A Cross-Sectional Study of Sphenoid Sinus through Gross and Endoscopic Dissection in North Karnataka, India

Anatomographic Variants of Sphenoid Sinus in Ethiopian Population

Neurosurgeons often neglect the sphenoid sinus due to its deep location and difficulties in accessing during surgical interventions. Disease of the sphenoid sinus is difficult to diagnose since its presenting symptoms are difficult to recognize. Moreover, compared with other paranasal sinuses, the sphenoid sinus is considered the most variable air sinus in terms of its degree of pneumatization, number and position of inter-sinus septa, and its relationship with the surrounding anatomical structures. Anatomical variations of the sphenoid sinus are significant from a neurosurgical point of view. Understanding of these variations and its relationships with surrounding structures such as the internal carotid artery, optic nerve, and pituitary gland are clinically relevant to minimize injuries associated with surgical procedures that involve sphenoid sinus. We implemented principles of imaging using computed tomography to elucidate any anatomical variations of the sphenoid sinus in the Ethiopian population. We conducted a prospective study in 200 patients with ages 18-79, who underwent scans of the sphenoid sinus at the Tikur Anbessa Referral Teaching Hospital in 2017-2018. Our findings revealed an incidence of anatomographical variations in terms of pneumatization that varied between 2-50%. These variants include 2% conchal, 25.5% presellar, 50% sellar, and 22.5% postsellar pneumatization. We also demonstrated anatomographic variants in terms of septation, 77.5% single complete septa, 11.5% single incomplete, 10% double septa, and 1% absence of septa. In summary, the sellar pneumatization was found to be the most clinically relevant anatomographic variant among Ethiopians participating in the study, of which 90% were tomographically single septated. These variants must be taken into consideration during trans-sphenoidal surgery and knowledge of the variations has clinical implication in minimizing injuries during invasive surgical procedures involving the sphenoid sinus.

Sphenoid sinus septations and their interconnections with parasphenoidal internal carotid artery protuberance: radioanatomical study with literature review

Introduction

Internal carotid artery (ICA) injury is the most dangerous and life-threatening complication in patients operated on due to parasellar tumors via a minimally invasive endoscopic endonasal approach. Sphenoid septal attachment to the ICA protuberance within the sphenoid sinus was found to be one of the anatomical risk factors for ICA injury during transsphenoidal surgery.

Aim

To determine the relationship between the sphenoid sinus septa and the parasellar or paraclival internal carotid artery prominence based on our own material and a literature review.

Material and methods

The axial plane scans of computed tomography angiography and a literature review of previously published papers on the septum variation and its connection with the ICA prominence are provided.

Results

Out of 100 sphenoid sinuses, 49 (49%) had at least one septum inserted at the ICA prominence. In the majority of cases 42 (86%) one septum was inserted at the prominence of one of the ICAs. In 7 (14%) cases, two separate septa were inserted at the prominences of both ICAs. Patients with multiple septa and those having an incomplete septum were at higher risk of at least one of them being inserted at the ICA prominence within the sinus. Including cases from the literature review, the average number of septa per patient was 1.42. The risk of intersection between the septum and the ICA prominence was 32%.

Conclusions

A significant percentage of the intrasphenoidal septa are inserted at the sphenoidal ICA protuberance.

Optic Nerve Canal Relation to Posterior Paranasal Sinuses in Indian Ethnics: Review and Objective Classification

INTRODUCTION

Posterior paranasal sinuses consisting of posterior ethmoid and sphenoid sinuses show varying pneumatization and relationship to Optic Nerve Canal (ONC). Most commonly ONC is superolateral to sphenoid sinus, however varied protrusion of ONC into the sinuses may occur. Rarely it may pass completely through the sinus. Optic Nerve (ON) is covered by a thin bony layer or by periosteum and sinus mucosa without bone. Extensive pneumatization of sphenoid sinus and bony dehiscence predisposes to ON injury. The posterior ethmoid cell namely the Onodi cell is of great surgical importance when the ON is along its lateral wall and surrounds the nerve. These varied relations imply that a detailed knowledge of the intimate relationship of ONC with the posterior paranasal sinuses is necessary to avoid unintentional complications during the surgeries involving the ONC region.

AIM

To assess relationship of ONC to the posterior paranasal sinuses in Indian Ethnic study group.

MATERIALS AND METHODS

Retrospective review of 100 paranasal sinus Computed Tomography (CT) scans were done using 64 row Multi Detector Computed Tomography (MDCT). Multiplanar reformation images were assessed for ONC relation to posterior ethmoid and sphenoid sinuses, wall dehiscence, and Pneumatization of Anterior Clinoid Process (PACP).

RESULTS

200 optic nerve canals were assessed and grouped into four types based on the modification of Delano et al., classification. The most common OCN was Type-1 (60%), followed by Type-2 (15%), Type-3 (14%) and Type-4 (11%). Dehiscence was seen in 35(17.5%) mostly in Type-3 canals. PACP was seen in 30 (15%).

CONCLUSION

Knowledge of ON relationship to posterior paranasal sinuses will reduce the devastating complications during sinus surgeries. Our modified ONC classification is based on the bony canal morphology and the degree of protrusion into sinuses. As with other reported studies worldwide, Type-1 ONC is the commonest among the Indians also. Type-2 and 3 ONC with sinus wall dehiscence and PACP are the most important anatomical variations which may potentially predispose to risk of surgical injury to the optic nerves.

Critical analysis of anatomical landmarks within the sphenoid sinus for transsphenoidal surgery

The transsphenoidal approach to the sellar region has been introduced more than a 100 years ago. It is the accepted standard operative corridor to pathologies of the pituitary gland and surrounding structures. There are anatomical landmarks within the sphenoid sinus that are used for orientation directing to the sella floor or the cavernous sinus. Yet, little data can be found on the consistency of these landmarks. It is the aim of this study to evaluate the reliability of these anatomical landmarks for the surgeon's orientation. A total of 245 computed tomography (CT) volume data sets of the cranium performed according to a standardized protocol were analyzed for study purposes. CT scans of the cranium of 125 patients admitted to the emergency room of our hospital receiving a trauma spiral according to the local protocol were employed as a control group when no pathology in the sellar region was observed. In addition, preoperative CT scans of a group of 120 patients diagnosed with pituitary adenomas between 2009 and 2013 were analyzed. Image analysis of the anatomical landmarks included the minimal intercarotid distance (ICD), diameter of the sphenoid sinus (DSS), direction of the septum sinuum sphenoidalium (SSS), and the distance between vomer and clivus (VCD). The overall mean ICD was 16.2 mm, with patients suffering from adenomas showing a mean ICD of 15.8 mm compared with an average 16.5 mm in the control group. DSS was equal for both groups (adenoma group: mean 31.5 mm; controls: mean 31.3 mm). Mean VCD was 27.9 mm in patients with pituitary adenomas compared with 26.7 mm in controls. A septum of the sphenoid sinus located in the midline was found in overall 23 % only. SSS was directed into the bony shield of the internal carotid artery in 28 % of underlying tumors and in 37 % of the control group. This is the first detailed description of landmarks of the sphenoid sinus based on a large radiologic-anatomical analysis of CT scans yielding a wide variation and high inconsistency of these landmarks. From out data, we suggest that the surgeon approaching the sphenoid sinus should handle the anatomical landmarks with care bearing their inconsistency in mind. A thorough planning of the procedure up front is highly recommended. Usage of a navigation system considering the bony structures might as well facilitate as steady the approach to the sellar region in some cases for the patient's sake.