Endoscopic Fenestration of the Lamina Terminalis: Alternatives to the Classic Third Ventriculostomy

We read with great interest the recent paper by Vulcu et al.[1] In this radiologic and cadaveric study, the authors evaluated the feasibility of performing a transventricular lamina terminalis (LT) fenestration using rigid and flexible endoscopes and two approaches, anterior and posterior to the coronal suture.

The authors verified that when inserted 2 cm behind the coronal suture in the posterior approach (the ideal trajectory to the LT), both the rigid and flexible endoscopes caused moderate to severe damage to the foramen and fornix. Additionally, the posterior approach posed a risk of injury to the primary sensory and motor cortices. They also found that using the standard approach (Kocher point) with a flexible endoscope reduced the risk of damage to these structures. After completion of the anatomical investigation, the authors performed a transventricular fenestration of the LT using a flexible endoscope on one clinical case.

Over the past several decades, endoscopic third ventriculostomy (ETV) performed at the floor of the third ventricle through a precoronal burr hole has become a well-established surgical technique. It is the treatment of choice for many forms of obstructive hydrocephalus. However, anatomical variations of the basilar artery, clivus, and their relationships to the floor of the third ventricle may hinder the standard EVT in a small subpopulation of patients. Despite the description of different techniques (microscopic and endoscopic) and locations for ventriculostomy, each strategy has its limitations or disadvantages in the search for an alternative procedure that is as simple, safe, and minimally invasive as the classic ETV.[2] [3] [4] [5] [6] [7] [8]

Several advantages are gained when using a flexible endoscope in a transventricular approach, particularly the ability to use the same burr hole to change surgical strategy upon the location of fenestration of the third ventricle. However, we believe its disadvantages outweigh this benefit and that a good alternative to the classic ETV has yet to be found.

Vulcu et al highlighted the strengths and limitations of the flexible endoscope compared with the rigid endoscope. We agree that the handling of thin and long instruments is more difficult because instruments are seen in the periphery of the field of view and the optical image is poor. This would thus necessitate switching endoscopes when performing this procedure clinically.

We have studied in cadavers an interhemispheric endoscopic approach to the LT through a single frontal burr hole immediately lateral to the superior sagittal sinus (unpublished data). In our study, the fenestration of the LT was demonstrated to be feasible through a 15-mm burr hole and easier to perform when closest to the anterior cranial base without violating the frontal sinus.

It is important to point out that transcranial endoscopic approaches to the LT do not necessitate crossing of the brain parenchyma. This is of particular importance considering that the ideal entry point in the transventricular LT fenestration is located in close proximity to the premotor area. Moreover, the transcranial approach also avoids maneuvering close to the important functional structures (fornix, hypothalamus, and thalamus). The LT ventriculostomy through a transcranial route has the advantage of providing optimal control of the vessels around the stoma site, which is not attainable in a transventricular approach. Furthermore, the arachnoid membranes and adhesions that are dissected to reach the LT in the transcranial approach have the potential to reduce the failure of cerebrospinal fluid outflow from the third ventricle.

The pursuit of safe, simple, and minimally invasive alternatives to the classic ETV is not over. The development and improvement of flexible endoscopy and endoscopic instrumentation will likely facilitate further development and refinement of such procedures. Nonetheless, we applaud Vulcu et al for their stimulating work and valuable contribution to the literature.

• References

• 1 Vulcu S, Tschabitscher M, Mueller-Forell W, Oertel J. Transventricular fenestration of the lamina terminalis: the value of a flexible endoscope: technical note. J Neurol Surg A Cent Eur Neurosurg 2013; August 12 ( Epub ahead of print)
• 2 Abdou MS, Cohen AR. Endoscopic surgery of the third ventricle: the subfrontal trans-lamina terminalis approach. Minim Invasive Neurosurg 2000; 43 (4) 208-211
• 3 Spena G, Fasel J, Tribolet Nd, Radovanovic I. Subfrontal endoscopic fenestration of lamina terminalis: an anatomical study. Minim Invasive Neurosurg 2008; 51 (6) 319-323
• 4 Daniel RT, Lee GY, Reilly PL. Suprapineal recess: an alternate site for third ventriculostomy? Case report. J Neurosurg 2004; 101 (3) 518-520
• 5 van Lindert EJ. Microsurgical third ventriculocisternostomy as an alternative to ETV: report of two cases. Childs Nerv Syst 2008; 24 (6) 757-761
• 6 Rangel-Castilla L, Hwang SW, Jea A, Torres-Corzo J. Efficacy and safety of endoscopic transventricular lamina terminalis fenestration for hydrocephalus. Neurosurgery 2012; 71 (2) 464-473 ; discussion 473
• 7 Oertel JM, Vulcu S, Schroeder HW, Konerding MA, Wagner W, Gaab MR. Endoscopic transventricular third ventriculostomy through the lamina terminalis. J Neurosurg 2010; 113 (6) 1261-1269
• 8 Schroeder HW, Oertel J, Gaab MR. Endoscopic treatment of cerebrospinal fluid pathway obstructions. Neurosurgery 2007; 60 (2, Suppl 1): ONS44-ONS51 ; discussion ONS51–ONS52