Conference Coverage

Scalp EEG predicts temporal lobe resection success



– In a review of 43 temporal lobe epilepsy patients at Yale University in New Haven, Conn., anteromedial temporal resection (AMTR) failed in every case in which initial ictal rhythm on scalp EEG spread beyond the medial temporal lobe to other brain regions within 10 seconds.

Among the 33 patients who had no spread on preoperative scalp EEG or who spread in 10 or more seconds, 31 (94%) had a good outcome, meaning they were seizure free or had only auras after AMTR. The findings could mean that scalp EEG can predict surgery outcome.

AMTR works in the majority of patients with refractory temporal lobe epilepsy, but about 10-20% continue to have seizures. Senior investigator Pue Farooque, DO, from Yale University wanted to find a way to identify patients likely to fail surgery beforehand to help counsel patients on what to expect and also to know when other treatment options might be a better bet.

“If you see seizures are spreading quickly to another area, like the frontal lobe or the temporal neocortex, you could implant RNS [responsive neurostimulation]” instead of doing an ATMR, “and that might improve your outcomes,” she said at the American Epilepsy Society’s annual meeting.

The findings are essentially the same as when the group used intracranial EEG to detect fast spread in a previous report, but scalp EEG is noninvasive and allows for easy preoperative assessment (JAMA Neurol. 2019 Apr 1;76[4]:462-9).

The team also found in their new study that diffuse hypometabolism in the entire temporal lobe on quantitative PET also predicted poor ATMR outcomes (P less than .001), but Dr. Farooque said more work is needed to quantify the finding. The investigators also plan to assess the predictive value of resting functional MRI.

The take home, she said, is that “we can do better” with epilepsy surgery, and “there are noninvasive markers we can use to help guide us.”

It’s unclear why more rapid seizure spread would predict AMTR failure. In the earlier study with intracranial EEG, the investigators said “the results are best explained by attributing epileptogenic potential to sites of early seizure spread that were not included in resection. This mechanism of failure implies that a distributed epileptogenic network rather than a single epileptogenic focus may underlie surgically refractory epilepsy.”

Patients in the new report had epilepsy for a mean of 24.4 years, and 25 (58%) were women; 30 cases (69%) were lesional, and follow-up was at least a year. The contralateral or lateralized seizure spread ranged from 1 to 63 seconds, with a mean of 18.5 seconds. Among patients who failed AMTR, seizure spread occurred at a mean of 7.1 seconds.

Electrographic pattern at onset and location of interictal epileptiform discharges did not predict outcome

There was no industry funding, and Dr. Farooque didn’t have any relevant disclosures.

SOURCE: Chiari J et al. AES 2019, Abstract 1.36.

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