Síndrome de Isaacs: relato de três casos

Abstract

RESUMO -Relatamos três casos de síndrome de Isaacs, que apresentavam mioquímia clínica, cãibras, dificuldades para o relaxamento muscular, hipertrofia muscular e aumento da sudorese. A eletromiografia de agulha mostrou atividade muscular contínua involuntária, caracterizada como descargas mioquímicas. Os estudos da condução nervosa foram normais. Biópsia de músculo, realizado nos três casos, mostrou atrofia de fibras do tipo 2. Dois casos apresentaram melhora clínica com a utilização de carbamazepina e um com prednisona. PALAVRAS-CHAVE: atividade muscular contínua involuntária, mioquímia, descarga mioquímica Isaacs' syndrome: report of three cases ABSTRACT -We report two females, and one male with Isaacs' syndrome. The patients presented with clinical myokymia activity, muscle cramps, delayed relaxation, and muscle hypertrophy and increased sweating. Needle electromyography in several muscles showed generalized continuous motor unit discharges, myokymic discharges, and normal nerve conduction studies. Muscle biopsy showed type two fiber atrophy. Treatment with carbamazepine was effective in two cases and prednisone in one.KEY WORDS: continuous motor fiber activity, myokymia, myokymic discharge.A síndrome de Isaacs caracteriza-se pela atividade muscular contínua involuntária (mioquímia clínica), atraso do relaxamento muscular, rigidez e aumento da sudorese 1-5 . Descargas espontâneas de potenciais de unidade motora (PUM) são os principais achados da eletromiografia (EMG) de agulha, observados como descargas mioquímicas ou neuromiotônicas generalizadas [6][7][8][9][10][11] . As descargas dos PUM ocorrem por alterações do estado de excitabilidade das porções terminais dos axônios motores, devido a ação de anticorpos, contra canais de potássio voltagem dependente (CKVD) [12][13][14][15][16] . Pela raridade desta doença relatamos os achados clínicos, laboratoriais, eletroneurofisioló-gicos de três casos de síndrome de Isaacs, afim de contribuir para a melhor compreensão dos fenômenos fisiológicos. RELATO DOS CASOSCaso 1. OVN, 40 anos, branca, iniciou os sintomas há 4 anos, durante o terceiro trimestre de gestação, com fraqueza da musculatura proximal de membros inferiores (MMII), cãibras e contrações musculares involuntárias contínuas generalizadas. Nega quadros semelhantes na família, contato com substâncias tóxicas e uso de medicações. Ao exame apresentava atrofia da musculatura distal, força muscular proximal de MMII e distal de membros superiores (MMSS) grau 4 + (Medical Research Council-MRC), hipertonia global, hiporreflexia profunda, fasciculações Serviço de Neurologia (Doenças

Issacs Syndrome in a Pediatric Patient and Voltage-Gated Potassium Channels Antibodies

“…1,4 Its pathophysiology is still unknown but may be because of acquired autoimmunity or genetic changes in VGKC. 1,3,4 VGKC antibodies have been identified in 40% of patients, which supports their autoimmune mechanism. 1,4 There are 2 types of VGKC antibodies, one directed against LGI1 and the other directed against CASPR2.…”

“…Myokymia is present in approximately 90% of patients being the main clinical finding of IS. 3 By contrast, pseudomyotonia is present in only one-third of patients. 4 Patients may also experience hyperhidrosis, paresthesias, mild muscle weakness, or even CNS symptoms, such as hallucinations or insomnia.…”

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Isaacs syndrome (IS), also known as acquired neuromyotonia, is a rare neuromuscular disease, manifested by involuntary continuous motor activity. 1 Although there are reports in children, 2,3 IS is more frequent in adults. 1 The clinical presentation can include muscle cramps, fasciculations, myokymia, and pseudomyotonia.

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“…1,4 Dysfunction of peripheral nerve voltagegated potassium channels (VGKCs) seems to be related to the development of the disease. 1,[3][4][5] Paraneoplastic factors also play an important role in IS. 5 Anticonvulsants are the first therapeutic option.…”

“…Nerve conduction studies are usually normal, but electromyographic recordings present spontaneous irregular and continuous discharges, even at rest. 1,[3][4][5] Typical discharges make the diagnosis and can be divided into neuromyotonic and myokymic discharges. Neuromyotonic discharges are irregular high-frequency discharges, whereas myokymic discharges consist of irregular spontaneous low frequency discharges, both present during sleep.…”