Commentary on the Article of M. N. Pamir, S. Peker, S. Özgen, T. Kılıç, U. Türe, M. M. Özek: Anterior Transcallosal Approach to the Colloid Cysts of the Third Ventricle: Case Series and Review of the Literature

The paper of Pamir et al. is an interesting contribution to the current debate about the optimal treatment of colloid cysts of the third ventricle. It deserves some comment though. The statement that colloid cysts should be completely excised is very welcome and cannot be repeated often enough. But then there is the issue of choice of the microsurgical approach. It is very rare to find a case in which there is not at least unilateral enlargement of the ventricles and therefore also thinning of the cortex. When comparing the transcortical and transcallosal approach, no proof is provided to date that the transcallosal approach is generally better in all cases. From the literature it may even be concluded that it is more dangerous and has more complications and that is easily understood when just looking at the beginning of the surgery where the interhemispheric cleft has to be opened in the presence of dilated ventricles and relatively raised intracranial pressure. When a small precoronary craniotomy is used and ultrasound guidance, a sulcus can be opened and from the bottom the ventricle punctured. Following that ventriculostomy path a white matter opening of 8 mm to 10 mm is sufficient to gain access and exposure of the foramen of Monro. With collapsing ventricles and relieved pressure this opening is mobile and can be moved as angulation requires. This allows for a constantly changing keyhole view which meets the foramen from a lateral perspective and allows for very good views inside the third ventricle. The beauty about colloid cyst surgery is the consistency of most cysts which can be collapsed and then detached from all their adherences in the choroids plexus. The transcallosal approach does not allow that flexibility and angulation because the corpus callosum is much more rigid than a thinned cortex and each change in the angulation of instruments or retractors will be accompanied by more injury fiber dissection. It is true, that the transcortical approach is used best only for cysts and that there may be large cysts with calcifications or extensions far back into the third ventricle where the shape of the cysts already leads to the suspicion that it will be adherent and cannot be mobilized. Then, as in tumors, a direct approach into the third ventricle may be needed and that may undisputedly be best achieved by transcallosal routes. But that is mainly for entities other than cysts and in that respect, one of the shortcomings of this article is a mix up of literature arguments for the virtues of the transcallosal approach in which many literature references are textbook articles and not original research series which refer to technique but not the issues at question. They mostly refer to tumors of the third ventricle and not colloidal cysts. It is problematic to compare apples to oranges. A tumor of the third ventricle should by all means be exposed by the transcallosal route which is optimal in that case. Of course is the transsection of the fornices associated with poor outcome but that must not occur in the present age when mobilizing a colloidal cyst.

When commenting on transcallosal versus transcortical approaches, it may even be concluded from the data reviewed and presented that the transcallosal approach might be more complicated and dangerous and should be reserved for very large cysts and tumor. With enlarged ventricles and the average cysts in the anterior part of the third ventricle a transcortical micro-approach in the non dominant hemisphere is safer, simply from the structures encountered during the approach and its flexibility. In the days of modern microsurgical skills, cortical injury will be minimal, the approach very small and the fiber density lower compared to the transcallosal approach. Unfortunately there are too few comparable cases and too few centers with equal skills to perform a study either in a randomized fashion or as a matched pair analysis.