Bilateral perisylvian ulegyria: An under-recognized, surgically remediable epileptic syndrome

A Rare Cause of Epilepsy: Ulegyria Revisited in a Series of 10 Patients

Introduction. Ulegyria results from perinatal hypoxic-ischemic brain injury in term infants. The specific mushroom-shaped configuration of ulegyria results from small atrophic circumvolutions at the bottom of a sulcus underlying an intact gyral apex. Clinically, ulegyria is generally associated with epilepsy. Here, we aimed to delineate the characteristics of patients with ulegyria and the epileptic seizures they experience. Material and methods. Medical records including radiology and pathology reports, video-electroencephalographic (EEG) analysis, operative notes, hospital progress and outpatient clinic notes were reviewed retrospectively in a total of 10 ulegyria patients. Results. Patients ages ranged between 24 and 58 years (mean, 32 ± 9.8 years). Past medical history was confirmed for neonatal asphyxia in 2 (20%). Neurological examination was remarkable for spastic hemiparesis in 1 (10%) patient with perisylvian ulegyria and for visual field deficits in 2 patients (20%) with occipital ulegyria. Ulegyria most commonly involved the temporoparietal region (n = 5, 50%) followed by the perisylvian area (n = 2, 20%). Except the one with bilateral perisylvian ulegyria, all patients had unilateral lesions (n = 9, 90%). Hippocampal sclerosis accompanied ulegyria in 2 patients (20%). All patients experienced epileptic seizures. Mean age at seizure onset was 8.8 ± 5.4 years (range, 2-20 years). Interictal scalp EEG and EEG-video monitoring records demonstrated temporoparietal and frontotemporal activities in 5 (50%) and 2 (20%) patients, respectively. The seizures were successfully controlled by antiepileptic medication in 8 patients (n = 8, 80%). The remaining 2 patients (%20) with concomitant hippocampal sclerosis required microsurgical resection of the seizure foci due to medically resistant seizures. Discussion. Ulegyria is easily recognized with its unique magnetic resonance imaging characteristics and clinical presentation in the majority of cases. It is highly associated with either medically resistant or medically controllable epileptic seizures. The treatment strategy depends on the age at onset and extends of the lesion that has a significant impact on the severity of the clinical picture.

Epilepsy surgery in stroke-related epilepsy

PURPOSE

To provide a descriptive analysis on the presurgical evaluation and surgical management of a cohort of patients with stroke related epilepsy (SRE).

METHODS

We retrospectively examined the clinical characteristics, results of non-invasive and invasive presurgical evaluation, surgical management and outcome of consecutive patients with drug-resistant SRE in our institution from January 1, 2013 to January 1, 2020.

RESULTS

Twenty-one of 420 patients (5%) who underwent intracranial EEG (iEEG), resective epilepsy surgery and/or vagus nerve stimulation (VNS) placement, had SRE. Of 13 patients who had iEEG, the ictal onset (IO) was exclusively within the stroke lesion in only one patient. In five patients the IO was extra-lesional and in the remaining seven patients it included the stroke lesion as well as extra-lesional structures. The IO included the mesial temporal region in 11 of the 13 patients (85%). The posterior margin of the stroke lesion was always involved. Five patients underwent surgery without iEEG. In total, 10 patients underwent resective surgery, four VNS placement and two had both corpus callosotomy and VNS placement. Of the patients who had resective surgery, nine were Engel I or II at last follow up.

CONCLUSION

We found that seizures in patients with drug resistant SRE were more frequently originated in the mesial temporal region than in the stroke lesion itself. Despite the complex epileptic network underlying drug-resistant SRE, a thorough presurgical assessment and adequate use of surgical options can lead to excellent surgical outcomes.

Is intracranial electroencephalography useful for planning resective surgery in intractable epilepsy with ulegyria?

OBJECTIVE

Intractable epilepsy patients with ulegyria could be candidates for resective surgery. Complete resection of ulegyria in the epileptogenic hemisphere is associated with favorable seizure outcome, although the risk of postoperative functional deficits is higher. The authors evaluated the extent of resection and postsurgical outcomes in epilepsy patients with ulegyria who underwent intracranial electroencephalography (iEEG) monitoring prior to resection to clarify the efficacy of iEEG-guided partial resection of ulegyria.

METHODS

Ten consecutive epilepsy patients with ulegyria (7 males and 3 females, age range at surgery 7-34 years) underwent iEEG prior to resective surgery between 2011 and 2017 with a minimum follow-up of 12 months (range 12-72 months). The diagnosis of ulegyria was based on the typical pattern of cortical atrophy especially at the bottom of the sulcus on MRI. An iEEG study was indicated after comprehensive preoperative evaluations, including high-field MRI, long-term video-EEG, magnetoencephalography, and FDG-PET. The resection planning was based on iEEG analysis. Total lesionectomy was not always performed, as preservation of cortical function was prioritized.

RESULTS

Ulegyria was seen in the occipital and/or parietal lobe in 9 patients and bilaterally in 5 patients. Ictal EEG onset involved the temporal neocortex in 6 patients. Intracranial electrodes were implanted unilaterally in all except 1 patient with bilateral lesions. The extent of MRI lesion was covered by the electrodes. Seizure onset zones (SOZs) and irritative zones (IZs) were identified in all patients. SOZs and IZs were completely resected in 8 patients but were only partially removed in the remaining 2 patients because the eloquent cortices and the epileptogenic zones overlapped. Ulegyria of the epileptogenic side was totally resected in 1 patient. Seizure freedom was achieved in 4 patients, including 3 after partial lesionectomy. Extended resection of the temporal neocortex was performed in 4 patients, although postoperative seizure freedom was achieved only in 1 of these patients. Visual field deficit was seen in 4 patients. Three of 5 patients with bilateral lesions achieved seizure freedom after unilateral resective surgery.

CONCLUSIONS

Intracranial EEG-guided partial lesionectomy provides a reasonable chance of postoperative seizure freedom with a lower risk of functional deficits. Patients with bilateral ulegyria should not be excluded from consideration as surgical candidates.

Clinical neurophysiology of stroke

Stroke constitutes the third most common cause of death and the leading cause of acquired neurologic handicap. During ischemic stroke, very early after the onset of the focal perfusion deficit, excitotoxicity triggers a number of events that can further contribute to tissue death. Such events include peri-infarct depolarizations and spreading depolarizations (SDs) within the ischemic penumbra. SDs spread slowly through continuous gray matter at a typical velocity of 2-5mm/min. SDs exacerbate neuronal injury through prolonged ionic breakdown and SD-related hypoperfusion (spreading ischemia). Scalp EEG alone is not yet sufficient to reliably diagnose SDs. Hyperexcitability occurs in parallel, both in the acute and chronic phases of stroke. Stroke is a common cause of new-onset epileptic seizures after middle age and is the leading cause of symptomatic epilepsy in adults. The last part of this chapter is dedicated to noninvasive neurophysiologic techniques that can be used to promote stroke rehabilitation. These techniques mainly include repetitive transcranial magnetic stimulation and tDCS. These approaches are based on the concept of interhemispheric rivalry and aim at modulating the imbalance of cortical activities between both hemispheres resulting from stroke.

Evaluation of different ulegyria patterns with magnetic resonance imaging

Ulegyria is a parenchymal sequel of hypoxic ischemic encephalopathy causing mushroom-like appearance in gyri. Aim of the present study was to evaluate clinico-radiological findings of patients who applied with different clinical features, predominantly epilepsy, and who were found to have ulegyria formations in MRI examinations. The study included a total of 30 patients (12 female and 18 male) who applied with different types of seizures in February 2011-August 2016 period and had brain MRI examinations using 1.5T MRI scanner. Mushroom-shaped gyri accompanied by gliosis and atrophy in subcortical white matter were considered ulegyria. Locations, MRI features and accompanying pathologies of ulegyria formations were studied. Age of the patients ranged from 4 to 62 (mean 26.0 ± 13.8). Both cerebral lobes were involved in 18 patients. In terms of involved area, symmetrical or asymmetrical involvements were observed in occipital lobes in 26 patients, parietal lobes in 19, frontal lobes in 12 and temporal lobes in 4. The most common involvement type was bilateral occipital and bilateral parieto-occipital lobe involvements with five patients each. Lesions were symmetrical in 11 patients. Six patients had cingulate gyrus atrophy. Nineteen patients had different levels of symmetrical or asymmetrical ventricular dilatation. Cranial asymmetry was observed in six patients with unilateral involvement and in one patient with generalized involvement. Although ulegyria predominantly involves parasagittal watershed areas in MRI examinations of patients applying with epilepsy, clinical manifestations and appearance of lesions could vary depending upon the size of involved area and level of injury.

Diagnostic utility of invasive EEG for epilepsy surgery: Indications, modalities, and techniques

Many patients with medically refractory epilepsy now undergo successful surgery based on noninvasive diagnostic information, but intracranial electroencephalography (IEEG) continues to be used as increasingly complex cases are considered surgical candidates. The indications for IEEG and the modalities employed vary across epilepsy surgical centers; each modality has its advantages and limitations. IEEG can be performed in the same intraoperative setting, that is, intraoperative electrocorticography, or through an independent implantation procedure with chronic extraoperative recordings; the latter are not only resource intensive but also carry risk. A lack of understanding of IEEG limitations predisposes to data misinterpretation that can lead to denying surgery when indicated or, worse yet, incorrect resection with adverse outcomes. Given the lack of class 1 or 2 evidence on IEEG, a consensus-based expert recommendation on the diagnostic utility of IEEG is presented, with emphasis on the application of various modalities in specific substrates or locations, taking into account their relative efficacy, safety, ease, and incremental cost-benefit. These recommendations aim to curtail outlying indications that risk the over- or underutilization of IEEG, while retaining substantial flexibility in keeping with most standard practices at epilepsy centers and addressing some of the needs of resource-poor regions around the world.