The variants of paranasal sinuses (PNS)and nasal cavity are of clinical importance since some variants are susceptible to recurrent infection. Moreover, during functional endoscopic sinus surgery, knowledge of anatomy is of utmost importance in order to prevent injury of vital structures like optic nerves, carotid arteries etc. However, there is lack of study enrolling adequate number of patients in our country. Critical variants are often underreported by radiologists. Thus, it is imperative to know true prevalence of different anatomical variants.

The nasal cavity and paranasal sinuses(PNS) together constitute single anatomical and functional unit. There are different anatomical variants of paranasal sinuses and nasal cavity. This is the anatomical structure with most variation and computed tomography(CT) is frequently done to evaluate anatomy of PNS and nasal cavity. Knowledge of anatomical variants is important for early diagnosis of pathology in the region and to prevent complications during functional endoscopic sinus surgery(FESS). Different anatomical variants frequently seen in CT of PNS and nasal cavity include deviated nasal septum, bony spur, concha bullosa, paradoxical nasal turbinate, agger nasi cells, bulla ethmoidalis, haller cells, onodi cells, different degree of pneumatization of sphenoid sinus etc. Anatomical variation of these structures differs in different ethnic groups. Some variants like onodi cells, complete sellar pneumatization of sphenoid sinus, anterior ethmoid artery traversing ethmoid air cells, dehiscent optic nerve and carotid artery pose structure around them into risk during surgery. If exact prevalence of these anatomical variations is known, it becomes easy for surgeons to approach lesions in the area easily. Some variants like haller cells, ager nasi cells, bulla ethmoidalis block osteomeatal complex and drainage pathway of frontal sinuses. Sinusitis may be refractory to medications due to these variants. We could find three studies done in our country and the sample size ranges from 76 to 218. We are aiming for larger study which could provide more accurate picture of prevalence of different anatomical variants. CT of PNS is done frequently in our hospital and we rarely collect data from the images for research purpose. There would be utilization of those data as well. Patient need not pay extra or receive extra radiation for the study. We think the study is very noble and would be a great help for surgeons and clinicians in the country.

Inclusion Criteria:

• CT scan of PNS of patients > 13 years referred for various reasons.
• CT scan of Head referred to our department for various reasons.

Exclusion Criteria:

• CT of PNS and head done for evaluation of trauma and tumors
• CT of Patients age less than 13 years .

Nepali Population

I, the principal investigator choose not to share the plan