Fluid in the mastoid is a common finding on MRI and CT: a radiologist and otolaryngologist perspective

Abstract

We have read with great interest the article ‘Fluid signal in the mastoid is a common incidental finding on MRI of the brain’ written by Johannes Gossner and published in European Archives of Oto-Rhino-Laryngology [1]. We would like to make some comments concerning this problem based on our experience. Fluid in the mastoid air cells or mastoid cavity is a common incidental finding in magnetic resonance imaging (MRI). To report fluid in mastoid radiologists use different terms, most often mastoiditis and inflammation, but also fluid and increased signal [2]. It has been proven that the incidence of fluid in mastoid reaches up to 25% in the healthy adult population [1], 47.5% in children population between 1 and 2 years of age [3] and 10.3% in intensive care units’ patients [4]. However, the number of healthy patients needing clinical attention due to effusion in mastoid on MRI is much smaller. Recently, Gossner reported that none of 21 patients with fluid in mastoid on MRI had any clinical symptoms, and only in 2 cases, the cause of effusion in mastoid was revealed [1]. Previously, Meredith et al. found symptoms in physical examination consistent with fluid in mastoid in 32% of patients with ‘mastoiditis’ on MRI [2]. Those issue rise question if radiologist should report fluid in mastoid in case of lack of relevant information in clinical data, especially when the number of MRI examination increases each year. Radiologist rises solitude over a possible lack of important information in clinical data, especially if a patient is referred by a non-ENT doctor. On the other hand, one has to remember that patients with otologic symptoms are likely to look for medical advice from an ENT specialist. Another question is if there is a specific amount of fluid that should prompt a radiologist to report effusion. Gossner in his paper graded the fluid amount in minor effusion and major effusion [1]. The radiologist should also distinguish fluid only in the apex of mastoid, in the mastoid cavity and tympanic cavity. Further investigation is needed to provide guidelines for radiologist similar to those proposed by Bhattacharyya et al. [5] and based on the Lund and Mackay scoring system for sinusitis [5]. Moreover, radiologists should not only report fluid in mastoid but also look for possible causes, especially in the nasopharynx, skull base, and parapharyngeal space (Fig. 1). In a paper presented by Huyett et al. concerning intensive care unit patients, the incidence of effusion was significantly higher in patients with an endotracheal tube or a nasogastric tube [4]. Meredith et al. indicated Eustachian tube dysfunction as the most common cause of fluid in mastoid [2]. After radiotherapy of nasopharyngeal cancer, ‘mastoiditis’ was reported on MRI in up to 32% of the patients. Fluid in mastoid is a common radiological finding with little significance in case of no relevant clinical data. More study is needed to present guidelines for radiologists for reporting fluid in mastoid, to prevent unnecessary stress for patients and the cost of the further clinical investigation. This letter refers to the article available at https ://doi.org/10.1007/ s0040 5-018-5197-8.