Safety and efficacy of bihemispheric sampling via transmidline stereoelectroencephalography.

OBJECTIVE: Stereoelectroencephalography (SEEG) is designed to target distributed cortical networks responsible for electroclinical seizure syndrome and to enable localization of the site of seizure onset in patients with intractable epilepsy. When the preimplantation hypothesis invokes the bilateral mesial frontal lobes, sampling of several deep-seated cortical sites in both hemispheres is required. In this study, the authors have demonstrated the feasibility of sampling bihemispheric areas with intentional implantation of an SEEG electrode crossing the midline (SECM) for sampling the cortex on both sides of the interhemispheric fissure. METHODS: An analysis of 231 consecutive SEEG procedures over 8 years was used to identify instances of bihemispheric sampling by using the transmidline SEEG technique. RESULTS: The authors identified 53 SEEG cases, with a total of 126 electrodes that crossed the interhemispheric fissure; all were in the frontal lobes. Eighty-three electrodes targeted the cingulate gyrus (18 rostral, 43 anterior, and 22 middle), 31 targeted the posterior orbitofrontal region, 8 sampled the medial prefrontal cortex, and 4 targeted nodular heterotopia around the frontal horns. The ictal onset zone was localized to the frontal lobe in 16 cases. SECM isolated interictal and ictal activity in the contralateral hemisphere in 6 cases and independent bihemispheric seizure activity in 2 cases. No hemorrhagic or infectious complications were noted in any of these cases. CONCLUSIONS: Based on this extensive experience of bihemispheric sampling, the authors concluded that this technique is safe and effective. In this series, SECM showed contralateral interictal and/or ictal epileptiform activity in 8 (15%) cases, and 9 (16%) cases (with unilateral implantation) had sufficient data to discard contralateral involvement, contributing to support of the epileptogenic network. SECM may reduce the number of electrodes used to sample bilateral mesial frontal or orbitofrontal cortices, and such an approach may lower the risk of hemorrhage and costs.

Ambulatory EEG to Classify the Epilepsy Syndrome.

SUMMARY: Recording of interictal epileptiform discharges to classify the epilepsy syndrome is one of the most common indications for ambulatory EEG. Ambulatory EEG has superior sampling compared with standard EEG recordings and advantages in terms of cost-effectiveness and convenience compared with a prolonged inpatient EEG study. Ambulatory EEG allows for EEG recording in all sleep stages and transitional states, which can be very helpful in capturing interictal epileptiform discharges. In the absence of interictal epileptiform discharges or in patients with atypical events, the characterization of an epilepsy syndrome may require recording of the habitual events. Diagnostic ambulatory EEG can be a useful alternative to inpatient video-EEG monitoring in a selected number of patients with frequent events who do not require medication taper or seizure testing for surgical localization.

Automated seizure detection accuracy for ambulatory EEG recordings.

OBJECTIVE: To investigate the accuracy of preselected software automatic seizure files to detect at least one seizure per study in prolonged ambulatory EEG recording. METHODS: All the prolonged ambulatory EEG recordings (>24 hours) read at the Northwestern Memorial Hospital from January 2013 to October 2017 were included. We selected only the first study of each patient. We reviewed the studies entirely, and processed the recordings through 1 of 3 different detection software that are commercially available (Persyst 11, Persyst 12, and Gotman TM Event Detection). The proportion of patients with at least one electrographic seizure (≥10 seconds) correctly identified by a seizure detector was calculated. Finally, we evaluated whether the type of seizure (focal vs generalized) may affect the chances of being automatically detected. RESULTS: We read 1,478 ambulatory EEG studies entirely (2,323 days of EEG recording; average 1.6 d/study). From the first study of each patient (1,257 studies), we found electrographic seizures in 70 (5.6%) studies. In 37 of 70 patients (53%), the automatic detectors correctly identified at least one seizure. Detections happened slightly more frequently in generalized seizures (14/20, 70%) compared to focal seizures (23/50, 46%) (p = 0.06). CONCLUSION: Seizures were found in 5.6% of the studies. Automatic seizure detectors identified at least one electrographic seizure in only 53% of the studies. They performed slightly better detecting generalized than focal seizures. Therefore, the review of only automatically selected segments may be of decreased value to identify seizures, in particular when focal seizures are suspected.

Clinical Benefit of 3 Tesla Magnetic Resonance Imaging Rescanning in Patients With Focal Epilepsy and Negative 1.5 Tesla Magnetic Resonance Imaging.

BACKGROUND: Magnetic resonance imaging is an essential tool in the pre-surgical evaluation of patients with drug-resistant epilepsy. OBJECTIVE: Our aim was to assess the value of re-imaging patients with focal drug-resistant epilepsy. METHODS: Thirty patients with negative or non-conclusive 1.5 Tesla magnetic resonance imaging were rescanned with 1.5T and 3T. All of them had previous 1.5 scans with no seizure protocol in a non-specialized center. Two neuroradiologists who were blinded to prior imaging results randomly reviewed the magnetic resonance images. Kappa score was used to assess the reliability. RESULTS: Mean age of patients was 30 (SD ± 11) years. The intra-observer agreement for the first radiologist was 0.74 for 1.5T and 0.71 for 3T. In the second radiologist it was 0.82 and 0.66, respectively. Three lesions (10%) were identified by general radiologists in non-specialized centers using a 1.5T standard protocol. In our center a consensus between two neuroradiologists using epilepsy protocol identified seven lesions (23%) using 1.5T and 10 (33%) using 3T (p < 0.01). In 28% of patients this additional information resulted in a change in clinical management. CONCLUSIONS: 3T magnetic resonance imaging rescanning improves the diagnostic yield in patients with focal epilepsy and previous negative 1.5T magnetic resonance imaging. Use of 3T magnetic resonance imaging, epilepsy protocols, and interpretation by experienced neuroradiologists is highly recommended.

[Correlation between the magnetic resonance imaging morphometry and the clinical and electroencephalographic findings in patients diagnosed with ulegyria and epilepsy]. / Correlación de la morfometría por resonancia magnética con los hallazgos clínicos y electroencefalográficos de pacientes con diagnóstico de ulegiria y epilepsia.

INTRODUCTION: Ulegyria is a cortical lesion affecting neighbouring vascular zones, which gives the convolutions a mushroom-like appearance. It is an important cause of occipital epilepsy. AIM. To correlate patients diagnosed clinically, electrically and morphometrically with ulegyria and epilepsy by comparing the thickness of the cortex in the zones affected by ulegyria with the normal cortical thickness reported in the literature and the average cortical thickness of healthy subjects. PATIENTS AND METHODS: Ten patients with ulegyria confirmed by magnetic resonance imaging were included in the study; all of them were submitted to a clinical interview, an electroencephalographic study and cortical morphometric analysis based on volumetric T1 sequences. RESULTS: Findings included a predominance in males, neurodevelopmental retardation and epilepsy. Ulegyria was mainly parietooccipital, frequently bilateral, with statistically significant thinning of the cortical thickness in the site of the lesion and an increase in the thickness of the cortex in the areas surrounding the lesion. CONCLUSIONS: We report on a series of patients with ulegyria with characteristics similar to those existing in the literature and by means of morphometry we detected an increase in the thickness of the cortex around the areas affected by ulegyria. These findings could point to the presence of adaptive neuroplasticity in the neurons that surround the scar tissue or they may be the result of mechanical changes of normal tissue in response to the loss of volume of the ulegyria-affected area, although these data need to be replicated in a study with a greater number of patients.