Journal ofNeurology, Neurosurgery, and Psychiatry 1991;54:325-329 325 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.54.4.325 on 1 April 1991. Downloaded from Isolated muscle hypertrophy as a sign of radicular or peripheral nerve injury

Heinrich P Mattle, Christian W Hess, Hans-Peter Ludin, Marco Mumenthaler

Abstract Case reports Two patients with isolated neurogenic Patient I This 39 year old athletic man was hypertrophy of the trapezius muscle due involved in a head-on car collison nine years to accessory nerve injury and a patient previously. He was wearing a seat belt and with neurogenic hypertrophy of the suffered only minor injuries. Subsequently he anterior tibial muscle due to chronic noticed increasingly painless wave-like muscle radicular lesion L4 are described. motions above his right shoulder. There was no Electromyography of the affected weakness or sensory disturbance. The right muscles showed dense continuing spon- trapezius muscle bulk gradually increased, and taneous discharges of complex poten- because oftwo episodes oftorticollis the patient tials. Muscle biopsy performed in two sought medical advice. patients showed abundant hypertrophic The family history for muscle or nerve muscle fibres, identified in one case by was negative. The clinical examination ATP-ase reaction as being of predomin- showed normal cranial nerves, normal neck antly type I. In the majority of mobility, and symmetrical tendon jerks. The previously reported patients with Babinski sign was negative. Motor and sensory neurogenic muscle hypertrophy confined functions, coordination, and gait were normal. to the calf muscle, a passive stretch Sweating was symmetrical. There was mechanism was suggested as a cause of increased muscle bulk of his right trapezius the hypertrophy. It is assumed that the muscle (fig 1) and frequent muscle twitching. excessive spontaneous muscle activity General physical examination was normal. gave rise to the hypertrophy in these Laboratory tests such as erythrocyte sedimen- patients. This may also be true in tation rate (ESR), white cell count (WCC), previously reported patients with serum chemistries including glucose and cal- neurogenic hypertrophy and similar cium, and creatine phosphokinase (CPK) were spontaneous activity in electromyo- unremarkable. Radiographs of the chest, graphy. shoulders, and scapulae and EKG were

normal. CT (fig 2) of the cervico-thoracic http://jnnp.bmj.com/ region confirmed an increased size and Neurogenic lesions normally cause muscle decreased density ofthe right trapezius muscle. wasting. But occasionally a neurogenic lesion Electrophysiological studies: electromyo- results in hypertrophy of a single muscle. In graphy of the right trapezius muscle showed 1848 R J Graves reported a man with sciatica continuous spontaneous activity at all sites as and subsequent calf enlargement.' A second numerous mostly polyphasic and large poten- case was published in France: in 1918 Lher- tials (peak to peak amplitudes of up to 1-2 mV) mitte noticed a man with calf enlargement on September 28, 2021 by guest. Protected copyright. after a bullet injury to the sciatic nerve.2 In 1932 he reported a second3 and a third patient with the same enlargement after sciatica.4 Further cases of calf enlargement after sciatica were published later."'7 Both Valenstein et al'5 and Vasilescu et al'9 described calf en- largement with chronic relapsing poly- neuropathy. In his first report2 Lhermitte also Department of commented on a soldier who experienced a Neurology, University a forearm of Bern, Bern, thenar hypertrophy after injury, Switzerland and neurogenic hypertrophy of the hand and H P Mattle forearm muscles with chronic relapsing C W Hess has been des- H-P Ludin inflammatory polyneuropathy M Mumenthaler cribed in a recent report.'6 that Correspondence to: Our three patients illustrate neurogenic Dr Mattle, hypertrophy of muscles due to radicular or Departnent ofNeurology, not restricted to the Inselspital, CH-3010 Beme, peripheral nerve lesions is Switzerland calves and may also affect the trapezius and Received 4 April 1990 anterior tibial muscles. They suggest a com- and in revised form for 13 July 1990. mon pathogenetic pathway neurogenic Figure I Patient 1 presenting with a hypertrophied Accepted 23 July 1990 muscle hypertrophy. right trapezius muscle (R = right). 326 Mattle, Hess, Ludin, Mumenthaler J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.54.4.325 on 1 April 1991. Downloaded from

Figure 4 Biopsy from the same specimen as in fig 3 showing a sample with groups of atrophic, angulated fibres, all belonging to type II. Type grouping and targetoid fibres are also present (A TP-ase, pH 46, 7 x) .

months after the lymph node biopsy. Except Figure 2 CT scan of an axial section through the trapezius muscles ofpatient 1. Note the enlarged right trapezius muscle compared with the normal left side (R = right). for the of the upper part of his left trapezius muscle, the general physical and neurological examinations were normal. Bulk occurring at random or as brief grouped dis- and function of the sternocleidomastoid muscle charges. The interference pattern during was normal. ESR, WCC, CPK, and maximal voluntary effort was normal. Motor radiographs of the shoulder were normal. The unit potential analysis revealed a moderate clinical diagnosis was a left accessory nerve prolongation of the average potential duration lesion and it was corroborated by electro- (18 6 mis, 23 potentials measured). myography. Electromyography of the right sterno- As there was no spontaneous improvement, cleidomastoid muscle was normal. Both acces- the patient had surgery for his nerve lesion. sory nerves showed normal motor latencies to The surgical findings showed a completely the trapezius muscles. transsected left accessory nerve at the site of the Muscle biopsy from the right trapezius lymph node biopsy. The proximal and distal showed sections with abundant hypertrophic nerve endings were easily found, an anasto- fibres predominantly oftype I as well as sections mosis was made, and the nerve was sutured. Six with small groups of atrophic, elongated type months later electromyography showed "high II fibres according to the ATP-ase reaction, and frequency complex repetitive discharges" in type grouping was evident (figs 3, 4). The the left trapezius muscle. A year later there was overall distribution of type I and II fibres was a prominent hypertrophy of the left trapezius normal. A diagnosis of right accessory nerve muscle. The muscle weakness was still present, lesion was made. with force against very slight resistance (Grade Patient 2 The family history of this 20 year 3 to 4 according to the MRC scale). old asthenic man was negative. At the age of 18 Electromyography of the upper portion of

he had a scalenic lymph node biopsy on his left the left trapezius muscle showed continuous http://jnnp.bmj.com/ side. The lymph node histology was com- and dense repetitive discharges of simple or patible with a cat scratch disease. Approxi- polyphasic potentials mostly of high frequency mately one month later he felt pain in his left ( > 10 Hz) at all sites in the completely relaxed shoulder and subsequently noticed weakness of muscle. Additional discharges were triggered his left shoulder and arm. He was referred six by needle movements and voluntary contrac- tions. There was a fair amount of voluntary activity, which yielded an intermediate pattern on September 28, 2021 by guest. Protected copyright. at maximal voluntary activation. Stimulation of 12 T I...... the left accessory nerve produced a muscle response of prolonged latency in the trapezius muscle. A diagnosis of left accessory nerve lesion was made. Patient 3 This was a 41 year old farmer and ski instructor with a negative family history for ._ 54 muscle and nerve . At the age of 29 he 0 0 z ...... 81...... h...... l050 ...... 00 15 ...... 200S1!Ell

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50 100 150 200 Fibre diameter (,um) Figure 3 Musclefibre histogram of the biopsyfrom the trapezius muscles ofpatient 1 Figure 5 CT scan through the lower legs ofpatient 3. showingfibre diameters and type distribution. There are abundant hypertrophicfibres, Note the hypertrophic left anterior tibial muscle predominantly of type I and also atrophic type IIfibres. Fibre type distribution is normal (arrowheads) compared with the normal right side (Specimen10 860916, A TP-ase, pH 4-6, 10 x ). (R = right). Isolated muscle hypertrophy as a sign of radicular or peripheral nerve injury 327 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.54.4.325 on 1 April 1991. Downloaded from Figure 6 Needle-EMG normal. The motor conduction velocity of the from the left tibialis left peroneal nerve was normal over all anterior muscle ofpatient O, 3 showing continuous slow segments. frequency rhythmic lOOmfs A diagnosis of muscle hypertrophy due to repetitive activity of longstanding left L4 root lesion was made. complex potentials typical of "myokymic discharges". i1 0 5 m v~~~~~~~~~0m Discussion ; i;*- Hypertrophy is a physiological response of muscle to work.202' Stretch may also induce + . 4 @ __i~~~~~~~, 500ms muscle hypertrophy,22 even in the absence of innervation. Pathological conditions leading to had an operation for a left lumbar 3/4 disc muscle hypertrophy include myotonia hernia and a spondylodesis. In the following congenita and other forms of myotonias,23 years he had intermittent back pain radiating to dystonias, acromegaly, chronic spinal muscle his left thigh distally and medially and to his atrophy,24 26 a familial27 and a sporadic ataxia,28 lower leg anteriorly and medially. Nonsteroidal the Schwartz-Jampel syndrome,29 30 the anti-inflammatory drugs reduced the pain. At Hoffmann's syndrome,3' post-poliomyelitis the age of 40, however, he experienced a muscle hypertrophy,32 and polyneuropathy substantial increase in discomfort, and for the associated with continuous spontaneous first time noticed a gradually increasing swell- activity. 19 3131 Muscle hypertrophy following ing, lateral to his left tibia. Suspecting a muscle nerve injury has been the subject of experi- sarcoma, a biopsy was taken and was con- mental work.36 The phenomenon has been sidered negative. CT showed an increased bulk reported occasionally in humans''7 but rarely of the anterior tibial muscle with a normal cited in textbooks.37 density (fig 5). One year later he was referred for All reported human cases of muscle hyper- further investigation since the muscle swelling trophy due to radicular or peripheral nerve was still increasing. injuries were restricted to the calves except one The clinical examination showed a painless of Lhermitte's cases.2 Bernat and Ochoa swelling of the left anterior tibial muscle. proposed combined work- and stretch-induced Elevation of the left foot was slightly weaker post-denervation muscle hypertrophy as an than on the right side. The left knee jerk was explanation.8 They supported their hypothesis decreased. The remaining tendon jerks were with biopsy findings from the gastrocnemius symmetric and brisk. The circumference of the muscle. These showed changes of partial den- thighs was equal, but the left lower leg ervation and reinnervation, with small groups measured 34 cm and the right only 32 cm. of type I and II atrophic muscle fibres and There were no other neurological abnor- abundant hypertrophic fibres of both types but malities. Skin temperature was 32°C over both mostly type II. They postulated that, in addi- anterior tibial muscles ruling out an inflam- tion to compensatory work-induced type II matory process. ESR, WCC, electrolytes, muscle fibre hypertrophy, there was an element

glucose, creatinine, serum aspartate amino- of stretch-induced type I hypertrophy of http://jnnp.bmj.com/ transferase, alkaline phosphatase, and chest denervated fibres. Such a condition has been radiographs were normal. Serum alanine well recognised experimentally but had not aminotransferase was 46 mU/ml (normal up to been documented previously. 27 mU/ml) and CPK was 159 mU/ml (normal The assumption of work- and stretch- up to 125 mU/ml). induced hypertrophy ofdenervated fibres is not The muscle biopsy specimens obtained a an entirely satisfactory explanation. If it was, year earlier in another laboratory were revised. then calf hypertrophy would be a much more Only HE and van Gieson stains were available. common finding in longstanding S1 root on September 28, 2021 by guest. Protected copyright. The fibre size showed an abnormal variability. lesions. The hypothesis might explain some of Hypertrophic fibres were present in large the effects on the calf muscles, which are the number, some with segmentation and an muscles most often used and stretched in the increased number of central nuclei. The aspect daily activities because of the upright posture was non-specific and was considered consistent of humans. Biopsy findings in two of our with both a myopathic process and with patients are compatible with this assumption secondary myopathic changes due to a chronic and also with chronic denervation and rein- denervation. nervation.38 However, the fact that in two ofour Electromyography of the left anterior tibial patients the trapezius muscle and in another muscle showed continuing high and low patient the anterior tibial muscle were hyper- frequency repetitive discharges ofmostly poly- trophied weakens the hypothesis of combined phasic potentials at all sites in the relaxed work and stretch as a major cause and raises the muscle (fig 6). In addition, there were grouped question of further pathogenetic factors. discharges of regularly occurring bursts of In our three patients dense continuing spon- several potentials. The density of this spontan- taneous discharges of complex potentials were eous activity obscured the motor unit poten- the prominent finding in electromyography of tials of volitional activation at the optical signal the hypertrophied muscles. Lapresle et al,6 display. The left gastrocnemius muscle showed Mielke and Ricker,9 Cooper et al," Lagueny et a reduced pattern at maximal voluntary activity al,'4 Valenstein et al'8 and Vasilescu et al'9 also but no spontaneous activity. Electromyo- described striking spontaneous activity in the graphy of the left lateral vastus muscle was needle electromyography of the hypertrophied 328 Mattle, Hess, Ludin, Mumenthaler

muscles denoted as "spontaneous motor unit muscle hypertrophy can be a sign of partial J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.54.4.325 on 1 April 1991. Downloaded from potentials", "fasciculations", "myotonic", peripheral nerve or root lesion, and it probably "pseudomyotonic", or "trains of repetitive" may occur in any skeletal muscle. Since discharges. neurogenic muscle hypertrophy is rare, focal Depending on firing rate and rhythm, dif- myositis or primary muscle might ferent terms have been used to characterise be suspected. This may lead to unnecessary, complex discharges: "fasciculations" generally costly, and sometimes invasive investigations denote motor-unit type potentials firing at ran- which could be avoided when the possibility of dom. The terms "pseudomyotonic", "bizarre neurogenic hypertrophy is considered. The high frequency", or "complex repetitive" dis- electromyographic finding in a hypertrophied charges have been used, when the potentials fire muscle of profuse spontaneous activity con- at a uniform frequency of 5 to 100 Hz. The firms the diagnosis. terms "grouped fasciculations" or "bizarre low frequency", "bizarre repetitive" and "myo- We thank Mrs Th Lauterburg and Mrs U Walker for technical kymic" discharges have been used for more or assistance. less rhythmical firing at 5 Hz or less either of single complex potentials or of short bursts of Graves RJ. Clinical lectures on the practice ofmedicine, Vol potentials. Common to all these types of 1, 2nd ed. Dublin: Fannin, 1848:498. 2 Lhermitte MJ. Hypertrophie des muscles de la jambe complex discharges is that they usually occur in conseutive a une lesion du nerf sciatique par balle. Rev chronic or longstanding neuromuscular dis- Neurol (Paris) 1918;26:56-8. 3 Lhermitte MJ. Sur l'Hypertrophie musculaire consecutive orders. High frequency complex repetitive aux lesions graves des nerfs peripheriques. Une observa- discharges have been found in a variety of tion nouvelle. Rev Neurol (Paris) 1918;25:529-30. 4 Lhermitte J, Albessard. L'hypertrophie musculaire de la peripheral neurogenic disorders such as mus- jambe dans la nevrite sciatique. Rev Neurol (Paris) cular , polymyositis, spinal muscular 1932;39:78-90. 5 Coste F, Hervet E. Diagnostic d'un gros mollet. Revue du atrophy, amyotrophic lateral sclerosis, and Rhumatisme 1942;9:69-72. chronic neuropathies.40 Myokymic (low 6 Lapresle J, Fardeau M, Said G. L'hypertrophie musculaire vraie secondaire a une atteinte nerveuse periph&rique: frequency) discharges and fasciculations have Etude clinique et histologique d'une observation frequently been found in partial old nerve d'hypertrophie du mollet consecutive aune sciatique. Rev Neurol (Paris) 1973;128:153-60. lesions such as chronic entrapment,4 42 7 McComas AJ. 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