A combined intradural presigmoid-transtransversarium-transcondylar approach to the whole clivus and anterior craniospinal region: anatomic study

Quantitative Comparative Analysis of the Endoscope-Assisted Expanded Retrosigmoid Approach and the Far-Lateral Approach to the Inframeatal Area: An Anatomic Study With Surgical Implications

BACKGROUND

The inframeatal area (IFMA) is a complex anatomic region of the posterior cranial fossa. Given its deep-seated location, tumors involving the IFMA represent a surgical challenge.

OBJECTIVE

To objectively compare the endoscope-assisted expanded retrosigmoid approach (ERSA) and the far-lateral supracondylar transtubercular approach (FLTA) to address the IFMA.

METHODS

Anatomic dissections were performed on 5 cadaveric heads (10 sides). The ERSAs were performed before and after the FLTAs. The surgical exposure, surgical freedom, and angles of attack to the IFMA were measured and compared for each approach. In addition, 2 illustrative clinical cases are reported.

RESULTS

Compared with FLTA, ERSA yielded a nonsignificantly smaller mean area of exposure, whereas FLTA provided a significantly larger mean area of surgical freedom, compared with ERSA ( P = .002). The mean horizontal and vertical angles of attack were significantly different between the approaches. In the vertical plane, FLTA yielded the broadest angle of attack at the root entry zone of the lower cranial nerves (CN; P < .004), whereas ERSA did so at the dural entry zone of CN VII/VIII ( P = .006). In the horizontal plane, FLTA achieved its broadest angle of attack at the root entry zone of the lower CNs ( P = 1.83) while ERSA at the dural entry zone of CN VII/VIII ( P = .37).

CONCLUSION

ERSA and FLTA granted a comparable exposure with the IFMA. Although FLTA may afford a larger area of surgical freedom, ERSA may be a suitable alternative to approach the IFMA, particularly to reach the most medial and superior aspects of this region. Conversely, FLTA may facilitate access to more caudally targets.

[Partial transcondylar approach - analysis of the surgical technique in cadaver simulation]

The aim of the study was to present consecutive stages of the partial transcondylar approach. Six simulations of the partial transcondylar approach were performed on non-fixed human cadavers without any known pathologies in the head and neck. The consecutive stages of the procedure were documented with photographs and diagrams. The starting point for the partial transcondylar approach is a posterior repositioning of the suboccipital segment of the vertebral artery. The approach is achieved by partial removal of the occipital condyle and lateral mass of the atlas as well as by suboccipital craniectomy. Elevation of the cerebellar hemisphere presents an important supplement of the approach. The partial transcondylar approach is a reproducible technique, which provides surgical penetration of the anterior part of the cranio-cervical junction and related regions. This approach is particularly useful in the treatment of intradural tumours localized ventrally to the medulla.

Anatomo-radiological evaluation of lateral approaches to the skull base

Our objective is to correlate the anatomical exposure provided by complex skull base approaches to the lateral skull base with their CT and MRI scans counterparts and to introduce a modular concept emphasizing the derivation of complex skull base approaches from simpler ones.We executed 10 lateral approaches to the skull base in 20 embalmed cadaveric heads (40 sides). Each approach was executed a minimum of three times on each specimen. These approaches were the pterional and its modifications, the subtemporal and its modifications, and the suboccipital and its modifications. We correlated the approaches and the areas of the skull base exposed by scanning the surgical cavity filled with material imageable by CT and MRI and throughly surveying the operative field.Visualization of the area of the skull base exposed was excellent using our CT-MRI imageable cadaveric preparation. The topographic areas of the skull base exposed correlated well with their radiological counterparts.The areas of the skull base exposed by each of the complex surgical approaches to the skull base were clearly delineated by using our anatomo-radiological correlation. Complex approaches to the skull base are formed by simple neurosurgical approaches (building blocks) to which different modules are added.

Combined transpetrosal-subtemporal craniotomy for clival tumors with extension into the posterior fossa

Tumors of the clivus, such as chordoma and chondrosarcoma, are generally amenable to an anterior surgical approach. However, approaches that traverse the pharynx or paranasal sinuses do not adequately expose tumor posterolateral to the horizontal course of the intrapetrous carotid artery. In addition, when tumor extends into the posterior fossa, supplemental exposure of neurovascular structures is necessary. A combination petrosectomy and subtemporal craniotomy can provide simultaneous access to the entire clivus as well as the lateral aspect of the midbrain, pons, and upper medulla. The extent of petrosectomy performed depends on a number of factors including status of hearing, facial nerve function, and degree of brainstem compression. In our experience with three patients (two chordomas and one chondrosarcoma), using either the retrolabyrinthine-subtemporal or transcochlear-subtemporal approach, excellent resection was achieved with acceptable morbidity considering the extensive nature of the disease.