筋強直性ジストロフィー1型の嗅覚障害

Impairment of Odor Recognition in Myotonic Dystrophy Type 1

嗅覚情報は視床を介さずに情動を司る辺縁系に直接送られる特徴を持つ。アルツハイマー病，パーキンソン病において扁桃体，海馬を含む辺縁系の異変が，最初に嗅覚異常として認められる理由はそこにある。同時期に情動反応の低下，社会性の欠如が認められることも特徴である。また筋硬直，筋萎縮を特徴とする筋強直性ジストロフィー1型においても最初の徴候として嗅覚異常を認める。本稿では嗅覚レベルの測定法，嗅覚関連部位を把握し脳の異変をすばやく捉えるための基礎を紹介する。

Abstract

There is evidence that impaired human cognitive abilities are reflected in loss of olfactory abilities. Declining olfactory perception may be a biomarker for impairment of cognitive function and of impending illnesses in neurodegenerative disorders such as Parkinson's disease (PD) and Alzheimer's disease (AD). Previously, we reported that patients with myotonic dystrophy type 1 (DM 1) had lower sensitivity to emotional facial expressions as well as abnormal olfactory threshold or recognition level. In DM 1, pathological studies have reported neurofibrillary tangles in several temporal areas including the entorhinal cortex (ENT), hippocampus (HI), and the amygdala. We observed that patients with DM 1 showed signal abnormalities in the olfactory limbic areas on magnetic resonance imaging. Our findings underscore the need to pay careful attention to significant decreases in odor identification abilities caused by diverse forms of abnormal brain function, especially in the AMG, ENT and HI.