Li G. Huang, Ph.D., D.ABNM, Jeffrey Oppenheim, M.D., Daniel E. Spitzer, M.D., G. Alexander Jones, M.D. Jeffrey W. Degen, M.D

Hudson Valley Brain and Spine Surgery, Suffern, NY, 10901

Good Samaritan Hospital, Suffern, NY, 10901

SEP-PR can be optimized by:

Using a 1x8 subdural contact grid to provide better coverage for the large brain tumor and lessen

the chance of the electrode being entirely anterior or posterior

Avoiding “off-axis” placement of the electrode

Selection of bandpass at 30-3000Hz

Total Intravenous Anesthesia

The patient is a 39 year-old male who presented with 1 week of memory loss, and one day of severe headache associated with emesis. The patient had no motor deficit. A CT scan of the brain demonstrated a large left frontotemporal ring-enhancing lesion. A true phase reversal was identified, and the operating surgeon incorporated the information to his surgical strategy. A gross total resection was achieved. The patient did well initially, and had normal strength postoperatively. The tumor was found to be a glioblastoma multiforme, and the patient ultimately died approximately 2.5 years after surgery. .

Figure 1 CT showed a Large frontotemporal

brain tumor

Figure 4. Phase reversal was observed between

contacts 2 and 4.Figure 6. Gross total resection of the

tumor was achieved.

An understanding of the optimal recording of the phase reversal aids in providing reliable and

useful information to the surgeon. Our technique is applicable to the resection of large and central

brain tumors as these are the surgeries in which accurate identification of the central sulcus is of

particular importance.

Optimize the phase reversal recording in challenging situations

Figure 7. Postoperative MRI

demonstrated gross total resection of the

tumor.

Figure 5. Median Nerve SSEPs were stable

throughout the procedure.

Figure 3. Phase reversal was not appreciated

with initial placement of the grid due to “off-

axis” recording

Figure 2. A subdural contact grid was placed

following dural opening (Adapted from

Medscape.com)

Somatosensory Evoked Potential- Phase Reversal

(SEP-PR) has been widely used to identify the

central sulcus during brain tumor resection by

cortical recording of the somatosensory evoked

potential to medial nerve stimulation. It provides

reliable information regarding the sensorimotor

region, and lays a foundation for functional

preservation(1,2). Studies showed that the

successful rate of SEP-PR recording is relatively

low among those patients with large central and

postcentral brain tumors(3).

1. Use of a 1x8 subdural contact grid to provide enough

length for SSEP recording.

2. Total intravenous anesthesia during surgery to

optimize sensitivity.

3. Set the recording filter at 30-3000Hz.

4. Ensure placement of the grid perpendicular to the

direction of the central sulcus and avoid “off-axis”

recording ( The recording electrode was not placed

over the sensory and motor hand areas(4))

1. Neoplasma, 2006;53(1):37-42.

2. Techniques in Neurosurgery, 2001; 7 (1): 4-11

3. J Neurol Neurosurg Psychiatry 2002; 72:221-229

4. NeuroSurgery, 1996; 38(5): 962-970