Introduction: Commercial DBS systems include a mechanism for securing the brain lead to the skull to prevent movement of the electrode tip. Nonetheless lead retraction has been noted, though the mechanism remains unclear. We describe failure of a DBS strain relief loop combined with decreased elasticity of the Infinity DBS lead as one possible cause of lead retraction.
Methods: A case report of simultaneous lead migration, and subsequent lead revision, is presented in a Parkinson’s patient treated with bilateral STN DBS using the St. Jude Infinity System.
Results: 71M underwent bilateral DBS STN lead placement using interventional MRI. Immediate postoperative scans demonstrated leads in excellent position. Two weeks later, patient underwent routine dissection of the distal leads with connection to lead extenders/generator. No excessive manipulation occurred. Postoperative head CT, for headache, demonstrated ~8 mm retraction of the lead tips. X-ray showed no change in the shape/radius of the strain relief loop for leads. DBS leads were revised. Severe scar had encased the extra-cranial brain leads. Lead retraction was confirmed by examining a black mark on each lead made at the original surgery immediately above the burrhole exit; at revision, these marks were several millimeters beyond the edge of the locking device rim despite intact locking devices.
Conclusions: Scar formation may occur around strain relief loops following DBS lead placement. Envelopment of leads by pericranium may prevent loops from tightening with distal pressure during surgical manipulation or patient movement, which may transmit any distal pressure directly to the locking device exit point. Commercial devices are not designed to withstand even mild tension with a break-point of ~0.6 lbs. The St. Jude Infinity lead is stiffer than the Medtronic lead to reduce its likelihood of in vivo damage; this reduced elasticity may make it more prone to movement from mild connector site manipulation.
Patient Care: Alert authors to a potential technical issue when using a new directional lead system that requires a different approach to securing the lead than what is used for the classic (Medtronic) system.
Learning Objectives: Understand a possible mechanism of lead retraction when using the St. Jude directional lead system and how to avoid this issue.