HSC Section 8_April 2017

Imaging in pulsatile tinnitus

studies were poorly sensitive and MRI/A de- tected only 68% of cases. Although contempo- rary imaging is likely to be more diagnostically accurate overall, catheter angiography may still be needed for the diagnosis of AVFs.

Intrameatal vascular loops

Based on radiological and surgical data some investigators hypothesize that there is a relation- ship between vascular loops extending deep into the internal auditory meati and PT ( Fig. 10 ). There are reports relating neurovascular contact with the vestibulocochlear nerve to non-PT and microvascu- lar decompression has abolished tinnitus in some cases. 23,24 Other studies found no significant rela- tionship between intrameatal vascular loops and tinnitus and a similar incidence of vestibuloco- chlear neurovascular contact in the asymptomatic population. 25,26 More recently, there have been data specifically related to patients with PT. Nowe´ et al. 27 found a significantly higher number of vascular loops in the IAC (as opposed to within the cerebellopontine angle) on MRI in patients with PT compared with those with continuous tin- nitus. It is proposed that turbulent flow within the arterial loop creates sound waves that are con- ducted within the cerebrospinal fluid and then through the perineural spaces, via the fundus of the IAC to the cochlea (by bone conduction). Otospongiosis (commonly called otosclerosis) is the replacement of the normally dense middle layer of the bony labyrinth with areas of ‘‘spongy’’ haver- sian bone. Fenestral otospongiosis, which affects the lateral bony labyrinth, is the most common type and most frequently manifests as spongiosis in the area anterior to the oval window (fissula antefenestrum) with or without involvement of the Bone dysplasia

Figure 11 Transverse CT section demonstrates conflu- ent pericochlear radiolucency in a patient with cochlear otospongiosis.

stapes footplate ( Fig. 11 ). The condition is the most common cause of mixed hearing loss in adults and is bilateral in 85% of cases. 21 There is a 65 e 85% reported prevalence of tinnitus (usually continu- ous but occasionally pulsatile), which improves in 85% of patients following stapes surgery. 28,29 Paget’s disease may cause demineralization of the temporal bone resulting in hearing loss, vestibular dysfunction, or tinnitus. 21 Continuous

Figure 12 Transverse CT section in a patient with ex- tensive lytic Paget’s disease of the skull base and vault with biochemical and isotope bone scintigraphy features of the disease. Note the lucency on the right petrous temporal bone (arrowhead), basisphenoid, and left pe- trous apex. Bone thickening and heterogeneity is more typical in the later phases.

Figure 10 Three-dimensional, T2-weighted, turbo spin-echo, driven equilibrium (TSE DRIVE) transverse im- age in a patient with continuous left-sided tinnitus. The presence of bilateral deep intrameatal vascular loops (seen to arise from the anterior inferior cerebellar ar- teries) are most likely incidental.

75