Botulinum Toxin A for Treatment of Diaphragmatic Myoclonus

Correspondence To the Editor: Diaphragmatic myoclonus, as a typical unusual focal dyskinesia, is characterized by repetitive involuntary synchronous contractions of the diaphragm and other respiratory muscles. [1] Various clinical presentations and difficulties in identifying etiology might lead to its late diagnoses and ineffective treatment in many cases. Botulinum toxin A has a paralyzing effect on muscles. However, to the best of our knowledge, there have been few reports of injecting botulinum toxin A to the diaphragm. In this case, we reported that diaphragmatic myoclonus was successfully treated by injecting botulinum toxin A into the diaphragm and the rectus abdominis (RA) under needle electromyography (EMG) guidance. A 51-year-old man presented with a 5-year history of involuntary abdominal movements [Video 1]. These movements, which were suppressed by sitting, standing, or distraction and exacerbated by lying down or relaxing, did not persist when he was asleep. Due to these abdominal movements, he could not concentrate on his work and lost confidence in interpersonal relationships. He even twice attempted to commit suicide. Previous treatments with scopolamine, baclofen, valproate, clonazepam, carbamazepine, traditional Chinese herbal medicine, and acupuncture had no effect on his abdominal movements and brought side effects such as drowsiness. The patient had a 20-year history of depression and two manic episodes, taking sertraline 50 mg, lithium carbonate 500 mg, and clozapine 25 mg daily. Given the possible adverse effects, his psychiatrist suggested stopping taking clozapine over a period, but he got no improvement. In the clinical examination, the patient showed symptoms of irregular twitches and spasms of the abdominal wall associated with sagittal oscillations of the upper body and sounds from the larynx. No abnormal movements in his limbs, neck, or head were observed. The 24-h video electroencephalogram and magnetic resonance imaging of the brain showed no abnormality. Outcomes of blood tests, including thyroid hormones, liver and renal function, and autoimmune tests, were all normal. Considering body's bending up and interruption to speech during the twitches, both RA and diaphragm were speculated to participate in these abnormal movements. Further examination with fluoroscopy and needle EMG confirmed the speculation by revealing the involvement of the diaphragm and RA [Video 1] during these abdominal movements, and the diagnosis of " diaphragmatic myoclonus " was verified. With the consent of the patient and his family regarding potential risks and benefits, we performed botulinum toxin A (Allergen Pharmaceuticals Ltd., Westport, Ireland) injection into the diaphragm under EMG …