trigeminal nerve and its branches are, however, much more common.

It is important to know that the nerve is divided into three main branches. These nerve branches can be injured more quickly in an accident and then cause a disturbance of sensitivity in only a certain area of the face. Another cause that can lead to trigeminal paresis is trigeminal neurinoma, a benign tumor of the nerve sheath.

Diagnosis

Since trigeminal nerve palsy causes very specific deficits in facial sensitivity and motor function, diagnosis is relatively easy. Patients often initially report facial sensitivity deficits, which is the reason for a presentation to the doctor. Now it is first necessary to distinguish whether there is a central injury to the nerve in the area of the brain stem or whether only individual nerve branches show a loss of function.

For this purpose, the physician checks the sensitivity in the entire face and the function of the masticatory muscles. If only one branch of the nerve is affected, for example, the loss of sensitivity only occurs in the area of the forehead or lower jaw. On the other hand, if there is a central injury to the nerve or its nuclei, the pattern of failures is different from that of a peripheral injury.

The loss of sensitivity then follows the so-called Sölder lines. As a rule, an MRI (magnetic resonance imaging) should also be performed to rule out further injuries or causes. It is also important to differentiate between this and trigeminal neuralgia, which can be determined on the basis of the symptoms.