January 07, 2016
Infiltrating tumor affecting the anterior corticospinal tract can be quite challenging to resect. This video reviews innovative mapping strategies to maximize resection of spinal cord tumors. This patient presented with gait disturbance and hand numbness, and on MRI evaluation was noted to have a cystic tumor at the level of the cranial cervical junction. As you can see on the axial enhanced T1 sequence, there is a cystic portion of the tumor associated with a small nodule. The patient subsequently underwent a minimal suboccipital craniotomy and C1 laminectomy. The patient was positioned in the lateral position, a midline durotomy was completed. A midline myelotomy was also completed just over the cyst. After drainage of the cyst, you can see the nodule that is very much infiltrating the anterior corticospinal tracts along its margins. Motor evoked potentials were monitored during this procedure, and mapping of the corticospinal tracks was feasible using a monopolar probe. The margins of the tumor were stimulated, and the location of the important functional tracks are identified in this illustration. You can see the thenar, hypothenar muscles controlled by this part of the tract on the left side, this is tibialis anterior, medial gastrocs, abductor and extensor hallucis longus and again, as expected, the distribution of the corticospinal tracts on the left and the right side. I attempted the resection along the inferior and lateral aspect of the tumor initially, first stimulating over the very thin margins of the tumor before these thin margins are entered. I continued resection in these areas while again stimulating over the thin tumor margins; however, in this part of the tumor, stimulating over the margin of the tumor led to movement of the lower extremities, and therefore a small part of the tumor was left behind to avoid any resultant morbidity. Again, transcranial motor evoked potentials were monitored during the procedure. The tumor was opened along its midsection and debulked using pituitary rongeurs. The capsule of the tumor was dissected away where the tumor margins were noted to be safe based on monopolar stimulation. Parameters we just discussed a moment ago. Here you can see the tumor is safely dissected from the anterior corticospinal tracks, although it is somewhat adherent. This portion of the tumor, however, was noted to very much be associated with function intimately, and a small piece of tumor was left behind to avoid neurological morbidity. Here you can see where the stimulation over this small thin capsule of the tumor led to motor activity. The postoperative MRI demonstrated near gross total resection of the mass with small residual tumor along the anterior aspect of the spinal cord. This video is an excellent demonstration of using stimulation mapping techniques in the supratentorial space for increasing the safety of gliomas in the spinal cord. The pathology of the tumor was consistent with a pilocytic astrocytoma. The patient awoke from the anesthesia with minimal left lower extremity weakness, which resolved within a week after surgery. Thank you.
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