Abstract
Introduction Morvan syndrome is a rare neurological disorder consisting of a combination of neuromyotonia with cognitive symptoms and dysautonomia or insomnia. It is associated with antibodies against the voltage-gated potassium channel (VGKC) associated proteins – most commonly, against CASPR2.
Case A 74-year-old male presented with six-months of worsening psychobehavioural changes, insomnia, amnesia, and neuromyotonia. At presentation, he complained of visual hallucinations and unsteadiness of gait. He subsequently developed urinary retention, labile blood pressure and atrial fibrillation. Neurologic examination revealed disorientation to time and place, dysarthria, diffuse hyperreflexia, and multifocal fasciculations.
Brain and whole cord MRI with contrast, was unremarkable. EEG showed moderate encephalopathy. CSF findings were unremarkable. Paraneoplastic antibodies and infectious and vasculitis screens were normal; malignancy was not found despite extensive investigation.
In serum, CASPR2-antibody was strongly positive, titre of 535pM, and also weakly positive for LGI1. Nerve conduction studies and electromyography showed post-CMAP after-discharges, and myokymia respectively. Overall, the study was suggestive of peripheral nerve hyper-excitability.
He was induced with intravenous immunoglobulins and pulsed with, and maintained, on steroids. He had excellent clinical response – his modified Rankin score improved from 4 to 1.
Conclusion Antibodies against the VGKC-complex proteins, most commonly CASPR-2, are associated with a wide spectrum of clinical diseases, often associated with an underlying malignancy. Morvan syndrome is one such rare and treatable manifestation. Awareness of this constellation of symptoms and consideration of prolonged clinical course are crucial in early diagnosis and prompt immunotherapy, or tumour therapy. Improvement can be pronounced, though relapse may occur.
