MADSAM neuropathy
An unusual cause of pseudoathetosis

A 68-year-old man complained of several years of an uncoordinated, weak left arm. Clinical examination revealed pseudoathetosis and mild global weakness of the left arm, stocking pattern vibration and pinprick insensitivity, and only mild proprioceptive impairment of the left hand (video on the Neurology® Web site at Neurology.org). Nerve conduction study showed generalized absent or severely attenuated sensory potentials and multiple upper limb motor conduction blocks (figure 1). MRI demonstrated asymmetrically enlarged left nerve roots and trunks of the brachial plexus (figure 2). Chronic inflammatory demyelinating polyradiculoneuropathy can cause tremor,¹ but multifocal acquired demyelinating sensory and motor neuropathy,² an asymmetric form, has not been reported to cause pseudoathetosis.