The 5th 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. Paralysis refers to a temporary or permanent loss or impairment of motor or sensory function in a part.

Paralysis may be caused by tumors or lesions of the nerve or nerve root, brainstem; central nervous system (CNS) infections; or cranial trauma or collagen vascular diseases.

Manifestations of the condition may involve loss of sensation to the face, to the cornea, and to the upper eyelids. There may be weakness of the muscles involved in chewing and deviation of the jaw.

Diagnostic measures may include: complete history; physical and neurological examinations; cerebrospinal fluid (CSF) test; blood studies; sensory and motor tests; electromyography (EMG); computed tomography (CT) scan; and magnetic resonance imaging (MRI).

Treatment may be directed to the underlying cause, and may include anti-inflammatory drugs, antibiotics, anticonvulsants, or surgery.

The potential for injury to the eye or face exists with patient's lack of awareness related to loss of sensation. There may be an inability to chew correctly, and partial or permanent paralysis depending on the cause and extent of nerve involvement or damage.

• 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].

• 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.