Presurgical evaluation in adults: noninvasive

High-density electric source imaging patterns and outcomes following temporal lobectomy in patients with hippocampal sclerosis

OBJECTIVE

The objective of this study was to ascertain specific patterns of electrical source imaging (ESI) that are associated with a good surgical outcome (no seizure recurrence) using 256-channel high-density (HD) electroencephalography (EEG) in patients with temporal lobe epilepsy with hippocampal sclerosis (TLE-HS) who underwent temporal lobectomy.

METHODS

Adult patients (age ≥ 18 years) were prospectively recruited from September 2016 to May 2020 at the authors' center. All patients underwent phase I presurgical evaluation and were subsequently advised to proceed with surgery based on consensus from a multidisciplinary epilepsy conference, without knowing HD-ESI results. All recruited patients were followed for at least 12 months after surgery. The outcome of interest was a status of no seizure recurrence, which was assessed at the end of the study. The association between ESI patterns and outcome was assessed using the chi-square or Fisher exact test. Associated p values as well as odds ratios and 95% CIs were reported. The diagnostic performance of the significant pattern associated with the outcome was also evaluated.

RESULTS

Fifty-eight patients with known predictors for either good or worse surgical outcomes were recruited. The mean postoperative follow-up period was 33.34 (SD 13.88) months. Forty-seven patients had sufficient interictal epileptiform discharges for HD-ESI analysis. Thirteen of these 47 patients experienced seizure recurrence. The most common source localizations were at Brodmann area (BA) 20 (inferior temporal area) and BA 21 (middle temporal area). A specific ESI pattern of BA 21 without extratemporal sources was significantly associated with no seizure recurrence (p = 0.047). This pattern had a high positive predictive value of 100% and false-positive rate of 0% associated with no seizure recurrence following the surgery.

CONCLUSIONS

A specific ESI pattern that was highly associated with no seizure recurrence following surgery was demonstrated by a 256-channel HD-EEG. If this pattern can be reproducibly proven in further studies, some TLE-HS patients may be able to proceed with surgery without further investigations.

Changes in Pre- and Postsurgery for Drug Resistant Epilepsy: Cognition and Sleep

BACKGROUND

Most patients with drug-resistant epilepsy (DRE) have cognitive impairment and sleep disturbance. There was a significant correlation between sleep disorders and cognitive dysfunction. This study performed surgical treatment on patients with DRE and observed seizures, sleep, and cognition in patients with DRE in 6th month after operation to clarify the correlation between sleep and cognition in DRE patients.

METHODS

21 individuals with DRE were recruited to enroll in this trial. Each participant completed epileptic focus resection. Seizure frequency was the principle index; the mean seizure frequency was 1 month before surgery and six months after surgery. Cognitive function was assessed by MMSE, and sleep status was assessed by PSQI and ActiGraph; assessments were performed before and 6 months after surgery.

RESULTS

There were significant differences between conditions on all outcome measures; after 6 months of surgery, compared with before treatment, the monthly average seizure frequency of DRE decreased, which was statistically significant (P < 0.001) compared with that before treatment. The MMSE score of DRE patients was significantly higher than before (P < 0.01), especially the ability of attention, calculation, and recall in MMSE score, which was significantly higher than before operation (respectively, P < 0.001 and P < 0.01). The subjective sleep evaluation index PSQI and objective measurement of sleep latency, total sleep time, and sleep efficiency of patients with DRE by ActiGraph were statistically significant (respectively, P < 0.01) compared with that before treatment. There was a correlation between seizure frequency and MMSE (r = -0.8887, P < 0.0001), PSQI (0.5515, P < 0.01), sleep latency (0.5353, P < 0.05), total sleep time (-0.7814, P < 0.0001), and sleep efficiency (-0.4380, P < 0.05).

CONCLUSIONS

Surgery can effectively reduce the epileptic seizures frequency in patients with DRE and indirectly improve the computational power, attention, recall ability, and sleep status of patients. However, this result did not show a correlation between improved cognitive function and sleep, so the patient's cognitive function may be caused by surgery to improve the frequency of seizures. So, whether the improvement of patients' sleep conditions can also significantly improve the frequency of attacks and cognitive function in patients with DRE needs further exploration.

Presurgical epilepsy evaluation and epilepsy surgery

With a prevalence of 0.8 to 1.2%, epilepsy represents one of the most frequent chronic neurological disorders; 30 to 40% of patients suffer from drug-resistant epilepsy (that is, seizures cannot be controlled adequately with antiepileptic drugs). Epilepsy surgery represents a valuable treatment option for 10 to 50% of these patients. Epilepsy surgery aims to control seizures by resection of the epileptogenic tissue while avoiding neuropsychological and other neurological deficits by sparing essential brain areas. The most common histopathological findings in epilepsy surgery specimens are hippocampal sclerosis in adults and focal cortical dysplasia in children. Whereas presurgical evaluations and surgeries in patients with mesial temporal sclerosis and benign tumors recently decreased in most centers, non-lesional patients, patients requiring intracranial recordings, and neocortical resections increased. Recent developments in neurophysiological techniques (high-density electroencephalography [EEG], magnetoencephalography, electrical and magnetic source imaging, EEG-functional magnetic resonance imaging [EEG-fMRI], and recording of pathological high-frequency oscillations), structural magnetic resonance imaging (MRI) (ultra-high-field imaging at 7 Tesla, novel imaging acquisition protocols, and advanced image analysis [post-processing] techniques), functional imaging (positron emission tomography and single-photon emission computed tomography co-registered to MRI), and fMRI significantly improved non-invasive presurgical evaluation and have opened the option of epilepsy surgery to patients previously not considered surgical candidates. Technical improvements of resective surgery techniques facilitate successful and safe operations in highly delicate brain areas like the perisylvian area in operculoinsular epilepsy. Novel less-invasive surgical techniques include stereotactic radiosurgery, MR-guided laser interstitial thermal therapy, and stereotactic intracerebral EEG-guided radiofrequency thermocoagulation.

Look back to leap forward: The emerging new role of magnetoencephalography (MEG) in nonlesional epilepsy

This review considers accumulating evidence for a new role of MEG/MSI in increasing the diagnostic yield of supposedly negative MRIs, and suggests changes in the use of MEG/MSI in presurgical epilepsy evaluations. Specific alterations in practice protocols for both the MEG practitioner (i.e. physician magnetoencephalographer) and MEG user (i.e. referring physician) are proposed that should further enhance the overall value of MEG/MSI. Although advances in MEG analysis methods will likely become increasingly assisted by computers, interpretive competency and prudent clinical judgment remain irreplaceable.