Endoscopic Approach to Intraventricular Brain Tumors

Published on 13/03/2015 by admin

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Last modified 13/03/2015

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Chapter 29 Endoscopic Approach to Intraventricular Brain Tumors

Endoscopic surgery for intraventricular brain tumors is a logical application of endoscopic technology. Because of the central and deep location of intraventricular brain tumors, conventional neurosurgical approaches have a relative increase in potential morbidity. Auspiciously, the location of intraventricular tumors being within a cerebrospinal fluid (CSF) compartment affords excellent light and image transmission. The fact that most intraventricular tumors cause hydrocephalus makes endoscopic surgery particularly attractive since simultaneous procedures can be employed both for CSF diversion and tumor management. In addition, the inherent benefits of minimally invasive techniques including reduced surgical time, improved cosmetic results, shortened hospital stay, and reduced cost also factor into the appeal of neurosurgical endoscopy for managing intraventricular tumors.1 Five commonly employed endoscopic procedures are highlighted including endoscopic fenestration, endoscopic tumor biopsy, simultaneous tumor biopsy with endoscopic third ventriculostomy (ETV), endoscopic removal of solid tumors and endoscopic removal of colloid cysts.

Endoscopic Tumor Procedures

Endoscopic Fenestration

Septal fenestration and tumor cyst fenestration are two of the simplest endoscopic procedures owing the relative avascular nature of these membranes. Fenestration of the septum pellucidum should be considered in any patient in which a tumor mass is situated in the anterior third ventricle or within the lateral ventricle at the foramen of Monro resulting in compartmentalized hydrocephalus (Fig. 29-3). Shunt burden can thus be reduced in the former situation or eliminated in the latter by simple endoscopic septal fenestration. Endoscopic fenestration of the septum pellucidum generally is performed via an entry site that lies more lateral than the conventional coronal burr hole. The entry site is thus positioned at least 4 cm from the midsagittal plane. It is recommended that the site of septal fenestration be positioned between the larger tributaries of the septal veins and as superior as possible from the fornix. Generous fenestrations are made with cautery and confirmation of effective communication is established with identification of contralateral ventricular landmarks including the choroid plexus and ependymal veins.

Tumor cyst fenestration is an appealing therapeutic option when a patient’s symptoms can be relieved by cyst decompression and when aggressive tumor resection may be avoided (Fig. 29-4). Craniopharyngiomas, hypothalamic/chiasmatic astrocytomas, and suprasellar germ cell tumors are examples of such tumors.3 Transventricular endoscopic cyst decompression is a minimally invasive method for temporarily or permanently alleviating obstructive hydrocephalus or visual loss. For most cystic tumors causing obstructive hydrocephalus at the level of the third ventricle, a standard coronal approach is an ideal trajectory. The transcavum interforniceal endoscopic approach4 to the third ventricle is a further refinement of the technique for biopsy or fenestration of lesions within the third ventricle in those patients a large cavum vergae.

Tumor Biopsy

Endoscopic biopsy is a well-established method for sampling intraventricular brain tumors.57 The procedure should always be considered in situations in which surgical tumor removal may not be necessary or when the diagnosis would significantly alter the therapeutic approach. Primary examples of these situations include marker-negative germ cell tumors, Langerhans cell histiocytosis, and infiltrative hypothalamic gliomas. Candidates should have overt intraventricular extension of their tumor mass rather than a lesion that is entirely subependymal in location. The diagnostic yield is high and the risk is low.8 In the authors’ current series of 65 patients who have undergone endoscopic tumor biopsy the diagnostic yield was 98%. To maintain diagnostic accuracy it is imperative to avoid cauterizing the tumor prior to sampling. The samples are small and histologic interpretation can be challenging without superimposed artifact from cautery. If bleeding is encountered, continuous irrigation through the endoscope or an external catheter is recommended until the efflux clears.