Occipitalis muscle: using for repetitive facial nerve stimulation in myasthenia gravis

Repetitive nerve stimulation (RNS) is a highly sensitive electrophysiological test used for diagnosing myasthenia gravis (MG). Here, we evaluated electrodiagnostic value of RNS using facial nerve and occipitalis muscle. Patients with generalized MG were included. Clinical findings were assessed. RNS test was performed on occipitalis, nasalis, trapezius, abductor policis brevis (APB) and abductor digiti minimi (ADM) muscles. Twenty-five (78%) patients had relevant decrement during RNS test of at least one muscle. Nasalis muscle had the highest diagnostic potential (68.8%), followed by trapezius (53.3%), occipitalis (50%), APB (30%) and ADM (16.7%) muscles. There was not a significant relationship between clinical symptoms and facial RNS recorded on occipitalis muscle. In conclusion, we suggest that facial RNS recording over occipitalis muscle can be added in electrodiagnosis of MG because of cranial nerve innervation and proximal location. Facial RNS recording over occipitalis muscle provides a good choice under the conditions such as atrophy, cosmetic surgery, or botulinum toxin application in which nasalis muscle is unavailable for use.