Quantitative analysis of surgical exposure and maneuverability associated with the endoscope and the microscope in the retrosigmoid and various posterior petrosectomy approaches to the petroclival region using computer tomograpy-based frameless stereotaxy. A cadaveric study

Object

Most of the approaches used to expose the petro-clival region require a certain degree of temporal bone resection with its associated approach morbidity such as potential hearing and facial nerve compromise.Endoscopes are becoming more and more popular in neurosurgical practice. To gain insight into the benefits of using endoscopy to operate on the petro-clival region, we evaluated and compared the exposure and maneuverability obtained employing the endoscope and the microscope in retrosigmoid and pre-sigmoid approaches by using quantitative analysis based on frameless stereotaxy.

Methods

We evaluated the retrosigmoid (RS), retrolabyrinthine (RL), translabyrinthine (TL), and transcochlear (TC) approaches. Each approach was performed 4 times for a total of 16 approaches. We used a navigation system for intraoperative navigation. Each approach was evaluated vis-a-vis the area of the petro-clival/brainstem region exposed and the afforded maneuverability, both using a rigid endoscope or an operating microscope.

Results

The TC approach exposed the largest area at the brainstem compared to all other three approaches both in microscopic and endoscopic modes and there was no significant difference between the 2 modes (P = 0.42). In the RS approach use of the 30° angled endoscope increased significantly the exposure compared to the operating microscope (respectively 460 ± 49.7 mm² vs 235 ± 25 mm²; P = 0.002). On the other hand, maneuverability was significantly decreased with the endoscope compared to the microscope in all the approaches evaluated (P = 0.006).

Conclusions

Integration of the endoscope into conventional petrosectomy approaches could significantly reduce the amount of temporal bone drilling for adequate visualization of the petro-clival region. However maneuverability as assessed by our model was better with the microscope than with the endoscope.     

Endoscope-assisted supraorbital approach to the retroinfundibular area: a cadaveric study

The purpose of this study is to investigate and evaluate the exposure and maneuverability of this areas provided by an endoscope-assisted supraorbital approach and to compare that to a microscopic supraorbital approach. We exposed microscopically the optico-carotid and the infrachiasmatic windows after a supraorbital craniotomy executed using an eyebrow incision. We then proceeded to explore the retroinfundibular area using these two windows either using the microscope alone or using the endoscope–microscope combination where the microscope was used to (1) guide instrument and endoscope insertion into the surgical field, and (2) explore (with microscopic 3-d vision) subsegments of the endoscopic field of view. We compared the exposure and surgical maneuverability of the approach utilizing the microscopic mode alone with the endoscope-assisted mode. We evaluated the exposure and the surgical maneuverability of key anatomical structures of the retroinfundibular area. The structures evaluated included the diaphragma sellae, the dorsum sellae, the posterior clinoid process, the pituitary stalk, the mammillary bodies, the tuber cinereum, the oculomotor nerves, the basal pons, the upper trunk of the basilar artery, the superior cerebellar arteries, the posterior cerebral arteries, the posterior communicating arteries and the basilar bifurcation. The exposure and the surgical maneuverability were significantly higher in the endoscope-assisted mode (P?<?0.0001). Based on our study, the endoscope-assisted supraorbital retroinfundibular approach is associated with larger exposure and maneuverability than the pure microscopic approach. Further clinical information is required to verify the results of this study.     

CyberKnife stereotactic radiosurgical rhizotomy for refractory trigeminal neuralgia

Stereotactic radiosurgery (SRS) has been established as an option for the treatment of trigeminal neuralgia (TN). Here, we report our experience of CyberKnife®-based (Accuray, Sunnyvale, CA, USA) stereotactic rhizotomy on medically refractory patients to determine its clinical effectiveness. Between January 2007 and December 2009, 14 selected patients underwent SRS for TN at our CyberKnife Center. Patients were evaluated for pain relief using a visual analog scale (VAS) score, time to reach pain relief (latency), duration of pain control, decrease of pain medication, occurrence of new dysesthesia, and side effects at the 3-month, 6-month, 1-year and 2-year follow-up. A literature analysis revealed that compared with other SRS systems, which can provide a high rate of pain control, CyberKnife® stereotactic rhizotomy yielded an earlier onset of pain relief in our cohort.     

Intradural endoscope-assisted anterior clinoidectomy: A cadaveric study

Objective

The anterior clinoid process (ACP) is critically related to the clinoidal portion of the internal carotid artery (ICA). The deep location of the ACP makes treatment of vascular and neoplastic lesions related to the ACP challenging. Removal of the ACP is advocated to facilitate treatment of such lesions. However injury to the clinoidal ICA remains a potential and dreadful complication of ACP removal. The aim of this study was to demonstrate an endoscopic assisted technique to perform intradural removal of the ACP via a pterional approach with continuous visualization of the clinoidal ICA.

Methods

Sixteen bilateral pterional dissections were performed in 8 glutaraldehyde embalmed, colored silicone injected, adult cadaveric heads. Using a standard pterional approach, we performed drilling of the ACP in 2 stages. Stage 1 consisted of extradural microscopic removal of the sphenoid ridge so as to gain access to the origin of the ACP. Stage 2, the endoscopic stage, consisted of intradural endoscopic removal of the ACP and mobilization of the clinoidal segment of the ICA. We used 2.7 mm, 0° and 30° angled endoscopes.

Results

In all the specimens we were able to remove the ACP while at the same time continuously visualizing the clinoidal ICA. The exposure of the clinoidal ICA and of adjoining neuro-vascular structures including the intracranial optic nerve was excellent and was accomplished with minimal frontal lobe retraction. Mobilization of the clinoidal ICA led to unhindered exposure of the parasellar region.

Conclusions

Endoscopic assisted ACP removal with continuous ICA visualization was feasible in our model. Continuous visualization of the clinoidal ICA should theoretically decrease the risk of inadvertent ICA injuries. Clinical studies to validate this laboratory study are necessary.