A case of primary spinal myoclonus: clinical presentation and possible mechanisms involved

Abstract

-Spinal myoclonus is a rare movement disorder characterized by myoclonic involvement of a group of muscles supplied by a few contiguous segments of the spinal cord. Structural lesions are usually the cause, but in primary spinal myoclonus the etiology remains unknown. We present the case of a 26-year-old woman with cervical spinal myoclonus in which both clinical and electromyographic findings pointed to the segment C1-C3 as the origin of the myoclonus. Laboratorial examinations were normal and no structural lesion was found in magnetic resonance imaging (MRI). Botulinum toxin type A was injected in infrahyoid muscles and cervical paraspinal musculature. The patient remained free of symptoms for almost five months. The pathophysiology of spinal myoclonus remains speculative, but there is evidence that various possible mechanisms can be involved: loss of inhibitory function of local dorsal horn interneurons, abnormal hyperactivity of local anterior horn neurons, aberrant local axons re-excitations and loss of inhibition from suprasegmentar descending pathways.KEY WORDS: spinal myoclonus, segmental myoclonus, primary myoclonus.Um caso de mioclonia espinhal primária: apresentação clínica e possíveis mecanismos envolvidos Um caso de mioclonia espinhal primária: apresentação clínica e possíveis mecanismos envolvidos Um caso de mioclonia espinhal primária: apresentação clínica e possíveis mecanismos envolvidos Um caso de mioclonia espinhal primária: apresentação clínica e possíveis mecanismos envolvidos Um caso de mioclonia espinhal primária: apresentação clínica e possíveis mecanismos envolvidos RESUMO -A mioclonia espinhal é um raro distúrbio do movimento, caracterizado pelo envolvimento mioclônico de um grupo de músculos inervados por segmentos medulares contíguos. Lesões estruturais costumam ser a causa, mas na mioclonia espinhal primária a etiologia não é definida. Apresentamos o caso de uma mulher de 26 anos com mioclonia cervical espinhal em quem os achados clínicos e eletrofisiológicos apontaram o segmento C1-C3 como origem das mioclonias. Os exames laboratoriais foram normais e nenhuma lesão estrutural foi encontrada à ressonância. A toxina botulínica tipo A foi injetada nos músculos infrahioideos e na musculatura paraespinhal cervical. A paciente permaneceu assintomática por cinco meses. A patofisiologia da mioclonia espinhal continua especulativa, mas há evidências de que vários mecanismos possam estar envolvidos: perda da função inibitória de interneurônios da coluna dorsal, hiperatividade anormal de neurônios do corno anterior da medula, re-excitações axonais locais aberrantes e perda do efeito inibitório de vias descendentes suprasegmentares.PALAVRAS-CHAVE: mioclonia espinhal, mioclonia segmentar, mioclonia primária.

History of Botulinum Toxin Treatment in Movement Disorders

“…Another case report described a 26-year-old female with segmental C1–C3 spinal myoclonus in whom injection of botulinumtoxin A into the infrahyoid and cervical paraspinal muscles stopped the movements. The effect lasted for 5 months 63. In a recent review article on propriospinal myoclonus, the authors reported 20 patients from the world literature who had responded to botulinum toxin treatment 64…”

Spinal segmental myoclonus as an unusual presentation of multiple sclerosis

“…Proposed mechanisms included the loss of inhibitory function of local dorsal horn interneurons, abnormal hyperactivity of local anterior horn neurons, aberrant local axons re-excitations and loss of inhibition from supra-segmental descending pathways [1,5,6]. Demyelinated axons can be abnormally hyper-excitable and can display spontaneous discharges, which alone, or driven reflexibly, could lead to myoclonus [7].…”

Spinal myoclonus following a peripheral nerve injury: a case report

“…loss of inhibitory function of local dorsal horn inter-neurons, abnormal hyperactivity of local anterior horn neurons, aberrant local axons re-excitations and loss of inhibition from supra-segmentar descending pathways [2]. …”

“…Though structural lesions are usually found in spinal myoclonus, the pathophysiology remains speculative. But there is evidence that various possible mechanisms can be involved: loss of inhibitory function of local dorsal horn interneurons, abnormal hyperactivity of local anterior horn neurons, aberrant local axons re-excitations and loss of inhibition from suprasegmentar descending pathways [2]. …”