[Superior oblique myokymia--a case report and pathogenetic consideration]

A 30-year-old male visited us with complaints of dizziness and diplopia of abrupt onset in September, 1988. Neurological studies demonstrated paroxysmal rotatory to-and-fro oscillations of the left eye. There has been the same clinical episode at 25 years of age, lasting approximately 6 months. The characteristics of his ocular involuntary movement with the mild IVth cranial nerve paresis were as follows: quick, nonrhythmic, initially counterclockwise-rolling, more prominent in moving the left eye to the lower medial side, persisting for 1-10 seconds and rapidly repeated oscillations. When oscillations were prominent, he complained of faintness in addition to double vision. Except for the ocular signs, other neurological and laboratory examinations including cerebrospinal fluid, brain MRI and brain stem auditory evoked response, failed to disclose the precise location and nature of the lesion. Abnormal ocular movement was fluctuating for 4 months and gradually disappeared without any medication. In conclusion, the faintness could be considered to result from a lesion of reticular activating system adjacent to the IVth cranial nerve nucleus and its rostral (excitatory or inhibitory) supranuclei, and it suggests that a responsible lesion of the abnormal ocular movement is located at a region of the dorsomedial midbrain.