The work of Nielsen and Janetta demonstrates that microsurgical decompression of the root with the interposition of a pledget between the vessel and the facial nerve relieves the facial spasm in most patients. These results were corroborated by Barker and associates in a series of 705 patients followed postoperatively for an average period of 8 years; 84 percent achieved an excellent result. An even higher rate of benefit was obtained in a prospective series by Illingworth and colleagues (cure of 81 of 83 patients).
Surgical decompression involves exploration of the posterior fossa, and carries some risk. The facial muscles may be weakened, sometimes permanently. Another complication has been deafness as a result of injury of the adjacent eighth nerve. Also, there is a risk of recurrence of the spasms, usually within 2 years of the operation (Piatt and Wilkins). Tight dural closure is required to prevent CSF leakage from the posterior fossa.
Other Disorders of the Facial Nerve
Facial myokymia is a fine rippling activity of all the muscles of one side of the face (discussed further in Chap. 46). It develops most often in the course of multiple sclerosis or a brainstem glioma, and can be seen in some disorders of the neuromuscular junction (e.g., neuromyotonia). It has also occurred after other diseases of the facial nerve, for example, in GBS, in which case it is usually bilateral. We have seen it more often in the recovery stage than in the early phase of GBS. The fibrillary nature of the involuntary movements and their arrhythmicity tend to distinguish them from the coarser intermittent facial spasms and contracture, tics, tardive dyskinesia, and focal motor seizures. The EMG pattern is one of spontaneous asynchronous discharge of adjacent motor units, appearing singly or in doublets or triplets at a rate varying from 30 to 70 cycles per second. The myokymia seen in the facial muscles is believed to result from demyelination of the intrapontine part of the facial nerve and possibly supranuclear disinhibition of the facial nucleus but the observation of facial myokymia following some cases of GBS informs us that the abnormal movement may have its origin in a lesion at any point along the nerve.
A clonic or tonic contraction of one side of the face may be the sole manifestation of a cerebral cortical seizure. When the seizure focus involves a very limited amount of motor cortex, demonstrable changes may not be evident on scalp EEG. Focal motor seizures, or epilepsia partialis continua, can often be difficult to extinguish despite multiple AEDs, though carbamazepine can be particularly helpful.
Involuntary recurrent spasm of both eyelids (blepharospasm, as discussed in Chaps. 4 and 13) may occur with almost any form of dystonia, but is most frequent in elderly persons as an isolated phenomenon, and there may be varying degrees of spasm of the other facial muscles. Although relaxant and tranquilizing drugs are of little help in this disorder, injections of botulinum toxin into the orbicularis oculi muscles can reduce the excessive blinking. A few of our patients have been helped (paradoxically) by l-dopa; baclofen, clonazepam, and tetrabenazine in increasing doses may be helpful as well. In the past, failing these measures, the periorbital muscles were destroyed by injections of doxorubicin or surgical myectomy. With the advent of botulinum treatment, there is no longer a need to resort to these extreme and irreversible measures. In some cases, blepharospasm subsides spontaneously. Rhythmic unilateral myoclonus, akin to palatal myoclonus (actually a tremor as noted in Chap. 4), may be restricted to facial, lingual, or laryngeal muscles.