Language activation distributions revealed by fMRI in post-operative epilepsy patients: Differences between left- and right-sided resections

Abstract

Objective: To reveal differences of cerebral activation related to language functions in post-operative temporal lobe epilepsy (TLE) patients. Methods: Right (RTL) and left temporal lobe (LTL) resected patients, and healthy controls were studied using functional magnetic resonance imaging (fMRI). Only patients with complete left-hemispheric language dominance according to the intracarotid amytal procedure (IAP) were included. Language-related activations were evoked by performing word generation and text reading language tasks. Activation lateralization and temporo-frontal distribution effects were analysed. Results: For word generation, only LTL patients showed reduced left lateralized activation compared to controls, due to a decrease in activation in the left prefrontal cortex and an increase in the right prefrontal cortex. For reading, the left-hemispheric lateralization in RTL patients increased because of enhanced activity in the left prefrontal cortex, whereas for LTL patients the activation became bilaterally distributed over the temporal lobes. Lateralization results between pre-operative IAP and postoperative fMRI were highly discordant. Significant temporo-frontal distribution changes manifested from the reading but not from the word generation task. * Corresponding author. Backes et al. / Epilepsy Research 66 (2005) [1][2][3][4][5][6][7][8][9][10][11][12] Conclusion: The cerebral language representation in post-operative LTL epilepsy patients is more bi-hemispherically lateralized than in controls and RTL patients. Post-operative temporo-frontal and interhemispheric redistribution effects, involving contralateral homologuous brain areas, are suggested to contribute to the cerebral reorganisation of language function.

What do patients with epilepsy tell us about language dynamics? A review of fMRI studies

“…Some authors have suggested that the lateralization of the EZ is the determining factor in language reorganization in patients with TLE. Patients with left EZ are more likely to show atypical language representation than healthy subjects or patients with right EZ (Adcock et al, 2003;Backes et al, 2005;Berl et al, 2005;Schwarz and Pauli, 2009;Karunanayaka et al, 2011). Similarly, Brázdil et al (2003) found that atypical organization was more common in patients with left TLE (23.1%) than patients with right TLE (0%).…”

“…These factors may include demographic and clinical characteristics of patients, such as the age at which the lesion or epileptic seizures occur (Vargha-Khadem et al, 1997;Staudt et al, 2001;Hertz-Pannier et al, 2002;Liégeois et al, 2004;Brázdil et al, 2005;Tracy et al, 2009), the size, location, and lateralization of the EZ (Adcock et al, 2003;Backes et al, 2005;Berl et al, 2005;Karunanayaka et al, 2011), frequency of interictal epileptiform discharges (Janszky et al, 2003(Janszky et al, , 2006, gender (Strauss et al, 1992;Helmstaedter et al, 2004), handedness (Berl et al, 2014), and individual differences in potential plasticity (Zatorre, 2013). Furthermore, the pattern of organization may be different before and after surgery (Helmstaedter et al, 2006;Bonelli et al, 2012;Perrone-Bertolotti et al, 2012a).…”

Interhemispheric differences of spectral power in expressive language: A MEG study with clinical applications

“…They identified expressive language sites substantially anterior and superior to canonical Broca's area, which they attributed to intrahemispheric reorganisation associated with left hemisphere insult from a young age resulting in an anterior displacement of language within the frontal lobe. Neuroimaging studies reporting reorganisation of language function also suggest a degree of inherent cortical plasticity (Hertz-Pannier et al, 2002;Backes et al, 2005;Pataraia et al, 2005;Yuan et al, 2006). Evidence of reorganisation of left hemisphere language function to mirrored sites in the right hemisphere following left hemispherectomy suggests that there may be a pre-existing bilateral language network (Hertz-Pannier et al, 2002).…”

An fMRI case study of visual memory in a patient with epilepsy: comparison before and after temporal lobe surgery

“…About 70% of patients who undergo resection surgery for seizures originating from regions within the anterior/mesial temporal lobes have a positive outcome and the majority are completely seizure free after the procedure (Backes et al 2005). Despite careful pre-surgical screening, about 30% of patients undergoing a temporal lobectomy experience temporary or permanent deficits related to language and/or memory functions (Baxendale et al 2008).…”