Fibrous Dysplasia Involving Eustachian Tube on 99mTC-MDP Whole Bone Scintigraphy and SPECT/CT: A Rare Case of Tinnitus.

Tinnitus is a phantom auditory perception in the absence of external stimuli which can be caused by various etiologies including infectious causes, neurological etiologies such as whiplash injury and acoustic neuroma, side effects of certain medication and mechanical causes. Neoplasms that block the Eustachian tube (ET) may also lead to tinnitus. This is a case of fibrous dysplasia (FD) seen on Technetium-99m methyl diphosphonate (99mTc-MDP) whole body bone scintigraphy and SPECT/CT causing blockage of the ET. Fibrous dysplasia (FD) is a rare, congenital, and benign neoplasm that affects the bones. FD can be broadly categorized as mono-ostotic and poly-ostotic types. It often extends from its primary site into other bones and may cause symptoms due to compression, which may not be seen by conventional radiological imaging. We present a case of FD in a young woman, who had unilateral right-sided tinnitus and headache. Conventional imaging identified a lesion involving the paranasal bones with no involvement of the temporal bones or middle ear. 99mTc-MDP whole-body bone scintigraphy was performed to delineate the extent of the disease, which revealed complete blockage of the right sided paranasal sinuses that could have led to a Patulous ET (PET), hence indirectly causing tinnitus. This illustrates the role of nuclear medicine imaging, over conventional imaging, in accurately delineating the functional extent of fibrous dysplasia. [ABSTRACT FROM AUTHOR]