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Madras motor neuron disease variant, clinical features of seven patients
1Department of Neurology, National Institute of Mental Health and Neurosciences, 506 029, Bangalore, India. mgd@nimhans.kar.nic.in
Abstract:
Madras motor neuron disease (MMND) has the characteristic features of onset in the young, atrophy and weakness of the limbs, multiple cranial nerve palsies particularly the seventh, ninth to twelfth and sensorineural hearing loss with unique geographic distribution to southern part of India. During a period of 28 years (1974-2001), 7 (13%) among 54 patients of MMND seen at a tertiary referral center at Bangalore, India, had the additional features of optic atrophy in all and cerebellar involvement in three of them. There were three males and four females, the mean age at onset was 11.7 years, with a mean duration of illness of 6.4 years. All except one patient were ambulant and independent in the activities of daily living. Family history of MMND was present in more than a quarter (28.6%) of patients. Compared to MMND, these patients had onset of illness at a younger age and family history was more frequently observed, however, these differences were not statistically significant. Bulbar palsy was an invariable feature, being present in all patients compared to 38.3% of MMND and the difference was statistically significant (p=0.003). This clinical profile may be considered to be a variant of Madras motor neuron disease (MMNDV).
Insights
Madras motor neuron disease variant (MMNDV) presents in young individuals with bulbar palsy, optic atrophy, and cerebellar signs. This distinct clinical profile suggests a unique subtype of MMND found in Southern India.
Area of Science:
- Neurology
- Genetics
Background:
- Madras motor neuron disease (MMND) is a rare neurological disorder endemic to Southern India.
- Characterized by early onset, limb atrophy, cranial nerve palsies, and sensorineural hearing loss.
Observation:
- A study identified 7 patients (13%) with MMND exhibiting additional optic atrophy and cerebellar involvement.
- These patients presented with earlier onset and a higher familial incidence compared to typical MMND.
- Bulbar palsy was a consistent feature in all observed cases, significantly more frequent than in general MMND.
Findings:
- The observed clinical features, particularly the invariable bulbar palsy, suggest a distinct variant of MMND.
- Optic atrophy and cerebellar signs are notable additions to the MMND phenotype in these cases.
- The younger age of onset and increased family history, though not statistically significant, warrant further investigation.
Implications:
- This variant, provisionally termed Madras motor neuron disease variant (MMNDV), may represent a genetically distinct subtype.
- Further research is needed to elucidate the specific genetic and pathophysiological mechanisms underlying MMNDV.
- Understanding this variant can improve diagnostic accuracy and potentially guide targeted therapeutic strategies for affected individuals.