Severe hippocampal atrophy is not associated with depression in temporal lobe epilepsy

Abstract

Depression in temporal lobe epilepsy (TLE) is common, is a strong predictor of subjective disability, and may have unique pathophysiological characteristics. Previous studies showed that reduced hippocampal volume is associated with significant depressive symptoms in TLE patients. We utilized regions of interest analysis of high-resolution brain MRI and a reliable and valid measure of depressive symptoms to evaluate 28 consecutive adult subjects with video/EEG confirmed TLE. Regions of interest were based on prior human and animal studies of mood and behavioral dysfunction. Forty-three percent of the entire group had significant symptoms of depression, defined by a Beck Depression Inventory (BDI) score of greater than 15. Total hippocampal volumes were significantly smaller in the group with BDI< 15, (p< 0.007). None of the subjects in the quartile with the smallest left hippocampal volume had a BDI score greater than 15, compared to 57% of the subjects in the upper three quartiles (p< 0.008). No other limbic brain structures that we assessed: amygdala, subcallosal gyrus, subgenual gyrus, gyrus rectus, or total cerebral volume, were associated with depressive symptoms. Adequate hippocampal integrity may be necessary to maintain depression symptoms in mesial temporal lobe epilepsy. This finding also supports the possibility of a unique mechanism for depression in mesial temporal lobe epilepsy, such as hyerexcitable neuronal influence on the limbic network.

Dorsal bed nucleus of stria terminalis in depressed and nondepressed temporal lobe epilepsy patients

“…The observation that the dBNST is enlarged in the TLE patients in this study is contrary to the decrease in gray matter volume and neuron loss commonly seen in other major structures commonly seen to be morphologically abnormal in TLE patients, such as the hippocamus 35 . In our study, we find that hippocampal sclerosis seen in many of our TLE patients is not associated with the presence of depression, a finding that is consistent with other studies demonstrating the lack of a relationship between hippocampal sclerosis and decreased hippocampal volume with depression 36 . Furthermore, the hippocampal sclerosis is not associated with the enlargement of the dBNST, suggesting that whereas the dBNST may be a part of the neural network involving depression in TLE, the hippocampus is not.…”

A systematic review of neuroimaging studies of depression in adults with epilepsy

“…Shamim [32] and Baxendale [25] found that in those patients with right TLE and depression (regardless of whether HS was present) there were also reduced contralateral (left) hippocampal volumes compared to patients without concomitant depression. However, this finding was not replicated in a later study by Hecimovic et al 2014 [33] who found larger hippocampal volumes in those patients with TLE and depression compared to those without depression. Richardson and collaborators [34] found larger amygdala volumes in patients with TLE and depression as compared to patients without depression.…”

Epilepsy Benchmarks Area I: Understanding the Causes of the Epilepsies and Epilepsy-Related Neurologic, Psychiatric, and Somatic Conditions

“…75 The severity of depression is associated with the risk of epilepsy. 76 Depression and suicidality tend to be more prominent in individuals with TLE compared with those who have genetic generalized epilepsies, 77,78 and within TLE, depression severity correlates with pharmacoresistance but does not correlate with the side 57 or the extent of hippocampal atrophy, 79 if present. Improvements in depression that follow temporal lobectomy are strongly associated with improvements in seizure control.…”