Benign monomelic amyotrophy of lower limb: report of three cases

Study of monomelic amyotrophy of the lower limbs in the territory of the Western Balkans: Case series

RATIONALE

Monomelic amyotrophy is a rare form of motor neuron disease in which the neurogenic atrophy is restricted to 1 limb, mostly the distal part of the arm. The disease most often occurs in Asia, especially in Japan and India, while in European countries, this disease is rarely recognized. Registration and publication of new cases of this disease aims to increase the awareness of clinicians about the existence of this disease in European countries, and with the aim of easier recognition and faster diagnosis of this essentially benign disorder.

PATIENT CONCERNS

Five patients with signs of atrophy of the muscles of 1 leg were examined at our Institution.

DIAGNOSES

The criteria for selecting patients were as follows: clinical evidence of wasting and weakness confined to the 1 lower limb; progressive course, or initial progression followed by stationary course; absence of any definite sensory loss or central nervous system involved; no evidence of compression lesion of the spinal cord.

INTERVENTIONS

The clinical characteristics of our patients were similar to those previously described in the literature. The characteristic clinical features were sporadic occurrence, predominance in males with an initially progressive course for 2 to 5 years followed by a stationary state. There was no family history of neuromuscular disease.

OUTCOMES

The electromyographic finding was consistent with a chronic neuropathic disorder. Magnetic resonance imaging of the lumbosacral spine excluded intraspinal pathologies and root compression in all cases.

LESSONS SUBSECTION

Monomelic amyotrophy of the lower limb is a rare disease that should be considered in cases of slow progressive unilateral amyotrophy of a single leg, especially in younger and middle-aged men, not only in Asia but also in the Western Balkans and Europe.

Wasted leg syndrome: An atypical slowly-progressive form of lower motor neuron disease

We describe four male patients with wasted-leg syndrome, with predominant asymmetric thigh atrophy and weakness that stabilized after a period of slow progression (follow-up 7-18 years). Two patients had an Indian ethnic background and two were Portuguese, without known Indian ancestry. Other mimicking disorders were excluded, but one Indian patient was later diagnosed with CADASIL. Electromyography (EMG) revealed severe chronic neurogenic changes in proximal leg muscles, and mild changes in distal leg muscles, but EMG of the upper limbs was normal. Upper motor neuron signs were absent clinically and on transcranial magnetic stimulation. This seems to represent a variant of the common wasted-leg syndrome presentation.

Benign monomelic amyotrophy of lower limb in a cohort of chinese patients

BACKGROUND

Benign monomelic amyotrophy of lower limb (BMALL) is a neurogenic syndrome representing an unclear field. Further studies might be helpful to elucidate uncertainties regarding causation, outcome, and the risk of progression to amyotrophic lateral sclerosis (ALS).

METHODS

According to the inclusion and exclusion criteria, 37 patients with BMALL were retrospectively collected in three neuromuscular centers from January 2012 to October 2018. The detailed medical data were summarized. Multiple laboratory tests were examined. Routine electrophysiological examinations, muscle MRI of lower limbs, and muscle biopsy were conducted.

RESULTS

The cohort included 24 male and 13 female cases with median age of onset 47 years. Muscle MRI revealed that the distribution of involved muscles matched with the extent of fat infiltration, so the pattern muscle atrophy can be divided into the following four types: six patients with thigh atrophy (type I), 14 patients with leg atrophy (type II); 10 patients with disproportionate atrophy in both thigh and leg (type III); and seven patients with well-proportionate atrophy in both thigh and leg (type IV). Electrophysiological findings showed neurogenic pattern, spontaneous activity, and abnormal H reflex, which suggested a disorder of spinal anterior horn cell in the patients with types I-III. However, no electrophysiological abnormalities were found in the patients with type IV. Muscle pathology varied from almost normal pattern to advanced neurogenic pattern in nine biopsied patients. Follow-up showed that two patients with type II developed to ALS four years later, and all patients with type IV were in stable condition without any complaints.

CONCLUSION

Muscle MRI was useful to exactly localize the distribution of involved muscles in BMALL patients. The distribution of atrophic muscles can be roughly divided into four types based on the MRI features. The classification of distributing types might be as an indicator for the prognosis of BMALL.

PROXIMAL BRACHIAL MONOMELIC AMYOTROPHY OR HIRAYAMA DISEASE: NO LONGER AN ALIAS? (case report)

Background. Brachial Monomelic Amyotrophy (BMMA) has been called as Hirayama disease (HD) when it is characterized by unilateral distal upper limb weakness and atrophy that shows progression for a limited period and is associated with typical features on MRI of cervical spine in flexion. Objective was to explore the differences when BMMA affects the proximal upper limb muscles with the help of case report. Methods. A case report of BMMA in an adult Indian male is represented. Results. A 30-year-old man presented to us with a history of weakness in the proximal aspect of his left upper limb that began four years ago. The weakness was progressive up until 6 months prior to his presentation since when the weakness had neither worsened nor improved. Cervical spine contrast enhanced MRI revealed mild loss of cervical lordosis, but no features of HD like localized cord atrophy, loss of attachment of dura from subjacent lamina on neutral position axial T2WI MRI, nor any presence of posterior epidural crescentic enhancing mass on flexion contrast sagittal T1WI MRI. The patient was managed with supportive therapy and has been under regular follow up ever since. His clinical status has been stable. Conclusions. We support the suggestion to consider proximal Brachial Monomelic Amyotrophy to be a separate entity and to be distinguished from Hirayama disease that should be reserved for patients with distal upper limb involvement with cervical MRI findings on flexion studies.

Benign monomelic amyotrophy with lower limb involvement in an adult: A case report

RATIONALE

Monomelic amyotrophy (MMA) is a benign motor neuron disease with bilateral muscular atrophy in asymmetry and abnormal in the electromyography (EMG). However, we report a case by the muscle biopsy which shows symptoms of slowly progressive amyotrophy despite having a normal EMG.

PATIENT CONCERNS

A 51-year-old male was diagnosed with a lower limb amyotrophy, insidious at the onset and located in the distal thigh and the proximal crus near the knee, slowly progressive weakness, and wasting of his right gastrocnemius muscle for the last 20 years.

DIAGNOSES

He was diagnosed with MMA by the clinical profile, natural history, examinations, and the biopsy.

INTERVENTIONS

We perform dynamic physical therapy for the patient in this case.

OUTCOMES

The positive effects of dynamic physical therapy in this case with MMA were shown in this report.

LESSONS

The outcome of physical therapy is satisfactory.

Benign focal amyotrophy

Within lower motor neuron diseases, benign focal amyotrophy is a rare syndrome characterized by insidious neurogenic asymmetric atrophy restricted to upper or lower limbs with a good prognosis over time. Described under several terms, the nosology is probably heterogeneous. In juvenile distal upper-limbs forms, specific MRI signs with in particular a compression of the spinal cord by forward displacement of dura, lead to evoke a mechanical process. In other forms, occurring later in the life, affecting proximal part of upper limbs or lower limbs, the physiopathology is still unknown and a focal spinal muscular atrophy is suspected. In this review, we will discuss the clinical, electrophysiological and radiological features of each presentation.

Monomelic amyotrophy: clinical profile and natural history of 279 cases seen over 35 years (1976-2010)

Our objective was to study the clinical characteristics and natural history of monomelic amyotrophy (MMA). We used a retrospective study of 279 patients diagnosed to have either upper (Hirayama disease) or lower limb MMA. Results showed that brachial MMA (BMMA) occurred in 224 patients (male:female, 9:1). Mean age of onset was 19.5 ± 4.18 years. Progression occurred over less than five years in the majority (95.9%) of patients. Duration at the last follow-up was: up to five years in 61.4%, 5-10 in 21.3%, 10-15 in 7.2%, > 15 years in 10.1%. MRI showed asymmetrical lower cervical cord atrophy in 44.6% of patients. Crural MMA (CMMA) occurred in 55 patients (male:female, 13:1). Mean age of onset was 21.38 ± 5.3 years. Similar to BMMA, most cases (65.5%) had onset between 15 and 25 years of age. Total duration of illness at the last follow-up was up to five years in 52.7%, 10 and beyond in 47.3%. In conclusion, a large cohort of patients with monomelic amyotrophy seen over 35 years (1976-2010) is described. Study data support the clinical findings and its natural history with long term follow-up, and the findings emphasize that monomelic amyotrophy is a 'benign' condition with a self-limiting course.

Monomelic amyotrophy is not always benign: a case report

Monomelic amyotrophy (MA) is a variant of motor neuron disease (MND), characterized by muscle weakness and atrophy restricted to one limb. We describe the case of a 56-year-old Italian patient who developed a segmental muscular atrophy limited to the lower left limb. After 11 years of clinical stability he developed progressive spread of the disease to all limbs and to bulbar and respiratory muscles. The patient died from respiratory failure 15 years after disease onset. This case demonstrates that monomelic amyotrophy may rarely evolve to a diffuse fatal MND, even after more than a decade of clinical stability. Our findings support the idea that MA is part of the clinical continuum of MND.

Benign monomelic amyotrophy with proximal upper limb involvement: case report

Monomelic amyotrophy (MA) is a rare condition in which neurogenic amyotrophy is restricted to an upper or lower limb. Usually sporadic, it usually has an insidious onset with a mean evolution of 2 to 4 years following first clinical manifestations, which is, in turned, followed by stabilization. We report a case of 20-years-old man who presented slowly progressive amyotrophy associated with proximal paresis of the right upper limb, which was followed by clinical stabilization 4 years later. Eletroneuromyography revealed denervation along with myofasciculations in various muscle groups of the right upper limb. We call attention to this rare location of MA, as well as describe some theories concerning its pathophysiology .

Monomelic neurogenic syndromes: a prospective study

Monomelic neurogenic syndromes are rare. Their classification and prognostic features have not been addressed in the European population. A prospective study of 17 patients with monomelic neurogenic amyotrophy, of upper or lower limb onset, with progression limited to one limb for three or more years. Clinical and neurophysiological studies were performed in the subsequent 3 or more years. Fifteen patients were of European origin and two were Asian. Those presenting with proximal monomelic weakness or with involvement of the posterior compartment of the lower leg showed no further progression after the initial period of development of the syndrome. Brisk reflexes in wasted muscles did not predict progression. Electromyographic signs of denervation in the opposite limb at presentation did not predict later progression. Transcranial magnetic stimulation (TMS) features of corticospinal dysfunction were a useful predictor of subsequent progression (p=0.01). One patient with lower limb onset developed conduction block with weakness in an upper limb nine years after presentation, and this upper limb weakness responded to IVIg therapy. This adult-onset European group of patients is different as compared with juvenile-onset Asian cases. The clinical syndromes appear heterogeneous, but neurophysiological investigations, in particular TMS, can be helpful in determining prognosis. Multifocal motor neuropathy should be considered when there is progression, even years after onset.

IgM antibodies to N-acetylgalactosaminyl GD1a in benign monomelic amyotrophy of the lower limb

A male Caucasian patient is presented with a greater than 10-year history of painless weakness of the right leg, stable over the last 7 years. His examination demonstrated severe wasting and moderate weakness of his right calf muscle. Electrodiagnostic study revealed acute denervation of the right calf and chronic partial denervation of multiple right leg muscles. MRI demonstrated atrophy and fatty infiltration of the right calf muscles. Based on previous clinical, electrophysiologic, and radiologic descriptions of this disorder, a diagnosis was made of benign monomelic amyotrophy of the lower limb. Serologic examination for anti-glycoconjugate antibodies revealed high titers of IgM antibodies with selective binding to the disialoganglioside N-acetylgalactosaminyl GD1a (GalNAcGD1a). Testing for antibodies to GalNAcGD1a should be considered in patients with this phenotype. Their presence could suggest a role for immunomodulatory therapy.

Multifocal motor neuropathy presenting as chronic progressive proximal leg weakness

We report on a 47-year-old man with a 12-year history of progressive and ultimately severe proximal weakness of his right lower limb. Motor conduction block at the unaffected tibial nerve and positive IgM antibodies against GM1 gangliosides lead us to suggest a diagnosis of oligosymptomatic multifocal motor neuropathy. He rapidly responded to intravenous immunoglobulins, with complete remission lasting 4 weeks, and had a repeated treatment response to intravenous immunoglobulins during subsequent exacerbations. The proximal involvement may represent another unusual clinical manifestation of multifocal motor neuropathy.

Sympathetic skin response in monomelic amyotrophy

OBJECTIVES

Monomelic amyotrophy (MMA) a variant of motor neuron disease, has the characteristic features of wasting and weakness usually confined to a single upper or lower limb occurring predominantly in young males and a benign outcome. Symptoms of increased sweating, coldness and cyanosis have been observed in a few patients. The objective was to evaluate the involvement of the sympathetic nervous system in MMA by measuring sympathetic skin response.

METHODS

Electromyography, motor and sensory nerve conduction studies were done in all the four limbs of 9 patients with atrophy of one upper limb. Stimulation at Erb's point, and above and below elbow was done to look for evidence of conduction block. The sympathetic skin response (SSR) was recorded in all the limbs of these patients. Wasting and weakness of right upper limb in 7 patients and left upper limb in 2 patients was seen. The mean age was 28.3+/-10.1 years. Twenty-five age matched (24.8+/-4.8 years) healthy subjects served as controls.

RESULTS

The mean SSR latency in the affected upper limbs of 9 patients was prolonged compared to the 25 control subjects (1.51+/-0.07 s vs 1.42+/-0.19 s, P=0.03). The mean value of SSR latency in 18 upper limbs of the 9 patients which included atrophied and unatrophied limbs was also prolonged compared to the controls (1.50+/-0.08 s vs 1.42+/-0.19 s, P=0.05). There was no significant difference of the mean latency of SSR between the atrophied upper limbs and the clinically normal upper limbs (1.51+/-0.07 s vs 1.49+/-0.09 s, P=0.51). The mean SSR latency in the lower limbs of the patients (2.09+/-0.09 s) did not significantly differ from the control subjects (1.97+/-0.28 s, P=0.09). Motor and sensory nerve conduction was normal and there was no evidence of conduction block.

CONCLUSION

In MMA the sympathetic nervous system is involved in the atrophic upper limb and also in the clinically unaffected upper limb but not in the lower limbs.

Non-progressive juvenile spinal muscular atrophy of the distal upper limb (Hirayama's disease): a clinical variant of the benign monomelic amyotrophy

Hirayama's disease (HD) is frequently found in Asia, and is rarely referred among westerners. It affects young people with higher incidence in males. It is a focal distal amyotrophy with unilateral or asymmetric bilateral involvement of C7, C8 and T1 innervated muscles. HD appears sporadically and has a benign evolution with clinical stabilization in around one year. We report four young male patients with clinical and electrophysiological alterations described in HD, which were followed-up during 5 years. Electromyographic findings were indicative of lower motor neuron involvement. We analyzed cervical MRI aiming at understanding if a questionable spinal cord compression could be implicated in the pathogenesis, but no abnormality was verified. In view of its clinical, and EMG characteristics, HD is no more than a benign monomelic amyotrophy (BMA) clinical variant, and not a specific disease. This eponym could be considered only for the distal upper limb variant (Hirayama's variant) of the BMA.

Benign monomelic amyotrophy: a study of twenty-one cases

A consecutive series of 21 patients with single limb atrophy (monomelic amyotrophy) is reported. Sixteen had lower limb atrophy and five had upper limb involvement. The median age of the onset was 20 years. Characteristic features were sporadic occurrence, wasting confined to one limb, insidious onset with slow progression, stabilizing in 1 to 4 years, and absence of pyramidal signs. All the patients with upper limb involvement were male, however in our cases with lower limb amyotrophy there were no male preponderance. We observed wasting of the entire length of the lower limbs in six patients. There were nine cases with amyotrophy restricted to the leg and one with amyotrophy only in the thigh. In the upper limb in four cases the involvement was distal and in one patient the atrophy was proximal. The electromyographic features were suggestive of anterior horn disease not only in the affected limb but also, in some cases, in clinically uninvolved limb. Cervical or lumbar MRI was normal. MRI of the lower limb disclosed increased signal intensity in the gastrocnemius and soleus muscles in one patient suggesting denervation.

MRI findings of benign monomelic amyotrophy of lower limb

We report here magnetic resonance imaging (MRI) findings of two patients with benign monomelic amyotrophy of lower limb. Both subjects showed unilateral amyotrophy of the lower limb with a benign clinical course, and the affected muscles demonstrated neurogenic changes. On T1- and T2-weighted MRI, marked atrophy and increased signal intensity were found mainly in gastrocnemius and soleus muscles. Moreover, MRI examination also revealed that thigh muscles including semitendinosus, semimembranosus, and vastus intermedius and lateralis muscles were involved in one of the patients. We concluded that muscle MRI is very useful for detecting affected muscles, especially deep skeletal muscles in patients with benign monomelic amyotrophy of lower limb.

Delayed focal involvement of upper motor neurons in the Madras pattern of motor neuron disease

We report the case of a young man from the south of India, initially presenting the typical signs of benign monomelic amyotrophy (BMA) in the left upper limb. After several years, the involvement of other limbs and the appearance of bulbar signs suggested the possible diagnosis of the Madras pattern of motor neuron disease (MMND). Serial motor evoked potential (MEP) recordings allowed detection of the onset of a focal involvement of upper motor neurons (UMN) controlling innervation in the originally amyotrophic limb. Therefore, serial MEP recordings can be useful for the early detection of sub-clinical UMN damage in motor neuron disease presenting with pure lower motor neuron (LMN) signs.

Monomelic amyotrophy following trauma and immobilization in children

Two children aged 9 and 11 years suffered from left elbow sprain and right anterior tibial tuberosity cortical fracture respectively and were treated with plaster cast immobilization for about 30 days. They regained normal strength afterwards, but 9 and 2 months later developed insidious progressive weakness and wasting in the affected limb, mainly evident in the musculature surrounding the site of injury and sparing hand and foot muscles. Two to three years later the condition stabilized. Sensory abnormalities were not found. Electromyographic examination showed neurogenic pattern confined to the impaired extremity. The focal quality and the unusual disposition of muscle involvement suggest a correlation between trauma and/or immobilization and monomelic amyotrophy.

Benign monomelic amyotrophies of upper and lower limb are not associated to deletions of survival motor neuron gene

Benign monomelic amyotrophies (BMAs) are rare conditions in which neurogenic atrophy is restricted either to the upper or lower limb. BMAs are usually sporadic, have insidious onset and slow progression followed by stabilization, are clinically confined for many years to a single limb and lack of sensory, bulbar, and pyramidal signs. Although the aetiology and pathogenesis of BMAs are unknown they are considered variants of spinal muscular atrophy with focal emphasis and a benign course. We studied 7 patients with BMAs to investigate whether they present alterations of the survival motor neuron gene (SMN) which has been found deleted or disrupted in proximal spinal muscular atrophy. All 7 patients showed the presence of both exon 7 and 8 of SMN gene. These findings indicate that deletions at the SMN locus are not present in BMA of upper and lower limb and suggest that these disorders are not only clinically but also genetically separate entities from proximal spinal muscular atrophies.

Benign monomelic amyotrophy of lower limb: a rare entity with a characteristic muscular CT

Six patients presented with amyotrophy confined to a single lower limb and characterized by insidious onset, slow progression and later stabilization. Wasting was out of proportion with disability and there were no sensory, pyramidal tract or bulbar signs. All cases were sporadic, and there was no history of poliomyelitis. CK, anti-ganglioside antibodies, motor and sensory conductions were normal. Quantitative EMG and muscle biopsy revealed neurogenic features also in clinically unaffected limbs. Muscular CT showed selective or predominant, asymmetrical involvement of posterior leg muscles and caput longus of biceps femoris. Monomelic amyotrophy of lower limb is a clinically localized variant of spinal muscular atrophy with a particularly benign course. Although in the early stage there are no clinical or laboratory findings which allow differential diagnosis with other motor neuron diseases, the history of an amyotrophy clinically localized for more than 3 years to a lower single limb and the characteristic muscular CT pattern suggest the diagnosis since the first observation and indicate a favorable prognosis.

AAEM case report #28: monomelic amyotrophy

Monomelic amyotrophy is a rare form of motor neuron disease usually presenting as painless asymmetric weakness and atrophy in the distal upper extremities of young adults. Only rarely are the legs involved and pyramidal findings are uncommon. Monomelic amyotrophy is most often observed in people of Japanese and Indian heritage and affects men almost exclusively. Most cases are sporadic. Laboratory testing is frequently normal or nonspecific except for electrophysiologic studies which typically demonstrate reduced compound muscle action potential amplitudes, fasciculations, and features consistent with acute and chronic denervation in distal upper extremity muscles. Necropsy in 1 patient identified anterior horn cell shrinkage, necrosis, and gliosis in appropriate spinal cord segments. Symptoms and signs often progress for several years before spontaneously arresting. The differential diagnosis for monomelic amyotrophy is broad, including processes which affect the cervical cord, roots, brachial plexus, and individual or multiple nerves in the upper extremity.