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

Neurogenic muscle hypertrophy in Type III spinal muscular atrophy

“…One hypothesis for the pathogenesis of neurogenic muscular hypertrophy is a pathologic muscle fiber hyperactivity, which is seen as complex repetitive discharges, neuromyotonia, or continuous MUAP firings in EMG [2,11]. The EMG findings for our patient support the assertion that the continuous discharge of muscle fibers may result in muscle hypertrophy.…”

Myopathic changes in bilateral hypertrophy of the first dorsal interosseus muscle of the hand

“…Bähr [3] analyzed muscle biopsies of patients with primary myopathies and found variation of muscle fiber size with increased fiber diameter. Hypertrophic muscle fibers type I and atrophic fibers type II were detected in a patient with spinal muscular atrophy [18]. Except for myopathic changes with predominantly type II fiber hypertrophy, histological findings were subtle and nonspecific in our case, supporting its benign nature.…”

An unusual cause of calf hypertrophy: severe lumbar canal stenosis with S1 nerve root radiculopathy

“…Although neurogenic conditions usually result in calf atrophy, S1 radiculopathy is an unusual cause for calf enlargement. Calf hypertrophy has been reported in several other neuromuscular conditions including adult‐onset spinal muscle hypertrophy, 1 hereditary sensorimotor neuropathies, 2 post‐polio syndrome 3 and traumatic peripheral nerve lesions.…”

“…EMG frequently revealed evidence of denervation and in half of the cases, complex repetitive discharges. The latter represents bursts of spontaneous muscle action potential which may contribute to chronic stimulation of myofibres and this in turn results in muscle hypertrophy 1 . In other cases there are alternative mechanisms: work‐induced hypertrophy of remaining type II fibres, 9 stretching with enlargement of type I fibre mass in both denervated and innervated fibres 10 and the potential role of neurotrophic growth factors such as insulin growth factor‐1 11 and myostatin 12 have been proposed to explain this paradoxical hypertrophy.…”