BS17. The “Uncommonly Common” horner syndrome following a VNS insertion

Abstract

The Vagus nerve stimulation (VNS) therapy is approved in the USA as an adjunctive treatment in reducing the frequency of seizures in patients aged 4 years and older with partial-onset seizures refractory to antiepileptic drugs (AEDs). Globally, it has been implanted in more than 100,000 patients. Some of the commonly reported surgical complications of the device include infection, postoperative hoarseness, and pain. Here, we report a case of Horner syndrome subsequent to a VNS placement. Case report and literature review. A 61 year-old woman with drug-resistant focal epilepsy who previously underwent a selective left amygdalohippocampectomy at an outside hospital and achieved class 4 ILAE Epilepsy surgery outcome scale, underwent a VNS placement. There were no reported intraoperative complications. When seen in a follow-up 2 weeks post-operatively, the patient reported new onset excessive lacrimation and blurry vision in the left eye. A detailed examination revealed a left miotic pupil and partial left ptosis. She denied hemifacial anhidrosis and no changes in skin temperature or appearance were detected on the exam. Based on the above findings a diagnosis of left Horner syndrome was established. These signs and symptoms remained without improvement upon a subsequent follow-up, about 4 weeks post-operatively. When her findings first became apparent to the treating neurologist, the surgeon who placed the device was immediately contacted. The surgeon, however, did not find the discovery alarming, stating that Horner syndrome is “commonly observed” post-VNS implantation. An extensive literature search of VNS-related Horner syndrome returned maximum 7 references (both human and animal data) on PubMed and several book references on the Google search engine. Additionally, a limited poll of the epileptology colleagues and LivaNova representatives yielded zero personal reports of the phenomenon. Only two human studies with sizable patient samples that referenced the syndrome were identified. The first study retrospectively reviewed the charts of all adult epilepsy patients treated by VNS with ⩾1 year follow-up. Out of 34 patients (14 males; mean age = 29.9 years) who received a VNS, 1 patient developed Horner syndrome (2.9% of the patient group). The second study analyzed 251 procedures that were performed on 143 patients (81 males, 98 adults (mean age 35.8 years) and 45 children (mean age 10.1 years)). They found 1 case (0.7% of the group) of the syndrome. Based on the reviewed studies, Horner syndrome complicating a VNS implant was seen in 0.7–2.9% procedures. The pathophysiology of Horner syndrome following VNS placement has been postulated to reflect traction on the sympathetic fibers along the internal carotid artery or injury to or manipulation of the sympathetic plexus immediately beneath the carotid sheath. Horner syndrome is a potentially avoidable neurological complication following VNS placement, and while rare, is in fact an “uncommon” complication.