Intracranial investigation of piriform cortex epilepsy during odor presentation

ABSTRACT

The piriform cortex (PC) is part of the olfactory system, principally receiving input from the lateral olfactory tract and projecting to downstream components of the olfactory network, including the amygdala. Based on preclinical studies, PC is vulnerable to injury and can be easily kindled as an onset site for seizures. While the role of PC in human epilepsy has been studied indirectly and the subject of speculation, cases of demonstrated PC seizure onset from direct intracranial recording are rare. We present a pediatric patient with drug-resistant focal reflex epilepsy and right mesial temporal sclerosis with habitual seizures triggered by coconut aroma. The patient underwent stereoelectroencephalography with implantation of olfactory cortices including PC, through which we identified PC seizure onset, mapped high-frequency activity associated with presentation of olfactory stimuli and performance on cognitive tasks, and reproduced habitual seizures via cortical stimulation of PC. Coconut odor did not trigger seizures in our work with the patient. Surgical workup resulted in resection of the patient’s right amygdala, PC, and mesial temporal pole, following which she has been seizure free for 20 months without functional decline in cognition or smell. Histological findings from resected tissue showed astrogliosis and subpial gliosis.

KEYWORDS:

• Piriform cortex
• stereoelectroencephalography
• high frequency activity
• epilepsy surgery
• focal epilepsy
• olfaction

Acknowledgements

The authors thank the patient and her family for participating in the study.

Author contributions

All authors contributed to the study conception and design. Data collection and analysis were performed by Joshua J. Chern, Robyn Selawski, and Ammar Kheder. The first draft of the manuscript was written by Donald J. Bearden and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Disclosure statement

N.P.P. is on the scientific advisory board of Dixi Medical USA.

Data availability statement

The data analyzed during the current study are not publicly available due to reasons of confidentiality of protected health information but are available from the corresponding author on reasonable request.

Ethics approval

This study was performed in line with the principles of the Declaration of Helsinki.

Additional information

Funding

N.P.P. is supported by the Woodruff Foundation, CURE Epilepsy, and NIH grants K08NS105929, R01NS088748, and R21NS122011. D. L. D. receives partial support from the NIH grant R01NS088748.