A 4-year-old boy with nighttime neck pain and progressive clumsiness of the right hand was diagnosed with a cervical intramedullary spinal cord tumor. On MRI, the lesion showed a marked heterogeneity and significant internal compression of the spinal cord by both solid tumor masses and cystic formations (Fig. 36.3). Tumor resection was recommended to obtain a histologic diagnosis and as optimal primary tumor treatment.

Routine monitoring for cervical intramedullary spinal cord tumors includes MEP and SSEP recordings from the upper and lower extremities. Thenar, tibialis anterior, flexor hallucis brevis are used. In this context, cortical SSEP responses are recorded from ulnar and tibial nerves, respectively. If possible, an epidural electrode is inserted to record D waves.

The patient was positioned prone with the head fixed in neutral position in a four-pronged Sugita headholder. A laminotomy C3 to T3 was made for surgical exposure. After a dorsal myelotomy , the extensive tumor tissue was removed in piecemeal fashion using the Cavitron ultrasonic aspirator (CUSA), regular suction, and the microsurgical laser. MEP and SEP signals for the entire right side were permanently lost during resection on the right side (Fig. 36.4). Waiting, irrigation, induced hypertension, and additional steroid administration did not achieve recovery of the recordings. The resection remained subtotal. No attempt was made to remove tumor residuals adherent to the still-functioning left side of the cord. The patient awoke with a severe right-sided hemiparesis. Over the long run he recovered motor function of the left side, learned how to walk and run, but remained with a severely impaired right hand and an abnormal gait.

A 4-year-old boy underwent surgical resection of a cervical intramedullary spinal cord pilocytic astrocytoma . At a critical stage of the resection, a significant change of MEPs of both upper and lower extremities occurred on the right side. MEP and SSEP signals for the entire right side were permanently lost. The resection remained incomplete and the patient had a severe right-sided hemiparesis. The leg recovered partially, the upper extremity remained significantly impaired.

This case demonstrates both the immediate feedback provided by the loss of MEPs on one side and the significant neurologic consequences of a complete loss of both upper and lower extremity recordings. Usually the leg recovers faster and easier than the hand, and unilateral loss of lower extremity MEPs usually recovers completely [14]. However, the complete loss of both extremities on one side appears to have graver consequences. This young patient recovered gross motor function of the arm but not the motor skills adequate for the dominant hand. He developed left-handedness and his rehabilitation was aimed at achieving this goal. His walking improved rapidly to independence but his gait remained massively abnormal.

The preoperative anatomy allowed a preassessment that the right side was under significant risk and that the left side must be preserved at all cost. This concept unfolded during the operation in that indeed the right side suffered, but the left could be preserved and thus useful functioning and social independence was saved. Continuation of the surgery to achieve an anatomically complete resection even of the tumor components involving the left side of the cord would likely have resulted in a complete loss of motor function bilaterally.

A 54-year-old woman with a year-long progressive history of nighttime back pain presented with a sensory level below Th7 and MR imaging revealed an intradural-extramedullary tumor at the level of Th9 (Fig. 36.5).

The monitoring routines for surgery of intradural-extramedullary tumors and intramedullary spinal cord tumors are identical with MEP and SEP recordings from the upper and lower extremities. Thenar, tibialis anterior, flexor hallucis brevis bilaterally were used.

The patient was positioned prone. During the laminectomy, baseline recordings were obtained. Upon opening of the dura, significant hemorrhage occurred from around the tumor and epidurally. Adequate exposure and hemostasis required some time and some blood loss. Left tibialis anterior MEPs disappeared at that time. Blood loss was rapidly compensated with fluid replacement. There was no significant hypotension during that time. MEPs reappeared after about 40 min (Fig. 36.6).

A 54-year-old woman underwent laminectomy and resection of an intradural meningioma at T9. This case differs little from intramedullary tumor resections and is therefore presented in this context. After dural opening, a significant hemorrhage occurred. Rapid fluid replacement was considered important and started immediately. Thus, significant hypotension was avoided. Nevertheless, during this time a temporary loss of muscle MEPs from the left tibialis anterior occurred. Both systemic and local factors could have contributed to these findings: local pressure on the tumor and subsequently to the spinal cord during hemostasis and initial tumor resection could have caused temporary MEP loss . In addition, the blood loss compensated through fluid replacement could have contributed to the MEP loss despite stable blood pressure in the situation of both local and systemic vulnerability of the corticospinal system originally due to tumor compression. We consider the proactive maintenance of stable circulatory parameters by the anesthesiologist essential to avoid lasting neurologic dysfunction. It would be an error to wait with fluid replacement until the blood pressure indeed decreases. Correction of the volume deficit at such a late time would be trailing events, carrying more risk for ischemic damage.