Polymyoclonus aggravated by neck flexion as the isolated presenting symptom of Hirayama disease: case report.

BACKGROUND: We report a rare case of an 18-year-old male with unilateral hand tremor who was finally diagnosed with Hirayama disease (HD). CASE PRESENTATION: An 18-year-old male presented with unilateral polymyoclonus that aggravated with neck flexion. The patient did not complain of muscle weakness or muscle atrophy. The needle electromyography showed giant motor unit potentials in right cervical 7 and 8 innervated muscles. The cervical magnetic resonance imaging on supine and flexion state showed prominent forward effacement of posterior dural sac that was compatible with HD. CONCLUSIONS: HD usually presents with unilateral distal hand weakness, muscle atrophy and tremor. Although it is a benign and self-limiting disease, early diagnosis may lead to less clinical deterioration. Moreover, electromyography should be completed in the differentiation of young male patients who present with polymyoclonus without hand weakness or atrophy.

Diffusion tensor imaging and voxel-based morphometry reveal corticospinal tract involvement in the motor dysfunction of adult-onset myotonic dystrophy type 1.

Magnetic resonance imaging (MRI) studies have demonstrated that patients with myotonic dystrophy type 1 (DM1) exhibit gray and white matter abnormalities that are correlated with various genetic and neuropsychological measures. However, few MRI studies have focused on the correlations between brain abnormalities and overall motor function including gait performance. Here, we investigated the correlations between brain abnormalities, as assessed with MRI including diffusion tensor imaging (DTI), and motor performance, as assessed with the Medical Research Council sum score (MRCSS), 6-minute walk test (6MWT), and hand grip power, in patients with DM1. Eighteen patients with DM1 and twenty healthy controls participated in this study. The MRCSS and 6MWT reflect patients' general motor performance, particularly gait, while hand grip reflects the presence of myotonia. We found significant relationships between DTI parameters in the corticospinal tract (CST) and genetic factors and motor performance in patients with DM1. These findings suggest that CST involvement reflecting deterioration of the motor tracts may play a significant role in clinical myotonia. Further, a direct relationship between the cortical gray matter volume and DTI measures in the CST suggests that white matter abnormalities in the CST are strongly associated with volume reductions in the sensorimotor cortex of patients with DM1.