Muscle hypertrophy in multifocal motor neuropathy is associated with continuous motor unit activity

Complex repetitive discharges: Cause or effect of neurogenic muscle hypertrophy?

“…It has been described in combination with radiculopathies, spinal muscular atrophy (SMA), and postpolio syndrome and in inherited as well as acquired polyneuropathies. 8 Even less common is the association of neurogenic muscle hypertrophy (NMH) with spontaneous motor activity on electromyographic studies, which has been reported in the setting of multifocal motor neuropathy, 13 chronic inflammatory demyelinating polyneuropathy, 8 Guillain-Barré syndrome, 21 and hereditary motor and sensory neuropathy (HMSN) type 2. 2 2 Neurogenic muscle hypertrophy with complex repetitive discharges (CRDs) in affected muscles has been reported occurring only unilaterally and almost exclusively in the setting of radiculopathies.…”

Diagnosis and treatment in inflammatory neuropathies

“…Occasionally, neurogenic muscle hypertrophy is evident, especially in areas affected by cramp 70. Fasciculation or, even rarely, myokimia is seen, which may be exacerbated by exercise.…”

Conduction block and continuous motor unit activity in chronic acquired demyelinating polyneuropathy

“…2 In fact, the term continuous muscle fiber activity is imprecise since it does not reflect the origin of this activity in peripheral motor axons. We prefer the term continuous motor unit activity 19,28 (CMUA) or ''sustained involuntary muscle activity of peripheral nerve origin'' 1 as more descriptive terminology. The excess muscle activity is thought to originate in the peripheral nerves and may represent the response of peripheral nerves to several different insults.…”

“…Patients with acquired inflammatory neuropathies may have CMUA as an associated feature. 4,11,13,18,19,29 The proposed mechanism implicates areas of focal demyelination which may serve as sites of ectopic impulse generation and, if multiple, may generate reverberating discharges producing self-sustained reexcitation. 3 Clinically, involuntary muscle contraction persisting during sleep and usually associated with an un- dulation of the overlying skin is a constant feature of these syndromes.…”

“…Acquired and hereditary demyelinating neuropathies occurring in association with CMUA have been described. 4,10,11,13,18,19,29 We describe a case of CMUA occurring in association with a chronic acquired demyelinating neuropathy in which the involuntary motor unit activity was particularly prominent in muscles affected by chronic motor conduction block.…”