The cognitive profile of occipital lobe epilepsy and the selective association of left temporal lobe hypometabolism with verbal memory impairment

Brain imaging derived phenotypes: a biomarker for the onset of inflammatory bowel disease and a potential mediator of mental complications

Background and aims

Inflammatory bowel disease (IBD), mainly categorized into Crohn's disease (CD) and ulcerative colitis (UC), is a chronic relapsing gastrointestinal disorder that significantly impairs patients' quality of life. IBD patients often experience comorbidities such as anxiety and depression, and the underlying mechanisms and treatment strategies remain areas of investigation.

Methods

We conducted a Mendelian randomization(MR) analysis utilizing brain image derived phenotypes (IDP) from the UK Biobank database to investigate the causal relationships between IBD and alterations in brain structural morphology and connectivity of neural tracts. This study aimed to identify biological evidence linking IBD to psychiatric disorders such as anxiety and depression.

Results

Specifically, the volume of grey matter in the Left Frontal Orbital Cortex exhibited a negative association with the onset of Crohn's disease (odds ratio (OR) [95% confidence interval (CI)]: 0.315[0.180~0.551], adjusted P=0.001), while the volume of the superior frontal cortex in the right hemisphere showed a positive correlation with the development of Ulcerative colitis (OR [95% CI]: 2.285[1.793~2.911], adjusted P<0.001), and the volume of lateral occipital cortex in the left hemisphere demonstrated a positive relationship with Crohn's disease onset (OR [95% CI]: 1.709[1.671~1.747], adjusted P<0.001). In the context of reverse causality, the onset of UC or CD has led to alterations in imaging derived phenotypes associated with five disorders (anxiety, depression, schizophrenia, bipolar disorder, pain) and three functions (memory, emotion, language).

Conclusion

Our study has demonstrated a causal relationship between IBD and IDPs. IDPs may serve as potential biomarkers for the progression of IBD and as predictive intermediaries for the development of neurological diseases in IBD patients.

Patterns of hypometabolism in frontal lobe epilepsy originating in different frontal regions

Objectives

Analysis of FDG‐PET imaging commonly shows that hypometabolism extends into extra‐epileptogenic zones (extra‐EZ). This study investigates the distribution patterns of hypometabolism in frontal lobe epilepsy (FLE) originating in different frontal regions.

Methods

Sixty‐four patients with FLE were grouped by EZ localization according to Brodmann areas (BAs): Group 1 (the frontal motor and premotor area), BAs 4, 6, and 8; Group 2 (the inferior frontal gyrus and opercular area), BAs 44, 45, and 47; Group 3 (the dorsal prefrontal area), BAs 9, 10, 11, and 46; and Group 4 (the medial frontal and anterior cingulate gyrus), BAs 32 and 24. Regions of extra‐EZ hypometabolism were statistically analyzed between FLE groups and healthy controls. Correlation analysis was performed to identify relationships between the intensity of hypometabolism and clinical characteristics.

Results

Significant hypometabolism in the ipsilateral (Groups 1 and 4) or bilateral (Groups 2 and 3) anterior insulae was found. Groups 1 and 4 presented with limited distribution of extra‐EZ hypometabolism, whereas Groups 2 and 3 showed widely distributed extra‐EZ hypometabolism in the rectus gyrus, cingulate gyrus, and other regions. Additionally, the intensity of hypometabolism was correlated with epilepsy duration in Groups 2 and 3.

Conclusions

All FLE groups showed hypometabolism in the anterior insula. In addition, distinct patterns of extra‐EZ hypometabolism were identified for each FLE group. This quantitative FDG‐PET analysis expanded our understanding of the topography of epileptic networks and can guide EZ localization in the future.

The relationship between structural MRI, FDG-PET, and memory in temporal lobe epilepsy: Preliminary results

Structural and metabolic abnormalities of the temporal lobe are frequently found in temporal lobe epilepsy (TLE). In the present retrospective study, we investigated whether structural abnormalities evident in magnetic resonance imaging (MRI) and hypometabolism evident in [¹⁸F]fluorodeoxyglucose positron emission tomography (FDG-PET) independently influence verbal and nonverbal learning and delayed memory in patients with TLE. Sixty-eight patients with refractory unilateral TLE (35 left TLE, 33 right TLE) were divided into three groups: (1) no evidence of pathology in either MRI or FDG-PET studies (MRI-/PET-, n=15), (2) temporal FDG-PET determined hypometabolism with normal MRI findings (MRI-/PET+, n=21), and (3) evidence of temporal abnormalities in both MRI and FDG-PET studies (MRI+/PET+, n=32). A fourth group (MRI+/PET-, n=4) was too small for further statistical analysis and could not be included. Patients with MRI+/PET+ showed worse verbal memory than patients with MRI-/PET- (p<0.01), regardless of side of seizure focus. Verbal memory performance of patients with MRI-/PET+ was located between patients with MRI+/PET+ and MRI-/PET-, although group differences did not achieve statistical significance (ps>0.1). No group differences were found for nonverbal memory (p=0.27). Our results may suggest an interactive negative effect of metabolic and structural temporal lobe abnormalities on verbal memory. Still, our results are preliminary and need further validation by studies involving larger patient groups and up-to date quantitative imaging analysis methods.

Cognitive and neurodevelopmental comorbidities in paediatric epilepsy

Cognitive and behavioural comorbidities are often seen in children with epilepsy, and are more common and severe in refractory epilepsy. These comorbidities are associated with worse quality of life, increased behavioural and language problems and worse social skills, all of which adversely affect long-term psychosocial functioning. To enable early intervention and therapy, children and teens with epilepsy should be periodically screened for cognitive comorbidities. The location of the epileptic focus can, to a certain degree, predict the type(s) of comorbidity; however, the spectrum of disability is often broad, presumably because focal perturbations can cause network dysfunction. Comorbidities often result from underlying structural or functional pathology that has led to seizures. In selected cases, therapy targeting the underlying cause, such as the ketogenic diet for GLUT1 deficiency syndromes, may be remarkably effective in ameliorating both seizures and cognitive concerns. In many cases, however, cognitive impairment persists despite seizure control. In epileptic encephalopathies, frequent seizures and/or interictal epileptiform abnormalities exacerbate neurocognitive dysfunction, owing to synaptic reorganization or impaired neurogenesis, or to other effects on developing neural circuits, and prompt initiation of effective antiepileptic therapy is essential to limit cognitive comorbidities.

Associations between the self-reported frequency of hearing chemical alarms in theater and regional brain volume in Gulf War Veterans

BACKGROUND

We previously reported evidence of reduced cortical gray matter (GM), white matter (WM), and hippocampal volume in Gulf War (GW) veterans with predicted exposure to low-levels of nerve agent according to the 2000 Khamisiyah plume model analysis. Because there is suggestive evidence that other nerve agent exposures may have occurred during the Gulf War, we examined the association between the self-reported frequency of hearing chemical alarms sound during deployment in the Gulf War and regional brain volume in GW veterans.

METHODS

Ninety consecutive GW veterans (15 female, mean age: 52±8years) participating in a VA-funded study underwent structural magnetic resonance imaging (MRI) on a 3T scanner. Freesurfer (version 5.1) was used to obtain regional measures of cortical GM, WM, hippocampal, and insula volume. Multiple linear regression was used to determine the association between the self-reported frequencies of hearing chemical alarms during the Gulf War and regional brain volume.

RESULTS

There was an inverse association between the self-reported frequency of hearing chemical alarms sound and total cortical GM (adjusted p=0.007), even after accounting for potentially confounding demographic and clinical variables, the veterans' current health status, and other concurrent deployment-related exposures that were correlated with hearing chemical alarms. Post-hoc analyses extended the inverse relationship between the frequency of hearing chemical alarms to GM volume in the frontal (adjusted p=0.02), parietal (adjusted p=0.01), and occipital (adjusted p=0.001) lobes. In contrast, regional brain volumes were not significantly associated with predicted exposure to the Khamisiyah plume or with Gulf War Illness status defined by the Kansas or Centers for Disease Control and Prevention criteria.

CONCLUSIONS

Many veterans reported hearing chemical alarms sound during the Gulf War. The current findings suggest that exposure to substances that triggered those chemical alarms during the Gulf War likely had adverse neuroanatomical effects.

Neuroimaging of epilepsy

Imaging is pivotal in the evaluation and management of patients with seizure disorders. Elegant structural neuroimaging with magnetic resonance imaging (MRI) may assist in determining the etiology of focal epilepsy and demonstrating the anatomical changes associated with seizure activity. The high diagnostic yield of MRI to identify the common pathological findings in individuals with focal seizures including mesial temporal sclerosis, vascular anomalies, low-grade glial neoplasms and malformations of cortical development has been demonstrated. Positron emission tomography (PET) is the most commonly performed interictal functional neuroimaging technique that may reveal a focal hypometabolic region concordant with seizure onset. Single photon emission computed tomography (SPECT) studies may assist performance of ictal neuroimaging in patients with pharmacoresistant focal epilepsy being considered for neurosurgical treatment. This chapter highlights neuroimaging developments and innovations, and provides a comprehensive overview of the imaging strategies used to improve the care and management of people with epilepsy.

The relationship between neuropsychological functioning and FDG-PET hypometabolism in intractable mesial temporal lobe epilepsy

We examined the relationship between baseline neuropsychological functioning and 18-fluorodeoxyglucose positron emission tomography (FDG-PET) in intractable mesial temporal lobe epilepsy (MTLE). We hypothesized relationships between dominant temporal lobe hypometabolism and verbal memory and between nondominant temporal lobe hypometabolism and nonverbal memory in line with the lateralized material-specific model of memory deficits in MTLE. We also hypothesized an association between performance on frontal lobe neuropsychological tests and prefrontal hypometabolism. Thirty-two patients who had undergone temporal lobectomy for treatment of MTLE and who completed both presurgical FDG-PET and comprehensive neuropsychological investigations with widely used standardized measures were included. Age-adjusted composite measures were calculated for verbal memory, nonverbal memory, relative material-specific memory, IQ, executive function, attention/working memory, and psychomotor speed. Fluorodeoxyglucose positron emission tomography was analyzed with statistical parametric mapping (SPM) to identify hypometabolism relative to healthy controls. Pearson's correlation was used to determine the relationship between regions of hypometabolism and neuropsychological functioning. Dominant temporal lobe hypometabolism was associated with relatively inferior verbal memory, while nondominant temporal lobe hypometabolism was associated with inferior nonverbal memory. No relationship was found between performance on any frontal lobe measures and prefrontal hypometabolism. Statistical parametric mapping-quantified lateralized temporal lobe hypometabolism correlates with material-specific episodic memory impairment in MTLE. In contrast, prefrontal hypometabolism is not associated with performance on frontal lobe measures. We suggest that this is because frontal lobe neuropsychology tests may not be good measures of isolated frontal lobe functioning.

Cognitive dysfunction in patients with epilepsy: focus on clinical variables

ABSTRACT 

A variety of factors can affect cognitive functions in patients with epilepsy, with the majority of cognitive problems having a multifactorial origin. In routine clinical practice, it can be difficult to dissect out the contribution of all of the different variables, because they are often interlinked together. In this article, all of the major variables implicated in cognitive dysfunction in epilepsy are discussed. In general terms, it is widely accepted that cognitive dysfunction in epilepsy can be trait dependent or state dependent. The former is a permanent condition due to the underlying brain damage or disorder, while the latter is a potentially reversible condition due to modifiable factors, such as antiepileptic drugs, seizure frequency and pattern and psychiatric comorbidity. Neuropsychological deficits also represent an important sequela in epilepsy surgery. Visual naming and visual memory loss have been clearly associated with temporal lobe surgery. It seems that the laterality of resection is not a major determinant, while the extension of resection is relevant for visual naming.