Retrolabyrinthine presigmoid transpetrosal approach for selective subtemporal amygdalohippocampectomy

Current state of the art of traditional and minimal invasive epilepsy surgery approaches

Introduction

Open resective surgery remains the main treatment modality for refractory epilepsy, but is often considered a last resort option due to its invasiveness.

Research question

This manuscript aims to provide an overview on traditional as well as minimally invasive surgical approaches in modern state of the art epilepsy surgery.

Materials and methods

This narrative review addresses both historical and contemporary as well as minimal invasive surgical approaches in epilepsy surgery. Peer-reviewed published articles were retrieved from PubMed and Scopus. Only articles written in English were considered for this work. A range of traditional and minimally invasive surgical approaches in epilepsy surgery were examined, and their respective advantages and disadvantages have been summarized.

Results

The following approaches and techniques are discussed: minimally invasive diagnostics in epilepsy surgery, anterior temporal lobectomy, functional temporal lobectomy, selective amygdalohippocampectomy through a transsylvian, transcortical, or subtemporal approach, insulo-opercular corticectomies compared to laser interstitial thermal therapy, radiofrequency thermocoagulation, stereotactic radiosurgery, neuromodulation, high intensity focused ultrasound, and disconnection surgery including callosotomy, hemispherotomy, and subpial transections.

Discussion and conclusion

Understanding the benefits and disadvantages of different surgical approaches and strategies in traditional and minimal invasive epilepsy surgery might improve the surgical decision tree, as not all procedures are appropriate for all patients.

The basal turning point of optic radiation (bTPOR): The location of optic radiation in the cerebral basal surface

BACKGROUNDS

Optic radiation protection is crucial in the basal temporal approach to the mesial temporal lobe. Clear description of the optic radiation in the basal brain surface is lacking. Our aim is to describe the anatomy of optic radiation in the basal cerebral surface and define safety zone of basal temporal approach avoiding of optic radiation injury.

METHODS

Five brain specimens (10 hemispheres) were dissected using Klingler method to observe the course of the optic radiation. Diffusion tensor imaging data of 25 volunteers were used to verify the fiber dissection results. The relationship of the optic radiation to nearby structures were illustrated and measured.

RESULTS

The optic radiation bends from the lateral wall of the lateral ventricle to its bottom at a basal turning point of optic radiation (bTPOR). The bTPOR is at the plane crossing the center point of the splenium of corpus callosum. MRI measurements showed no significant difference in the distance from the center of the splenium of corpus callosum and the bTPOR to the occipital pole (59.46 ± 4.338 mm vs 59.54 ± 3.805 mm, p = 0.95). Anterior to bTPOR, no optic radiation fibers were found at the basal brain surface.

CONCLUSIONS

The bTPOR was found as a landmark of the optic radiation in the cerebral basal surface. With neuronavigation, the splenium of corpus callosum can be a landmark of the bTPOR. By approaching mesial temporal lesions using the basal temporal approach anterior to bTPOR, optic radiation injury can be prevented.

Neuropsychological outcomes of subtemporal selective amygdalohippocampectomy via a small craniotomy

OBJECT

The objectives of this study were to describe a novel minimal-access subtemporal approach for selective resection of the amygdala and hippocampus in patients with medically refractory mesial temporal lobe epilepsy (MTLE) due to hippocampal sclerosis, and to analyze the related outcomes.

METHODS

The authors analyzed data from all cases involving patients with unilateral MTLE due to hippocampal sclerosis who were treated with selective amygdalohippocampectomy via the posterior subtemporal approach through a relatively small craniotomy, without a neuronavigation system, at their institution during the period from September 2010 to September 2012. Data were obtained on baseline characteristics, preoperative evaluations of unilateral mesial temporal sclerosis, surgical complications, and Engel class seizure outcomes. All patients underwent memory testing, IQ testing, and language testing.

RESULTS

The mean duration of follow-up was 33.6 months (range 24–48 months). There were no deaths and no cases of significant postoperative morbidity. One patient had a mild complication. At 2-year follow-up, 19 patients were seizure free (Engel Class I outcome). Verbal memory scores obtained at 3 months and at 2 years after surgery were significantly lower than preoperative scores for patients who underwent surgery on the left side of the brain (p < 0.05). Pictorial memory scores were higher following surgery compared with before surgery regardless of whether patients underwent left- or right-sided brain surgery. There was also improvement in performance IQ and total IQ following surgery in both groups. For patients who underwent right-sided brain surgery, verbal comprehension and semantic fluency testing scores were significantly higher at both 3 months and 2 years after surgery than before surgery. For patients who underwent left-sided brain surgery, scores on all language tests were significantly lower at 3 months after surgery than before surgery. Verbal comprehension testing scores returned to the preoperative level at 2 years after surgery.

CONCLUSIONS

The posterior subtemporal approach through a relatively small craniotomy allows adequate exposure and safe resection of mesial temporal structures and effectively reduces medically intractable MTLE. It preserves IQ but may have a detrimental effect on verbal memory and language ability.

Minimally Invasive Transpalpebral Endoscopic-Assisted Amygdalohippocampectomy

BACKGROUND: Although anterior temporal lobectomy may be a definitive surgical treatment for epileptic patients with mesial temporal sclerosis, it often results in verbal, visual, and cognitive dysfunction. Studies have consistently reported the advantages of selective procedures compared with a standard anterior temporal lobectomy, mainly in terms of neuropsychological outcomes.

OBJECTIVE: To describe a new technique to perform a selective amygdalohippocampectomy (SAH) through a transpalpebral approach with endoscopic assistance.

METHODS: A mini fronto-orbitozygomatic craniotomy through an eyelid incision was performed in 8 patients. Both a microscope and neuroendoscope were used in the surgeries. An anterior SAH was performed in 5 patients who had the diagnosis of temporal lobe epilepsy with mesial temporal sclerosis. One patient had a mesial temporal lesion suggesting a ganglioglioma. Two patients presented mesial temporal cavernomas with seizures originating from the temporal lobe.

RESULTS: The anterior approach allowed removal of the amygdala and hippocampus. The image-guided system and postoperative evaluation confirmed that the amygdala may be accessed and completely removed through this route. The hippocampus was partially resected. All patients have discontinued medication with no more epileptic seizures. The patients with cavernomas and ganglioglioma also had their lesions completely removed. One-year follow-up has shown no visible scars.

CONCLUSION: The anterior route for SAH is a rational and direct approach to the mesial temporal lobe. Anterior SAH is a safe, less invasive procedure that provides early identification of critical vascular and neural structures in the basal cisterns. The transpalpebral approach provides a satisfactory cosmetic outcome.

Minimally invasive surgical approaches for temporal lobe epilepsy

Surgery can be a highly effective treatment for medically refractory temporal lobe epilepsy (TLE). The emergence of minimally invasive resective and nonresective treatment options has led to interest in epilepsy surgery among patients and providers. Nevertheless, not all procedures are appropriate for all patients, and it is critical to consider seizure outcomes with each of these approaches, as seizure freedom is the greatest predictor of patient quality of life. Standard anterior temporal lobectomy (ATL) remains the gold standard in the treatment of TLE, with seizure freedom resulting in 60-80% of patients. It is currently the only resective epilepsy surgery supported by randomized controlled trials and offers the best protection against lateral temporal seizure onset. Selective amygdalohippocampectomy techniques preserve the lateral cortex and temporal stem to varying degrees and can result in favorable rates of seizure freedom but the risk of recurrent seizures appears slightly greater than with ATL, and it is not clear whether neuropsychological outcomes are improved with selective approaches. Stereotactic radiosurgery presents an opportunity to avoid surgery altogether, with seizure outcomes now under investigation. Stereotactic laser thermo-ablation allows destruction of the mesial temporal structures with low complication rates and minimal recovery time, and outcomes are also under study. Finally, while neuromodulatory devices such as responsive neurostimulation, vagus nerve stimulation, and deep brain stimulation have a role in the treatment of certain patients, these remain palliative procedures for those who are not candidates for resection or ablation, as complete seizure freedom rates are low. Further development and investigation of both established and novel strategies for the surgical treatment of TLE will be critical moving forward, given the significant burden of this disease.

Evaluation of Posterior Hippocampal Epileptogenicity During Epilepsy Surgery For Temporal Lobe Cavernoma by the Occipital Approach

BACKGROUND

Cavernomas frequently are associated with intractable epilepsy. When cavernomas located in the temporal lobe are associated with intractable epilepsy, the hippocampus also may have an epileptic focus. The objective in the present study was to clarify the importance of evaluation of the posterior hippocampal epileptogenicity during epilepsy surgery for posteromedial temporal lobe cavernoma.

CASE DESCRIPTIONS

In this study, we describe 2 rare cases of medically intractable epilepsy in patients with posteromedial temporal lobe cavernomas who underwent surgery via the occipital approach. Using longitudinal insertion of depth electrodes into the hippocampus, we evaluated epileptogenicity in both patients from the cavernoma cavity and its surrounding hemosiderin, as well as from the posterior hippocampus near the cavernoma. We show that the transoccipital approach to the posteromedial temporal lobe is compatible with depth electrode insertion and subdural electrode placement on the temporal lobe, enabling an accurate evaluation of potential epileptogenic zones in the posterior part of the hippocampus. Both patients did not experience any seizures and had no postoperative neurologic deficits, and their cognitive functions were intact.

CONCLUSIONS

The transoccipital approach enables the optimization of the extent of posterior hippocampectomy while avoiding unnecessary resection for seizure control. We suggest resecting the posterior part of the hippocampus in addition to the cavernoma and surrounding areas in patients with medically refractory epilepsy due to a posteromedial temporal cavernoma. Tailored systematic resection guided by intraoperative electrocorticography and electroencephalography with a depth electrode was important and necessary in the present cases.

Surgical techniques for the treatment of temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is the most common form of medically intractable epilepsy. Advances in electrophysiology and neuroimaging have led to a more precise localization of the epileptogenic zone within the temporal lobe. Resective surgery is the most effective treatment for TLE. Despite the variability in surgical techniques and in the extent of resection, the overall outcomes of different TLE surgeries are similar. Here, we review different surgical interventions for the management of TLE.

Anterior Selective Amygdalohippocampectomy: Technical Description and Microsurgical Anatomy

Objective:

We introduce a technique for performing a selective amygdalohippocampectomy (AH) through a minisupraorbital approach.

Methods:

A minisupraorbital craniotomy and an anterior selective AH were performed in 8 cadaver heads (16 sides). The anatomic specimens were analyzed, and the extent of resection of the hippocampus and amygdala was evaluated. Surgically relevant measurements were performed using anatomic specimens. An image-guided system was used to document the extent of the anterior AH. Laboratory data were used to support the clinical application of the technique.

Results:

The anterior route allowed removal of the amygdala and hippocampus, as confirmed by anatomic assessment. The image-guided system and anatomic evaluation confirmed that the amygdala and hippocampus can be accessed and removed through this route. The mean distance between the anterior aspect of the uncus and the tip of the temporal horn was 17.0 ± 4.6 mm; the mean distance from the head of the hippocampus to the posterior border of the cerebral peduncles was 26.0 ± 3.2 mm. Clinical application resulted in satisfactory removal of the amygdala and hippocampus.

Conclusion:

The anterior route for selective AH is a logical and straightforward approach to the mesial temporal lobe. Compared with other variations, it is less invasive and destructive, especially in terms of the fibers of the optic pathway, temporal stem, and lateral temporal neocortex.

Small petrosal approach to the middle portion of the mediobasal temporal region: technical case report

BACKGROUND

The mediobasal temporal region has been divided into three portions: anterior, middle, and posterior. Surgical access, especially to the middle portion, presents a formidable challenge to neurosurgeons, and much controversy still exists regarding the selection of the surgical approach to this region.

CASE REPORT

We used the small petrosal approach to the middle portion of the mediobasal temporal region in a patient with intractable seizures caused by a cavernous angioma in this region. Using this approach, we selectively removed the lesion without postoperative deficits.

CONCLUSIONS

The small petrosal approach was found to be useful and safe as an alternative technique for selective removal of the lesion in the middle portion of the mediobasal temporal region.

Supracerebellar transtentorial approach to posterior temporomedial structures

The supracerebellar transtentorial (SCTT) approach, a modification of the infratentorial supracerebellar approach, facilitates simple and minimally invasive access to posterior temporomedial structures without requiring retraction of the temporal or occipital lobe. The SCTT approach was used in 16 patients over a 3-year period. Eleven patients harbored tumors confined to, or located mainly within, the posterior hippocampal formation, three patients harbored aneurysms (one ruptured posterior cerebral artery [PCA] aneurysm at the P2-P3 junction, one ruptured giant PCA [P2] aneurysm, and one giant basilar artery-superior cerebellar artery aneurysm), one patient had juvenile-type moyamoya disease, and one patient suffered from medically intractable epilepsy. In these patients, the SCTT approach enabled tumor removal, aneurysm clipping, and vascular bypass procedures. The authors' experience suggests that this approach can be used routinely in treating lesions in the posterior temporomedial region.