The Vth cranial nerve is one of twelve pairs of nerves connected with the brain which supplies sensation to the skin of the face and front half of the head, as well as innervating the masseter and pterygoid masticatory muscles. The nerve also provides sensory input from the eye surface, tear glands, and upper eyelids. Neuritis refers to inflammation of a nerve with pain and tenderness, anesthesia and paresthesia, paralysis, wasting, and disappearing of the reflexes.

In some cases, the cause may be unknown. Identifiable causes may include: tumors; lesions; hemorrhage into a nerve; systemic malignancy; leprosy; trauma; continuous pressure on a nerve; and destruction of the nerve from viruses or infectious disease such as Lyme disease. Other causes may include: metabolic diseases such as diabetes mellitus; collagen vascular diseases; toxic agents such as lead or mercury poisoning; certain medications; vitamin deficiency; alcoholism and poor nutrition; exposure to cold or radiation; or genetic factors.

There may be sensory loss to the face, to the cornea, and to the upper eyelids. In addition, other manifestations include: weakness of the jaw muscles; deviation of the jaw when opened; loss of sensation over the chin; numbness; paresthesias; and burning or painful sensations.

Diagnostic measures include: physical and neurological examinations; sensory and motor tests; laboratory studies; x-ray; metabolic tests; electromyography (EMG); computed tomography (CT) scan; magnetic resonance imaging (MRI); spinal tap; or nerve biopsy.

Treatment may depend on the underlying cause and may include: anti-inflammatory and pain medications; antibiotics; and vitamin therapy. In some cases, physical therapy is possibly included.

Recovery may be complete. However, in some disorders, symptoms may recur or may become chronic for months or years. Corneal ulceration is a possible risk.

• This disease shall be granted service connection although not otherwise established as incurred in or aggravated by service if manifested to a compensable degree within the applicable time limits under 38 CFR 3.307 following service in a period of war or following peacetime service on or after January 1, 1947, provided the rebuttable presumption provisions of 38 CFR 3.307 are also satisfied [38 CFR 3.309 [Disease subject to presumptive service connection], 38 CFR 3.309(a). [chronic disease].

Notes

• Dependent upon relative degree of sensory manifestation or motor loss.

• Disability from lesions of peripheral portions of first, second, third, fourth, sixth, and eighth nerves will be rated under the Organs of Special Sense. The ratings for the cranial nerves are for unilateral involvement; when bilateral, combine but without the bilateral factor.

• Neuritis, cranial or peripheral, characterized by loss of reflexes, muscle atrophy, sensory disturbances, and constant pain, at times excruciating, is to be rated on the scale provided for injury of the nerve involved, with a maximum equal to severe, incomplete, paralysis. See nerve involved for diagnostic code number and rating. The maximum rating which may be assigned for neuritis not characterized by organic changes referred to in this section will be that for moderate, or with sciatic nerve involvement, for moderately severe, incomplete paralysis. (38 CFR 4.123)