Malformations of cortical development: New surgical advances

Abstract

Epilepsy related to malformations of cortical development is frequently drug resistant or requires heavy medication, therefore surgery is key in their management. The role of stereotactic surgery has recently changed the diagnosis and treatment of focal cortical dysplasias (FCD), hypothalamic hamartomas (HH) and periventricular nodular heterotopias (PNH). In HH, radiosurgery using Gammaknife ® leads to 60 % of seizure control and is associated with excellent neuropsychological results without significant endocrine function impairment. The seizure control rate is even higher (more than 80 %) with monopolar multiple stereotactic thermocoagulations and Laser interstitial Thermal Therapy (LiTT). While the first technique is associated with a 2 % complications rate (but with excellent neuropsychological outcomes), the latest has up to 22 % side effects in some series. All three of these techniques have encouraging results, but controlled studies are still lacking to provide evidence-based new therapeutic algorithms. With regard to the PNH, surgical management has long been limited by the depth of the lesions and their close anatomical relations with the functional brain connectome. Stereotactic approaches required to perform a SEEG, to locate the part of the PNH responsible for the seizure onset, are later followed by a stereotactic lesioning procedure, therefore doubling the bleeding risk. That is why SEEG-guided radiofrequency-thermocoagulation (SEEG guided-RF-TC), which makes it possible to perform these two steps in a single procedure, was considered as a promising option. A recent meta-analysis confirmed this intuition and reported 38 % of seizure-free patients and 81 % of responders with only 0.3 % of complications, making this approach the first treatment line, followed by LiTT. Among the multiple advances in the FCD identification by non-invasive investigations, a new modality of per-operative diagnostic procedure, the three-dimensional electrocorticography

Surgical treatment of hypothalamic hamartomas

“…These results, when compared to equivalent studies related to surgical approaches 46 , indicate comparable or better results for radiosurgery, with a reduced rate of adverse effects 7,44 . Nevertheless, no comparison has been conducted with the endoscopic or stereotactic approach recently developed to overcome the open microsurgery limits.…”

“…Since the first description of a surgical treatment of an hypothalamic hamartoma in 1969 53 , the discussion has been dominated by the opposition between two micro-neurosurgical techniques: one aiming to reach the lesion from below (pterional and transtemporal-transchoroidal approaches), versus another aiming to reach the lesion from above (transcallosal and transventricular) 7,46,64 . Whatever the technique (Figure 2), the possibility of complete removal is correlated to the importance of the attachment to the mamillary bodies (neuropsychological risk) and to the tuber cinereum (endocrine risk) 62 .…”

“…Although the reported seizure control is higher than 90% in some series, the morbidity is important, including transient third nerve palsy, thalamo-capsular infarcts, postoperative central diabetes insipidus, and hyperphagia. 47 These limits lead to the development of alternative surgical approaches reaching the lesion from above 7,46,64 . This technique was associated with good resection results for intraventricular lesions (Delalande Type II and IV) but remained limited in case of cisternal expension of the lesion.…”

Optimization and high‐density array of stereoelectroencephalography‐guided radiofrequency thermocoagulation for the treatment of pediatric tuberous sclerosis complex with epilepsy

“…The initial intention was to alleviate seizures by generating disorganization in the epileptogenic zone using a radiofrequency generator connected to the electrode contacts 10 . This minimally invasive approach has been considerably applied in recent years due to its ability to perform well‐circumscribed lesion ablation, as well as stimulation and recording simultaneously 10‐12 . Up to now, SEEG‐guided RF‐TC has been indicated for patients with small, deeply seeded and well‐demarcated epileptogenic lesions such as periventricular nodular heterotopias, 13 hypothalamic hematomas, 14 and malformations of cortical development 15 .…”

Multiple Stereoelectroencephalography-Guided Radiofrequency Thermocoagulations for Polymicrogyria With Startle Seizures: A Case Report

“…Stereoelectroencephalography (SEEG)-guided radiofrequency thermocoagulation (RF-TC) is a safe stereotactic invasive treatment of drug-resistant epilepsy. A recent study found that RF-TC had higher seizure control rate related to three well-limited malformations: hypothalamic hamartomas, periventricular nodular heterotopias, and focal cortical dysplasias (3). In a meta-analysis of 296 patients, four etiologies were assessed for efficacy, and the greatest efficacy was observed in patients with periventricular nodular heterotopia (4).…”