進行性核上性麻痺の眼球運動障害—その特徴と推移について—

OCULAR MOTOR ABNORMALITIES IN PROGRESSIVE SUPRANUCLEAR PALSY

　抄録　進行性核上性麻痺（PSP）の眼球運動障害の特徴と推移を明らかにする目的で，本症の11例に神経耳科学的検索を行なった。垂直性眼球運動障害の出現する時期は症例により異なるが，輻輳の障害とともに早期から高度の異常を呈した。ENGによる検索では，衝動性運動の方が滑動性運動に先行して冒される傾向にあった。水平性の眼球運動も進行とともに障害がつよくなり，4例では両側内転麻痺が加わり，MLFから動眼神経核にかけての中脳病変の反映が推測された。ENG上，眼振を含む異常眼運動が高率に認められ，rebound nystagmus, transitory altemating saccadeなど小脳核とその連絡路の障害を示唆する所見が得られた。OKNは著明に障害され，特に垂直方向は初回検査時からほとんど無反応で，中脳レベルでの障害が強いことをうかがわせた。温度眼振反応は9例中4例で無反応ないし低反応で，無反応例ではtonicdeviationも認めなかった。本症では末梢前庭障害よりも前庭神経核以上の中枢病変がその責任病巣として考えられた。これらの所見はPSPの眼球運動障害を理解する上で示唆に富むものと考えられた。

Eleven patients, 7 males and 4 females, of pro-gressive supranuclear palsy (PSP) were examined neurotologically for the purpose of elucidating the characteristics of ocular motor abnormalities. All cases were admitted to our hospital and age at onset was from 52 to 71 years old, duration of illness was 2 to 11 years. Range of voluntary eye movements and abnormal eye movements in-cluding nystagmus were examined on naked eyes and with electronystagmography (ENG). Smooth pursuit movements and saccadic eye movements were tested both horizontally and vertically by using visual tracking method with ENG recordings. Optokinetic nystagmus test and caloric test with visual suppression test were also performed. These neurotological examinations were made repetitive-ly in 5 cases and their progressions were observed.

Vertical gaze palsy and convergence palsy were observed in all cases as the initial symptom. In this study downward gaze was more severely disturbed than upward gaze. Using ENG, saccadic eye movements (saccades) were disturbed earlier than smooth pursuit movements. Hypometric sac-cades and decreased saccadic velocity were com-mon abnormalities. In the later stage of the dis-ease, horizontal eye movements were also dis-turbed. In four cases bilateral adduction palsy was added to vertical gaze paralysis so that the lesion of the MLF to oculomotor nucleus was suggested to exist. These voluntary eye movements were worsened gradually as the disease progressed.

By using ENG we could find so called abnormal eye movements more frequently than the previous reports. Eight patients demonstrated horizontal gaze nystagmus, and rebound nystagmus were ob-served in four cases. Transitory alternating sac-cades (Komatsuzaki) and square wave jerks were found in three cases presumed as a sign of fixation instability due to cerebellar dysfunction.

Optokinetic nystagmuses (OKN) were diminished in all cases, and vertical responses were markedly decreased. We can deduce that the pathology of the level of midbrain is responsible for diminished vertical OKN and voluntary vertical gaze paralysis. Caloric tests were performed in nine cases, but in four cases caloric responces were diminished or absent. In the cases of absent response, tonic deviation of the eye balls were also absent. In PSP diminished calaric nystagmus was presumed not due to peripheral vestibular lesion but due to central pathology. Visual suppression tests revea-led abnormal in three cases out of four cases.

These neurotological observations were con-sidered to be useful for presuming neuropathology of the PSP patients alive.