Neurosurgery of the Visual Pathway

A. Gharabaghi, J. Honegger, and M. Tatagiba

The visual pathways take an extraordinary and extensive intraorbital and intracranial course from the globe to the visual cortex within the occipital lobes. Hence, a large number of orbital and intracranial pathologies interfere with the optic pathways. The diagnosis and treatment of these pathologies demands an interdisciplinary team with ophthalmologists, neuroradiologists, neurosurgeons, and radiation therapists. The management algorithm takes into consideration presenting signs and symptoms, as well as ophthalmologic and imaging findings. It requires a multimodal treatment protocol depending on the biological nature and location of the pathology.

Modern neurosurgery applies a vast range of operative approaches and microsurgical techniques to remove intra- and extra-axial lesions of the optic pathways. The neurosurgical management is enhanced by recent advances of intraoperative image guidance and electrophysiological monitoring to face the challenge of preserving function.

Tumors Compromising the Visual Pathway

When visual loss is associated with a mass lesion, the physician in charge has to consider a large variety of aspects such as the biological nature and the location of the lesion. Is the tumor extra-axial, i.e., originating in the vicinity of the optic system and compressing it, or is it intra-axial, i.e., arising from the visual pathway itself? Is the lesion slow or fast growing? Does it threaten the patient's life? What is the probable time course of further deficits to be expected? Can the lesion be removed completely, or does the surgery have to be limited to decompression of the visual pathways? Furthermore, the surgical accessibility and appropriate operative approach has to be considered in terms of adequate tumor exposure and minimal invasiveness with satisfying cosmetic results at the same time. Which additional imaging and electrophysiological information is available to increase the safety of the intervention?

The intention of the following chapter is to address these questions for the most frequent tumors of the orbita, anterior skull base, sellar/parasellar region, and intraparen-chymal hemispheres that compromise visual function, and to introduce the required neurosurgical techniques including intra- and extracranial approaches to treat these lesions.

Intraorbital Lesions Definition

Intraorbital tumors include optic nerve sheath menin-geomas, optic nerve gliomas, cavernous hemangiomas, peripheral nerve tumors, dermoid and epidermoid cysts, osteomas, fibrous dysplasia, hemangiopericyto-ma, metastatic lesions, and less frequent pathologies.

0 0

Post a comment