Abstract
ObjectivesCurrently in Sri Lanka otorhinolaryngologists are vastly involved in functional endoscopic sinus surgery (FESS), while transsphenoidal approach to sellar lesions is becoming popular among neurosurgeons. There is a possibility of endoscopic supra sellar, lateral skull base and clival surgery to take off in near future although no sufficient database is available about the anatomical variations of the sphenoid sinuses of Sri Lankans. This research is aimed at filling this deficit.Design and MethodsA cross sectional retrospective study of 200 CT scans of 0.5mm intervals of the ‘nose, paranasal sinus and brain” of Sri Lankans who were seen at district general hospital Trincomalee were analyzed. Details were collected regarding pneumatization, sellar budge, protrusion and dehiscence of the walls of maxillary nerve (MN), optic nerve (ON), vidian nerve (VN) and internal carotid artery (ICA) and the different types and attachment of the sphenoid sinus septum.ResultsWe found no conchal pneumatization but 100% of the study population to have presellar area of the sphenoid body pneumatization, 87% to have sellar and 39.5% to have post sellar area of the sphenoid bone pneumatization. Superior extension of pneumatization into anterior clinoid process (ACP) was found among 13.5% and extension in to posterior clinoid process (PCP) in 4.5%. Lateral extension in to opticocarotid recess was found in 60% and pneumatization in to greater wing of sphenoid (GWS) was found in 42% while 13.5% had pneumatization of lesser wing of sphenoid (LWS). Anterior pneumatization extended in to vomer and ethmoid bones and was 25%and 19% respectively. Posterior extension in to clivus was 34.5% while pneumatization extended inferiorly in to pterygoid process in 54.5 %. The sellar bulge was well defined in 75.5% and not so in 24.5%. The Intersinus septum was absent in 0.5% while single Intersinus septum was present in 86.5% and 8% had a transverse septum. 29.5% had multiple Intrasinus septum while 64.5 % had accessory septa. Occurrence of protrusion and dehiscence in optic nerve, maxillary nerve, vidian nerve and internal carotid artery were, 54%, 8.5%, 24.5% and 79% and, 23%, 7%, 14% and 57.5% respectively.ConclusionsThe sinus anatomy has a racial difference and regional anatomy varies randomly. Posterior, inferior and lateral extensions of pneumatization could make orientation and relative positioning of vital structures confusing. Septal attachments to vessels and nerves are much higher than appreciated previously. Individual study with greater attention to detail in CT scans is recommended prior to surgery to minimize complications.
Highlights
Lateral extension in to opticocarotid recess was found in 60% and pneumatization in to greater wing of sphenoid (GWS) was found in 42% while 13.5% had pneumatization of lesser wing of sphenoid (LWS)
The sphenoid bone, located deep with in the skull base has a variable anatomy, which is best studied using computerized tomography .It occupies a central position, in the skull anatomically, as well as in skull base surgery and sphenoid sinus acts as a safe passage to the sellar turcica, optic nerve, planum sphenoidale, tuberculum, and the sellar orbital junction for various skull base, sellar, suprasellar lesions and cerebrospinal fluid leak repairs [1] .The level of intervention in sphenoid sinus varies from wide sphenoidotomy in sinusitis, for improvement of drainage and ventilation to liberal removal of inter/intra sphenoidal bone for access in neuro endoscopic surgery
Even though we defined pneumatization of greater wing of sphenoid as extension of pneumatization extending beyond a vertical foramen rotundum, as the other two researches we found somewhat dissimilar results to them emphasizing the difference that could be due to racial difference [6].Optico carotid recess pneumatization was found in 120(60.%) of the study population and we could not find any significant association between presence of pneumatized opticocarotid recess and neither protrusion and dehiscence of internal carotid artery no optic nerve, unlike the results published by Hewaidi et al.[6]
Summary
The sphenoid bone, located deep with in the skull base has a variable anatomy, which is best studied using computerized tomography .It occupies a central position, in the skull anatomically, as well as in skull base surgery and sphenoid sinus acts as a safe passage to the sellar turcica, optic nerve, planum sphenoidale, tuberculum, and the sellar orbital junction for various skull base, sellar, suprasellar lesions and cerebrospinal fluid leak repairs [1] .The level of intervention in sphenoid sinus varies from wide sphenoidotomy in sinusitis, for improvement of drainage and ventilation to liberal removal of inter/intra sphenoidal bone for access in neuro endoscopic surgery. On top of the existing diversity in anatomy the highly variable and unpredictable nature of pneumatization, could place the surgeon in a precarious and dangerous situation due to the proximity to surrounding vital structures such as the optic, vidian, maxillary, oculomotor, trochlear nerves, brain stem, cavernous sinuses and the internal carotid arteries [1]. All these factors demand the understanding of subtle variations in sphenoid anatomy for safe and successful sphenoidal sinus surgery. There is no data relevant to the Sri Lankan population and the global availability of similar information is relatively spares [7]
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