Non-pulsatile subjective tinnitus without hearing loss may be caused by undetectable sounds originating from venous system of the brain.

Bektas D, Caylan R.

Department of Otolaryngology, KTU Medical Faculty, KBB Anabilim Dali, Trabzon, Turkey.

Tinnitus is a common otologic symptom, which can interfere with the daily activities of life. Subjective tinnitus is perception of sound only heard by the patient. The most common type of tinnitus is non-pulsatile subjective tinnitus (NST), which is believed to originate from auditory pathway, mostly from central nervous system. This hypothesis proposes that an important percentage of NST cases are actually misdiagnosed venous type tinnitus cases. Recent studies have demonstrated that dural-jugular system is dominant only in the horizontal body position. Jugular flow is at maximum during this position possibly making any noise generated within the dural-jugular system louder. As body assumes more vertical positions it gradually leaves its function to the extrajugular venous system of the brain. When there is an objective and/or a pulsating sound it is easier to suspect a vascular etiology and diagnose it clinically or radiologically. However, if a vascular pathology causes a non-pulsatile complaint that can not be heard by the examiner or can not be detected clinically or radiologically, it is bound to be misdiagnosed as central tinnitus. Most NST cases experience their symptoms especially at night. Night time usually allows the combination of silent ambience and horizontal body position to take place. We believe that in some NST cases, especially those without hearing loss (HL), the main cause of tinnitus is venous in origin.