1. Intraoperative Monitoring During CEA
Christopher Loftus M.D, DHC (Hon.), FACS
Zakaria Hakma, MD
Department of Neurosurgery,
Temple University School of Medicine,
Philadelphia, USA
HYPOTHESIS - EEG and SSEP used
concurrently would be equally sensitive
and timely in predicting the need for
intraoperative shunt placement during
CEA
Methods:
We studied 34 patients and performed
selective shunting. Using the standard 10-
20 system, baseline digital EEGs were
performed pre-operatively, and continuous
monitoring was used in the operating room.
SSEPs were likewise recorded, by
stimulating bilateral median and posterior
tibial nerves.

2. Results
In 24/34 (70%) patients, there was no
Predictive value
change in either EEG or SSEPs. There
were concurrent changes in 4/34. There
of EEG/SSEP
were only EEG changes in 5/34 (15%). • EEG predicted 9/34
In one case (3%), SSEPs alone predicted
the need for shunting. All patients with times and missed 1/34
significant, enduring changes in either
EEG or SSEPs (9/34) underwent shunt
• SSEP predicted 5/34
placement. There were no times and missed 5/24.
postoperative strokes.
EEG predicted ischemia 9/34 times,
including one patient with transient
changes not requiring a shunt (3%).
SSEPs predicted ischemia which
no CHanges
required shunting 5/34 times; SSEPs EEG alone
missed ischemia in 5 patients, but one Both
of those patients did not need a shunt. SSEP alone

3. Discussion: In our 24 CEA patients, EEG and SSEP
correlated in 28/34 (82%).
We shunt for any monitoring change, and
Addition of SSEP identified one false
were curious if the addition of SSEP would
negative in the EEG group; in this case
augment EEG in detecting clamp ischemia,
the SSEP changes happened much
and if there were cases where SSEP alone
earlier than EEG (possibly secondary to
would change with normal EEG, since
residual anesthetics) and the shunt was
SSEP is less affected by anesthesia and
placed based on the SSEP changes;
medication.
later during the case (shunt removal)
EEG and SSEP changes did correlate.
In 33/34 cases EEG was sufficient to
Conclusions: predict shunt need.
• Clearly these two techniques are not completely overlapping
• Combining EEG and SSEP during CEA adds a safety factor (burst
suppression), and slightly increases the rate of ischemia detection.
• We are not prepared to use SSEP alone to detect cross-clamp ischemia in our
patients for two reasons
– Signal averaging time
– Potential insensitivity