Unilateral pulsatile tinnitus can be attributed to a variety of causes, often related to vascular abnormalities or anomalies in the auditory pathway.
Vascular causes
- Venous abnormalities: Venous variants and pathologic abnormalities are the most common causes of pulsatile tinnitus. These include turbulence within normally located veins and sinuses, and abnormally enlarged or abnormally located veins in close proximity to the conductive auditory pathway. Disorders such as transverse sinus stenosis, sigmoid sinus wall anomalies, and anomalies of the jugular bulb and jugular vein are included in this category
- Arterial abnormalities: Atherosclerotic carotid artery disease is a recognized cause of pulsatile tinnitus . Additionally, a vascular loop entering the internal auditory meatus can cause arterial, pulse synchronous tinnitus
- Venous sinus diverticulum: Pulsatile tinnitus can also be caused by venous sinus diverticulum, which can be treated successfully with transmastoid resurfacing of the venous wall
Auditory pathway anomalies
- Cochleovestibular nerve compression: Compression of the cochleovestibular nerve by an intrameatal anterior inferior cerebellar artery loop can cause unilateral pulsatile tinnitus. This condition can be effectively treated by decompression of the cochleovestibular nerve, including opening of the internal auditory canal and transposition of the artery
Diagnostic considerations
- Audiologic examination: A comprehensive audiologic examination is recommended in patients with unilateral, persistent (> 6 months) tinnitus or when associated with hearing difficulties
- Diagnostic imaging: For patients with unilateral or bilateral pulsatile tinnitus with no retrotympanic lesion on otoscopy, a combination of parenchymal and vascular imaging (either head/head and neck CTA or a combination of head and internal auditory canal MRI, MRA, and/or head MRV) is recommended . If a retrotympanic lesion is suspected, a temporal bone CT is recommended to evaluate for lesions such as glomus tympanicum, glomus jugulotympanicum, and vascular variants like aberrant internal carotid artery, dehiscent jugular foramen, and persistent stapedial artery
In conclusion, unilateral pulsatile tinnitus can be caused by a variety of vascular abnormalities and anomalies in the auditory pathway. Comprehensive audiologic examination and appropriate diagnostic imaging are crucial for accurate diagnosis and management.