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Letters to the Editor

Indian Pediatrics 2003; 40:1211-1212

Distal Asymmetric Spinal Muscular Atrophy Involving Upper Limbs

I read with interest the recent article by Mishra, et al.(1). They describe an interesting case of distal asymmetric spinal muscular atrophy involving upper limbs associated with high serum lead levels. However, I would like to make certain comments.

Firstly, the case presented here has several features against a diagnosis of Hirayama disease:

1. One year duration of symptoms: A diagnosis of Hirayama disease is typically made after at least four to five years of symptoms(2) (after demonstrating a stationary clinical course following a progressive disease during initial four to five years of illness),

2. Symmetrical onset of symptoms: Hirayama disease is characterized by a unilateral-predominant involvement of upper limbs. Though a bilateral upper limb involvement is seen in about 20% of cases, it is highly asymmetric, showing a peculiar "oblique atrophy"(3),

3. Female sex: Hirayama disease is ten times more common in males(2),

4. Age of six and a half years: The commonest age of onset is between 15-25 years and onset below 10 years of age has not been reported before.

5. Normal MRI of the spine: MRI abnormalities are almost universal. In an Indian study, focal cord atrophy was seen in 100% of cases at the level of cervical 4 to 7 vertebral bodies in MRI done in neutral neck position(4).

Secondly, I disagree with the inclusion of Madras motor neuron disease (MMND) as a differential diagnosis in this case. MMND typically presents with the involvement of lower cranial nerves (seventh and ninth to twelfth) and sensorineural deafness along with features of chronic anterior horn cell disease(5,6).

The diagnosis in this child could still be a genetically determined distal spinal muscular atrophy. Genetic and molecular studies to identify survival motor neuron (SMN) 1 and 2 gene mutations would have been useful towards making a definite diagnosis(7).

Finally, the association of elevated serum lead level in this child appears to be coincidental. However, chelating therapy is required for the same.

In conclusion, the diagnosis of Hirayama disease cannot be made confidently in this case. Genetic studies would have been useful in making a definite diagnosis of spinal muscular atrophy.

Sudhir Kumar,
Department of Neurological Sciences,
Christian Medical College Hospital,
Vellore, Tamilnadu 632 004.
E-mail: drsudhirkumar@yahoo.com



1. Mishra D, Agrawal A and Gupta VK. Distal spinal muscular atrophy of upper limb (Hirayama disease) associatemd with high serum lead levels. Indian Pediatr 2003; 40: 780-783

2. Gouri-Devi M, Nalini A. Long-term follow-up of 44 patients with brachial monomelic amyotrophy. Acta Neurol Scand 2003: 107: 215-220.

3. Hirayama K. Juvenile muscular atrophy of the distal upper limb–three decades of description and it’s treatment. Rinsho Shinkeigaku 1993; 33: 1235-1243.

4. Pradhan S, Gupta RK. Magnetic resonance imaging in juvenile asymmetric segmental spinal muscular atrophy. J Neurol Sci 1997; 146: 133-138.

5. Meenakshisundaram E, Jagannathan K, Ramamurthi B. Clinical pattern of motor neuron disease seen in younger age groups in Madras. Neurol India 1970; 18: Suppl 1: 109-112.

6. Gourie-Devi M, Nalini A. Madras motor neuron disease variant, clinical features of seven patients. J Neurol Sci 2003; 209: 13-17.

7. Panigrahi I, Kesari A, Phadke SR, Mittal B. Clinical and molecular diagnosis of spinal muscular atrophy. Neurol lndia 2002; 50: 117-122.



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