Hirayama Disease: Case Report / Doença de Hirayama: Relato de caso

Abstract A 26-year-old previously healthy patient who, at the age of 18 years, began progressive loss of distal strength, rest tremor, and muscle atrophy in the left upper limb. Upon examination, the patient presented moderate distal atrophy, degree 4 in muscular strength, and minipolymioclonus. Electromyoneurography revealed (EMNG) chronic preganglionic bilateral involvement of bilateral C7/C8/T1, worse on the left, with signs of active C8/T1 denervation. A cervical spine magnetic resonance imaging (MRI) scan showed spondylodiscal degenerative changes with central protrusions in C4-C5, C6-C7, and right central in C5-C6, which touched the dural sac. The anteroposterior diameter of the medulla in neutral position, in the C5-C6 plane, was of 5.1 mm. There was a reduction of the spinal cord caliber to 4.0 mm after the dynamic maneuver of forced flexion of the spine, as well as signal increase in the anterior horns. The clinical findings and those of the complementary tests were compatible with Hirayama disease (HD), a rare benign motor neuron disease that affects cervical spinal segments and is most prevalent in men, with onset in the early 20s. Unilateral and slowly progressive weakness is typical, but self-limited. Sensory disturbances, and autonomic and upper motor neuron signals are rare. Management is usually conservative, with the use of a soft cervical collar. Although rare, HD should be considered in young patients with focal asymmetric atrophy in the upper limbs. The early diagnosis of HD depends on the degree of suspicion, as well as on the cooperation and communication among the various specialties involved in the investigation.

Resumo Paciente de 26 anos, previamente hígido, que, aos 18 anos, iniciou perda progressiva de força distal, tremor de repouso, e atrofia muscular no membro superior esquerdo. Ao exame, apresentou atrofia moderada, distal, força muscular de grau 4, e minipolimioclonus. A eletroneuromiografia (ENMG) revelou comprometimento pré-ganglionar crônico de C7/C8/T1 bilateral pior à esquerda, com sinais de desnervação ativa em C8/T1. A ressonância magnética (RM) de coluna cervical mostrou alterações degenerativas espondilodiscais com protrusões centrais em C4-C5, C6-C7, e central direita em C5-C6, que tocavam o saco dural. O diâmetro anteroposterior da medula na posição neutra, no plano de C5-C6, era de 5,1 mm. Houve redução do calibre da medula para 4,0 mm após a manobra dinâmica de flexão forçada da coluna, e aumento de sinal nos cornos anteriores. Os achados clínicos e os dos exames complementares eram compatíveis com doença de Hirayama (DH), uma doença benigna rara dos neurônios motores, que afeta os segmentos espinhais cervicais e é mais prevalente em homens e de início próximo aos 20 anos. É típica a fraqueza unilateral e lentamente progressiva, porém autolimitada. Perturbações sensoriais, sinais autonômicos e do neurônio motor superior são raras. O manejo geralmente é conservador, com uso de colar cervical macio. Apesar de rara, a DH deve ser considerada em pacientes jovens que apresentam atrofias assimétricas focais de membros superiores. O diagnóstico precoce de DH depende do grau de suspeição, e da cooperação e comunicação entre as diversas especialidades envolvidas na investigação.

Resonancia magnética de columna cervical con secuencia en flexión para el diagnóstico de la enfermedad de Hirayama / Magnetic resonance of the cervical spine with sequence in flexion for the diagnosis of Hirayama disease

La enfermedad de Hirayama o atrofia muscular espinal juvenil no progresiva de las extremidades superiores es una clase de mielopatía relacionada con la flexión del cuello. Afecta principalmente a hombres jóvenes (entre 15 y 25 años) y se caracteriza por una debilidad muscular asimétrica y unilateral de miembros superiores con atrofia. Suele presentarse de manera insidiosa, con curso progresivo y autolimitado a los 3-4 años del inicio del cuadro. Se cree que es producida por trastornos isquémicos en la microcirculación de las astas anteriores del segmento medular cervical entre C8 y T1 por la compresión en el segmento medular anterior debido al desplazamiento anterior de la duramadre al flexionar el cuello. Si bien existen varias teorías sobre la causa de este deslizamiento, la más aceptada se relaciona con la falta de crecimiento de la duramadre con respecto a la columna durante la pubertad. Esto provocaría un aumento de la tensión de la dura posteriory, como consecuencia, el desplazamiento anterior durante la flexión. Dado su excelente contraste tisular y la posibilidad de realizar adquisiciones en distintos planos, la resonancia magnética es el estudio de elección. Las imágenes deben ser obtenidas en posición neutra y en flexión cervical máxima para poner de manifiesto el desplazamiento de la dura, con el consiguiente aumento de la sensibilidad y especificidad de la prueba. Así, se logra mayor confianza en el diagnóstico y menor cantidad de falsos positivos, en comparación con la posición neutra como única adquisición.

Hirayama disease is a type of myelopathy related to neck flexion. It affects young male adults between 15 and 25 years, and is characterised by unilateral and asymmetric upper limb muscle weakness with atrophy. It usually presents insidiously, with a progressive course and self-limits in 3-4 years. It is believed that it could be produced by ischaemic disorders in the microcirculation of the anterior horns of the cervical spine segment C8 and T1 due to anterior displacement of the dura. There are several theories for the cause of this displacement, with the most accepted being the relationship between the lack of growth of the dura mater and the spine during puberty. This increases the tension of the posterior dura mater and consequently the anterior displacement during flexion. Due to its excellent tissue contrast and the possibility of acquisitions in different planes, magnetic resonance imaging is the study of choice. Images must be obtained in both neutral and cervical flexion to highlight the displacement of the dura mater. This increases the sensitivity and specificity of the test, giving greater confidence in the diagnosis, and reducing false positives compared to neutral as a single acquisition.