Authors :
Presenting Author: Maria Sablik, BSc, MRes, Phd Candidate – UCL Queen Square Institute of Neurology
Marine Fleury, BSc, MSc – PhD candidate, Department of Clinical and Experimental Epilepsy (DCEE), UCL Queen Square Institute of Neurology; Lawrence Binding, BSc, MSc – PhD candidate, Department of Clinical and Experimental Epilepsy (DCEE), UCL Queen Square Institute of Neurology; John S. Duncan, MD, PhD, Professor – Principal Clinical Research Fellow, Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology; Meneka K. Sidhu, MBChB, MRCP, PhD – Principal Clinical Research Fellow., Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology
Rationale:
Anterior temporal lobe resection is an effective treatment for refractory Temporal Lobe Epilepsy, offering seizure freedom in up to 80% of patients. Surgery in the language-dominant hemisphere may be associated with up to a 40% risk of decline in naming function. Four months after ATLR functional reorganization related to better cognitive outcome associated with activations in the remnant left posterior hippocampus and left middle frontal gyrus (MFG) in people with left TLE(LTLE). In right TLE (RTLE), left inferior frontal gyrus (IFG), MFG and right MFG were indicative of better language performance. We recently demonstrated that long-term plasticity continues long-term (seven to ten years) post-surgery in both patient groups. We now aim to examine specific brain regions associated with better language outcome at long-term follow-up.
Methods:
We studied 34 subjects (ten controls, 24 TLE (12 LTLE) across three time points; pre-operatively and at one year and long term (7-10 years) after ATLR, and equivalent time points in controls. All participants performed verbal fluency fMRI task and neuropsychological testing:phonemic fluency (PF) and naming tests. We quantified activation in pre-defined ROIs in the left and right IFG, MFG, parahippocampal gyri and hippocampi and correlated this with PF and naming performance. Changes in scores were used as a continuous regressor in ANCOVA analysis exploring positive and negative correlations with regard to brain activation.
Results:
LTLE: Neuropsychology: A total of 52% and 50% of patients improved improved between one to ten years post-op on PF and naming tests, respectively.
ROI parameter estimate correlation: Long-term post-op worse performance of PF was associated with fMRI activity in the remnant left posterior hippocampus (p< .001,R2=.71), right hippocampus (p=.004, R2=.58) and left IFG (p=.05, R2=.33).
ANCOVA analysis using change in language scores: Right frontal areas (IFG, SFG), left ACC and left insula were positively correlated with naming and PF improvements whilst the reduction in these scores associated with the right ACC and angular gyrus activations.
RTLE: A total of 25% and 33% of patients improved long-term post-op on PF and naming tests, respectively. Better PF associated with left hippocampus (p=.006, R2=.63) and left IFG (p=.007,R2=.62) activity whilst right MFG (p=.01,R2=.56) was associated with better naming performance. PF scores correlated positively with the VF activity in the left parahippocampus (p=.015, R2=.56), left MFG (p=.046,R2=.34), and right posterior part of remnant hippocampus (p=.003,R2=.61). ANCOVA showed that left MFG and left temporal regions (ITG, STG, left hippocampus) associated with improvements in memory performance from one to ten years, whilst right supramarginal and ANG correlate with a decline.
Conclusions:
Our findings suggest that ongoing plasticity long-term following ATLR may be supportive for improvements in language function. In LTLE, plasticity involving the contralateral frontal lobe and left cingulum is supportive of language improvement whilst in RTLE, engagement of typical language areas including the left IFG, MFG and left hippocampus is associated with improvements in language performance.
Funding: UCLH BRC,Wellcome Trust,MRC