JosepGamez, ALS Unit, Neurology Dept., Hospital Universitari Vall d'Hebron, Passeig Vall d'Hebron 119, 08035, Barcelona, SPAIN12784jgc@comb.es
Submitted September 02, 2009
Pradhan reported bilateral symmetric involvement in eleven cases within a series of 106 patients with Hirayama disease (HirD). [1] The iconographic information is important for the correct diagnosis of this rare form of motor neuron disease. However, the author’s suggestion that “the symmetric involvement has never been described” is incorrect.
Hirayama reported a small subset of patients with symmetric atrophy and weakness on many occasions. For example, of the 333 cases analyzed in a National Japan Survey, 3.1% presented with the variant described by Pradhan. [2] Other authors have reported similar cases. [3,4]
The diagnosis of HirD variants is difficult and diagnosis criteria are supported by lab and neuroimaging tests to rule out other entities. [2] Identification of HirD has led to a search for labels that cover these clinical variants of HirD including: late onset, familial forms, proximal muscle involvement, and bilateral and progressive forms. [5] Since the first definition of this entity as “juvenile muscular atrophy of unilateral upper extremity” was coined by Hirayama in 1959, other terms have been used to improve the definition of the different clinical variants of the disease, including “chronic segmental spinal muscular atrophy of the upper extremities”, “anterior tephromalacia”, and “O’Sullivan-McLeod syndrome.”
In addition to the anatomical abnormalities in the cervical/dural canal mentioned by the author, there are other pathogeneses of HirD. EMG observation of chronic denervation signs in the proximal muscles of all four limbs in at least one third of patients suggests that it may be an adult-onset diffuse lower motor neuron disease, or a clinical variant of spinal muscular atrophy with a focal symptomatology and benign course.
There may also be genetic factors which play a role in the disease’s etiopathogenesis, considering the patients’ male predominance, Asian origin, and the descriptions of familial cases.
References
1. Pradhan S. Bilaterally symmetric form of Hirayama disease. Neurology 2009;72:2083-2089.
2. Tashiro K, Kikuchi S, Itoyama Y, et al. Nationwide survey of juvenile atrophy of distal upper extremity (Hirayama disease) in Japan. Amyotroph Lateral Scler 2006;7:38–45.
3. Tataroglu C, Bagdatoglu C, Apaydin FD, Celikbas H, Koksel T. Hirayama's disease: a case report. Amyotroph Lateral Scler Other Motor Neuron Disord 2003;4:264-265.
4. Gaio JM, Lechevalier B, Hommel M, Viader F, Chapon F, Perret J. Chronic spinal amyotrophy involving the upper limbs in young adults (O'Sullivan and McLeod syndrome). MRI study of the cervical spinal cord. Rev Neurol (Paris). 1989;145:163-168.
5. Gamez J, Also E, Alias L, et al. Investigation of the role of SMN1 and SMN2 haploinsufficiency as a risk factor for Hirayama's disease: clinical, neurophysiological and genetic characteristics in a Spanish series of 13 patients. Clin Neurol Neurosurg 2007;109:844-848.
Pradhan reported bilateral symmetric involvement in eleven cases within a series of 106 patients with Hirayama disease (HirD). [1] The iconographic information is important for the correct diagnosis of this rare form of motor neuron disease. However, the author’s suggestion that “the symmetric involvement has never been described” is incorrect.
Hirayama reported a small subset of patients with symmetric atrophy and weakness on many occasions. For example, of the 333 cases analyzed in a National Japan Survey, 3.1% presented with the variant described by Pradhan. [2] Other authors have reported similar cases. [3,4]
The diagnosis of HirD variants is difficult and diagnosis criteria are supported by lab and neuroimaging tests to rule out other entities. [2] Identification of HirD has led to a search for labels that cover these clinical variants of HirD including: late onset, familial forms, proximal muscle involvement, and bilateral and progressive forms. [5] Since the first definition of this entity as “juvenile muscular atrophy of unilateral upper extremity” was coined by Hirayama in 1959, other terms have been used to improve the definition of the different clinical variants of the disease, including “chronic segmental spinal muscular atrophy of the upper extremities”, “anterior tephromalacia”, and “O’Sullivan-McLeod syndrome.”
In addition to the anatomical abnormalities in the cervical/dural canal mentioned by the author, there are other pathogeneses of HirD. EMG observation of chronic denervation signs in the proximal muscles of all four limbs in at least one third of patients suggests that it may be an adult-onset diffuse lower motor neuron disease, or a clinical variant of spinal muscular atrophy with a focal symptomatology and benign course.
There may also be genetic factors which play a role in the disease’s etiopathogenesis, considering the patients’ male predominance, Asian origin, and the descriptions of familial cases.
References
1. Pradhan S. Bilaterally symmetric form of Hirayama disease. Neurology 2009;72:2083-2089.
2. Tashiro K, Kikuchi S, Itoyama Y, et al. Nationwide survey of juvenile atrophy of distal upper extremity (Hirayama disease) in Japan. Amyotroph Lateral Scler 2006;7:38–45.
3. Tataroglu C, Bagdatoglu C, Apaydin FD, Celikbas H, Koksel T. Hirayama's disease: a case report. Amyotroph Lateral Scler Other Motor Neuron Disord 2003;4:264-265.
4. Gaio JM, Lechevalier B, Hommel M, Viader F, Chapon F, Perret J. Chronic spinal amyotrophy involving the upper limbs in young adults (O'Sullivan and McLeod syndrome). MRI study of the cervical spinal cord. Rev Neurol (Paris). 1989;145:163-168.
5. Gamez J, Also E, Alias L, et al. Investigation of the role of SMN1 and SMN2 haploinsufficiency as a risk factor for Hirayama's disease: clinical, neurophysiological and genetic characteristics in a Spanish series of 13 patients. Clin Neurol Neurosurg 2007;109:844-848.
Disclosure: The author reports no disclosures.