Pearls: neuromuscular disorders

Various brief clinical observations helpful in the evaluation of patients with neuromuscular disorders are discussed and illustrated. These include features of focal neuropathies, including the neurologic thoracic outlet syndrome, apparent ulnar nerve-innervated hand weakness in radial neuropathies, scapula movement in long thoracic compared with spinal accessory neuropathies, and diaphragm paralysis in segmental zoster paresis. Potential diagnostic errors include multifocal motor neuropathy mistaken for nerve tumor, the pseudoconduction block of vasculitic neuropathy leading to a diagnosis of Guillain-Barré syndrome, and leg paralysis in myelopathy mistaken for early ascending paralysis in Guillain-Barré syndrome. Very focal weakness of limb muscles occurs in myasthenia gravis, similar to the more familiar focal cranial muscle involvement. Fluctuation, not fatigability, in myasthenia gravis is discussed. The presentation of Lambert-Eaton myasthenic syndrome as a nonfluctuating subacute myopathy is emphasized. Patterns of weakness in inclusion body myositis and facioscapulohumeral muscular dystrophy are illustrated.