Neuroanatomical correlates of psychosis in temporal lobe epilepsy: voxel-based morphometry study

Temporal lobe epilepsy is associated with a significant risk of psychosis but there are only limited studies investigating the underlying neurobiology.

To characterise neuroanatomical changes in temporal lobe epilepsy and comorbid psychosis.

The study population comprised all individuals with temporal lobe epilepsy on the epilepsy database at the National Centre for Epilepsy and Epilepsy Neurosurgery in Ireland (Beaumont Hospital) between 2002 and 2006. Ten people with temporal lobe epilepsy with psychosis were matched for age, gender, handedness, epilepsy duration, seizure laterality, severity of epilepsy and anti-epileptic medication with ten comparison participants with temporal lobe epilepsy only. Participants received a magnetic resonance imaging scan and voxel-based morphometry analyses were applied to grey and white matter anatomy.

Significant grey matter reduction was found bilaterally in those with temporal lobe epilepsy with psychosis in the temporal lobes in the inferior, middle and superior temporal gyri and fusiform gyri, and unilaterally in the left parahippocampal gyrus and hippocampus. Significant extratemporal grey matter reduction was found bilaterally in the insula, cerebellum, caudate nuclei and in the right cingulum and left inferior parietal lobule. Significant white matter reduction in those with temporal lobe epilepsy with psychosis was found bilaterally in the hippocampus, parahippocampal/fusiform gyri, middle/inferior temporal gyri, cingulum, corpus callosum, posterior thalamic radiation, anterior limb of internal capsule and white matter fibres from the caudate nuclei, and unilaterally in the left lingual gyrus and right midbrain and superior temporal gyrus.

Significant grey and white matter deficits occur in temporal lobe epilepsy with psychosis. These encompass the medial temporal lobe structures but also extend to lateral temporal and extratemporal regions. Some of these deficits overlap with those found in schizophrenia.