SunilPradhan, Professor of Neurology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Raebareli Road, Lucknow, India.drspradhan@rediffmail.com
Submitted September 02, 2009
I thank Dr. Gamez for his comments. Evolution of a syndrome into specific diseases repeatedly suggests that an apparently single disorder may be a group of etiologically different diseases. The initial description of "monomelic amyotrophy" included pure motor wasting of one upper and one lower limb. [6]
The description of upper limb weakness and wasting was similar to Hirayama disease and that of lower limb more or less akin to what has been described from North India as "wasted leg syndrome." [7] After the demonstration of mechanovascular changes in flexion MRI of the cervical spine [8], the upper limb monomelic amyotrophy was soon considered a different disease than that of lower limb. A subsequent description of Hirayama disease was referred to as "brachial monomelic amyotrophy". [9]
Hirayama disease primarily involves C7, C8 and T1 myotomes with distal upper limb wasting. Inclusion of patients with evidence of chronic denervation in proximal muscles of all four limbs as mentioned by Gamez may prompt debate on what to accept as Hirayama disease. We did not find evidence of chronic denervation in the right quadriceps and tibialis anterior muscles screened under a standard EMG protocol for upper limb diseases. Some patients with juvenile onset motor neuron disease and distal spinal muscular atrophies have focal onset, benign course, and a widespread chronic denervation on EMG.
Inclusion of these and other unknown benign anterior horn cell disorders under the category of Hirayama disease may falsely convey diffuse denervation in this disorder. Several of these patients may show bilateralism. Some studies showing diffuse denervation in monomelic amyotrophy have included patients with one lower limb involvement. This may misclassify patients as having Hirayama disease. [10]
The nationwide survey in Japan supports our finding of bilateralism in several patients with Hirayama disease. [2] Symmetrical involvement in some of these patients calls for the need to avoid terminologies suggesting unilateralism to denote this disorder.
Our study is unique as it maintained a gold standard in the selection of patients because we included those having visible dynamic changes in flexion MRI particularly during the acute phase of illness. We do not know whether it is proper to classify other patients as having Hirayama disease but we were clear in the selection of our patient group. It is a good demonstration of symmetric and asymmetric bilateralism in patients with Hirayama disease.
7. Prabhakar S, Chopra JS, Banerjee AK, Rana PV. Wasted leg syndrome: a clinical, electrophysiological and histopathological study. Clin Neurol Neurosurg 1981;83:19-28.
8. Pradhan S, Gupta RK. Magnetic resonance imaging in juvenile asymmetric segmental spinal muscular atrophy. J Neurol Sci 1997;146:133-138.
9. Gourie-Devi M, Nalani A. Long-term follow-up of 44 patients with brachial monomelic amyotrophy. Acta Neurol Scand 2003;107:215–220.
10. Khandelwal D, Bhatia M, Singh S, et al. Widespread electromyographic abnormalities in patients with monomelic amyotrophy: a detailed EMG study. Electromyogr Clin Neurophysiol 2005;45:63-67.
Disclosure: Dr. Pradhan is an Associate Editor for Neurology India.
I thank Dr. Gamez for his comments. Evolution of a syndrome into specific diseases repeatedly suggests that an apparently single disorder may be a group of etiologically different diseases. The initial description of "monomelic amyotrophy" included pure motor wasting of one upper and one lower limb. [6]
The description of upper limb weakness and wasting was similar to Hirayama disease and that of lower limb more or less akin to what has been described from North India as "wasted leg syndrome." [7] After the demonstration of mechanovascular changes in flexion MRI of the cervical spine [8], the upper limb monomelic amyotrophy was soon considered a different disease than that of lower limb. A subsequent description of Hirayama disease was referred to as "brachial monomelic amyotrophy". [9]
Hirayama disease primarily involves C7, C8 and T1 myotomes with distal upper limb wasting. Inclusion of patients with evidence of chronic denervation in proximal muscles of all four limbs as mentioned by Gamez may prompt debate on what to accept as Hirayama disease. We did not find evidence of chronic denervation in the right quadriceps and tibialis anterior muscles screened under a standard EMG protocol for upper limb diseases. Some patients with juvenile onset motor neuron disease and distal spinal muscular atrophies have focal onset, benign course, and a widespread chronic denervation on EMG.
Inclusion of these and other unknown benign anterior horn cell disorders under the category of Hirayama disease may falsely convey diffuse denervation in this disorder. Several of these patients may show bilateralism. Some studies showing diffuse denervation in monomelic amyotrophy have included patients with one lower limb involvement. This may misclassify patients as having Hirayama disease. [10]
The nationwide survey in Japan supports our finding of bilateralism in several patients with Hirayama disease. [2] Symmetrical involvement in some of these patients calls for the need to avoid terminologies suggesting unilateralism to denote this disorder.
Our study is unique as it maintained a gold standard in the selection of patients because we included those having visible dynamic changes in flexion MRI particularly during the acute phase of illness. We do not know whether it is proper to classify other patients as having Hirayama disease but we were clear in the selection of our patient group. It is a good demonstration of symmetric and asymmetric bilateralism in patients with Hirayama disease.
References
6. Gouri-Devi M, Suresh TG, Shankar SK. Monomelic amyotrophy. Arch Neurol 1984;41:388-394.
7. Prabhakar S, Chopra JS, Banerjee AK, Rana PV. Wasted leg syndrome: a clinical, electrophysiological and histopathological study. Clin Neurol Neurosurg 1981;83:19-28.
8. Pradhan S, Gupta RK. Magnetic resonance imaging in juvenile asymmetric segmental spinal muscular atrophy. J Neurol Sci 1997;146:133-138.
9. Gourie-Devi M, Nalani A. Long-term follow-up of 44 patients with brachial monomelic amyotrophy. Acta Neurol Scand 2003;107:215–220.
10. Khandelwal D, Bhatia M, Singh S, et al. Widespread electromyographic abnormalities in patients with monomelic amyotrophy: a detailed EMG study. Electromyogr Clin Neurophysiol 2005;45:63-67.
Disclosure: Dr. Pradhan is an Associate Editor for Neurology India.