Clinical, Electrophysiological, and Serological Evaluation of Patients with Cramp-Fasciculation Syndrome.

Introduction: Cramp-fasciculation syndrome (CFS) is a rare peripheral nerve hyperexcitability syndrome. There are only a few reports on clinical and serological profile of a CFS cohort that was followed up by a single outpatient clinic.

Methods: Clinical, electrophysiological, and serological features of 6 CFS patients (5 men, 1 woman; 27-65 years old) were investigated.

Results: All patients presented with cramps, fasciculations, muscle pain, and autonomic symptoms, and 2 also reported numbness and burning sensation in limbs, suggestive of neuropathic pain. Antibodies to uncharacterized voltage-gated potassium channel (VGKC)-complex proteins were found in 2 patients and to contactin-associated protein-like 2 (CASPR2) in 1 patient. None of the patients had a tumor. Most of the patients revealed prolonged after-discharges following tibial nerve stimulation. Nerve conduction studies and R-R interval variability tests were normal, whereas sympathetic skin responses were increased in amplitude in 3 seronegative patients. Five patients showed favorable response to carbamazepine or pregabalin treatment, whereas 1 VGKC-antibody-positive patient was resistant to carbamazepine and immunosuppressant treatment.

Conclusion: Neuropathic pain and VGKC-complex antibodies may be encountered in CFS patients. Although autonomic symptoms are commonly found in CFS, routine autonomic system tests which are done in electrophysiology laboratories might yield normal results.