BILATERALLY SYMMETRIC FORM OF HIRAYAMA DISEASE

The reversible effect of neck flexion on the somatosensory evoked potentials in patients with Hirayama disease: a preliminary study

The aim of this study was to examine and characterize the reversibility of the cervical somatosensory electrophysiological pathways during neutral and flexed neck positions. The parameters of somatosensory evoked potentials (SEPs) during neutral and flexed neck positions (N9, N13, and N20 SEP latencies; N9-N13 and N13-N20 inter-peak latencies; and the changes in N9-N13 and N13-N20 inter-peak latency during neutral and flexed neck positions) were measured in the patients with Hirayama disease (HD) and also in the healthy controls. In patients with HD, there was a significant difference in the mean value of N13-N20 inter-peak latency during the flexed neck position compared to that of the healthy controls (p < 0.05). In a multivariate logistic regression analysis, N13-N20 inter-peak latency during the flexed neck position significantly correlated with the presence of HD (p < 0.05). Collectively, in this cohort of patients with HD, the neck flexion of patients with HD showed a reversible effect on the SEP parameter, especially in N13-N20 inter-peak latency. Conventional diagnosis of HD is based on nerve conduction studies and electromyography along with a cervical flexion MRI, and our study suggests the possibility of an additional and cost-effective electrophysiological marker that may be helpful in the diagnosis of HD.

Revisiting the spectrum of lower motor neuron diseases with snake eyes appearance on magnetic resonance imaging

BACKGROUND AND PURPOSE

The 'snake eyes' sign refers to bilateral hyperintensities of the anterior horns on axial spinal cord imaging. Based on sporadic reports, it has been associated with a range of lower motor neuron (LMN) syndromes, such as spondylotic amyotrophy and Hirayama disease, as well as spinal cord infarction. The objective of our study was to comprehensively characterize the full diagnostic spectrum of LMN syndromes with this radiological clue and discuss potential aetiological factors.

METHODS

A large patient cohort with snake eyes sign and upper limb LMN degeneration was recruited from three French neuromuscular units. Patients underwent detailed electrophysiological, radiological, clinical and anamnestic profiling.

RESULTS

Twenty-nine patients were ascertained and followed up for 9.5 ± 8.6 years. The majority of the patients were male (86.2%) with a mean age of 37.3 ± 14.4 years. Symptoms were bilateral in most cases (86.2%). Patients with predominantly proximal and distal deficits were equally represented (44.8% and 55.2%, respectively). A history of preceding trauma or intense physical activity was confirmed in 58.6% of the cases; 27.6% of the patients were given an initial clinical diagnosis of amyotrophic lateral sclerosis (ALS), and 51.7% were originally suspected to have multifocal motor neuropathy. None of the patients developed ALS on longitudinal follow-up.

CONCLUSION

The snake eyes sign on magnetic resonance imaging is associated with a wide spectrum of neurological conditions and is more common in young men with a history of strenuous activity or antecedent trauma. The recognition of this syndrome is crucial as many of these patients are initially misdiagnosed with ALS.