視床出血にみられる水平眼球運動障害

Horizontal eye movement disorders in thalamic hemorrhage

　高血圧性視床出血の3例について，水平眼球運動を検討した．症例1は60歳，男性．上方注視麻痺，輻湊麻痺，輻湊後退眼振，skew devia-tionを認めた．症例2は67歳，男性．上，下方注視麻痺，輻湊麻痺，外斜視を認めた．症例3は41歳，女性．水平，垂直方向とも眼球運動制限は認めず，輻湊運動も保たれていた．CT上では高吸収域が，症例1,2では視床から中脳へ広がりを示したが，症例3ではほぼ視床に限局していた．

　photo-electric oculogram （pEOG）を用いて水平眼球運動を検討したところ，3例すべてに，健側向きの衝動性眼球運動の推尺障害（hypometricsaccade）と病側向きの滑動性追従運動の衝動化（saccadic pursuit）を認めた．

　したがって，従来報告されているように血腫が中脳背側部へ伸展すると，上方（垂直）注視麻痺を来すが，一方，これら水平眼球運動の障害は，視床に存在する水平眼球運動に関する神経伝導路の障害または制御機構の障害によって生じたものと思われ，視床出血の特徴的な眼所見と考えられる．

We evaluated the horizontal eye movements in 3 cases with small to moderate sized hemorrhage in the thalamus due to systemic hypertension. One case manifested upper gaze palsy, convergence palsy, skew deviation and convergence-retraction nystagmus. The second case showed vertical gaze palsy and convergence palsy. The third case showed normal findings on routine ophthal-mological examination. Computed tomography showed enhanced lesions in the left thalamus exten-ding toward the dorsal midbrain in the first two cases. A localized lesion in the right thalamus was detected in the third case.

Infrared electrooculography (pEOG) recorded disturbed horizontal eye movements in all the 3 cases. Hypometric saccades were elicited when directed away from the side of the thalamic lesion. Saccadic pursuit appeared when directed toward the side of the lesion. The vestibulo-ocular reflex was intact.

The findings indicate that horizontal eye move-ment disorders may develop, beside vertical gaze palsy, in thalamic hemorrhages. While vertical gaze palsy is consequent to dorsal midbrain lesion, the disturbed horizontal saccadic and pursuit eye movements would be due either to interrupted efferent pathway of horizontal eye movement, which is mediated through the thalamus, or by the failure in gaze control mechanism in the thalamus.

Rinsho Ganka (Jpn J Clin Ophthalmol) 42(11) : 1243-1247, 1988