Integration of multimodality imaging and surgical navigation in the management of patients with refractory epilepsy. A pilot study using a new minimally invasive reference and head-fixation system

Optimization of Curvilinear Needle Trajectories for Transforamenal Hippocampotomy

BACKGROUND

The recent development of MRI-guided laser-induced thermal therapy (LITT) offers a minimally invasive alternative to craniotomies performed for tumor resection or for amygdalohippocampectomy to control seizure disorders. Current LITT therapies rely on linear stereotactic trajectories that mandate twist-drill entry into the skull and potentially long approaches traversing healthy brain. The use of robotically-driven, telescoping, curved needles has the potential to reduce procedure invasiveness by tailoring trajectories to the curved shape of the ablated structure and by enabling access through natural orifices.

OBJECTIVE

To investigate the feasibility of using a concentric tube robot to access the hippocampus through the foramen ovale to deliver thermal therapy and thereby provide a percutaneous treatment for epilepsy without drilling the skull.

METHODS

The skull and both hippocampi were segmented from dual CT/MR image volumes for 10 patients. For each of the 20 hippocampi, a concentric tube robot was designed and optimized to traverse a trajectory from the foramen ovale to and through the hippocampus from head to tail.

RESULTS

Across all 20 cases, the mean distances (error) between hippocampus medial axis and backbone of the needle were 0.55 mm, 1.11 mm, and 1.66 mm for best, mean, and worst case, respectively.

CONCLUSION

These curvilinear trajectories would provide accurate transforamenal delivery of an ablation probe to typical hippocampus volumes. This strategy has the potential to both decrease the invasiveness of the procedure and increase the completeness of hippocampal ablation.

Applications of blood-oxygen-level-dependent functional magnetic resonance imaging and diffusion tensor imaging in epilepsy

The lifetime prevalence of epilepsy ranges from 2.7 to 12.4 per 1000 in Western countries. Around 30% of patients with epilepsy remain refractory to antiepileptic drugs and continue to have seizures. Noninvasive imaging techniques such as functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) have helped to better understand mechanisms of seizure generation and propagation, and to localize epileptic, eloquent, and cognitive networks. In this review, the clinical applications of fMRI and DTI are discussed, for mapping cognitive and epileptic networks and organization of white matter tracts in individuals with epilepsy.

Intraoperative coregistration of magnetic resonance imaging, positron emission tomography, and electrocorticographic data for neocortical lesional epilepsies may improve the localization of the epileptogenic focus: a pilot study

OBJECTIVE

To objectively mark out abnormal areas of magnetic resonance imaging (MRI), positron emission tomography (PET), and electrocorticography (ECoG) using neuronavigation so as to 1) enhance the accuracy of margins of the epileptogenic zone and 2) understand the relationships of all the three modalities with each other.

METHODS

A prospective study was conducted of 37 patients with intractable epilepsy due to lesional, neocortical pathologies from noneloquent areas. Prior to surgery, fusion and transfer of MRI and PET images onto a neuronavigation system was performed. At surgery, this was correlated to intraoperative ECoG using the electrode as referential points. An objective score was created for every electrode point that was correlated with MRI and PET abnormality at the point. The extent of surgical resection was mapped out using these data.

RESULTS

From a total of the data recorded from 1280 electrode points, 23.5% were located over the lesion. In addition, over the lesions, 93% of PET and 66% of ECoG points were abnormal. Over the perilesional areas, 43% of PET and 45% of ECoG points were abnormal. Using these data for surgery, both lesional and perileisonal areas were resected; 33/37 patients had good outcome (25 Engel I, 8 Engel II) (mean follow-up: 23.6 ± 3.2 months; range 18-31 months).

CONCLUSION

Multimodal imaging and ECoG using this method seems to provide a better objective localization of the epileptogenic foci.

Operation-microscope-mounted touch display tablet computer for intraoperative imaging visualization

OBJECTIVE

The authors have developed a novel sterile draped touch display solution for convenient intraoperative access to imaging data. This study describes the technology and clinical experience of the system.

METHODS

We developed a flexible, mounted touch display solution (Apple iPad) that allows fixation of the display on the operation microscope and fine adjustments during surgery when the microscope is moved. We compared this setup with a conventional wall-mounted flat-panel and a mobile display stand in illustrative cases of vestibular schwannoma.

RESULTS

The surgeon was able to employ the system without the need to leave the operation field or the need for external assistance while referring to imaging data. Commanding through imaging data with sterile gloves on the touch display was more convenient, more precise, and faster compared with other modalities.

CONCLUSION

The operation-microscope-mounted touch display provides useful assistance for intraoperative imaging visualization in neurosurgical procedures.