両側視床病変と末梢神経障害を伴う急性脳症の1成人例

An Adult Case of Acute Encephalopathy Associated with Bilateral Thalamic Lesions and Peripheral Neuropathy

　要旨　症例は76歳女性。発熱と意識障害で発症し，髄液蛋白細胞解離を伴う急性脳症と診断された。ステロイドパルス療法と免疫グロブリン大量静注療法を実施したが，神経徴候は不変であった。頭部MRIでは，視床や淡蒼球，橋被蓋部を中心に両側対称性の病変分布を認めた。いわゆる小児急性壊死性脳症（acute necrotizing encephalopathy： ANE）に類似した画像所見を呈し，発症年齢以外はANEの診断基準を満たしていた。また，本例では急性期の血清・髄液中のサイトカイン高値を認め，病態の活動性や予後の評価に有用であった。急性壊死性脳症では，病態の中心を炎症性サイトカインが担っていると推測されており，視床などにおける血液脳関門の局所的破綻を引き起こしていると考えられている。本例の視床病変は，ANEとしては非典型的であり，疾患の異同を中心に考察した。

　A 76-year-old woman developed fever and consciousness disturbance. The next day, she became delirious and was brought to our hospital. On arrival, she was unconscious and showed hypopnea and hypotension. She was immediately intubated and placed on a respirator. CSF protein was 65.8mg/dl with 1 cell/μl, and no oligoclonal bands were present. An electroencephalogram showed diffuse theta background activity without epileptic discharges. A nerve conduction study showed damaged motor and sensory peripheral nerve functions in the upper and lower limbs. The neurological findings showed no improvement after methylprednisolone pulse therapy and administration of intravenous immunoglobulin. Magnetic resonance imaging of the brain, including diffusion-weighted images showed bilateral symmetric lesions in the thalamus, globus pallidus and pontine tegmentum. These radiologic findings are not typically, but are similar to those of acute necrotizing encephalopathy （ANE） of childhood as proposed by Mizuguchi et al. After 10 months, brain MRI showed bilateral brain atrophy and a reduction of the abnormal thalamic lesions. There are very few reports of adult cases of ANE, in which, pathologically, local breakdown of the blood-brain-barrier causes acute edema and necrosis involving both gray and white matter. ANE is thought a proinflammatory cytokine-related disease. In our case, the concentrations of some cytokines （IL-6, IL-10） were elevated in serum and cerebrospinal fluid, which might suggest a relationship with them and local breakdown of the blood-brain-barrier in the thalamus.