Abstracts

Rationale:
This is a prospective cohort study of the cognitive and neurobehavioral impact of invasive EEG monitoring using depth electrodes, stereoelectroencephalography (SEEG). SEEG has become a prevalent method for invasive monitoring in the surgical evaluation of epilepsy patients given the limited morbidity. However, acute and chronic cognitive/neurobehavioral consequences of placing 10-15 stereotactic depth electrodes for a one to two week period are unknown.

Methods:
Adult subjects undergoing SEEG evaluation at Northwestern Memorial Hospital were recruited. Individuals with prior neurosurgical history were excluded. All subjects completed neuropsychological (NP) assessments two weeks post SEEG explanation, targeting frontal and mesial temporal functioning (given relevance to common SEEG placement): WAIS-IV Digit Span, CVLT-3 Alternate Form, WMS-IV Logical Memory-Schnabel Alternates & Designs Subtest, Phonemic & Semantic Verbal Fluency, NAB-Naming Subtest Form 2, STAI, BDI-II, and NPI-Q.  Post SEEG NP scores were compared to subjects own clinically obtained pre-surgical scores.

Results:
n=7; 6:1 male/female; Seizure side=3 left, 3 right, 1 bilateral; Seizure focus=2 frontal, 2 temporal, 3 possible multilobe; all were white; 29%=Hispanic/Latino; average education=14 years (range 11-18); average age=29 (range 26-34); average age of seizure onset=12 (range 1-21).  Most post SEEG NP scores were not significantly changed including: Digit Span Total, Designs I & II, NAB, Phonemic Fluency, Semantic Fluency, STAI State & Trait, BDI-II.  Verbal memory performances showed unexpected change in favorable direction (all listed pre vs. post)- CVLT-3: SD Free Raw 8.7 ± 3.5 vs 11.4 ± 3.3, p=0.02; LD Free Raw 9.6 ± 3.5 vs. 12.3 ± 3.2, p=0.04; LMI Raw 24.7 ± 7.4 vs. 30.6 ± 8.3, p=0.03; and LMII Raw 19.7 ± 8.9 vs. 28.1 ± 8.7, p=0.01. Despite statistically significant improvement, these scores are not favored to reflect meaningful improvement when considering practice effects and reliable change metrics.  Subjectively on the NPI-Q, in the two weeks following SEEG, five subjects (71%) reported sleep difficulty, three reported depression/low mood (43%), two reported irritability (29%), and one subject reported agitation (14%). Each of these were new, or worsening relative to pre-surgical baseline, temporally linked to SEEG (worse immediately after), but already improving back to baseline by the time of two week post-op SEEG research visit.  

Conclusions:
At present, findings do not indicate significant decline in circumscribed frontal/temporal cognitive performances nor anxiety/depression mood disorder scores two weeks post SEEG evaluation. Subjective neurobehavioral symptoms of sleep impairment, irritability/agitation, and depression/low mood were reported worse immediately post SEEG and improving throughout two week SEEG recovery time period.  Preliminary data is overall reassuring of no significant cognitive or mood disorder impact from SEEG, still needing future expanded study. However, patients may be counseled on possibly transient difficulty with sleep, low mood, agitation/irritability in the two week following SEEG. 

Funding:
The Women’s Board of Northwestern Memorial Hospital