Sina Sadeghzadeh, Medical Student, Stanford University School of Medicine, Stanford, CA, shares the findings of a study investigating the relationship between hippocampal high frequency oscillation (HFO) burden and cognitive status in patients with temporal lobe epilepsy (TLE). HFO load was assessed in 10 patients using intracranial EEG at baseline and during neuropsychological tests of memory and learning. Hippocampal HFO rate at baseline showed a strong negative relationship with performance during the verbal recognition memory test and Rey Auditory Verbal Learning Test (RAVLT). These preliminary data extend on previous findings linking HFOs to acute cognitive performance, showing the HFO burden may also be associated with overall memory function and chronic cognitive decline. This interview took place at the American Epilepsy Society (AES) Annual Meeting 2022 in Nashville, TN.
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Transcript (edited for clarity)
The poster on HFOs focuses on the relationship between the load of hippocampal HFOs and patient’s performance in an array of verbal memory tasks. So the background is that previously our lab has shown that the presence of HFOs is linked to impairments in acute cognitive performance. However, it’s not really clear if the total HFO burden can be indicative of overall cognitive status or more chronic cognitive decline...
The poster on HFOs focuses on the relationship between the load of hippocampal HFOs and patient’s performance in an array of verbal memory tasks. So the background is that previously our lab has shown that the presence of HFOs is linked to impairments in acute cognitive performance. However, it’s not really clear if the total HFO burden can be indicative of overall cognitive status or more chronic cognitive decline. And here, so we investigated this question and showed that the load of hippocampal HFOs has a strong negative relationship with verbal memory performance, both at baseline and during memory encoding.
And so briefly, at baseline we looked at the patient’s performance in the Rey Auditory Verbal Learning Test (RAVLT), which is a neuropsych test that patients complete pre-surgically, and we correlated those outcomes with the hippocampal HFO load at the first hour after the admission to the EMU. And at encoding, we looked at the patient’s performance in an in-house, we designed on our own, verbal memory tests and correlated that with the hippocampal HFOs when they were encoding those words.
And in both scenarios, interestingly, we saw that there was a strong negative relationship between hippocampal HFO rates and subject task performance, and the exact number is about negative 0.8. And so we concluded that HFO burden can be used as a biomarker for memory function in TLE patients and further research, obviously, should be done to investigate the potential for using that as a potential sort of biomarker for neuromodulation for patients with cognitive decline.
So this project, we’re putting in together more data from different types of stimuli. So this was focused on the HFOs. We’re looking at spikes and also seizures during these encoding tasks. So this is going to be a sort of the greater narrative of general brain abnormalities and how that would impact memory function.
Patients with epilepsy often have cognitive decline, and unfortunately, there is no real good treatment for that. So, if we find a specific biomarker that can be used to detect when these sort of decline in cognitive status arises, then that could potentially be used to say, treatment with the RNS system or other modalities. Obviously, the problem here right now with HFOs is that they can be both physiological and pathological. So, it’s not as clear as kind of a picture of let’s suppress HFOs and then maybe the patient’s memory get better, HFOs are actually needed as well. So it’s very tricky and it’s sort of a ongoing line of research to figure out how to distinguish these two and what their exact roles in memory and encoding in the brain.