[The EMG findings of spasmodic torticollis--the character of the EMG findings of neurogenic torticollis].
Spasmodic torticollis is a clinical entity that is hard to treat though various symptomatic therapy have been tried. On the other hand, microvascular decompression operation have been established for cranial nerve vascular compression syndrome such as hemifacial spasm. Case reports on the decompression of the spinal accessory nerve for the treatment of spasmodic torticollis have been published on the basis of the concept of cranial nerve vascular compression syndrome. Thus, spasmodic torticollis related to unilateral accessory nerve has attracted much attention for selecting an optimal treatment, although there have not been any diagnostic criteria with electromyographic study. From the viewpoint of the clinical electrophysiological findings on hemifacial spasm those we have acquired by EMG study, we have examined the EMG findings of various types of spasmodic torticollis and here report the classification of spasmodic torticollis based on the EMG study. Thirty-five patients with spasmodic torticollis were analyzed. The symptoms were classified to the horizontal rotation type, the lateral bending type and the mixed type with the number of each group of 23, 2 and 10, respectively. As we have shown the criteria of the EMG findings on hemifacial spasm, the EMG of the patients with spasmodic torticollis were analyzed on four conditions as follows; (1) distribution of the involved muscles, (2) maximum firing rate of the abnormal spontaneous activity of the sternocleidomastoid muscle, (3) synkinetic discharge between the muscles innervated by unilateral accessory nerve and (4) alteration of the spontaneous muscle discharge by posture change. Abnormal spontaneous muscle discharges were recorded only from the sternocleidomastoid muscle and the trapezius muscle on the same side in twelve patients. Maximum firing rate of spontaneous muscle discharge was higher than that of maximum voluntary contraction in twenty-two patients. Abnormal synkinetic discharge was recorded between the sternocleidomastoid muscle and the trapezius muscle on the same side in twenty-one patients. Spontaneous EMG activities of the muscles innervated by the accessory nerve increased when the patients stood up from the resting supine position in thirty-one patients. Thus, ten patients out of thirty-five subjects had all four conditions mentioned above as typical patients with hemifacial spasm usually had. These ten patients with spasmodic torticollis were thought to have strong similarity to the EMG characteristics of hemifacial spasm that suggested hyperexcitability of unilateral accessory nervous system. This classification with EMG is considered to be useful in diagnosing the spasmodic torticollis related to unilateral accessory nerve and can be applied for selecting an optimal treatment.