One-and-a-half 症候群発症後に後天性振子様眼振・上肢ミオクローヌス・オリーブ核肥大など多彩な症状が続発した橋出血例

抄録

　A 60-year-old man had a hypertensive hemorrhage at the right side of the pontine tegmentum, which resulted in right facial palsy and left hemiparesis, and one-and-a-half syndrome. Eighty days after a stroke, he manifested progressively blurred vision and oscillopsia, corresponding to a vertical pendular nystagmus. Additionally, the abnormal rhythmic involuntary movements of his left upper extremity (brachial myoclonus) appeared simultaneously. In addition to the disturbances of the horizontal eye movements, the vertical gaze was also disturbed. The patient also complained of photophobia and often tried to close his eyes. Although his hearing acuities were within the normal range (right ear 28.8 dB, left ear 25.0dB), he always complained of hearing disturbance of his right ear which might suggest the involvements of the central auditory pathways at the pontine lesion. T1-weighted MRI findings showed a hemosiderin- and ferritin- lined cleft confined to the right side of the dorsal pontine tegmentum and the central tegmental tract. Furthermore, T2-weighted or FLAIR MRI revealed the enlargement of the right inferior olivary nuclei with high intensity signals, which is the typical appearance of hypertrophic olivary degeneration (HOD). Electronystagmography (ENG) showed the acquired vertical pendular nystagmus was prominent with a frequency of 2.5c/s and the amplitude of 5-7 degrees. Although the vertical eye movements were slightly recorded in the light, they could not be completely detected in the dark. However, the vertical “doll's eye phenomenon” was identified in the vertical plane, suggesting supranuclear vertical gaze palsy, with the convergence being additionally preserved. In the eye tracking test (ETT), the pursuit was dysmetric intermingled with a catch-up saccade both horizontally and vertically. Optokinetic nystagmus (OKN) could hardly be induced in both the horizontal and vertical stimulation, though the fast phase of nystagmus to the left could be slightly induced. Furthermore, the ice water caloric stimulation almost failed to induce caloric nystagmus, though the fast phase of nystagmus to the left was slightly induced. In the literature, to the best of our knowledge, disturbances of vertical eye movements in pontine tegmental lesions as in our case have been rarely reported. It is potentially conceivable that the medial longitudinal fasciculi (MLF) or neighboring tegmental tracts convey bidirectional signals for vertical eye movements such as smooth pursuit or VOR, and that the present pontine lesions are interrupting such pathways causing impairments of the vertical eye movements.