[The Spectrum of Neuromyotonia: Clinics, Therapy and Outcome]

Background: Neuromyotonia (NM), Isaacs-Zschoke-Mertens syndrome or continuous muscle fiber activity (CMFA), is a rare condition associated with VGKC-antibodies. Clinically, fasciculations, myokymias, muscle stiffness and a myotonic appearance of movements after contraction are typical findings. In addition, CNS-symptoms vary from moderate fatigue, poor concentration and autonomic symptoms to severe encephalopathy in Morvan's syndrome. In electromyography, spontaneous irregular discharges can be found frequently with typical di-, tri- or multiplet single motor unit discharges. In up to 60 %, serum antibodies against VGKC-complexes can be detected.

Methods: Patients with neuromyotonia were evaluated for clinical symptoms, response to treatment and outcome over a five-year period of follow-up. For evaluation, we used video recording of clinical symptoms, electroneurography, electromyography and myosonography as well as immunological tests (VGKC-complex antibody including CASPR2 and IGL1). Furthermore, cerebral fluid and screening for neoplasias were done. Patients with evidence for neuropathy, myopathy or motor neuron disease, even if diagnosed in the follow-up, were excluded.

Results: In 3 of 5 patients, neuromyotonia was diagnosed by electromyography and positive VGKC antibodies. In two patients, diagnosis was based on typical clinical symptoms and electromyographical changes. Anticonvulsants (carbamazepine) for symptomatic treatment were moderately effective in four patients; treatment with i. v. immunoglobulins was highly successful in one patient with high positive VGKC-complex antibody titers. In one patient with low-titer VGKC antibodies, neither anticonvulsants nor i. v. immunoglobulins nor prednisone was a successful treatment.

Conclusions: Neuromyotonia is a rare, treatable condition. However, due to the high variability of symptoms, response to therapy and outcome, neuromyotonia treatment needs to be highly individualized.