Underlying pathology of TLE
> Hippocampal sclerosis – 22%
Developmental tumours – 40%
Cortical Dysplasia – 30%
Tuberous Sclerosis – 2%
TLE & medication
Often medication resistant
Epilepsy surgery in TLE
23% of cases
What is hippocampal sclerosis
Neuronal loss
Left Temporal lobe associated with _ memory
Verbal Memory
Right Temporal lobe associated with _ memory
Visual Memory
Anterior Temporal lobe associated with _ memory
Semantic memory
- General knowledge of objects
- No reference to time/space
- Shared across human cultues
The ATL is a hub where all information gets stored and consolidated
e.g. semantic dementia starts in ATL
Hippocampus associated with _ memory
Episodic Memory
- unique to time & place
- Specific to that individual
Hierarchical organisation of memory is…
Mischkin Hierarchical organisation
According to MHO ventral visual stream feeds into…
Perirhinal Cortex
‘What’
According to MHO Dorsal visual stream feeds into…
Parahippocampal Cortex
‘where’
Part of the MHO that interfaces the hippocampus & neocortex
Entorhinal cortex
IQ in epilepsy is correlated with
age of onset
Cormack et al. 2007
Hippocampal Scleorsis & dysembryoplastic neuroepithelial tumours has no impact on which type of memory?
STM memory - Digit Span
How is semantic memory impacted
lower in Left HS
but general reduction for all
Impact of TLE on regions connected to atrophic hippocampues
focal grey matter reductions controlatterally
Therefore there is a global impact
In adults - there was limbic system atrophy - all the parts that connect to the Hippocampus
What impacts degree of hippocampal atrophy?
Duration of TLE negatively impacted hippocampal volume
+
increase seizures
Cormack (2005)
Duzel (2006)
Decline in hippocampal volume correlates with:
decline in episodic memory
Skirrow et al. ICE abstracts (2014)
Wilson 2012 developmental statistics
52% - normal
37% altered
11% delayed
Predictors of developmental impact
- FSIQ
- Seizure Freedom
- Surgical intervention
- Male
What is the ‘release effect’?
release of skills as a result of seizure freedom
- they go closer to their pre-epilepsy developmental path
Seizure freedom after epilepsy surgery
87%
Cognitive outcomes after Epilepsy Surgery
More educational attainments Less diability Independent living improved QoL Employment (N.S.)
IQ increase of >15
in 26% of patients
IQ decrease od >10
2%
When were the greatest IQ gains seen?
6 years post op
- related to AED withdrawal
IMP note for neurosurgeons
the higher the brain volume the better the increase in IQ
- take out least possible
Semantic memory = extent of L. TL resection
-Verbal Episodic Memory extent of hippocampal resection (more left = lower score)
Difference in PIQ and VIQ improvements
PIQ improved in both
VIQ improved in left side surgery
- despite tissue loss
= release effect - due to seizure freedom
Release effect & Left resection
Verbal memory returns to pre-operative level
- but dips initially after surgery
- semantic memory was linked to extent of L.TL resection
Visual Memory: increases and follows a +ve developmental trajectory
Right Resection & release effect
Visual memory: returns to pre-op level -
Verbal memory: increases
Interesting finding… resection & release effect
improvement on the ‘contra-lateral memory’
Outcomes of epilepsy surgery impacted by:
Seizure Freedom - release effect
AED discontinuation
Follow-up time
Maybe:
duration of epilepsy
Seizure Frequency
Seizure type/severity
