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Pediatric RNS Lead Migration: Wandering Eyes or Electrode?

Year: 2025

Type: article

Abstract: euromodulation with responsive neurostimulation (RNS, NeuroPace, Mountain View, CA) is increasingly being used off-label in pediatric drug-resistant epilepsy (pDRE).A 7-year-old boy, with RNS depth electrodes targeting bilateral thalamic centromedian nucleus (CM); developed paroxysmal bilateral esotropia (left > right) 52 weeks after initial implantation.Esotropia worsened over 3 weeks and was discovered to be caused by a ventrally migrated left CM electrode.Bilateral CM implantation of narrowly spaced (3.5 mm) 13.6 mm RNS electrodes was achieved using direct magnetic resonance imaging (MRI) visualization and Robotic Surgical Assistant (ROSA) guidance after extensive presurgical evaluation.The RNS battery was housed over the right parietal region, with the left CM electrode inserted via a 2.5 mm left frontal burr hole.A lead protector sheath covered the electrode and was secured with a "dogbone" titanium cranial plate provided by NeuroPace.A 50% seizure reduction was achieved after 6 months, and stepwise charge density increases were well tolerated without adverse effects.At 40 weeks, the mother reported increased seizures and at 50 weeks, "tilting head to one side" and drifting of the left eye; which seemed to be "floating around."This was initially attributed to a refractive error.At 52 weeks, the family reported an episode of eyes "going in all directions" and occasional loss of vision.Urgent head computed tomography (CT) was initially reported as unchanged.The patient displayed left head tilt and intermittent right head turn.Neurologic examination, notable for intermittent esotropia (left > right; see Fig A) with normal mental status, pupillary response, and full eye excursions directed localization hypothesis to the midbrain.CT images were reexamined with co-registration to preoperative MRI and ROSA coordinates, confirming an 8 mm ventral and medial migration of the left CM electrode into the midbrain (see Fig A).Comparison to anatomic atlases using Lead-DBS software, 1 including previously published atlases of brainstem tractography 1,2 and histology 3 (see Fig B), revealed that the left CM tip had crossed the midline and was located within the medial longitudinal fasciculus (MLF), immediately adjacent to the oculomotor nucleus and approximately 3 mm anterior to the periaqueductal gray area.Within a few minutes of disabling RNS stimulation, the eye movements normalized.During surgical admission

Source: Annals of Neurology

DOI: 10.1002/ana.27273