Dominant inherited distal spinal muscular atrophy with atrophic and hypertrophic calves

Multifocal motor neuropathy and muscle hypertrophy

Multifocal motor neuropathy is frequently an asymmetrical neuropathy predominantly affecting the upper limbs. Patients present with weakness, fasciculations and distal muscle wasting. Hypertrophy of muscles is very infrequently reported. We present two cases of multifocal motor neuropathy with upper limb muscle hypertrophy and discuss possible pathophysiological mechanisms. Botulinum toxin may be useful to alleviate cramp.

Isolated spinal accessory mononeuropathy associated with neurogenic muscle hypertrophy: restricted neuralgic amyotrophy or stretch-palsy? A case report

A 55-year-old man developed transient bi-brachial paresthesias followed by severe pain over his left shoulder ridge and periscapular region within 8 hours of rigorous hand-over-hand hoisting of a 33.8-kg (75-lb) object. He experienced weakness in shoulder abduction followed several weeks later by focal hypertrophy of the left trapezius. Electrophysiologic studies showed significant spontaneous motor activity in the form of denervation potentials, fasciculations, and complex repetitive discharges. The 2 major diagnostic considerations were restricted neuralgic amyotrophy versus stretch palsy of the spinal accessory nerve. The clinical similarities and differences between restricted forms of neuralgic amyotrophy and stretch palsies are discussed.

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

We report a patient with adult-onset spinal muscular atrophy (SMA) of the scapulohumeral type with neurogenic muscle hypertrophy (NMH) in markedly weakened biceps muscles in association with continuous complex repetitive discharges (CRDs). This is an apparently unique case due to the bilaterality of the NMH associated with CRDs as well as the well-circumscribed symmetric upper extremity distribution of the hypertrophy. The possible mechanisms of NMH in association with spontaneous motor activity are discussed.

Congenital autosomal dominant distal spinal muscular atrophy

We present a father and son with congenital foot deformity. The father at age 41 years used crutches and the son at 7 years walked unaided. Both had atrophy and weakness of lower leg muscles and mild proximal and hand intrinsic weakness. Knee and ankle myotactic reflexes were absent and sensation was intact. Creatine kinase level was normal, nerve conduction studies wer normal and electromyography showed chronic neurogenic change. In both, nerve biopsies were normal and muscle biopsies showed type 1 predominance. The boy's serum hexosaminidase, spinal MRI and SMN gene were normal. This may be the first well documented example of congenital autosomal dominant distal spinal muscular atrophy affecting legs and arms.

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

Multifocal motor neuropathy (MMN) is typically associated with distal upper limb weakness and wasting. However, proximal muscle bulk, particularly of biceps brachii, may be well preserved even in the presence of severe proximal weakness. Here we report 3 patients with MMN who had true muscle hypertrophy of severely weakened biceps muscles and positive motor symptoms including cramp and fasciculations in these muscles. Electromyographic studies demonstrated markedly impaired recruitment in the affected muscles and continuous motor unit activity comprising multiple fasciculation potentials at a frequency of up to 30 per minute. We propose that this continuous motor unit activity may have contributed to the hypertrophy in these muscles.

Calf enlargement in neuromuscular diseases: a quantitative ultrasound study in 350 patients and review of the literature

Calf hypertrophy is a typical clinical feature in neuromuscular diseases such as X-linked muscular dystrophies of Duchenne and Becker type and can be seen as an atypical feature in numerous other diseases. The diagnosis of calf hypertrophy usually is based on subjective visual assessment. The aim of this prospective study was to examine the prevalence of calf hypertrophy in a large number of patients with various neuromuscular diseases based on quantitative ultrasound measurement of calf muscle thickness. Additionally, true and pseudohypertrophy should be distinguished according to the absence or presence of abnormal muscle echointensities caused by infiltration of fat tissue. Fifty adult normal controls and 350 patients with various neuromuscular diseases were investigated. Absolute calf hypertrophy was diagnosed if the combined thickness of the gastrocnemius and soleus muscles exceeded the mean value of the control persons by at least 3.0 standard deviations (SD). Relative calf hypertrophy was diagnosed when the ratio of the combined thicknesses of the gastrocnemius and soleus muscles divided by the combined thicknesses of the rectus femoris and vastus intermedius muscles lay at least 3.0 SD below the mean value of the controls. Pseudohypertrophy was present if the echointensities of the gastrocnemius and soleus muscles reached or exceeded 3.0 SD above the mean value of the controls. An absolute hypertrophy of the calves was detected in 80 patients (= 22,9%; 64 true and 16 pseudohypertrophies), 16 patients exhibited a relative hypertrophy of the calves (= 4.6%; 12 true and 4 pseudohypertrophies). A significantly increased portion of both absolute calf hypertrophies and pseudohypertrophies as compared to the control group were found in juvenile proximal spinal muscular atrophy type 3, central core disease, centronuclear myopathy, benign X-linked muscular dystrophy of Becker type, autosomal recessive limb girdle muscular dystrophy, acid maltase deficiency, polymyositis, and granulomatous myositis. A significantly increased number of relative calf hypertrophies was present in juvenile proximal spinal muscular atrophy type 3, facioscapulohumeral muscular dystrophy, and inclusion body myositis. In the majority of the diseases included in the study, calf hypertrophy occurred in at least some patients. In conclusion, calf hypertrophy is a frequent and unspecific clinical feature in many neuromuscular diseases. Ultrasound is a convenient method for the exact definition of calf hypertrophy.