Neurogenic muscle hypertrophy. Report of two cases

Muscle hypertrophy following acquired neurogenic injury: systematic review and analysis of existing literature

OBJECTIVES

Neurogenic muscle hypertrophy (NMH) is a rare condition characterized by focal muscle hypertrophy caused by chronic partial nervous injury. Given its infrequency, underlying mechanisms remain poorly understood. Inspired by two clinical cases, we conducted a systematic review to gain insights into the different aspects of NMH.

METHODS

We systematically searched online databases up until May 30, 2023, for reports of muscle hypertrophy attributed to acquired neurogenic factors. We conducted an exploratory analysis to identify commonly associated features. We also report two representative clinical cases.

RESULTS

Our search identified 63 reports, describing 93 NMH cases, to which we added our two cases. NMH predominantly affects patients with compressive radiculopathy (68.4%), negligible muscular weakness (93.3%), and a chronic increase in muscle bulk. A striking finding in most neurophysiological studies (60.0%) is profuse spontaneous discharges, often hindering the analysis of voluntary traces. Some patients exhibited features consistent with more significant muscle damage, including higher creatine phosphokinase levels, muscle pain, and inflammatory muscle infiltration. These patients are sometimes referred to in literature as "focal myositis." Treatment encompassed corticosteroid, Botulinum Toxin A, decompressive surgery, antiepileptic medications, and nerve blocks, demonstrating varying degrees of efficacy. Botulinum Toxin A yielded the most favorable response in terms of reducing spontaneous discharges.

INTERPRETATION

This systematic review aims to provide a clear description and categorization of this uncommon presentation of an often-overlooked neurological disorder. Though questions remain about the underlying mechanism, evidence suggests that aberrant fiber overstimulation along with increased workload that promotes focal damage may result in muscle hypertrophy. This may serve as a guide for therapeutic interventions.

Surgical Improvement of Neuropathy-Induced Calf Muscle Hypertrophy and Creatine Kinase Elevation: A Case Report

Peripheral neuropathy and radiculopathy often result in skeletal muscle disorders, typically leading to muscle atrophy. Concurrent muscle hypertrophy or persistently elevated creatine kinase (CK) is rare. While muscle hypertrophy is commonly observed in myogenic diseases, such as muscular dystrophy, acromegaly, inflammatory myopathies, and hypothyroidism, reports of muscle hypertrophy caused by neuropathy are infrequent. We encountered a patient with persistently elevated CK levels and unilateral lower leg muscle hypertrophy associated with neuropathy. The patient had cauda equina syndrome symptoms and pain in the left lower leg. Lumbar spine magnetic resonance imaging (MRI) revealed central spinal stenosis, which was believed to be the cause of the symptoms. Lower-limb MRI revealed high signal intensity in the gastrocnemius muscle on fat-suppressed T2-weighted imaging. Surgical treatment improved the radiculopathy, hypertrophy, and pain in the left lower leg. During the one-year follow-up, improvement was confirmed with both MRI and nerve conduction studies. Calf muscle hypertrophy associated with neuropathy has been reported; however, no reports have demonstrated pre- and postoperative changes with MRI and nerve conduction studies. We report a patient with lower leg muscle hypertrophy and persistent CK elevation associated with neuropathy, along with a literature review.

Neurogenic calf amyotrophy with CK elevation by entrapment radiculopathy; clinical, radiological, and pathological analyses of 18 cases

OBJECTIVE

To characterize the clinical, radiological, and pathological manifestations of 18 cases showing neurogenic calf amyotrophy with creatine kinase (CK) elevation by entrapment radiculopathy (NCACKEER).

METHODS

We retrospectively reviewed and evaluated the medical records of patients who complained of weakness or atrophy of the calf muscles in our department between 2004 and 2019. We identified 18 cases fulfilling the proposed criteria of NCACKEER. We extracted neurological, laboratory, neurophysiological, and neuroradiological data from all cases. Moreover, we evaluated biopsy specimens from the gastrocnemius in four cases.

RESULTS

Eighteen NCACKEER cases exhibited the characteristic findings that can discriminate previously known myopathies or polyneuropathies affecting distal legs. We noticed male predominance (72%) with an average age at diagnosis of 65.6 years. Muscle weakness or atrophy was localized in the distal legs, with Achilles tendon reflexes absent in all cases. We observed elevated serum CK levels with a range from 237 to 2294 IU/L. All electromyography (EMG) studies showed neurogenic changes in the affected muscles. Lumbar spinal MRI exhibited either spinal canal stenosis at various vertebral levels or intervertebral foraminal stenosis at L4/5 and L5/S1 in all cases with significant straightening spinal and sacral alignments. All muscle biopsy specimens showed findings of neurogenic muscular degeneration with no inflammatory infiltrations. Cases with higher CK elevation had more necrotic muscle fibers.

CONCLUSION

We established the clinical characteristics of NCACKEER. Evaluations of serum CK level and skeletal muscle CT imaging are useful for screening, and lumbar spinal MRI, EMG and/or muscle biopsy are necessary for diagnostic confirmation.

Neurogenic muscle hypertrophy in a 12-year-old girl

Muscular hypertrophy secondary to denervation is very rare, but well-documented phenomena in adults. This is the first report of a child with neurogenic unilateral hypertrophy due to S1 radiculopathy. A 12-year-old girl presented with left calf hypertrophy and negative history of low back pain or trauma. The serum creatinine kinase level and inflammatory markers were normal. Magnetic resonance imaging showed muscle hypertrophy of the left gastrocnemius and revealed a protruded lumbar disc at the L5-S1 level. The protruded disc abuts the S1 root on the left side. Electromyography showed mild left S1 radiculopathy. Passive stretching and work load might clarify the origin of neurogenic hypertrophy but there is still a need for further evidence. Clinical, laboratory, magnetic resonance imaging and electromyography findings showed that S1 radiculopathy could be a cause of unilateral calf swelling in youth even in the absence of a history of back or leg pain.

Neurogenic muscle hypertrophy: a case report

Muscular hypertrophy is caused mainly due to myopathic disorder. But, it is also rarely produced by neurogenic disorder. A 74-year-old woman complained of right calf pain with hypertrophy for several years. Recent lumbar spine magnetic resonance imaging (MRI) showed central and lateral canal narrowing at the L4-L5 intervertebral space. Lower extremity MRI revealed fatty change of right medial head of the gastrocnemius and soleus, causing right calf hypertrophy. Electrodiagnostic examinations including electromyography and nerve conduction velocity testing demonstrated 5th lumbar and 1st sacral polyradiculopathy. Integrating all the results, the diagnosis was neurogenic muscle hypertrophy. Neurogenic muscle hypertrophy is very rare, but we recommend that clinicians consider this problem when a patient complains of lower limb hypertrophy and pain.

An unusual case of unilateral limb hypertrophy: Lipoma of sacral roots

We report an unusual case of unilateral limb pseudo hypertrophy in a 21-year-old lady who developed progressive enlargement of the right calf followed by thigh in association with chronic leg pain. Magnetic resonance imaging (MRI) of the affected limb confirmed enlargement of various muscles. Electromyography revealed neurogenic features consistent with S1 radiculopathy. MRI of the lumbosacral spine showed tethered cord with a lipoma infiltrating multiple sacral roots. Our case illustrates that muscular pseudo hypertrophy may follow chronic denervation as a consequence of spinal neural compressive disease. The various mechanisms postulated for this distinct condition are outlined.

Pathological mechanism of lumbar disc herniation resulting in neurogenic muscle hypertrophy

We present a 33-year-old man with 5-year history of low back pain who presented with an enlarging right calf. The patient underwent an extensive workup including biopsy without diagnosis. The patient's examination was significant for diminished pinprick sensation in the right L5/S1 dermatome. Reflexes were absent in the right ankle. The circumference of the right calf (58 cm) was twice that of the left. MRI revealed a herniated lumbar disc at the L5/S1 level. He then underwent a L5/S1 microdiscectomy. Following this surgery, the patient noted complete resolution of all sensory deficits in his lower extremity. His calf circumference had decreased by 5 cm at 4 months and by a total of 8 cm at his 2-year post-operative visit. Histological examination of the affected muscle demonstrated severe grouped atrophy of both type I and type II fibers. There was also evidence of compensatory fiber hypertrophy as well as fiber splitting. We concluded that the patient suffered from a herniated lumbar disc causing radiculopathy with calf hypertrophy (neurogenic hypertrophy). To our knowledge this is the first report of both grouped atrophy and compensatory hypertrophy of both muscle fiber types seen in this phenomenon.

Muscle hypertrophy of the lower leg caused by L5 radiculopathy

We report on a case with hypertrophy of the tibial muscles and to a lesser extent of the calf muscles preceded by a lumbar syndrome and sciatica. Lumbar myelography disclosed a discogenic compression of the L5 nerve root. Muscle biopsy of the peroneal muscles showed a marked type I fibre predominance and hypertrophy but no inflammatory infiltration. We consider the possibility that radiculopathy not only of the S1 nerve root but also of the L5 root can trigger hypertrophy of the musculature and must be taken into account of the differential diagnosis of unilateral focal hypertrophy of the lower leg.

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.

Hypertrophie musculaire neurogène : à propos de trois cas, imagerie et revue de la littérature

OBJECTIVE

To review the literature on well-documented cases of neurogenic muscle hypertrophy in order to define significant features of this disease.

PATIENTS AND METHODS

The PUBMED and SCIENCE DIRECT web-sites were used to conduct an inventory of all reported cases of this disease. We entered the key-words "hypertrophy", "muscle" and "neurogenic", and found 48 articles, describing 129 cases. Our criteria of inclusion included hypertrophy of one or several muscles of a lower limb, previous realization of at least one imaging study (CT or MRI) and electromyography of lower limbs; criterion of exclusion was hypertrophy related to hereditary or acquired polyneuropathies. Twenty-five cases were retained for investigation along with 3 recent cases observed in our department.

RESULTS

Results show that neurogenic muscle hypertrophy is usually presents with painful enlargement of a calf in a male, aged 32 to 60 years, with previous history of low back pain and sciatica, 68% of the time due to disk herniation or lumbar stenosis. Other clinical findings may include radiation therapy or trauma.

CONCLUSION

The symptoms of neurogenic muscle hypertrophy may lead to MRI examination before electromyography. This disease should be included in the differential diagnosis.

EMG myokymia as a cause of ptosis in hypothyroidism

Ptosis is known to be associated with thyroid disorders. We describe two biochemically corrected hypothyroid patients presenting with isolated bilateral ptosis. EMG of the orbicularis oculi showed continuous grouped motor unit potentials. In the absence of obvious aetiology, it is hypothesised that focal demyelination of terminal branches to the orbicularis oculi may play a role in the generation of the discharges.

Segmental neurogenic muscle hypertrophy associated with radiation injury

A 48-year-old man presented with painless left trapezius hypertrophy 20 years after radiotherapy for nasopharyngeal carcinoma. EMG sampling showed myokymic discharges, reduced polyphasic motor unit recruitment and no signs of active denervation. The relationship between radiotherapy, brachial plexopathy and neurogenic muscle hypertrophy is discussed.

Unilateral calf hypertrophy seen in lumbosacral stenosis: case report and review of the literature

STUDY DESIGN

A case report of a patient with neurogenic unilateral calf hypertrophy and review of the literature are reported.

OBJECTIVES

To provide further evidence that S1 radiculopathy is predisposed to develop neurogenic muscle hypertrophy.

SUMMARY OF BACKGROUND DATA

Calf hypertrophy, specifically hypertrophy of the gastrocnemius muscle, is a rare but recognized presentation of S1 and less commonly L5 radiculopathies. The pathophysiology of this is incompletely understood.

METHODS

We present a 59-year-old patient with painless progressive distal right leg weakness and calf enlargement. Electrodiagnostic studies and MAGNETIC RESONANCE IMAGING scanning were performed to evaluate the extent and cause of radicular damage as the etiology for unilateral calf hypertrophy.

RESULTS

Examination and electrodiagnostic studies revealed right L5, right S1, and left L5 radiculopathies. Imaging studies demonstrated lumbar stenosis at L3-L4, L4-L5, and L5-S1 vertebral levels as well as L4-L5 and L5-S1 foraminal stenosis. After decompressive surgery the progressive nature of the patient's symptomatology halted, and he had partial resolution of his deficits.

CONCLUSION

Although the patient had bilateral L5 radiculopathies, he only had hypertrophy in the distribution of his right S1 radiculopathy. This supports the hypothesis that dysfunction of the S1 nerve root or its distribution is a predisposing factor to develop neurogenic muscle hypertrophy. Furthermore, patients presenting with unilateral calf hypertrophy need a careful diagnostic evaluation for S1 radiculopathy as well as to exclude asymmetric presentation of systemic neuromuscular conditions.

Imaging of sports-related muscle injuries

Muscle derangements in athletes have a wide variety of causes, treatments, and prognoses. Given that the cause and severity of sports-related injuries may be difficult to determine clinically in some cases, MR imaging is utilized increasingly to evaluate muscle injuries in athletes. After reviewing useful MR imaging techniques, this article focuses on MR imaging of the most common causes of muscle pain and disability in athletes, including myotendinous strain, delayed onset muscle soreness, muscle contusion, myositis ossificans, muscle laceration, muscle herniation, and compartment syndrome. The differential diagnosis of various signal intensity abnormalities in muscle also is reviewed.

A congenital dermal sinus presenting the muscle fasciculation and hypertrophy

OBJECTIVE

To report unique and unknown clinical features of muscle fasciculation and muscle hypertrophy in a case of congenital dermal sinus.

PATIENTS

A 16-year-old girl presented with continuous fasciculation, often cramp, and hypertrophy of the left calf muscle. The radiography showed spina bifida of L4, L5 and S1. MRI revealed dermal sinus tract from the skin dimple of the back to the dura mater, and connected to the intradural inclusion tumor. At surgery the inclusion tumor contained many short hairs, and the cauda equina were severely adherent. Microdissection of the tumor and the adhesion was performed. At 2 years after surgery fasciculation decreased but continued; however, painful cramps of the calf muscle do not occur.

CONCLUSIONS

Short hairs of dermoid and the adherence might be irritative to the cauda equina. The hyperactivity of the stimulated motor neuron may cause the muscle fasciculation leading to hypertrophy of the calf muscle.

Abnormal signal intensity in skeletal muscle at MR imaging: patterns, pearls, and pitfalls

Abnormal signal intensity within skeletal muscle is frequently encountered at magnetic resonance (MR) imaging. Potential causes are diverse, including traumatic, infectious, autoimmune, inflammatory, neoplastic, neurologic, and iatrogenic conditions. Alterations in muscle signal intensity seen in pathologic conditions usually fall into one of three recognizable patterns: muscle edema, fatty infiltration, and mass lesion. Muscle edema may be seen in polymyositis and dermatomyositis, mild injuries, infectious myositis, radiation therapy, subacute denervation, compartment syndrome, early myositis ossificans, rhabdomyolysis, and sickle cell crisis. Fatty infiltration may be seen in chronic denervation, in chronic disuse, as a late finding after a severe muscle injury or chronic tendon tear, and in corticosteroid use. The mass lesion pattern may be seen in neoplasms, intramuscular abscess, myonecrosis, traumatic injury, myositis ossificans, muscular sarcoidosis, and parasitic infection. Some of these conditions require prompt medical or surgical management, whereas others do not benefit from medical intervention. The ability to accurately diagnose these conditions is therefore necessary, and biopsy may be required to establish the correct diagnosis. Clues to the correct diagnosis and whether biopsy is necessary or appropriate are often present on the MR images, especially when they are correlated with clinical features and the findings from other imaging modalities.

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.

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.

AAEM minimonograph #46: neurogenic muscle hypertrophy

Muscle hypertrophy occurs uncommonly in several neurogenic disorders including neuropathies, radiculopathies, spinal muscular atrophy, and post-polio syndrome. Its pathogenesis varies in different circumstances. In the presence of generalized myokymia and neuromyotonia (Isaacs' syndrome), symmetrical hypertrophy appears to be the result of continuous spontaneous electrical stimulation of myofibers and, in some cases, results in type 1 myofiber preponderance. Focal hypertrophy occurring with radiculopathies and mononeuropathies was associated with complex repetitive discharges (CRDs) in approximately half the cases. CRDs may play a role in the pathogenesis of myofiber hypertrophy by continuous myofiber stimulation, but in some cases, with and without CRDs, myofiber hypertrophy may be related to mechanical events. Muscle enlargement seen in old polio appears to involve a significant degree of pseudohypertrophy, although some myofiber hypertrophy occurs. The symmetrical occurrence of hypertrophy in genetically determined disorders, such as spinal muscular atrophy, and hereditary motor and sensory neuropathy types 1 and 2 may have both a genetic and a mechanical basis in addition to pseudohypertrophy in some cases.

Neurogenic muscle hypertrophy in radiculopathy

The course of radiculopathy is sometimes associated with weakness and wasting of muscles. Very rarely in such cases, however, is hypertrophy of muscle fibres observed. Three cases are presented of sciatica with enlarged calves caused by hypertrophy of type 1 or types 1 and 2 muscle fibres. In light of the literature and the results obtained, an attempt is made to explain the cause of rare clinical symptoms and draw attention to diagnostic and therapeutic difficulties.

Hereditary motor and sensory neuropathy with calf hypertrophy is associated with 17p11.2 duplication

The demyelinating type of hereditary motor and sensory neuropathy (HMSN I) is characterized by progressive weakness and atrophy of leg muscles. Six patients (age, 25-79 yr) belonging to three generations had calf hypertrophy (6 of 6), foot drop or difficulty with heel walking (4 of 6), pes cavus (3 of 6), absent or depressed tendon jerks in the lower limbs (4 of 6), and mild distal sensory loss (3 of 6). No other family member had leg atrophy. Motor conduction velocities ranged from 20 to 40 m/sec. Sural nerve biopsy showed loss of large myelinated fibers, numerous onion bulbs, and segmental demyelination and remyelination. Computed tomographic scans of leg muscles and histological and morphometric findings in gastrocnemius revealed true muscular hypertrophy. Southern blot and fluorescence in situ hybridization documented the duplication of the entire 17p11.2 segment associated with classical HMSN IA. The pathogenesis of muscle hypertrophy in our cases is unclear. Chronic leg muscle weakness and long-standing partial denervation might cause calf enlargement by a combination of compensatory "work-induced" and "stretch-induced" fiber hypertrophy. Alternatively, that all the affected family members presented calf hypertrophy might suggest the action of a genetic factor associated with the duplication at 17p11.2.

Hereditary motor and sensory neuropathy with calf muscle enlargement

We report three related patients with autosomal dominant hereditary motor and sensory neuropathy (HMSN). An unusual and characteristic feature was calf enlargement, caused by muscle fiber hypertrophy predominantly of type 1 fibers. None of the family members showed atrophy of the legs. Sural nerve pathology disclosed marked loss of myelinated fibers and numerous onion bulb formations. While cases of HMSN with calf muscle hypertrophy have been reported, the present pedigree was different from that in any of the previous cases in that no family member showed clinically apparent leg atrophy.

Isolated muscle hypertrophy as a sign of radicular or peripheral nerve injury

Two patients with isolated neurogenic hypertrophy of the trapezius muscle due to accessory nerve injury and a patient with neurogenic hypertrophy of the anterior tibial muscle due to chronic radicular lesion L4 are described. Electromyography of the affected muscles showed dense continuing spontaneous discharges of complex potentials. Muscle biopsy performed in two patients showed abundant hypertrophic muscle fibres, identified in one case by ATP-ase reaction as being of predominantly type I. In the majority of previously reported patients with neurogenic muscle hypertrophy confined to the calf muscle, a passive stretch mechanism was suggested as a cause of the hypertrophy. It is assumed that the excessive spontaneous muscle activity gave rise to the hypertrophy in these patients. This may also be true in previously reported patients with neurogenic hypertrophy and similar spontaneous activity in electromyography.