Hirayama disease: three cases assessed by F wave, somatosensory and motor evoked potentials and magnetic resonance imaging not supporting flexion myelopathy

Abstract

Traumatic chronic injury of the cervical spinal cord caused by neck flexion ("flexion myelopathy") is one of the suggested pathogenetic mechanisms for Hirayama disease (HD). Neurophysiological data, especially reporting particularly N13 cervical somatosensory response, are scarce and conflicting in HD. F wave, somatosensory evoked potentials (SEP), motor evoked potentials (MEP) and magnetic resonance imaging (MRI) studies were assessed in 3 HD male patients (aged 22, 36, and 51 years) with the aim of evaluating the functional effects of neck flexion in HD. Median and ulnar F waves, median, ulnar and posterior tibial SEP, and upper and lower limb MEP were performed bilaterally in standard conditions and during neck flexion in the patients. Cervical spinal MRI study was performed in standard position in two patients and both in standard and flexed positions in the third patient. F wave, SEP, and MEP findings did not show statistically significant differences in standard conditions and during neck flexion both in HD patients and controls. MRI with neck in standard position was normal in two patients, while in the third patient revealed cervical anterior horns signal changes and cord atrophy. In this patient, MRI with the neck in flexion showed that the spinal cord was normally located, was not compressed within the cervical canal and that there were no abnormalities of the dural sac. These findings suggest that in a complex disorder like HD no definite conclusions can be drawn from the present paper and some cases of HD without evidence of "flexion myelopathy" might have a different pathogenetic mechanism.

Nosology of Juvenile Muscular Atrophy of Distal Upper Extremity: From Monomelic Amyotrophy to Hirayama Disease—Indian Perspective

“…However, Misra et al found no significant change in somatosensory evoked potentials and F-wave parameters on neck flexion compared with neutral position in their study of eight patients of HD and controls [36]. Ammendola et al, in a small cohort of three cases, did not show statistically significant differences for F-wave, somatosensory evoked potentials and motor evoked potentials in standard conditions and during neck flexion both in HD patients and controls, suggesting that some cases of a complex disorder like HD might have a pathogenetic mechanism different from “flexion myelopathy” [37]. Misra and Kalita, in another study of seven patients of HD, found that the central motor conduction to lower limbs was normal in all while central motor conduction to upper limbs was marginally prolonged on one side [38].…”

Progressive muscular atrophy and other lower motor neuron syndromes of adults

“…The anatomical distortion might be aggravated by flexing the neck, but there seemed to be no role for decompressive surgery on the cervical spine 38. Neck flexion has been exonerated, at least in some patients 39. The clinical picture can be simulated by cervical myelopathy40 or in conditions caused by mutations of mitochondrial DNA 41.…”

Hirayama’s disease: an Italian single center experience and review of the literature

“…Since then, the greatest number of cases have been reported from Japan and other Asian countries (1)(2)(3)(4)(5)(6); in contrast, it is less common among the population of the North America and Europe, however lately some case series were published (7-10). Some case reports were reported in Italy (11)(12)(13) but to our knowledge this is the first reported Italian group of patients with HD.…”