The most important disorders of the fifth cranial nerve are neuralgia and headache, elsewhere considered. (See NEURALGIA AND _MIGRAINE.) The seventh cranial nerve may be af fected by spasm or convulsive tics, or by the not uncommon and clinically impor tant "Bell's palsy," or facial paralysis.
Facial Paralysis.
This is a motor paralysis affecting the muscles of usually one side of the face.
Symptoms. — The onset of a facial paralysis is usually sudden, or of rapid development, and is indicated by loss of power in the muscles of one lateral half of the face, with loss of emotional as well as of voluntary movements. The af fected side is expressionless and smooth, the lower eyelid droops, and the eye can not be entirely closed. The tears ac cumulate and run down the face. The lips are relaxed and powerless, and ability to drink, chew, articulate, etc., is impaired. The mouth is drawn toward the affected side, this and other evidences of paralysis being exaggerated when the patient laughs or smiles. The affected side may show some congestion or circulatory defect, and occasionally an herpetic eruption appears. The soft palate and tongue are not involved, al though, on account of the displacement of the mouth, the tongue seems to devi ate from the median line. The sense of taste in the anterior part of the tongue is lost in a small proportion of cases. There 'are few or no sensory abnormali ties.
Case observed in which the unilateral facial paralysis was noticed soon after birth. In the reported cases of con genital facial paralysis, either isolated or associated with ocular palsies, the muscles of the lips and chin were less affected than the other miiscles inner vated by the seventh nerve. :M. Bern hardt (Neurol. Centralb., No. 7, '97).
The electrical reactions are the same as are seen in other forms of peripheral neuritis, their exact character depending upon the severity of the case, and for this reason possessing an especial value in prognosis. Thus, if the electrical re actions are nearly normal the case is a mild one, and recovery will most likely take place within a few weeks. If the excitability of the nerve to galvanic and faradic currents is lessened and that of the muscles to galvanic current increased and formula altered (An.C1.C.>K.C1.0.: contraction sluggish) the case is still favorable, recovery being probable within six to eight weeks. When com plete reaction of degeneration is pres ent,—that is, when faradic and galvanic excitability of nerve is lost, faradic ex citability of muscle lost, galvanic excita bilitv of muscle increased, and formula and nature of contraction altered as above,—the case is serious and will not recover for many months.
The usual outcome of a peripheral facial paralysis is complete recovery. In the few cases which terminate unfavor ably the paralysis and resulting facial asymmetry may be permanent. There is atrophy of facial muscles in all severe cases, and some degree of atrophy as well as some contracture may, in the more serious cases, persist.
Diagnosis.—The diagnosis of a facial palsy is simple, inspection being all that is required in the majority of eases. The only question is Whether the lesion is central or peripheral. The peripheral eases show changes in electrical reaction, impairment of emotional movements. loss of reflex movements, and persistent paralysis of eyelid, these conditions be ing reversed in central paralysis. A central lesion also is usually associated with some other symptoms of intraera 1,111 1,,,a.pc, often a hemiplegia. The f the hsion can often be accurately ..:at«1. If the facial nerve alone is in v..I\ 01 and the sense of taste is unim p,ortd. the Itsion is in the trunk of the rvt.. ,qitsitle of the skull, or is just itlru the stvlo-mastoid foramen. If tlit sen,c of taste in the anterior portion ,,f the tonrme is affected, the lesion is in the Fallopian canal. If complete deaf For,: occur with the facial palsy, disease , in the trunk of the nerve at the base of ' tilt. brain is indicated, while, if there is associated paralysis of the sixth nerve, the lesion is probably located in tbe pons.
Etiology and Pathology.—Facial ralvsis may be due to a lesion involving any part of the facial nerve-tract from the motor centre in the lower Rolandic area of the cortex to the face-muscles of the opposite side. If the lesion lie in the cortex or between cortex and facial nucleus in the pons, we have a -supranuclear" facial paralysis. If the b_sion involve the nucleus in the pons, we have to deal with a "nuclear" pa ralysis. If the fibres of the nerve itself be affected, the term "infranuclear" is applied. A supranuclear or central paralysis is usually seen in association with a hemiplegia: the electrical re actions remain unaltered, the upper mus cles of the face are but little involved, and voluntary movements are more im paired than is the power of emotional expre.ssion.