Neuromyotonia: Clinical, Electrophysiological and Immunological Findings of 4 Cases (P02.244)

OBJECTIVE: To analyze a series of patients with neuromyotonia from neuromuscular disorders unit, Hospital de Clinicas da Universidade Federal do Parana. BACKGROUND: Neuromyotonia is a rare disease characterized by spontaneous and continuous muscle activity due to a disorder of the peripheral nerve hyperexcitability. Patients develop persistent muscle contraction, classically worsening after exercise. Electromyography is characterized by neuromyotonic discharges and about 40% of patients have detectable voltage-gated potassium-channel (VGKC) antibodies. DESIGN/METHODS: We studied four patients with neuromyotonia, regarding the clinical, electrophysiological and immunological findings. RESULTS: The average age of onset of symptoms was 17.5 (7-35) years and there was no gender predilection. The average time between onset of symptoms and diagnosis was 9.5 (1-29) years. The patients had muscle twitching (100%), muscle hypertrophy and hyperhidrosis (100%), muscle cramps and stiffness (75%), pseudomyotonia (25%), weakness (75%), paresthesias (25%), dysphonia, dysphagia and dyspnea (25%) and central nervous system symptoms (25%). Family history and exogenous intoxication were negative. All patients had the dosage of anti-VGKC negative. Electrophysiological findings: myokymia and neuromyotonic discharges were found in all patients, douplets and multiplets in 100% and triplets in 50% of cases. The maximum intraburst frequency ranged from 70 to 200 Hz. Three patients were treated with carbamazepine and gabapentin with a good response to treatment. Three used phenytoin, and of these, two had a partial response and one had intolerance to the drug. One patient had epilepsy, one patient developed ulcerative colitis idiopathic, glomerulonephritis and eczema on the face and another one hypothyroidism, arthralgia and myalgia. CONCLUSIONS: The diagnosis of neuromyotonia is accomplished primarily through clinical and electrophysiological findings. Electromyography often confirms diagnosis by the presence of neuromyotonic discharges. The dosage of anti-CKVD has a low sensitivity for the diagnosis of disease. The association with autoimmune diseases can be observed, as described in this series. Disclosure: Dr. Scola has received personal compensation for activities with Merck Serono as scientific advisor board. Dr. Paranhos has nothing to disclose. Dr. Lorenzoni has nothing to disclose. Dr. Kay has nothing to disclose. Dr. Vincent has received personal compensation for activities with Athena Diagnostics. Dr. Vincent has received royalty payments from Athena Diagnostics. Dr. Werneck has nothing to disclose.