小脳失調症を呈した成人における可逆性の脾臓病変を伴う軽度脳炎/脳症。症例報告

Mild Encephalitis/Encephalopathy with a Reversible Splenial Lesion in an Adult with Cerebellar Ataxia: A Case Report.

• Masataka Nakajima
• Satoshi Suda
• Kazumi Kimura

抄録

可逆性脾臓病変を伴う軽度脳炎・脳症（MERS）は、一過性の軽度脳症とMRI（磁気共鳴画像法）による可逆性脾臓病変を特徴とする臨床放射線学的症候群である。MERS患者は一般的に意識障害，頭痛，痙攣などの中枢神経系症状を呈するが，小脳失調を伴う成人発症のMERSはまれである．53歳の男性が1週間の発熱，頭痛，頸部のこわばり，歩行障害を呈して当院に入院した．神経学的検査では両側性の意図振戦（主に右手）と歩行失調を認めた．脳拡散強調MRIではSCCに局所的な高強度病変が認められた．脳脊髄液検査では単核球と蛋白質が高値を示した．I-iofetamine単光子放出型コンピュータ断層撮影法を用いた脳イメージングでは，左視床と右小脳の脳血流の低下が認められた．急性小脳失調症の患者では，小脳脳梗塞や急性小脳炎を含むいくつかの疾患が併存疾患として発症する．この症例は、成人の小脳失調症ではMERSを疑うべきであることを示唆している。

Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is a clinicoradiological syndrome characterized by transient mild encephalopathy and magnetic resonance imaging (MRI) findings of a reversible lesion in the splenium of the corpus callosum (SCC). Patients with MERS generally present with central nervous system symptoms such as consciousness disturbance, headache, and seizure; adult-onset MERS with cerebellar ataxia is rare. A 53-year-old man was admitted to our hospital with fever of 1 week's duration, headache, neck stiffness, and gait disturbance. Neurological examination revealed bilateral intention tremor (predominantly affecting the right hand) and gait ataxia. Diffusion-weighted brain MRI showed a focal hyperintense lesion in the SCC. Cerebrospinal fluid analysis revealed elevated levels of mononuclear cells and proteins. Brain imaging with I-iofetamine single-photon emission computed tomography showed reduced cerebral blood flow in the left thalamus and right cerebellum. Several diseases, including cerebellar stroke and acute cerebellitis, develop as comorbidities in patients with acute cerebellar ataxia. This case suggests that MERS should be suspected in adults with cerebellar ataxia.