BACKGROUND Incidental sinus mucosal abnormalities on MRI are a common finding. This study aims to investigate seasonality and reporting of these findings. METHODOLOGY Prospective, cross-sectional study of adult patients presenting for neuro-radiological assessment using MRI. 173 patients were recruited over `winter` and `summer` collection periods (mean maximum temperature 14.5(deg)C and 24.3(deg)C, respectively). Patients were classified as symptomatic for rhinosinusitis according to the European Position Paper on Rhinosinusitis and Nasal Polyps 2007 definition. A modified Lund Mackay score was used to assess sinus pathology. Mucosal thickening of > 3mm was considered pathological. Radiologist reports were reviewed for mention of incidental sinus abnormalities. RESULTS There was an incidental rate of 58.1% overall, with significantly more sinus abnormalities in winter. Sinus abnormalities were mentioned in 8.1% of radiologist reports, half of which were in asymptomatic patients. There were significantly more sinus abnormalities amongst symptomatic patients. CONCLUSIONS Incidental sinus changes on MRI are a common finding and are often reported on by radiologists. However, they bear little association with symptoms. Their prevalence is influenced by season and thus their significance is greater during cooler months. Specialist referral should be reserved for symptomatic patients that have failed medical therapy.