Madras Motor Neuron Disease

Madras motor neuron disease (MMND) is characterized by weakness and atrophy of limbs, multiple lower cranial nerve palsies and sensorineural hearing loss.

Epidemiology

Less than 200 cases have be reported to date, predominantly from Southern India. Isolated MMND cases have been reported from Thailand and Italy.

Clinical description

Onset occurs at a young age (often before the age of 15), with a slight male preponderance or equal sex distribution. Parental consanguinity has been reported in some cases. Main clinical features include thin habitus, wasting and weakness predominantly of the distal limb muscles, involvement of facial and bulbar muscles, and pyramidal dysfunction. Multiple cranial nerve palsies particularly involve the 7th, and the 9th to 12th cranial nerves. Hearing impairment was described in all patients. Optic atrophy is reported in some patients.

Etiology

The etiopathogenesis of MMND remains unknown. The majority of cases are sporadic. A few familial cases have been reported, but the mode of inheritance is yet to be determined. Inflammation and/or environmental factors may play a role in the etiology of MMND.

Diagnostic methods

Diagnosis is clinical and is supported by the association of benign focal atrophy of the extremities with hearing impairment. Neuroimaging studies may help to distinguish MMND from other motor neuron diseases.

Differential diagnosis

Differential diagnoses include amyotrophic lateral sclerosis, spinocerebellar ataxia syndromes, Brown-Vialetto-Van Laere syndrome, progressive muscular atrophy, post-polio progressive muscular atrophy, and spinal muscular atrophy (see these terms).

Management and treatment

Currently, there is no cure for MMND. Management should involve a multidisciplinary team (neurologists, physical therapists, occupational therapists, palliative care specialists, specialist nurses and psychologists) and should focus on the relief of symptoms. Symptomatic treatment and supportive care can help patients to maintain their daily living activities. Patients should be offered hearing aids.

Prognosis

The disease shows a slowly progressive but benign course. Most of the reported patients survived for over 30 years after the onset of the disease.