Elsevier

Surgical Neurology

Volume 66, Issue 5, November 2006, Pages 544-547
Surgical Neurology

Technique
Transcavum septum pellucidum interforniceal approach for the colloid cyst of the third ventricle: Operative nuance

https://doi.org/10.1016/j.surneu.2006.03.033Get rights and content

Background

Despite their unfavorable locations, lesions of the third ventricle can be successfully removed via an interhemispheric, transcallosal approach. In cases with normal ventricular anatomy, this approach requires unilateral or bilateral identification of the foramen of Monro.

Technique

However, in the presence of abnormal ventricular configuration such as cavum septum pellucidum (CSP), this basic knwoledge needs to be modified. After routine callosotomy, there may be a confusion while entering the CSP due to the invisualization of ventricular landmarks such as the foramen of Monro, thalamostriate vein, and choroid plexus. The floor of the CSP is formed by the fornices, and a direct approach to the interforniceal area is easier via the CSP. But the interforniceal approach is not a routine way to reach the third ventricle, which has higher risks than other modalities.

Conclusion

This approach should be planned and used in selected cases of the CSP. Opening of the walls of CSP is recommended both to expose both the foramen of Monro and to gain safe access to the third ventricle before manipulating the interforniceal area.

Introduction

The third ventricle is one of the most surgically inaccessible areas in the brain. It is impossible to reach its cavity without incising some neural structures [11]. Various methods to reach the third ventricle through the interhemispheric-transcallosal approach include transforaminal, transchoroidal fissure and interforniceal exposures [1], [2], [3], [5]. Anatomical and surgical studies on the transcallosal approaches well define this surgery in cases with normal ventricular anatomy [7], [10]. However, in the presence of anatomical variation such as CSP and CV, entrance to the cavum may confuse the inexperienced surgeon in this region. Because of the anatomical orientation, the surgeon may decide to stay in the CSP and reach the floor to open the interforniceal space [9]. This strategy needs to be discussed. The interforniceal approach has the advantage of giving access to the central portion of the third ventricle behind the foramen of Monro by displacing, rather than transecting, the fibers in the fornix [6]. Before deciding on the interforniceal approach, all routes, such as the transforamen of Monro and transchoroidal fissure, should be eliminated meticulously.

The midline anatomical structures including the fornices can be distorted by a third-ventricle tumor. The presence of CSP or CV does not imply reaching the interforniceal region in the midline. A disorientation in the CSP or CV may cause forniceal damage, which may result in serious memory deficits [4]. This disorientation may also cause injury to the internal cerebral veins, which may lead to mortality [8]. The walls of the CSP (the septal leaves) should be opened bilaterally above the fornices to visualize both the ventricles and the foramina of Monro to ensure the pathology and anatomy-oriented midline.

In this paper, the transcavum septum pellucidum interforniceal approach to the third ventricle of a 55-year-old female patient with colloid cyst is demonstrated using pictures and video recordings. She was referred to our department with the diagnosis of a mass lesion located in the third ventricle. She had the complaints of headache, nausea, vomiting, and dizziness, which started a week previously. The neurologic examination revealed no deficit. Magnetic resonance imaging with contrast showed a hyperintense, contrast-enhancing, cystic mass lesion in the third ventricle in T1-weighted images (Fig. 1). There was a moderate hydrocephalus with a CSP and CV variation.

Section snippets

Interhemispheric dissection, callosotomy, and exploration of the CSP

The bone flap was planned so that one third is posterior to the coronal suture and two thirds is anterior to it. Once the dura has been separated from the brain to the sagittal sinus, the leading edge of the hemisphere is retracted laterally away from the midline in a careful stepwise fashion. There were no bridging veins to the superior sagittal sinus. With gentle pressure, the retractor was placed on the cottonoid and advanced further forward into the interhemispheric fissure. After the

Conclusion

Interforniceal approach is not a standard approach to the third ventricle and should not be performed by inexperienced surgeons. Preoperative planning is very important in the third-ventricle approach, but in some cases like this, it may be inadequate and the approach can be changed during surgery. Alternative surgical techniques, such as endoscope-assisted surgery or the use of neuronavigation and favorable surgical positioning, must also be considered preoperatively.

Interforniceal approach

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