EEG-based P300 in mesial temporal lobe epilepsy and its correlation with cognitive functions: A case-control study

Objective: P300 is an event-related potential, being explored as an objective tool to assess cognition. This study aimed to investigate the characteristics of auditory and visual P300 in patients with TLE having unilateral HS using electroencephalography (EEG) and to study its correlation with cognition.

Methods: This is a cross-sectional case-control study, where P300 characteristics in thirty patients with unilateral hippocampal sclerosis with refractory epilepsy were compared with fifteen age-, gender-, and years of education-matched healthy controls (M: F-10:5, mean age-28 ± 4.76 years). Among patients, 15 belonged to the right HS group (M: F-9:6, age at onset-12.92 ± 10.22 years, duration of epilepsy-16.67 ± 9.38 years) and 15 to the left HS group (M: F-8:7, age at onset-10.62 ± 7.18 years, duration of epilepsy-15.53 ± 10.14 years). All subjects underwent EEG-based auditory and visual oddball tasks and cognitive assessment. The P300 latencies (in milliseconds) as well as amplitudes (in microvolts) were predicted in EEG and were correlated with cognitive scores. Source localization of P300 was performed with the CLARA algorithm.

Results: The auditory P300 latencies in controls, right HS, and left HS were 323.93 ± 40.28, 351.06 ± 47.23, and 328.80 ± 36.03, respectively (p = 0.18) and its amplitudes were 2.3040 ± 1.46, 2.77 ± 1.19, and 2.68 ± 1.78, respectively (p = 0.48). Visual P300 latencies in controls, right HS, and left HS were 365.87 ± 47.37, 359.67 ± 64.45, and 376.00 ± 60.06, respectively (p = 0.51) and its amplitudes were 3.93 ± 2.28, 2.09 ± 1.45, and 3.56 ± 1.74, respectively (p = 0.014). Further, when compared to the control group the cognitive scores were lower in the patient group (p < 0.05).

Significance: In comparison to the controls, patients with right HS recorded lesser amplitude on visual P300 and lower scores on cognitive tests. P300 and cognitive parameters exhibited varied relationship. P300 could be a complementary objective tool to assess cognition in patients with TLE.