Abstracts

Rationale:
The piriform cortex, at the confluence of the temporal and frontal lobes, has a propensity to generate epileptic seizures in response to chemical convulsants and electrical stimulation. Measurements of piriform cortex volume before and after anterior temporal lobe resection for refractory temporal lobe epilepsy (TLE) have shown that the chances of seizure freedom were 16-fold higher if at least 50% of the piriform cortex was resected. The objectives of the current study were to understand the degree of damage to the piriform cortex in TLE and to quantify the degree to which clinical characteristics of TLE correlate with volumetric changes in the piriform cortex.
Method:
Sixty individuals with unilateral TLE (33 left) and 20 healthy controls had volumetric analysis of left and right piriform cortex and hippocampi. A robust protocol for segmenting and measuring the volumes of the piriform cortices was implemented, with good inter-rater and test-retest reliability. Univariate and multivariate regression models were employed to examine the relationship of piriform cortex and hippocampal volumes with clinical variables collected.
Results:
The right piriform cortex volume was consistently larger than the left piriform cortex in both healthy controls and patients with TLE. In controls, the mean volume of the right piriform cortex was 17.7% larger than the left, and the right piriform cortex extended by a mean of 6 mm (Range: -4 to 12) more anteriorly than the left. This asymmetry was also seen in left and right TLE. In TLE patients overall, the piriform cortices were not significantly smaller than in controls. Hippocampal sclerosis was associated with decreased ipsilateral and contralateral piriform cortex volumes. The piriform cortex volumes, both ipsilateral and contralateral to the epileptic temporal lobe, were smaller with a longer duration of epilepsy. There was no significant association between piriform cortex volumes and the frequency of focal seizures with impaired awareness or the number of anti-epileptic medications taken.
Conclusion:
The data support a key role of the piriform cortices in the pathophysiology of TLE and the implementation of robust segmentation will enable consistent neurosurgical resection in anterior temporal lobe surgery for refractory TLE. Further longitudinal studies are required to confirm the findings of this study to enable the piriform cortex to be considered in treatment strategies for patients with refractory TLE.
Funding:
:N/A