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TP3-4 Changes in whole brain connectomes with simulated laser interstitial thermal therapy (LITT) using seizure free and non-seizure free ablation cavities in mesial temporal sclerosis: a graph theory approach
  1. N Vakharia1,
  2. M Manchini2,
  3. B Vos2,
  4. K Li3,
  5. A McEvoy1,
  6. R Sparks4,
  7. S Ourselin4,
  8. S Duncan1
  1. 1The National Hospital for Neurology and Neurosurgery, London, UK
  2. 2Wellcome EPSRC Centre for Interventional and Surgical Sciences (WEISS), University College London, London, UK
  3. 3Department of Clinical and Experimental Epilepsy, University College London, London, UK
  4. 4School of Biomedical Engineering and Imaging Sciences, St Thomas’ Hospital, King’s College London, London, UK


Objectives LITT is a novel means of focal lesioning. Improved seizure free outcome has been associated with the extent to which the mesial hippocampal head is ablated, but not overall ablation volume. We question whether specific changes in structural network connectivity exist in patients that achieve seizure freedom.

Design Retrospective

Subjects 25 MTS patients after LITT with 2 year outcome.

Methods Ablation cavities from 11 seizure free and 14 non-seizure free patients were combined to generate group masks. In 12 separate pre-operative patients with MTS (6 right), weighted normalized connectomes were generated with 1 × 10^7 streamlines. To simulate ablations the group cavity masks were excluded from the connectomes prior to normalization. Differences in connectomes were assessed by graph theory metrics.

Results Greater node strength (str) in non-seizure free patients were present in the ipsilateral basal temporo-occipital cortices in both right and left MTS. Str and local efficiency were relatively maintained in the ipsilateral thalamus of seizure free cavities. Betweenness centrality in non-seizure free cavities were greater in ipsilateral temporal poles in right and left MTS.

Conclusions Differences in network connectivity are present following simulated LITT for MTS between seizure free and non-seizure free ablation cavities. LiTT ablation cavities may be pre-operatively modelled to ensure the ablation cavity includes important structures and non-essential or inhibitory connectivity is spared. Prospective validation is required.

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