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Altered states of consciousness in epilepsy: a DTI study of the brain.

Fangfang Xie, Wu Xing, Xiaoyi Wang, Weihua Liao, Wei Shi

International Journal of Neuroscience August 2017 DOI: 10.1080/00207454.2016.1229668 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Observational case-control study Peer reviewed
Sample size 102
Population 51 patients with epilepsy (17 each with complex partial seizures, primary generalized tonic-clonic seizures, or secondary generalized tonic-clonic seizures) and 51 healthy volunteers
Measures apparent diffusion coefficient (ADC), fractional anisotropy (FA)
Topics Default mode network Altered states of consciousness Philosophy of mind
Keywords Apparent diffusion coefficient Consciousness Diffusion tensor imaging Fractional anisotropy Seizures
Key findings Patients with epilepsy showed higher ADC values in the bilateral dorsal thalamus and postero-superior midbrain and lower FA values in the bilateral dorsal thalamus than healthy controls; FA was also lower in the postero-superior midbrain in the primary generalized tonic-clonic subgroup. No significant differences were found in the precuneus/posterior cingulate, medial prefrontal, or supramarginal regions, or among the three epilepsy subgroups. The authors propose that the thalamus and upper brain stem may play a key role in impaired consciousness in epilepsy.

Abstract

A disturbance in the level of consciousness is a classical clinical sign of several seizure types. Recent studies have shown that altered states of consciousness in seizures are associated with structural and functional changes of several brain regions. Prominent among these are the thalamus, the brain stem and the default mode network, which is part of the consciousness system. Our study used diffusion tensor imaging (DTI) to evaluate these brain regions in patients with three different types of epilepsies that are associated with altered consciousness: complex partial seizures (CPS), primary generalized tonic-clonic seizures (PGTCS) or secondary generalized tonic-clonic seizures (SGTCS). Additionally, this study further explores the probable mechanisms underlying impairment of consciousness in seizures. Conventional MRI and DTI scanning were performed in 51 patients with epilepsy and 51 healthy volunteers. The epilepsy group was in turn subdivided into three subgroups: CPS, PGTCS or SGTCS. Each subgroup comprised 17 patients. Each subject involved in the study underwent a DTI evaluation of the brain to measure the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values of nine regions of interest: the postero-superior portion of midbrain, the bilateral dorsal thalamus, the bilateral precuneus/posterior cingulate, the bilateral medial pre-frontal gyri and the bilateral supramarginalgyri. The statistical significance of the measured ADC and FA values between the experimental and control groups was analysed using the paired t-test, and one-way analysis of variance was performed for a comparative analysis between the three subgroups. Statistically significantly higher ADC values ( p < 0.01) were observed in the bilateral dorsal thalamus and postero-superior aspect of the midbrain in the three patient subgroups than in the control group. There were no significant changes in the ADC values ( p > 0.05) in the bilateral precuneus/posterior cingulate, bilateral medial pre-frontal gyri or bilateral supramarginalgyri in the experimental group. Among the three patient subgroups and the ADC values of corresponding brain regions, there were no statistically significant changes. Statistically significantly lower FA values ( p < 0.05) were observed in the bilateral dorsal thalamus of the patients in the three subgroups than in the control group. Significantly lowered FA values from the postero-superior aspect of the mid brain ( p < 0.01) were observed in patients with PGTCS compared with the control group. There were no significant changes in the FA values ( p > 0.05) from the bilateral precuneus/posterior cingulate, bilateral medial frontal gyri or bilateral supramarginalgyri in the experimental group. Among the three patient subgroups and the FA values of the corresponding brain regions, there were no statistically significant changes. In epileptic patients with CPS, PGTCS or SGTCS, there seems to be a long-lasting neuronal dysfunction of the bilateral dorsal thalamus and postero-superior aspect of the midbrain. The thalamus and upper brain stem are likely to play a key role in epileptic patients with impaired consciousness.

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Default mode network Altered states of consciousness Philosophy of mind