Indications
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Intramedullary spinal cord lesion on magnetic resonance imaging (MRI) in the setting of neurologic symptoms (pain, sensory disturbances, motor weakness, nonspecific complaints)
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Intramedullary spinal cord lesion on MRI or an associated cyst or syringomyelia that has progressed on serial imaging and is likely to become symptomatic in the future
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Intramedullary spinal cord lesion on MRI that is of unclear etiology despite an extensive neurology work-up, warranting a need for tissue diagnosis
Contraindications
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Asymptomatic, incidentally noted lesions or lesions causing only minor symptoms can be treated conservatively with serial clinical assessments and MRI.
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Severely debilitated patients or patients with a short life expectancy because of comorbid illness or metastatic disease should be observed or treated with palliative therapy.
Planning and positioning
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The clinical assessment of a patient with a suspected intramedullary spinal cord tumor starts with a detailed history and physical examination.
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MRI is necessary to localize the lesion correlate with clinical findings and plan the operative approach, including establishing goals of operative intervention and considering deficits that may result from surgical resection. Other imaging modalities such as x-ray and computed tomography (CT) scan should be obtained to assess for associated scoliotic deformities and to determine the need for instrumented fixation at the time of surgery.
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Intraoperative neurophysiologic monitoring with motor evoked potentials (MEPs) provides the surgeon with real-time feedback on the integrity of the corticospinal tracts. Needle electrodes should be placed at the end muscles after the patient is asleep but before final prone positioning in the operating room. Because halogenated anesthetic agents cause depression of MEPs, the anesthetic regimen should be coordinated with the anesthesiologist. Propofol and fentanyl are commonly used agents that do not cause a decline in MEPs.
Figure 99-1:
Preoperative imaging, including MRI, plays a key role in surgical planning. Sagittal ( left ) and axial ( right ) T1-weighted MRI after administration of gadolinium contrast agent shows an intramedullary cervical spinal cord tumor with an associated rostral cyst.
Figure 99-2:
For most intramedullary spinal cord tumors, a dorsal approach is used. The patient is first intubated in the supine position, and all neurophysiologic monitors are placed. Awake fiberoptic intubation may be warranted in patients with cervical spine instability or cervical lesions causing significant canal impingement. For a cervical tumor the patient is positioned prone in Mayfield head holder. The neck is slightly flexed to aid in surgical exposure. For patients with thoracic or lumbar lesions, prone positioning can be accomplished on a Wilson frame or chest rolls without head fixation. All dependent surfaces (e.g., knees, elbows) are padded to avoid peripheral nerve injury or pressure-related tissue necrosis.
Procedure
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