Segmental Spinal Myoclonus After a Cervical Transforaminal Epidural Steroid Injection

In clinical practice, cervical transforaminal epidural steroid injection is commonly used for alleviating pain. We report a case of segmental spinal myoclonus that developed after cervical transforaminal local anesthetic and steroid injection. A 39-yr-old man presented involuntary movements of the bilateral upper trapezius muscles after cervical transforaminal epidural steroid injection on the right C6 and C7 roots with a 5 mg of dexamethasone injectate mixed with 0.5 ml of 1% lidocaine and 0.5 ml of normal saline at each level. His myoclonus was semirhythmic and continuously persisted at a frequency of approximately 30 episodes per minute. The myoclonus continued even at rest and during sleep. In addition, it was resistive to stimulus, such as touch and voluntary action. Based on the clinical features, the patient was diagnosed as having a segmental spinal myoclonus. Clonazepam 0.25 mg was administered three times daily. The myoclonus gradually improved and resolved completely within 2 wks. Segmental spinal myoclonus is one of rare complications after cervical transforaminal epidural steroid injection. Clinicians should be aware of the likelihood of this potential complication.