A Quantitative Meta-analysis of Olfactory Dysfunction in Epilepsy
Olfactory dysfunction in epilepsy is well-documented in several olfactory domains. However, the clinical specificity of these deficits remains unknown. The aim of this systematic meta-analysis was to determine which domains of olfactory ability were most impaired in individuals with epilepsy, and to assess moderating factors affecting olfactory ability. Extant peer-reviewed literature on olfaction in epilepsy were identified via a computerized literature search using PubMed, MEDLINE, PsycInfo, and Google Scholar databases. Twenty-one articles met inclusion criteria. These studies included a total of 912 patients with epilepsy and 794 healthy comparison subjects. Included studies measured olfaction using tests of odor identification, discrimination, memory, and detection threshold in patients with different types of epilepsy, including temporal lobe epilepsy (TLE), mixed frontal epilepsy (M-F), and mixed epilepsy (MIX). Olfactory deficits were robust in patients with epilepsy when compared to healthy individuals, with effect sizes in the moderate to large range for several olfactory domains, including odor identification (d = −1.59), memory (d = −1.10), discrimination (d = −1.04), and detection threshold (d = −0.58). Olfactory deficits were most prominent in patients with TLE and M-F epilepsy. Amongst patients with epilepsy, sex, age, smoking status, education, handedness, and age of illness onset were significantly related to olfactory performance. Overall, these meta-analytic findings indicate that the olfactory system is compromised in epilepsy and suggest that detailed neurobiological investigations of the olfactory system may provide further insight into this disorder.
KeywordsOlfaction Smell Epilepsy Seizures Seizure disorder
This work was supported by K01 MH102609 (Roalf), the Brain and Behavior Foundation NARSAD Young Investigator grant program (Roalf), and the John Hopkins Clinical Research Scholars Program KL2TR001077 (Kamath).
Role of the Funding Sources
The funding sources had no role in the design, collection, analysis or manuscript preparation for this study.
Compliance with Ethical Standards
Ethical Publication Statement
We affirm that we have read the Neuropsychology Review’s position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.
Conflicts of Interest Disclosures
The authors declare that they have no conflict of interest.
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