Verbal Fluency in Focal Epilepsy: A Systematic Review and Meta-analysis

Abstract

Testing of verbal fluency is currently part of standard presurgical neuropsychological assessment for patients with focal epilepsy. However, to date no systematic review has been conducted on semantic (SVF) and phonemic verbal fluency (PVF) in this patient group. The present review compares verbal fluency between healthy control subjects and subgroups of adult presurgical patients with focal epilepsy according to lateralisation and localisation of the dysfunction. PubMed was searched with a comprehensive search string. Abstracts of all studies and full-texts of potentially relevant studies were screened. Study quality was assessed by independent raters according to predefined criteria. 39 studies were included. Meta-analyses were performed to compare SVF and PVF across groups of patients with temporal (TLE) and frontal lobe epilepsy (FLE) as well as healthy controls (HC). Both patients with left- and right sided TLE were impaired on SVF and PVF compared to HC. Patients with left-sided TLE were slightly more impaired than patients with right-sided TLE. Patients with FLE showed a larger impairment in PVF than patients with TLE, whereas on SVF there was no difference between FLE and TLE. For TLE comparisons the study pool seems to have been sufficient, whereas more studies are needed to verify results for FLE. Semantic verbal fluency might not differentiate between FLE and TLE. While verbal fluency impairment was anticipated, especially in left-sided TLE and FLE patients, the impairment in patients with right-sided TLE was larger than expected. Results are discussed with regard to neuropsychological theory and practice.

Distinct functional connectivity of the hippocampus during semantic and phonemic fluency

“…This finding is in contrast to our hypothesis, as we expected, based on the consistent direction of asymmetry in language, that hippocampal activity would be lateralized to the left side, particularly during semantic fluency. In the literature on verbal fluency in temporal lobe epilepsy (TLE), a recent systematic review and meta-analysis demonstrated similar findings to ours (Metternich et al, 2014). Like us, the authors of this review were surprised by the findings as they noted that "the impairment in right TLE (RTLE) patients was more pronounced than expected" (Metternich et al, 2014, p. 211, italics added).…”

Hubs disruption in mesial temporal lobe epilepsy. A resting‐state fMRI study on a language‐and‐memory network

“…These changes are based on the neural plasticity phenomenon that can take place in TLE patients over the years (Berg & Scheffer, ). The reorganization patterns can be more or less cognitively efficient and various degrees of language and memory deficits have been described in patients with mTLE (Alessio et al, ; Jaimes‐Bautista, Rodríguez‐Camacho, Martínez‐Juárez, & Rodríguez‐Agudelo, ; McAndrews & Cohn, ; Metternich, Buschmann, Wagner, Schulze‐Bonhage, & Kriston, ). For instance, Hoppe et al determined that language and memory were the most affected functions in a large cohort of epileptic patients mainly composed of mTLE (Hoppe, Elger, & Helmstaedter, ).…”

Neuropsychological Characteristics of Verbal and Non-Verbal Fluency in Schizophrenia Patients

“…It is confirmed by results of studies conducted on patients with Alzheimer's disease and epilepsy. Such patients achieved lower scores in verbal fluency tasks due to verbal memory dysfunction (Herbert et al, 2014;Metternich et al, 2014;Tsantali & Economidis, 2014). Compared to healthy controls, schizophrenia patients create fewer clusters in semantic fluency test (Neill et al, 2014;Nicodemus et al, 2014;Sung et al, 2012).…”

“…Quantitative and qualitative results which can be obtained by means of those tests can be used to analyse the nature of cognitive and executive disorders (Stuss & Knight, 2013). Although there exist extensive data indicating various reasons for schizophrenia patients' low scores in verbal fluency tests (Bozikas, Kosmidis, & Karavatos, 2005;Dibben, Rice, Laws, & McKenna, 2009;Henry & Crawford, 2004;Herbert, Brookes, Markus, & Morris, 2014;Metternich, Buschmann, Wagner, Schulze-Bonhage, & Kriston, 2014;Neill, Gurvich, & Rossell, 2014;Nicodemus et al, 2014;Oh, Vidal, Taylor, & Pang, 2014;Robert et al, 1998;Sung et al, 2012;Tsantali & Economidis, 2014;Uchikawa et al, 2013;Vinogradov et al, 2003), the understanding of disorders underlying lower performance in non-verbal fluency tasks still remains limited (Pawełczyk et al, 2013;Phillips, James, Crow, & Collinson, 2004;Rinaldi, Lefebvre, & Trappeniers, 2013).…”