Madras motor neuron disease (MMND): clinical description and survival pattern of 116 patients from Southern India seen over 36 years (1971-2007)

Unveiling a Rare Case: Madras Motor Neuron Disease in an 18-Year-Old Patient

Madras motor neuron disease (MMND) is a rare childhood or juvenile motor neuron disease. Herein, we present a unique case of MMND in an 18-year-old patient, which challenges the conventional understanding of the disease's onset and progression. The patient, a previously healthy adolescent, presented with insidious onset and gradually progressive weakness of all four limbs, wasting, tongue fasciculation, and bilateral sensorineural hearing loss. Neurological examination revealed signs consistent with lower motor neuron involvement. Electromyography (EMG) and nerve conduction studies (NCS) supported the diagnosis of MMND. The patient's clinical course exhibited rapid deterioration, leading to significant functional impairment within a short timeframe. Treatment modalities, including supportive care and symptomatic management, were implemented; however, disease progression remained relentless. This case highlights the significance of considering MMND in the differential diagnosis of motor neuron diseases, even in young individuals. It highlights the importance of conducting more studies to comprehend the underlying mechanisms and consider potential therapeutic strategies for this uncommon ailment.

An emerging role for stress granules in neurodegenerative disease and hearing loss

Stress granules (SGs) are membrane-less cytosolic assemblies that form in response to stress (e.g., heat, oxidative stress, hypoxia, viral infection and UV). Composed of mRNA, RNA binding proteins and signalling proteins, SGs minimise stress-related damage and promote cell survival. Recent research has shown that the stress granule response is vital to the cochlea's response to stress. However, emerging evidence suggests stress granule dysfunction plays a key role in the pathophysiology of multiple neurodegenerative diseases, several of which present with hearing loss as a symptom. Hearing loss has been identified as the largest potentially modifiable risk factor for dementia. The underlying reason for the link between hearing loss and dementia remains to be established. However, several possible mechanisms have been proposed including a common pathological mechanism. Here we will review the role of SGs in the pathophysiology of neurodegenerative diseases and explore possible links and emerging evidence that they may play an important role in maintenance of hearing and may be a common mechanism underlying age-related hearing loss and dementia.

[A case of facial-onset sensory and motor neuronopathy (FOSMN) with cerebellar ataxia and abnormal decrement in repetitive nerve stimulation test]

A 59-year-old woman presented with a 7-year history of facial numbness on the left side, and gradual worsening of symptoms. Over several years, facial muscle weakness, dysarthria, tongue atrophy and fasciculation had progressed. Then, she developed cerebellar ataxia affecting the left extremities, in addition to earlier symptoms. Brain MRI revealed cerebellar atrophy, and ^99mTc-SPECT depicted cerebellar hypoperfusion. A repetitive nerve stimulation test (RNS) indicated abnormal decrement in the nasalis and trapezius muscles on the left side. Facial-onset sensory and motor neuronopathy (FOSMN) was diagnosed. Administration of intravenous immunoglobulin resulted in improvement of some symptoms. Although cerebellar ataxia is not a common symptom of FOSMN, a case showing TDP-43-positive glial cytoplasmic inclusions in cerebellar white matter has been reported. Therefore, it is possible that FOSMN may cause cerebellum impairment in some patients. Furthermore, RNS positive rate in the trapezius muscle is known to be high in amyotrophic lateral sclerosis (ALS) patients. It is speculated that RNS of the affected muscles in FOSMN may show abnormal decrement by the same mechanisms as ALS.

A Madras Motor Neuron Disease Patient With Cerebellar Atrophy: A New Clinical Feature

A 34-year-old Chinese Han female complaining of general muscle weakness and wasting for 9 years. She was admitted for aggravation of her symptoms caused by respiratory distress. She also suffered from bulbar palsy. She had no hearing loss, visual problems, or cerebellar signs. Her parents had a consanguineous marriage, though there was no family history of these symptoms. Pure tone audiometric findings demonstrated no definite abnormality. Electromyography demonstrated neurogenic damage. Brain magnetic resonance imaging revealed cerebellar atrophy, dominantly in anterior lobe. Gene sequencing of whole gene exomes was negative. She was finally diagnosed with Madras motor neuron disease (MMND), a rare subtype of motor neuron disease. No definite therapy was available for MMND, and she died of respiratory tract infection 1 year later. Previous studies have shown that cerebellar signs are positive in 17.2% patients of MMND, but no case with cerebellar atrophy has been reported before. Thus, here we describe cerebellar atrophy as a new clinical feature of MMND.

Progressive Muscular Atrophy

Progressive muscular atrophy (PMA) is a rare, sporadic, adult-onset motor neuron disease, clinically characterized by isolated lower motor neuron features; however, clinically evident upper motor neuron signs may emerge in some patients. Subclinical upper motor neuron involvement is identified pathologically, radiologically, and neurophysiologically in a substantial number of patients with PMA. Patients with subclinical upper motor neuron involvement do not fulfill the revised El Escorial criteria to participate in amyotrophic lateral sclerosis clinical trials. Intravenous immunoglobulin therapy is only marginally beneficial in a small subgroup of patients with lower motor neuron syndrome without conduction block.

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.

Neurological associations in auditory neuropathy spectrum disorder: Results from a tertiary hospital in South India

Aims:

To find out the prevalence and types of neurological abnormalities associated in auditory neuropathy spectrum disorder in a large tertiary referral center.

Settings and Design:

A prospective clinical study was conducted on all patients diagnosed with auditory neuropathy spectrum disorder in the ear, nose, and throat (ENT) and neurology departments during a 17-month period. Patients with neurological abnormalities on history and examination were further assessed by a neurologist to determine the type of disorder present.

Results:

The frequency of auditory neuropathy spectrum disorder was 1.12%. Sixty percent were found to have neurological involvement. This included cerebral palsy in children, peripheral neuropathy (PN), spinocerebellar ataxia, hereditary motor-sensory neuropathy, spastic paresis, and ponto-bulbar palsy. Neurological lesions did not present simultaneously with hearing loss in most patients. Sixty-six percent of patients with auditory neuropathy spectrum disorder were born of consanguineous marriages.

Conclusions:

There is a high prevalence of neurological lesions in auditory neuropathy spectrum disorder which has to be kept in mind while evaluating such patients. Follow-up and counselling regarding the appearance of neuropathies is therefore important in such patients. A hereditary etiology is indicated in a majority of cases of auditory neuropathy spectrum disorder.

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.

Complex genetic origin of Indian populations and its implications

Indian populations are classified into various caste, tribe and religious groups, which altogether makes them very unique compared to rest of the world. The long-term firm socio-religious boundaries and the strict endogamy practices along with the evolutionary forces have further supplemented the existing high-level diversity. As a result, drawing definite conclusions on its overall origin, affinity, health and disease conditions become even more sophisticated than was thought earlier. In spite of these challenges, researchers have undertaken tireless and extensive investigations using various genetic markers to estimate genetic variation and its implication in health and diseases. We have demonstrated that the Indian populations are the descendents of the very first modern humans, who ventured the journey of out-of-Africa about 65,000 years ago. The recent gene flow from east and west Eurasia is also evident. Thus, this review attempts to summarize the unique genetic variation among Indian populations as evident from our extensive study among approximately 20,000 samples across India.

Mitochondrial DNA variations in Madras motor neuron disease

Although the Madras motor neuron disease (MMND) was found three decades ago, its genetic basis has not been elucidated, so far. The symptom at onset was impaired hearing, upper limb weakness and atrophy. Since some clinical features of MMND overlap with mitochondrial disorders, we analyzed the complete mitochondrial genome of 45 MMND patients and found 396 variations, including 13 disease-associated, 2 mt-tRNA and 33 non-synonymous (16 MT-ND, 10 MT-CO, 3 MT-CYB and 4 MT-ATPase). A rare variant (m.8302A>G) in mt-tRNA(Leu) was found in three patients. We predict that these variation(s) may influence the disease pathogenesis along with some unknown factor(s).

Genomic view on the peopling of India

India is known for its vast human diversity, consisting of more than four and a half thousand anthropologically well-defined populations. Each population differs in terms of language, culture, physical features and, most importantly, genetic architecture. The size of populations varies from a few hundred to millions. Based on the social structure, Indians are classified into various caste, tribe and religious groups. These social classifications are very rigid and have remained undisturbed by emerging urbanisation and cultural changes. The variable social customs, strict endogamy marriage practices, long-term isolation and evolutionary forces have added immensely to the diversification of the Indian populations. These factors have also led to these populations acquiring a set of Indian-specific genetic variations responsible for various diseases in India. Interestingly, most of these variations are absent outside the Indian subcontinent. Thus, this review is focused on the peopling of India, the caste system, marriage practice and the resulting health and forensic implications.

Brown-Vialetto-Van Laere syndrome: a riboflavin-unresponsive patient with a novel mutation in the C20orf54 gene

Brown-Vialetto-Van Laere syndrome (Online Mendelian Inheritance in Man number 211530) is a neurodegenerative disorder characterized by pontobulbar palsy affecting cranial nerves (mainly VII-XII). Sensorineural deafness is often the leading sign, followed by other neurologic signs. Inheritance is often autosomal recessive, with mutations in the C20orf54 gene (Online Mendelian Inheritance in Man number 613350). Three previous patients with mutations in the C20orf54 gene and clinical signs of Brown-Vialetto-Van Laere or Fazio-Londe syndrome revealed a metabolic profile suggesting a multiple acyl-coenzyme A dehydrogenase defect. They benefited from riboflavin. We describe a 3-year-old girl with early-onset Brown-Vialetto-Van Laere syndrome and a novel mutation in the C20orf54 gene (c.989G>T). On T(2)-weighted imaging, increased signal intensity of the vestibular nuclei bilaterally, the pedunculus cerebellaris superior and the central tegmental tract were observed during acute clinical deterioration. Her metabolic profile was normal. Trials with steroids, immunoglobulins, and riboflavin produced no effect. The patient recovered slowly during subsequent months, with residual deficits. Brown-Vialetto-Van Laere syndrome should be considered in patients with sensorineural hearing loss and pontobulbar palsy. Patients should be screened for riboflavin deficiency and a therapy with riboflavin may provide effective treatment in some affected patients.

Triad of visual, auditory and corticospinal tract lesions: a new syndrome in a patient with HIV infection

OBJECTIVE

A case of a rapidly progressive degeneration of the visual, auditory and corticospinal tract in a patient with a HIV infection is presented.

METHODS AND RESULTS

The HIV-infected patient suffered from severe and rapidly progressive sensorineural hearing loss, blindness, dysarthria, dysphagia and tetraparesis. MRI showed degeneration of the visual, auditory and corticospinal tract. Diffusion tensor imaging showed reduced fractional anisotropy of the corticospinal tract. HAART and other salvage therapies did not save the patient from death 5 months after the onset of the symptoms.

CONCLUSION

The triad of auditory, visual and corticospinal lesions has been described in rare syndromes and hereditary diseases. This is the first case of this syndrome associated with a HIV infection.

Neurofilament localization and phosphorylation in the developing inner ear of the rat

Detailed understanding of neurofilament protein distribution in the inner ear can shed light on regulatory mechanisms involved in neuronal development of this tissue. We assessed the spatio-temporal changes in the distribution of neurofilaments in the developing rat inner ear between embryonic day 12 and 30 days after birth, using antibodies against phosphorylated as well as non-phosphorylated light (NFL), medium (NFM) and heavy (NFH) neurofilament subunits. Our results show that during development, the onset of neurofilament expression in the rat inner ear is on embryonic day 12, earlier than previously shown. We demonstrate that neurofilament subunits of different molecular weight emerge in a developmental stage-dependent order. In addition, we determined that neurofilaments of the vestibular nerve mature earlier than neurofilaments of the cochlear nerve. Cochlear neurofilament maturation progresses in a gradient from base to apex, and from inner to outer hair cells. The sequential pattern of neurofilament expression we describe may help understand the consequences of certain mutations, and contribute to develop therapeutic strategies.