Benign monomelic amyotrophy: a study of twenty-one cases

Abstract

-A consecutive series of 21 patients with single limb atrophy (monomelic amyotrophy) is reported. Sixteen had lower limb atrophy and five had upper limb involvement. The median age of the onset was 20 years. Characteristic features were sporadic occurrence, wasting confined to one limb, insidious onset with slow progression, stabilizing in 1 to 4 years, and absence of pyramidal signs. All the patients with upper limb involvement were male, however in our cases with lower limb amyotrophy there were no male preponderance. We observed wasting of the entire length of the lower limbs in six patients. There were nine cases with amyotrophy restricted to the leg and one with amyotrophy only in the thigh. In the upper limb in four cases the involvement was distal and in one patient the atrophy was proximal. The electromyographic features were suggestive of anterior horn disease not only in the affected limb but also, in some cases, in clinically uninvolved limb. Cervical or lumbar MRI was normal. MRI of the lower limb disclosed increased signal intensity in the gastrocnemius and soleus muscles in one patient suggesting denervation.KEY WORDS: lower motor neuron, monomelic amyotrophy, spinal muscular atrophy. Amiotrofia monomélica benigna: estudo de 21 casosRESUMO -Relatamos uma série consecutiva de 21 pacientes com amiotrofia de um só membro, denominada de amiotrofia monomélica. Em 16 casos a atrofia era no membro inferior e em 5 localizava-se no membro superior. Todos eram jovens e a idade média do início foi 20 anos. Os dados mais característicos da doença foram ausência de história familiar, comprometimento de um só membro, início e progressão lenta estabilizando em até 4 anos e ausência de sinais piramidais. Nossos enfermos com amiotrofia de membro superior eram todos do sexo masculino, entretanto naqueles com amiotrofia do membro inferior havia igualdade de sexos. Dos pacientes com atrofia de membro inferior, em 9 a atrofia era restrita a perna, em 6 era em todo o membro e somente um apresentava amiotrofia localizada só na coxa. Naqueles com comprometimento do membro superior a atrofia era distal em 4 e proximal em 1. Os achados na eletromiografia foram compatíveis com acometimento do II neurônio motor. Todos foram submetidos a RM da coluna cervical ou lombar que se mostrou normal. Em um caso realizamos RM da perna acometida que evidenciou sinais hiperintensos nos músculos gastrocnemius e soleus, o que sugere desnervação. PALAVRAS-CHAVE: neurônio motor inferior, amiotrofia monomélica, amiotrofia espinhal.

Non-progressive juvenile spinal muscular atrophy of the distal upper limb (Hirayama's disease): a clinical variant of the benign monomelic amyotrophy

“…The so called Hirayama disease is clinically characterized by juvenile male occurrence, insidious onset, and unilateral muscular atrophy in the hand and forearm [3][4][5][6] . The weakness and muscular atrophy progress for 1 to 3 years before stabilizing over a sufficient period to underline its benignity 4,5,6,13 . It is a rare condition 3,6,14 .…”

“…Most cases were initially described in India and Japan but several cases have been reported in Western countries 7,8,12,15,16 . We have recently reviewed our series of 21 cases of different clinical presentations of benign monomelic amyotrophy, the first from South America, including the four cases of this report 13 . Reviewing 375 cases of typical focal amyotrophy of upper limb in Western literature Robberecht et al 2 , in 1997, found that the age of onset in 94% of the cases were between 15 and 25 years.…”

“…In about 37% of the revised cases there was atrophy on both sides, although it was almost always markedly asymmetric, as occurried in our Patient 1. This condition is usually sporadic 2,13 . Familial occurrence of HD is very rare 4,5 .…”

“…In most published series patients have the upper limb more involved, including HD cases [4][5][6] . In our recent consecutive series of BMA the lower limb was the more involved 13 . In all these series the clinical and electrophysiological aspects are consistent with a benign involvement of the lower motor neuron 5,6,13 .…”

“…In our recent consecutive series of BMA the lower limb was the more involved 13 . In all these series the clinical and electrophysiological aspects are consistent with a benign involvement of the lower motor neuron 5,6,13 . In many cases some EMG findings are also seen in muscles of other segments of a limb or in other limb(s) 3,6 .…”