Background: Safe resection of intramedullary spinal cord tumors can be challenging, as they often alter the cord anatomy. Identification of neurophysiologically viable dorsal columns (DC) and of neurophysiologically inert tissue, e.g. median raphe (MR), as a safe incision site is crucial for avoiding post-operative neurologic deficits. We present our experience with and improvements made to our previously described technique of dorsal column mapping (DCM), successfully applied in a series of 12 cases.
Objective: To describe a new, safe, and reliable technique for intraoperative DCM.
Methods: The right and left DC were stimulated using a bipolar electric stimulator and the triggered somatosensory evoked potentials (SSEPs) recorded from the scalp. Phase reversal and amplitude changes of SSEPs were used to neurophysiologically identify the laterality of DC, the inert MR, as well as other safe incision sites.
Results: The MR location was neurophysiologically confirmed in all patients in whom this structure was first visually identified as well as in those in whom it was not, with one exception. DC were identified in all patients, regardless of whether they could be visually identified. In three cases, negative mapping using this method enabled the surgeon to reliably identify additional inert tissue for incision. None of the patients had postoperative worsening of the DC function.
Conclusion: Our revised technique is safe, reliable, and can be easily incorporated into routine intramedullary spinal cord tumor resection. It provides crucial information to the neurosurgeon in order to prevent post-operative neurological deficits.
From: Dorsal Column Mapping via Phase Reversal Method: The Refined Technique and Clinical Applications by Simon et al.