血管炎に伴う末梢神経障害

Vasculitic Peripheral Neuropathy

Ⅰ．臨床症状

1．基本的には多発性単神経炎が起きる

　血管炎に伴う末梢神経障害（vasculitic peripheral neuropathy）は，神経束の栄養血管（vasa nervorum)に炎症が及んで虚血が生じ，軸索変性をきたす病態である。基本的に多発性単神経炎（multiple mononeuritis；mononeuritis multiplex）を生じ，運動・感覚ともに障害される。進行により遠位優位の多発ニューロパチーに近くなるが，非対称性がある。空間的かつ時間的な多発性があることは診察と病歴で確認できることが多い。痛みを伴うことが多い。ただし，痛みはないこともある。

　神経束の一部分に虚血が生じ，それより遠位にワーラー変性が生じる。病変自体はat randomに生じたとしても，結果としては神経束が長いほど障害が目立つ傾向があるため，一般にはlength-dependentと考えられ，下肢遠位が障害されやすい。ただし多巣性であるため，上肢遠位から始まることもある。

Abstract

　The typical clinical manifestation of vasculitic peripheral neuropathy is sensory-dominant multiple mononeuropathy, although it can progress to distal-dominant sensorimotor polyneuropathy. It is painful in most cases. Peripheral nerves may be the most prone to produce symptoms of the vasculitis. Nerve conduction studies show reduced amplitude of M wave or sensory nerve action potential, which depends on the degree of injury of a nerve examined. Wallerian degeneration can cause pseudo-conduction block in the acute stage and temporal dispersion in the chronic stage. However, a definite diagnosis requires histological confirmation. Combined biopsy of the sural nerve and the peroneus brevis muscle can be performed by a single incision. Skin biopsy can also be performed. To increase the diagnostic yield, biopsy specimens are prepared in different manners to observe as many cross sections as possible: frozen unfixed, formalin-fixed paraffin-embedded, and glutaraldehyde-fixed epon embedded specimens, as well as teased fiber preparation of a nerve. Vasculitic peripheral neuropathy usually results from small-vessel vasculitis. There are still controversies regarding the classification of vasculitides. Differential diagnosis of vasculitis includes infection and lymphoma. Delayed diagnosis and treatment of neuropathy result in the impairment of ADL and QOL. Recovery from axonal degeneration usually takes time and is not always possible. Treatment includes corticosteroid, cyclophosphamide, and intravenous immunoglobulin administration; however, the intensity of treatment depends on the disease activity of vasculitis.