The Orbitomeningeal Band as a Way to Bloodless Transcavernous Dissection and Anterior Clinoidectomy

Orbitomeningeal Band in Transcavernous Dissection and Anterior Clinoidectomy: 3-Dimensional Operative Video

The orbitomeningeal or meningo-orbital band (MOB) has been described as the most superficial dural band responsible for tethering the frontotemporal basal dura to the periorbita.1,2 The MBO usually interferes with the surgical approach to the most profound areas of the anterior and middle skull base. It is known that there are no cranial nerves on the lateral surface of the superior orbital fissure; therefore, the neurosurgeon can cut the MOB without causing any neurological deficit and, at the same time, achieving fully exposure of the anterior clinoid process1-4 and/or the lateral wall of the cavernous sinus.5 The purpose of this video is to describe the microsurgical anatomy of the MOB and illustrate the technique for its detachment, accompanied by 2 illustrative cases. To achieve this, we use 3-dimensional recordings of 2 cadaveric specimens' dissections performed by the senior author. Case 1: 58-yr-old female with left blindness. Magnetic resonance imaging (MRI) shows an anterior and middle skull base lesion with orbital compression. Case 2: 32-yr-old male presenting with headache and trigeminal neuralgia. The MRI revealed an hourglass-shaped lesion in the posterior and middle fossa. Both patients signed an informed consent and agree with the use of their images for research purposes. We used a step-by-step approach for an adequate and secure dissection of the MOB highlighting the anatomic structures involved in the process. This approach allows safe and adequate access to the deeper structures of the anterior and middle skull base.

Anatomical meningo-orbital band evaluation and clinical implications: a cadaveric dissection study

BACKGROUND

The meningo-orbital band (MOB) is a dural structure which runs around the superior orbital fissure (SOF) tethering the frontotemporal basal dura to the periorbita, through the SOF. MOB division is important to expose and remove the anterior clinoid process, to access to proximal carotid artery and cavernous sinus area. The goal of the study was to measure how the MOB could be safely incised without cranial nerves and cavernous sinus injuries.

METHODS

Anatomical dissections and extradural exposure of the anterior clinoid process was performed on 20 cadavers (40 sides). Measurement of the MOB thickness was performed before its incision, after dura propria dissection, and retraction off the inner cavernous membrane, to expose the cranial nerves.

RESULTS

We analyzed 20 cadaveric formalin-fixed heads injected with colored silicone, 11 man and 9 woman of caucasian race. The average length of a safe incision of the MOB was 10.6 ± 1.1 mm on the right side, and 10.65 ± 1.09 mm on the left side.

CONCLUSIONS

In our study the average length of a safe incision of the MOB was 10.6 ± 1.1 mm. Thus, the incision length of the MOB should not exceed 9 mm; the peeling of the anterior cavernous sinus and of the SOF, dissecting the two layers of the dura throughout the incision of the MOB, is an useful technique to avoid cranial nerves and cavernous sinus lesions.