A 73-year-old man presented with a three-month history of muscle wasting, cramps and
marked weight loss. Examination revealed severe global amyotrophy ([Figure]), fasciculations, reduced deep tendon reflexes and flaccid quadriparesis. Nerve
conduction studies were unremarkable. Needle electromyography showed acute and chronic
partial denervation in the cervical, thoracic and lumbosacral segments. A full-body
CT scan disclosed a large mass in the anterior mediastinum, which showed a type B2
thymoma.
Figure Findings in subacute motor neuronopathy. Severe muscle wasting in proximal (A) and
distal muscle groups (B; black arrow). (C) Rarefaction of interference patterns in
submaximal voluntary contraction, and fibrillation and positive sharp wave at rest.
(D) Chest CT scan showed a large mass in the anterior mediastinum (white arrow).
Paraneoplastic neuropathies represent an expanding group of immune-mediated neuropathies
associated with a known or unidentified neoplasm[1]. Pure motor neuropathy is represented by subacute motor neuronopathy[1], commonly associated with Hodgkin’s and non-Hodgkin’s lymphoma[1],[2] and, rarely, with thymoma[2].
