Theuriet Julian, Bernard Emilien, Guy Nathalie, Taithe Frédéric, Even Cécilia, Maisonobe Thierry, Sangaré Aude, Lardeux Pierre, Tilikete Caroline Froment, Couratier Philippe, Lenglet Timothée, Pegat Antoine
Service ENMG et de Pathologies Neuromusculaires, Centre de référence Des Maladies Neuromusculaires PACA-Réunion-Rhône Alpes, Hôpital Neurologique Pierre Wertheimer, Hospices Civils de Lyon, Bron, France.
Service de Neurologie, Troubles du Mouvement et Pathologies Neuromusculaires, Hôpital Neurologique Pierre-Wertheimer, Hospices Civils de Lyon, Bron, France.
Muscle Nerve. 2025 Apr;71(4):644-650. doi: 10.1002/mus.28357. Epub 2025 Jan 23.
INTRODUCTION/AIMS: Finger Extension Weakness and DOwnbeat Nystagmus Motor Neuron Disease (FEWDON-MND) is characterized by motor weakness predominantly affecting finger extension, accompanied by downbeat nystagmus. To date, only 11 patients have been reported. The present study adds a further three and aims to provide a more detailed description of the electrodiagnostic features of these patients.
We present the clinical and electrophysiological features of three French patients from specialized motor neuron centers and review the electrophysiological findings of previously reported patients.
These three patients presented with pure motor weakness affecting finger extension and downbeat nystagmus. They exhibited a slowly progressive disease course without respiratory involvement. Nerve conduction studies showed decreased compound muscle action potential amplitudes in the extensor indicis muscles. Abnormal spontaneous activity on needle electromyography (EMG) was rare in two patients, absent in one, and otherwise limited to weak muscles. Additionally, chronic motor axon loss features suggestive of motor neuronopathy were seen in our patients. Importantly, they were also detected in distant asymptomatic muscles.
The three patients reported here confirm the typical phenotype of FEWDON-MND, characterized by slowly progressive distal motor weakness initially affecting finger extension, associated with downbeat nystagmus. Although chronic motor axon loss features have been found in all reported patients, our three patients show that active denervation can be absent or rare. Thus, finger drop and diffuse chronic neurogenic changes on EMG should lead clinicians to look for downbeat nystagmus and to consider FEWDON-MND.
引言/目的：手指伸展无力与下跳性眼球震颤运动神经元病（FEWDON-MND）的特征是运动无力主要影响手指伸展，并伴有下跳性眼球震颤。迄今为止，仅报道了11例患者。本研究又增加了3例，并旨在更详细地描述这些患者的电诊断特征。
我们介绍了来自专业运动神经元中心的3例法国患者的临床和电生理特征，并回顾了先前报道患者的电生理结果。
这3例患者均表现为单纯性运动无力，影响手指伸展并伴有下跳性眼球震颤。他们呈现出缓慢进展的病程，无呼吸受累。神经传导研究显示示指伸肌的复合肌肉动作电位幅度降低。针极肌电图（EMG）检查中，2例患者的异常自发电活动较少见，1例未出现，其他则仅限于无力肌肉。此外，在我们的患者中发现了提示运动神经元病的慢性运动轴突丢失特征。重要的是，在远处无症状肌肉中也检测到了这些特征。
本文报道的3例患者证实了FEWDON-MND的典型表型，其特征为最初影响手指伸展的缓慢进展性远端运动无力，并伴有下跳性眼球震颤。尽管在所有报道的患者中均发现了慢性运动轴突丢失特征，但我们的3例患者表明，主动失神经支配可能不存在或少见。因此，手指下垂和肌电图上的弥漫性慢性神经源性改变应促使临床医生寻找下跳性眼球震颤并考虑FEWDON-MND。
