Subdural motor cortex stimulation for central and peripheral neuropathic pain: a long-term follow-up study in a series of eight patients

In certain chronic neuropathic pain (CNP) conditions, extradural electrode implantation is preferred to a subdural location for motor cortex stimulation (MCS) therapy, but the rationale for this preference remains debatable. We provide documented long-term results of subdural MCS in CNP. Our eight consecutive patients (five men, three women; age range, 45-81 yr) had either central or peripheral CNP. We localized the central sulcus using anatomic landmarks and three-dimensional neuronavigation and by detecting the N20 wave inversion. We then created an elongated craniotomy (3 cm long x 1 cm wide), followed by a linear incision of the dura. An eight-polar plate electrode was slipped in subdurally. We used motor-evoked potentials to choose the optimal electrode position before fixing the electrode to the dura. Six patients had favorable outcomes, and two had poor outcomes at the time of the last assessment (mean, 54 mo; range, 19-69 mo). Three patients experienced five transient complications, each having an episode of partial motor seizure, one that evolved into a secondary generalized seizure. Seizures were related to an abrupt increase in stimulation intensity. Two of these three patients also had hardware infections that required system replacement, with the electrode implanted extradurally at the second implantation in one case because of severe arachnoiditis. This change necessitated a greater intensity and a longer duration of stimulation to deliver a therapeutic effect equivalent to that with subdural MCS. In this small series, subdural MCS seemed a tolerable approach in the long term for CNP patients. In addition, subdural MCS provided a therapeutic effect comparable to that obtained with extradural placement.