Paramyotonia congenita (PMC) is characterized by nondystrophic myotonia aggravated by exercise and cold exposure. SCN4A mutations manifest as various phenotypes of channelopathy, including PMC, myotonia congenita, and periodic paralysis. SCN4A-related channelopathy is characterized by autosomal dominant inheritance. Parental gonadal mosaicism is suspected in cases of recurrent de novo mutation in an autosomal dominantly inherited disease. We report a case of two Korean brothers presenting with PMC due to same de novo SCN4A point mutation, probably due to parental gonadal mosaicism.

Tram-track and doughnut-shaped enhancements of the optic nerve sheath in axial and coronal magnetic resonance imaging (MRI) views, respectively, play crucial roles in the diagnosis of optic nerve sheath meningioma (ONSM). However, this finding is not specific to ONSM since it can also be observed in optic perineuritis (OPN). Here we report a 42-year-old female with ONSM who presented with clinical and MRI findings similar to those of OPN.

Citations

• Freiburg Neuropathology Case Conference: Progressive Optic Nerve Lesion Over a 16-Year Period
  I. E. Duman Kavus, R. Sankowski, R. Rölz, A. Dressing, M. Prinz, H. Urbach, D. Erny, C. A. Taschner
  Clinical Neuroradiology.2025; 35(1): 215.     CrossRef

Some cases of myasthenia gravis (MG) with abnormal spontaneous activity (ASA) in needle electromyography (EMG) have been reported, but the associated clinical characteristics remain to be fully elucidated. We report the case of a 36-year-old male with MG in whom ASA was observed. This study highlights that ASA may appear in needle EMG in patients with severe MG who predominantly have bulbar and/or respiratory involvement. Care is needed because this often accompanies myopathic features and can be misdiagnosed as myopathy.