Abstracts

Rationale: Vagal nerve stimulation (VNS) is indicated for treatment of medically refractory epilepsy (MRE). Complications or side effects are rare and generally result from transient or permanent effects on recurrent laryngeal nerve, a branch of the left vagus nerve Methods: We conducted a retrospective chart review of patients with MRE treated with VNS therapy. We evaluated the reported side effects and identified symptoms that are not commonly described as sequelae of VNS implantation. Results: Of the 70 patients reviewed from our VNS database, we identified 3 cases where the device resulted in a rare presentation. Case 1: Neck and upper extremity tremor. A 32 year-old woman diagnosed with MRE with independent bitemporal onset and anti-GAD antibody syndrome, who continued to have seizures following right temporal resection. Five years after implantation of left VNS, she developed abnormal painless, rhythmic neck, head and arm movements at 2-3 Hz resembling tremors. On exam, rhythmic contraction of the left lateral neck muscles and biceps was noted during VNS on-phase and ceased with reduction in VNS output setting. Case 2: Pseudo-dystonia. A 31 year-old woman with MRE in the setting of brain tumor, cortical dysplasia and partially successful resective epilepsy surgery underwent VNS placement. After seven years, the system (including leads that were placed more inferiorly) was replaced due to malfunction. Two weeks later, she reported a pulling sensation of the left neck and contraction of left arm, on turning her head to the left during VNS on phase. On exam, sustained contraction of biceps akin to dystonic posture was demonstrated during VNS on-phase only when she would turn her head to the left. Case 3: Fatigable dysphonia. A 19 year-old woman with MRE since the age of two, underwent VNS placement for treatment of her seizures. Six months after implantation, she slipped and fell on ice while carrying cardboard boxes, and one of them hit the left side of her neck. The injury was trivial, but shortly thereafter, she developed fatigable dysphonia and would lose her voice completely after talking for 20-30 minutes which recovered with rest. In addition, her seizures recurred. During the revision surgery it was found that a lead was broken with the vagus nerve compressed and almost severed between the electrodes and anchor tether and a neuroma formation was seen between the helices of the positive and negative electrodes. Following release of compression and repositioning of the lead inferiorly, her symptoms resolved and her seizure control returned. Conclusions: Complications from VNS therapy can occur long after initial implantation of the device. A possible current leak to the adjacent structure can result in abnormal movements or damage to these structures. It is crucial to be aware of the possible complications related to the surgery itself or the device. Early recognition of such issues prevents unnecessary extensive workup and alterations in the patient therapeutic plan. Funding: None