Spontaneous Cerebrospinal Fluid Leak Presenting as Middle Ear Effusion Caused by Arachnoid Granulations

While middle ear effusion (MEE) is a common ailment in children with Eustachian tube dysfunction, it occurs less frequently in adults. In such cases, a meticulous assessment is essential to discern the underlying cause of MEE. We present an unusual case of spontaneous cerebrospinal fluid (CSF) leak attributed to arachnoid granulation presenting as MEE. A 59-year-old obese female presented with right ear fullness, reduced hearing, and a persistent postnasal drip for 2 years. Audiological testing shows unilateral mild-to-moderate conductive hearing loss in the right ear. Tympanometry assessment revealed a persistent type B pattern in the right ear, indicating persistent unilateral conductive hearing loss. However, despite receiving treatment with nasal decongestants and antihistamines for 2 weeks, no signs of improvement were observed. Subsequently, a right myringotomy and grommet insertion were performed, resulting in the drainage of clear watery fluid that persisted for 2 weeks. A high-resolution computed tomographic scan of the temporal bone revealed the right MEE, bony defect in the right tegmen tympani, and bony irregularities of both tegmen tympani. Magnetic resonance imaging unveiled herniation of the right inferior temporal lobe through the identified tegmen defect. The patient subsequently underwent cortical mastoidectomy, lateral skull base repair, and mastoid obliteration. The histopathological examination of the biopsy taken from the right middle ear tissue revealed fragments of glial tissue with small fragments of trabeculae, which were confirmed by the positivity of the glial fibrillary acidic protein stain. The patient has remained asymptomatic for 10 months following the operation, and her hearing has fully returned to normal. It is advisable to consider CSF effusion as a potential differential diagnosis, particularly among adults aged over 50 years, even in the absence of a history of head trauma, mastoid surgery, or meningitis, when confronted with persistent unilateral MEE.