Abstracts

RATIONALE: The current study is intended to determine whether unilateral seizure onset is related to differing mood states.
METHODS: We analyzed the Minnesota Multiphasic Personality Inventories (MMPI) completed during the pre-surgical evaluation of 103 epilepsy patients whose ictal and interictal EEG scalp recordings were lateralized to either the left (n=57) or right (n=46) frontal or temporal lobes. These patients were selected from a larger sample of pre-surgical epilepsy patients by excluding individuals with a history of neurologic disease or trauma thought to impact both cerebral hemispheres (e.g., head trauma, encephalitis), and those who had experienced a stroke, as the latter condition has been shown to be related to depression and mania in some patients.
RESULTS: Nonparametric tests showed that left and right hemisphere groups did not differ significantly in regards to age, gender, race, age at onset of seizures, general intelligence, reading ability, or psychiatric history. Results of t stastics with appropriate corrections to guard against Type I error occurring due to multiple comparisons revealed that patients with right unilateral onset had significantly higher hypomania scores (Scale 9: R=68.0, SD=11.5; L=60.3, SD=11.5) on the MMPI than did the left unilateral onset group (t=-3.30, p[lt].001). Both left and right seizure onset groups produced significantly elevated depression scores (Scale 2: R=70.2, SD=9.0; L=71.7, SD=14.4), but did not differ significantly from one another on this scale. After further dividing the original groups by regional cerebral onset (i.e., frontal versus temporal), multiple ANOVAs were performed in order to look at regional differences. Results of these analyses revealed that these groups again differed on the hypomania scale (F=4.10; p[lt].009). Post-hoc analyses showed that the right temporal and right frontal groups both obtained significantly higher scores on this scale than did the left temporal group (Scale 9: RT=66.5, SD=10.4; RF=70.7, 13.5; LT=60.1, SD=11.7). In addition, the right frontal group scored significantly higher on this scale than did the right temporal group (F=-4.18, p[lt].002). The left frontal group was too small to draw significant conclusions about the performance of these patients. Depression scores did not significantly differ between regional seizure onset groups.
CONCLUSIONS: These results indicate that symptoms of depression are common in focal epilepsy patients with unilateral seizure onset regardless of side of focus, while hypomanic symptoms seem to be more prevalent among epilepsy patients with right unilateral onset, particularly when seizures arise from the right frontal region. Elevated symptoms of hypomania observed in patients with right unilateral onset is consistent with lesional studies involving other patient groups (e.g., stroke) that have observed the onset of mania following right-sided insults. These findings contribute to existing research suggesting that mood states may be associated with specific brain regions or neural networks, and that disruption of such regions may not require the presence of a frank lesion. Moreover, this study highlights the need to address mood related symptoms in patients with focal epilepsy.