Brachial amyotrophic diplegia

To the Editor: I read with interest the article “Brachial amyotrophic diplegia. A slowly progressive motor neuron disorder” by Katz et al.1 We have recently diagnosed this syndrome in a young woman with features particularly noteworthy: an early age at onset, a long duration of symptoms, and the presence of subtle MRI abnormalities. This 35-year-old woman developed progressive weakness and wasting of the right hand at age 18. This was followed by gradual involvement of the right forearm and arm muscles, and a few months later of the contralateral upper limb muscles. Symptoms progressed very slowly for the next four years and have remained stable since then. To date, she is unable to use her upper limbs and there is only a mild residual left-fingers flexion. There have never been any motor or sensory symptoms in lower limbs, neck or bulbar muscles, or any sphincter disturbances. On examination, the patient displayed a peculiar posture with both hands hanging loosely at her sides. There was severe and generalized weakness and atrophy of upper limb muscles, including those of the shoulder girdles, arms, forearms, and hands, all slightly worse on the left side. Muscle trophism and power were normal in the neck, thoracic, abdominal, and lower limb muscles. There were widespread fasciculations in upper limb muscles. Tendon reflexes were absent in upper limbs and normal in lower limbs, and plantar responses were flexor. Sensory examination was unremarkable. Nerve conduction studies disclosed low amplitude compound muscle action potentials (CMAPs) and normal motor and sensory conduction velocities in the right median, ulnar, and radial nerves, with no evidence of conduction block or temporal dispersion. No responses were recorded upon stimulating the median, ulnar, and radial nerves of the contralateral limb. Needle electromyography (EMG) demonstrated denervation potentials and neurogenic motor unit potentials with reduced …