Morvan's syndrome: An underdiagnosed entity
Morvan's syndrome is an autoimmune neurological disorder characterized clinically by neuromyotonia and neuropsychiatric manifestations along with laboratory evidence of anti-voltage-gated potassium channel (VGKC) antibodies.

Despite a characteristic clinical and laboratory picture, it is frequently misdiagnosed and not commonly reported. Published in the journal Neurology India, the authors report a case of Morvan's syndrome that was diagnosed only after 6 months of disease onset.

A 60-year old gentleman presented with a 6-month history of episodic confusional state, paresthesias of all four limbs, and significant weight loss. During the episodes, he developed confusion, disorientation to person (inability to recognize family members), disorientation to time (brushing at 3AM in morning) and place, aggression (needed to be restrained), along with bowel and bladder incontinence. He was evaluated elsewhere found to have hyponatremia (serum Na: 118–122 mEq/L) during the episodes. Initially, the episodes used to improve following correction of hyponatremia.

However, during the last episode, alteration in behaviour persisted despite correction of hyponatremia and he was referred to our hospital. On examination, he was emaciated with generalized wasting; he had lost 24 kg in the last 6 months. He was disoriented and confused with a MMSE (mini-mental status examination) score of 16/30. He was inattentive and agitated with prominent visual hallucinations.

Motor system examination revealed generalized continuous muscle activity with fasciculations in the tongue, chest, arms, and legs. There were no other focal neurological deficits. Deep tendon reflexes were brisk and plantar responses were flexor. In view of the combination of neuromyotonia, sensory symptoms, hyponatraemia, and altered mentation, a possibility of Morvan's syndrome was considered and he was evaluated.

CSF analysis revealed a protein level of 41mg/dl, sugar level of 60mg/dl, and no cells. Electromyography (EMG) of the right quadriceps and paraspinal muscles showed continuous muscle fiber activity, whereas the routine nerve conduction studies were normal. MRI of the brain was unremarkable, and fluorodeoxyglucose positron emission tomography (FDG-PET) revealed hypometabolism in bilateral temporo-parieto-occipital and right inferior frontal cortices.

Serum and CSF VGKC (CASPR2: Contactin associated protein like 2) antibodies were positive. He was given a course of intravenous immunoglobulin at a dose of 1 gram over 5 days, following which he completely improved and was discharged. However, he came back after 1 month with altered sensorium at which time he was treated with rituximab, with which he improved and was doing well (MMSE-30; no neuromyotonia) at the 8-month follow-up visit.

A repeat positron emission tomographic (PET) scan revealed significant normalization of the hypometabolic activity. Rituximab pulses at 6 monthly intervals have been planned.

Key takeaways:-
-Morvan's syndrome should be considered in every patient who presents in a confusional state along with evidence of peripheral nervous system hyperexcitability.

- Appropriate immunological tests should be conducted to confirm the diagnosis. Once diagnosed, patients should be given immunotherapy for ensuring a rapid recovery.


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