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

Alex A Knopman; Chong H Wong; Richard J Stevenson; Judi Homewood; Armin Mohamed; Ernest Somerville; Stefan Eberl; Lingfeng Wen; Michael Fulham; Andrew F Bleasel

doi:10.1016/j.yebeh.2015.01.023

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

Epilepsy Behav. 2015 Mar:44:136-42. doi: 10.1016/j.yebeh.2015.01.023. Epub 2015 Feb 20.

Authors

Affiliations

¹ Department of Psychology, Macquarie University, NSW, Australia; Department of Medical Psychology, Westmead Hospital, NSW, Australia.
² Sydney Medical School, University of Sydney, NSW, Australia; Departments of Neurology, Westmead Hospital and The Children's Hospital at Westmead, NSW, Australia.
³ Department of Psychology, Macquarie University, NSW, Australia.
⁴ Sydney Medical School, University of Sydney, NSW, Australia; Department of Molecular Imaging, Royal Prince Alfred Hospital, NSW, Australia.
⁵ Institute of Neurological Sciences, Prince of Wales Hospital, NSW, Australia; Faculty of Medicine, University of New South Wales, NSW, Australia.
⁶ Sydney Medical School, University of Sydney, NSW, Australia; Departments of Neurology, Westmead Hospital and The Children's Hospital at Westmead, NSW, Australia. Electronic address: andrew.bleasel@sydney.edu.au.

PMID: 25703620
DOI: 10.1016/j.yebeh.2015.01.023

Abstract

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.

Keywords: Cognitive functioning; Epilepsy surgery; Episodic memory; Focal epilepsy; Frontal lobes; Positron emission tomography.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adolescent
Adult
Anterior Temporal Lobectomy / methods
Attention
Epilepsy, Temporal Lobe / diagnostic imaging*
Epilepsy, Temporal Lobe / surgery
Female
Fluorodeoxyglucose F18 / metabolism*
Frontal Lobe / physiopathology
Glucose Metabolism Disorders / diagnosis
Glucose Metabolism Disorders / etiology*
Humans
Male
Memory / physiology*
Memory Disorders / diagnosis
Middle Aged
Neuropsychological Tests
Positron-Emission Tomography / methods*
Temporal Lobe / diagnostic imaging
Temporal Lobe / metabolism*
Temporal Lobe / physiopathology
Temporal Lobe / surgery
Treatment Outcome

Substances

Fluorodeoxyglucose F18