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

Amyotrophic lateral sclerosis; clinical features, differential diagnosis and pathology

Amyotrophic lateral sclerosis (ALS) is a late-onset syndrome characterized by the progressive degeneration of both upper motor neurons (UMN) and lower motor neurons (LMN). ALS forms a clinical continuum with frontotemporal dementia (FTD), in which there are progressive language deficits or behavioral changes. The genetics and pathology underlying both ALS and FTD overlap as well, with cytoplasmatic misvocalization of TDP-43 as the hallmark. ALS is diagnosed by exclusion. Over the years several diagnostic criteria have been proposed, which in essence all require a history of slowly progressive motor symptoms, with UMN and LMN signs on neurological examination, clear spread of symptoms through the body, the exclusion of other disorder that cause similar symptoms and an EMG that it is compatible with LMN loss. ALS is heterogeneous disorder that may present in multitude ways, which makes the diagnosis challenging. Therefore, a systematic approach in the diagnostic process is required in line with the most common presentations. Subsequently, assessing whether there are cognitive and/or behavioral changes within the spectrum of FTD and lastly determining the cause is genetic. This chapter, an outline on how to navigate this 3 step process.

Characteristics of Hirayama Disease in Young South Korean Soldiers

BACKGROUND AND PURPOSE

The purpose of this study was to describe the clinical presentation and features in electrodiagnostic and imaging investigations of young South Korean males diagnosed with Hirayama disease (HD).

METHODS

We reviewed the electronic medical records of South Korean enlisted soldiers who were diagnosed with HD and discharged from military service during 2011-2021. We investigated the clinical characteristics and results of electrodiagnostic and magnetic resonance imaging (MRI) investigations. We analyzed laterality and identified the involved muscles using needle electromyography (EMG). Loss of lordosis, localized cervical cord atrophy, loss of attachment between the posterior dura and subjacent lamina, asymmetric flattening of the cord, crescent-shaped mass in the posterior epidural space, and noncompressive intramedullary T2-weighted high signal intensity were investigated using neutral- or flexion-position MRI.

RESULTS

Forty-two male patients aged 20.2±0.8 years (mean±standard deviation) were identified. All patients complained of hand weakness, and 10 complained of hand tremor (23.8%). Four patients (9.5%) had symptoms in both upper limbs, and five (11.9%) had sensory disturbances. Needle EMG revealed that muscles in the C7-T1 myotome were commonly involved, and C5-C6 involvement of the deltoid (10.5%) and biceps brachii (12.5%) was also observed. In cervical MRI, localized cord atrophy (90.0%) was the most characteristic finding, and cord atrophy was most severe at the C5-C6 level (58.3%).

CONCLUSIONS

This is the first description of a large number of patients with HD in South Korea. The clinical presentation and features found in electrodiagnostic and imaging investigations will improve the understanding of HD in the young South Korean male population.

Long term quality of life follow-up and functional impairment study in patients with Hirayama disease

Hirayama Disease (HD) is a focal motor neuron disorder generally affecting young adults with a male predominance who experience weakness and atrophy in distal upper extremity muscles in an asymmetric or unilateral pattern. Progression is insidious though significant weakness occurs during a progressive phase of the disease over 2-5 years. The long-term outcome of HD is not as well-known and, thus, this study presents self-reported outcomes from HD patients years after a diagnosis. Thirty HD patients reported quality of life (QOL) and other functional outcome measures after a mean of just over 11 years from diagnosis. Variables that predicted better or worse outcome were analyzed. Overall, QOL was affected by HD though most patients were functional with limitations. No clear attributes of patients or their disease predicted outcome.

Monomelic Amyotrophy/Hirayama Disease: Surgical Outcome in a Large Cohort of Indian Patients

BACKGROUND

Hirayama disease (HD) is a cervical compressive myelopathy. Anterior cervical discectomy and fusion (ACDF) is identified as the best surgical approach. We evaluated surgical outcomes and factors influencing ACDF in HD.

METHODS

Between 2015 and 2019, 126 patients with HD underwent ACDF. Contrast magnetic resonance imaging of the cervical spine in full flexion was performed. Clinical examination and preoperative/postoperative assessment of hand function using Fugl-Meyer assessment, Jebsen-Taylor hand function test, and handheld dynamometry were performed at 3-monthly intervals for 1 year. Surgical outcomes were assessed as per the Odom criteria and Hirayama outcome questionnaire.

RESULTS

Age at onset and duration of illness were 12-31 years (mean, 18 ± 2.7) and 1-96 months (32.7 ± 24.4), respectively. All patients had progressive weakness and wasting of the affected limb. Cord atrophy was seen in 97.1%, with epidural detachment and engorgement of the posterior epidural venous plexus in all. All patients underwent ACDF. Of these patients, 54% had an excellent/good outcome and 39% had a satisfactory outcome as per the Odom scale at last follow-up (mean, 44.9 ± 16.5 months) after surgery. Handheld dynamometry showed improvement from preoperative values to 1 year follow-up. Duration of illness and age at onset had a negative correlation and the preoperative Fugl-Meyer score had a positive correlation with improvement.

CONCLUSIONS

ACDF resulted in remarkable improvement or stabilization in neurologic deficits in many patients with HD. Because motor disability ensues over time, early surgical intervention during the progressive phase is advocated.

Venous pathology targeted surgical management in Hirayama disease: A comprehensive case series of nine cases exploring this potential etiology

Objective

Hirayama disease is a rare cause of cervical myelopathy predominantly affecting young individuals. The disease is classically characterized by muscle atrophy in the distal upper limbs. While various etiopathogenesis such as dural sac dysplasia, nerve root dysplasia, structural abnormalities of the spinal ligament, and venous dysplasia have been proposed, this study explores the potential role of venous pathology and surgical management on the basis of it.

Methodology

This is a prospective descriptive case series of nine cases. The diagnosis was made based on the Huashan diagnostic criteria which includes clinical manifestation, imaging, and electrophysiology. In cases where magnetic resonance imaging (MRI) failed to demonstrate engorged veins, a computed tomography (CT) venogram of the cervical spine was used as an imaging tool. All patients underwent cervical laminectomy and coagulation of the posterior epidural venous plexus with or without laminoplasty. All the patients were followed up regularly; clinical improvement and neck disability index were assessed.

Results

All nine patients were male and exhibited classical clinical features, electrophysiological abnormalities, and MRI findings except, in one patient where a CT venogram helped in establishing the diagnosis as the MRI was inconclusive. Postoperatively, all patients had neurological improvement and stabilization of the disease. All patients who underwent CT venogram and cervical spine X-ray in neutral and dynamic position demonstrated no recurrence of engorged venous plexus or significant instability except one patient developing kyphosis. One patient experiencing symptoms in the other limb underwent a second surgery.

Conclusion

This comprehensive case series strongly supports venous pathology as a potential etiology of Hirayama disease. Surgical management with laminectomy and venous coagulation with or without expansile laminoplasty has delivered consistent improvement in neurological outcomes and long-term disease stabilization without the restriction of movements and lesser complications. However, further research is warranted to elucidate the mechanism underlying cervical venous dilatation.

Clinical and Genetic Analysis of A Father-Son Duo with Monomelic Amyotrophy: Case Report

Monomelic Amyotrophy (MMA) is a rare neurological disorder restricted to one upper limb, predominantly affecting young males with an unknown aetiopathogenesis. We report a familial case of father-son duo affected by MMA. Whole exome sequencing identified genetic variations in SLIT1, RYR3 and ARPP21 involved in axon guidance, calcium homeostasis and regulation of calmodulin signaling respectively. This is the first attempt to define genetic modifiers associated with MMA from India and advocates to extend genetic screening to a larger cohort. Deciphering the functional consequences of variations in these genes will be crucial for unravelling the pathogenesis of MMA.

Amyotrophic Lateral Sclerosis and Other Motor Neuron Diseases

OBJECTIVE

This article reviews the clinical spectrum of amyotrophic lateral sclerosis (ALS), its variant presentations, and the approach to diagnosis and management. This review includes a detailed discussion of current and emerging disease-modifying therapies and the management of respiratory and bulbar manifestations of disease. An updated review of ALS genetics and pathophysiology is also provided. This article also touches on several other important motor neuron diseases.

LATEST DEVELOPMENTS

A new set of simplified diagnostic criteria may help identify patients at earlier stages of the disease. A coformulation of sodium phenylbutyrate and tauroursodeoxycholic acid has been shown to have a significant benefit on disease progression and survival, leading to approval by regulatory authorities in the United States and Canada. An oral formulation of edaravone and an antisense oligonucleotide to a SOD1 gene variation (tofersen) have also recently been approved by the US Food and Drug Administration (FDA). Phase 3 trials of intrathecal mesenchymal stem cells failed to meet primary end points for efficacy. Updated American Academy of Neurology quality measures for the care of patients with ALS were published in 2023.

ESSENTIAL POINTS

There has been continued progress in ALS genetics, diagnosis, and disease-modifying therapies. However, we still lack a definitive biomarker or a treatment that can halt the progression or reverse the course of disease. The evolving understanding of the genetic and pathophysiologic underpinnings of disease offers promise for more effective and clinically meaningful treatments in the future.

Correlation Study Between Spinal Cord Function, Spinal Cord Morphology and Cervical Spine Alignments in Patients With Hirayama Disease

OBJECTIVE

This study aimed to explore the relationship between diffusion tensor imaging (DTI) parameters, cervical spine alignments, and spinal cord morphological parameters in patients with Hirayama disease (HD).

METHODS

In this retrospective cohort study, 41 HD patients were recruited from the Huashan hospital from July 2017 to November 2021. Patients received X-rays, conventional magnetic resonance (MR), and DTI scans in flexion and neutral positions. The DTI parameters assessed were calculated using the region of interest (ROI) method. Paired t-tests were performed on the DTI parameters of neck flexion and neutral position. Cervical spine alignments, including flexion and neutral Cobb angles, were measured, and range of motion (ROM) was calculated. Spinal cord morphological parameters were measured, including spinal cord atrophy (SCA) and loss of attachment (LOA). Spearman's correlation analysis between DTI parameters, cervical spine alignments, and spinal cord morphological parameters was performed.

RESULTS

In comparing DTI parameters, segments of the C3/4, C4/5, C6/7, and lower cervical spine were significantly different, while segments of C5/6 were not significantly different. In Spearman's correlation analysis, the flexion Cobb angle was significantly correlated with the fractional anisotropy (FA) value (R2 = .111, P = .033) and apparent diffusion coefficient (ADC) value (R2 = .119, P = .027). Flexion FA values were correlated with SCA in C4/5 (R2 = .211, P = .003), C5/6 (R2 = .454, P < .001), and C6/7 (R2 = .383, P < .001) while flexion ADC values were correlated with SCA in the C4/5 (R2 = .178, P = .006), C5/6 (R2 = .388, P < .001) and C6/7 segments (R2 = .187, P = .005).

CONCLUSION

The DTI parameters were correlated with the flexion Cobb angle and the SCA. These data support the dynamic cervical flexion compression hypothesis and indicate that the degree of SCA may be used to assess the condition of HD patients quantitatively.

Surgical Management of Hirayama Disease (Monomelic Amyotrophy): Systematic Review and Meta-Analysis of Patient-Level Data

BACKGROUND

Hirayama disease or juvenile-onset monomelic amyotrophy is a clinical syndrome that disproportionately affects young males. Standard of care revolves around conservative management, but some patients experience disease progression that may benefit from surgical intervention.

METHODS

Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a systematic review of previous reports of surgical treatment for Hirayama disease was performed. Studies were included if they provided individual patient-level data, described the clinical presentation and surgical intervention, and reported neurological improvement at last follow-up. Comparison between those who improved and those with stable symptoms at last follow-up was performed. Decision-tree analysis was used to identify the best predictors of neurological improvement by last follow-up.

RESULTS

Of 624 unique articles, 30 were included in the qualitative review and 23 in the meta-analysis. Among the 70 patients in the meta-analysis, mean age was 21.2 ± 6.3 years, 91% were male, and mean symptom duration at presentation was 43.3 ± 61.8 months. Fifty-nine patients (84.3%) had improvement in their neurological symptoms by last follow-up. Univariable analysis showed the only significant predictor of improvement in neurological symptoms by last follow-up was the use of stabilization-alone versus decompression with or without stabilization. Baseline clinical symptoms nor radiographic features predicted outcome. Decision-tree analysis showed surgical strategy (stabilization-alone vs. decompression ± stabilization), age (<20 vs. ≥20), and surgical approach (anterior-only vs. posterior-only or anterior-posterior) predicted a higher likelihood of neurological improvement by last follow-up.

CONCLUSIONS

Nearly 85% of patients experienced improvement in neurological symptoms. Improvement was best for those who underwent stabilization-alone, and decision-tree analysis suggested that the likelihood of improvement was also superior for patients under 20 years of age and those treated with an anterior versus posterior or staged approach.

Atypical Presentation of Hirayama Disease Involving the Cervico-Thoracic Segment Causing Diagnostic Dilemma: A Case Report

Hirayama disease, also known as monomelic amyotrophy, usually affects young males who initially experience increasing muscle weakness and atrophy of the distal upper limb before experiencing a sudden plateauing of symptom progression a few years later. It is a form of cervical myelopathy characterized by self-limiting, asymmetrical lower motor weakness of the upper limbs affecting the hands and forearms. This condition is brought on by the cervical dural sac and spinal cord being abnormally displaced forward during neck flexion, which causes the anterior horn cells to atrophy. However, research into the precise process is ongoing. Patients presenting with such features with additional atypical symptoms, like back pain, weakness, atrophy and paresthesia of lower extremities cause a diagnostic dilemma. We describe a case of a male patient, age 21, who complained of weakness in both upper limbs mostly on the hand and forearm muscles along with weakness and deformity in both lower limbs. He was diagnosed with atypical Cervico-thoracic Hirayama disease and treated.

Do patients with Hirayama disease require surgical treatment? A review of the literature

The main clinic characteristic of Hirayama disease (HD) is atrophy of the distal muscles in the upper limbs. Recently, an increasing number of HD cases have been reported. Many HD patients have persistently progressive symptoms and conservative treatments failed. This article aims to review the current status of the field and summarizes the main surgical treatment options for patients with HD. A comprehensive search of the PubMed and the Web of Science databases was conducted from their inception to September 15th, 2022. Search terms included "juvenile muscular atrophy of upper extremity", "Hirayama disease" and "surgery". A total of 169 relevant publications were identified and 29 articles were finally reviewed. Current surgical treatments for HD are either anterior cervical surgery or posterior cervical surgery. The two approaches can effectively stop the disease. However, no studies have compared the advantages and limitations of the two surgical methods. The previous view that HD can be improved with conservative treatment has been challenged. In many studies, surgical treatment has been shown to improve the hand function in patients with HD. However, there is still controversy about the methods of anterior and posterior cervical surgery. Future research could focus on exploring the advantages and limitations of different surgeries.

Brachial monomelic amyotrophy as an initial manifestation of stiff person syndrome

Stiff person syndrome (SPS) is characterized by rigidity of truncal and proximal muscles. The presence of abdominal and paraspinal rigidity is a defining clinical feature of SPS. It is rarely associated with the lower motor neuron (LMN) features. We report a patient with SPS whose initial clinical presentation was that of brachial monomelic amyotrophy (BMA). A 24-year-old gentleman presented with a history of the left upper limb wasting and weakness. In addition, he reported stiffness of the lower limbs and abdomen while walking. On examination, patient had left upper limb monomelic amyotrophy and hypertonia, exaggerated deep tendon reflexes in all four limbs. He also had abdominal and paraspinal rigidity. Serum was strongly positive for GAD 65 antibodies suggestive of SPS. Patient showed dramatic improvement to immunomodulation. Patient presented with features of BMA. Symptoms related to SPS were mild. Abdominal rigidity was the clue to the diagnosis. LMN features have been reported previously in stiff person plus syndrome with an atypical course and progressive encephalomyelitis with myoclonus and rigidity, but not in classical SPS.

Monomelic amyotrophy with clinico-radiological and electrophysiological evaluation: A study from Eastern India

Background

Monomelic amyotrophy (MMA) is a benign, rare, sporadic disorder of adolescent and young adults with male predominance, where neurogenic amyotrophy is restricted to an upper or lower limb. It is a variant of lower motor neuron disorder with insidious onset and slow progression for 2-4 years. Paucity of cohort studies as well as relative unawareness among physicians in eastern India stimulated us to do this work.

Material and Methods

Prospective observational study involving 140 cases of MMA from 2012 to 2016, conducted at S.C.B.Medical College, cuttack, Odisha to evaluate clinical profile, electrophysiology and radiological features. All the data were analysed & subjected to statistical analysis through SPSS software version 24.

Results

Mean age at onset and presentation were 19.6yrs and 21.7yrs respectively and the average duration 3.2yrs. Upper limb involvement was more common (91.4%) with distal affection (83%) more than proximal (7%). Isolated Leg amyotrophy found in 12 cases (~9%) and 10 cases were having thigh weakness & atrophy. B/L Upper Limb distal involvement was present in 18.5% cases asymmetrically. Family history found in~2.8%. Autonomic symptoms were present in affected and bilateral homologous Limb in 21%, 5.8%(~6%) patients. Changes in electromyography (EMG) were present in affected limb (100%) and clinically unaffected limb (15%).

Conclusion

MMA is a benign disease of young males with weakness and atrophy confined to unilateral limb or asymmetrical homologous limb and areflexia without sensory loss. It progresses variably for 2-3 years followed by stabilization without progression to Motor neuron disease.

Update on the Pathogenesis, Clinical Diagnosis, and Treatment of Hirayama Disease

Hirayama disease (HD) is characterized by the juvenile onset of unilateral or asymmetric weakness and amyotrophy of the hand and ulnar forearm and is most common in males in Asia. A perception of compliance with previous standards of diagnosis and treatment appears to be challenged, so the review is to update on HD. First, based on existing theory, the factors related to HD includes, (1) cervical cord compression during cervical flexion, (2) immunological factors, and (3) other musculoskeletal dynamic factors. Then, we review the clinical manifestations: typically, (1) distal weakness and wasting in one or both upper extremities, (2) insidious onset and initial progression for 3-5 years, (3) coarse tremors in the fingers, (4) cold paralysis, and (5) absence of objective sensory loss; and atypically, (1) positive pyramidal signs, (2) atrophy of the muscles of the proximal upper extremity, (3) long progression, and (4) sensory deficits. Next, updated manifestations of imaging are reviewed, (1) asymmetric spinal cord flattening, and localized lower cervical spinal cord atrophy, (2) loss of attachment between the posterior dural sac and the subjacent lamina, (3) forward displacement of the posterior wall of the cervical dural sac, (4) intramedullary high signal intensity in the anterior horn cells on T2-weighted imaging, and (5) straight alignment or kyphosis of cervical spine. Thus, the main manifestations of eletrophysiological examinations in HD include segmental neurogenic damages of anterior horn cells or anterior roots of the spinal nerve located in the lower cervical spinal cord, without disorder of the sensory nerves. In addition, definite HD needs three-dimensional diagnostic framework above, while probable HD needs to exclude other diseases via "clinical manifestations" and "electrophysiological examinations". Finally, the main purpose of treatment is to avoid neck flexion. Cervical collar is the first-line treatment for HD, while several surgical methods are available and have achieved satisfactory results. This review aimed to improve the awareness of HD in clinicians to enable early diagnosis and treatment, which will enable patients to achieve a better prognosis.

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.

Clinical evaluation of a 31-year-old woman with crural monomelic amyotrophy

This report describes the clinical presentation of a female patient diagnosed with crural MMA. Careful clinical correlation is necessary to distinguish crural MMA from other motor neuron diseases. When crural MMA is diagnosed, treatment options aim to alleviate symptoms.

Hirayama's Disease in a Young Male: A Rare Case Report

Hirayama disease is a rare neurological condition also known as monomelic amyotrophy (MMA). It is a type of cervical myelopathy, which involves the anterior horn cells and affects the distal upper extremities. It is self-limited, asymmetrical lower motor weakness of hands and forearms. Young males are more commonly affected. The condition is hypothesized to occur due to an asymmetric compression of the cervical spinal cord by the dural sac, however, the exact mechanism(s) continue to be investigated. We report a case of a 20-year-old male who presented with complaints of right hand and forearm weakness, who was diagnosed with Hirayama disease and treated.

Are basketball players more likely to develop Hirayama disease?

Hirayama disease is a rare neurological disease affecting primarily men in the second to third decades. To date there are only few reports from Italy. We report the case of three young basketball players who presented with clinical, electrophysiological and MRI findings suggestive for Hirayama disease. Although the pathophysiology of the disease is still unknown, several hypotheses have been suggested and two of these are the disproportionate growth of cervical spine and cervical cord/roots during adolescence and the chronic traumatism. We think that, in our cases, the height of basketball players combined with the constant stress caused by the sport, could have contributed to the development of the Hirayama disease. With this report we would stress the importance to be careful to consider this pathology in order to avoid misdiagnosis predictive of poor prognosis in young patients.

Hirayama disease: analysis of cases in Russia

The fourteen cases of Hirayama disease (HD) are presented in this article. HD is seldom disease characterized by juvenile muscular atrophy of upper extremities and benign course. All cases were diagnosed in the Research Center of Neurology (Moscow, Russia) during the year 2015-2017. Such methods as MRI (magnetic resonance imaging), EMG (electromyography), and NCS (nerve conduction studies) have been used to confirm diagnosis of HD. Transcranial magnetic stimulation was used to exclude upper motor neuron involvement in two cases. The original scale of neurological disturbances in HD has been proposed by authors to reveal correlations of HD severity with age of patients and duration of disease.Most of patients with HD are young males with common clinical signs. Detected MRI and EMG data were also comparable with previous publications. Independence of HD severity from age and duration of the disease may be the result of individual physical characteristics of dura mater and other structures of the cervical vertebra. In some our cases, amyotrophic lateral sclerosis and other neurological disorders were misdiagnosed before. In view of different prognosis in these pathologies and possible correction of HD, early diagnosis is very important.

The Importance of Flexion MRI in Hirayama Disease with Special Reference to Laminodural Space Measurements

BACKGROUND AND PURPOSE

Hirayama disease is a benign focal amyotrophy of the distal upper limbs involving C7, C8, and T1 segmental myotomes with sparing of the brachioradialis and proximal muscles of the upper limb innervated by C5-6 myotomes. The objective of the present study was to study the utility of MR imaging in young patients presenting with weakness and wasting of the distal upper extremity and to evaluate the importance of the laminodural space during flexion cervical MR imaging.

MATERIALS AND METHODS

This was a prospective cross-sectional study conducted from January 2014 to July 2017 in a tertiary care center from Northeast India. Forty-five patients with clinically definite Hirayama disease underwent electrophysiologic evaluation followed by MR imaging of the cervical spine.

RESULTS

The mean age at recruitment was 22.8 ± 5.5 years. Forty patients (88.9%) had unilateral and 5 (11.1%) had bilateral upper extremity involvement. Cervical cord T2-weighted hyperintensities were demonstrated in 16 patients (35.6%), of which 15 (33.3%) had anterior horn cell hyperintensities. Flexion MR imaging showed loss of the posterior dural attachment, forward shifting of the posterior dural sac with postcontrast enhancement, and prominent posterior epidural venous plexus in all patients. The laminodural space at maximum forward shifting of the posterior dural sac ranged from 3 to 9.8 mm, with a mean distance of 5.99 mm (95% confidence interval, 5.42-6.57 mm).

CONCLUSIONS

Flexion cervical MR imaging is a very useful investigation in diagnosing Hirayama disease. The increase in the laminodural space and the presence of cervical cord flattening during flexion are essential for diagnosis.

What is in the Literature?

This edition of "What is in the Literature?" will focus on motor neuron disease (MND), including adult forms [amyotrophic lateral sclerosis (ALS), progressive muscular atrophy (PMA), primary lateral sclerosis (PLS), progressive bulbar palsy (PBA), and monomelic mononeuropathy (MMND)], and childhood forms [spinal muscle atrophy (SMA)].

Intrafamilial phenotypic variations in familial cases of cervical flexion induced myelopathy/Hirayama disease

Hirayama disease is generally considered to be a sporadic disorder, except for a few reports of familial occurrence. In this study, we describe eight patients from four families with cervical flexion induced myelopathy (CFIM)/Hirayama disease (HD) and intra-familial phenotypic variations. All underwent clinical and electrophysiological evaluation, while seven of them had contrast MR imaging of cervical spine in flexion. There was significant intra-familial variability: distal bimelic form in four patients, classical monomelic form in three and proximo-distal form in one. Irrespective of the clinical phenotype, MRI showed characteristic dynamic changes of posterior dural detachment with prominent epidural enhancement extending variably from C3 vertebral level to dorsal spine in six patients. One patient with 28 years of illness, had only lower cervical cord atrophy without dynamic changes while another patient demonstrated forward dural displacement with epidural enhancement even after 38 years of disease duration.

Cortical function and corticomotoneuronal adaptation in monomelic amyotrophy

OBJECTIVE

To evaluate corticomotoneuronal integrity in monomelic amyotrophy using threshold tracking transcranial magnetic stimulation (TT-TMS).

METHODS

Cortical excitability studies were prospectively performed in 8 monomelic amyotrophy patients and compared to 21 early-onset amyotrophic lateral sclerosis (ALS) patients and 40 healthy controls. Motor evoked potentials responses were recorded over abductor pollicis brevis.

RESULTS

Maximal motor evoked potential (MEP/CMAP ratio) was significantly increased in monomelic amyotrophy compared with controls (monomelic amyotrophy 51.2±12.4%; control 22.7±2.1%, p=0.04). Averaged short-interval intracortical inhibition (SICI, ISI 1-7ms) in monomelic amyotrophy patients was similar to controls (monomelic amyotrophy 9.6±2.1%; control 10.0±0.9%, p=0.98). However, it was significantly reduced in early-onset ALS in comparison with monomelic amyotrophy patients (monomelic amyotrophy 9.6±2.1%; ALS 2.3±1.7%, p<0.001). Averaged SICI is a good parameter (area under the curve 0.79, p=0.02) to discriminate between monomelic amyotrophy and early-onset ALS patients.

CONCLUSIONS

TT-TMS technique has identified normal cortical function in monomelic amyotrophy, a feature that distinguishes it from early-onset ALS. The greater corticomotoneuronal projections to spinal motoneurons may represent central nervous system adaptive change in monomelic amyotrophy.

SIGNIFICANCE

Corticomotoneuronal dysfunction does not drive the lower motor neurone loss presented in monomelic amyotrophy.

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.

Amyotrophic lateral sclerosis and motor neuron syndromes in Asia

While the past 2 decades have witnessed an increasing understanding of amyotrophic lateral sclerosis (ALS) arising from East Asia, particularly Japan, South Korea, Taiwan and China, knowledge of ALS throughout the whole of Asia remains limited. Asia represents >50% of the world population, making it host to the largest patient cohort of ALS. Furthermore, Asia represents a diverse population in terms of ethnic, social and cultural backgrounds. In this review, an overview is presented that covers what is currently known of ALS in Asia from basic epidemiology and genetic influences, through to disease characteristics including atypical phenotypes which manifest a predilection for Asians. With the recent establishment of the Pan-Asian Consortium for Treatment and Research in ALS to facilitate collaborations between clinicians and researchers across the region, it is anticipated that Asia and the Pacific will contribute to unravelling the uncertainties in ALS.

Clinical profile of Monomelic Amyotrophy (MMA) and role of persistent viral infection

OBJECTIVES

The objective of our study was to describe the clinical characteristics, electrophysiology, MRI features and conduct viral assays in patients with Monomelic Amyotrophy (MMA) and follow them up over one year.

METHODS

Consecutive patients with MMA who attended the Neurology services from April 2013 to March 2014 were included. Age and sex matched controls were taken for the purpose of viral assay analysis. The clinical evaluation was repeated at six months and one year.

RESULTS

109 cases and 109 controls were included in the study. The patients were predominantly males (98.2%; n=107/109) and had involvement of upper limbs (83.5%; n=91/109). 26 (23.8%) patients with clinically unilateral involvement had bilateral neurogenic changes in the electromyography. Serological assays of Japanese E, West Nile Virus, and Poliovirus 1, 2 and 3, HIV 1 and 2 were negative in all the cases and controls.

CONCLUSIONS

Patients with MMA are predominantly young males with upper limb wasting and weakness. MRI of the cervical cord is normal in most of the patients (67.9%). The present study did not find any evidence of the association of viral infection in MMA.