[Surgical complications of vagal nerve stimulation for intractable epilepsy: findings from 26 cases]

Vagal nerve stimulation (VNS) is a less invasive palliative treatment for intractable epilepsy and was approved for use in Japan in July 2010. Surgical complications of VNS such as vagal nerve dysfunction, cardiac arrhythmia with asystole, and vocal cord palsy as well as complications arising from fracture of the leads or generator and infections are well known in the West. The aim of the present report is to describe the surgical complications encountered in our hospital and discuss their countermeasures.

We reviewed the clinical records of 26 patients who underwent VNS therapy between March 2011 and June 2013. The cases involved 17 male and 9 female patients, including 8 children(<15 years of age).

Three patients(11.5%)experienced severe bradycardia and cardiac asystole following test stimulations of the vagal nerve with a stainless-steel surgical hook left in place, to extend the operative field. It was believed that the current spread through the hook and stimulated the cardiac branch of the vagal nerve. In an adult patient with severe intellectual disability, inappropriate dermatological therapy for a superficial purulent wound on the neck caused lead infection 10 months postoperatively. In a child with moderate intellectual disability, lead fracture was noted in association with rotation of the pulse generator at one month postoperatively. In the former case, the lead was cut off whilst the electrode and anchoring coil on the vagal nerve remained;the whole VNS system was removed in the latter case. Subfascial implantation of the generator was recommended. In an adult patient, disconnection between the leads and generator head was noted at 10 months postoperatively.

During intraoperative test stimulations of the vagal nerve, stainless-steel surgical hooks should be removed to avoid the spread of current. In intellectually disabled patients, the pulse generator should be placed in the subfascial area instead of the subcutaneous area, especially children. The connection between the leads and the generator should be performed with the aid of a microscope, after removal of the fluid and tissue.