Why does unilateral pulsatile tinnitus occur in patients with idiopathic intracranial hypertension?

To investigate the relevant factors of unilateral pulsatile tinnitus (PT) in patients with idiopathic intracranial hypertension (IIH) using CT.

CT angiography images of IIH patients with unilateral PT (n = 19), without PT (n = 13), and controls (n = 32) were reviewed. The characteristics including transverse sinus stenosis (TSS), venous outflow laterality (VOL), sigmoid sinus wall dehiscence (SSWD), and sigmoid sinus diverticulum (SSD) were quantitatively or/and qualitatively detected. VOL was compared between the symptomatic side of IIH patients with PT and the larger side of IIH patients without PT and the controls. TSS, SSWD, and SSD were compared between the symptomatic side of IIH patients with PT, and both sides of the latter two groups.

There was no statistical difference in body mass index or cerebrospinal fluid pressure between IIH patients with and without PT. The prevalence of TSS was significantly higher in IIH patients than that in the controls (p = 0.000), but TSS had no correlation with PT within IIH patients. The prevalence of SSWD successively decreased in IIH patients with PT, without PT, and the controls, with significant differences between each two of three groups (p = 0.000, p' = 0.000, p″ = 0.031). The proportion of VOL and the prevalence of SSD were significantly larger in IIH patients with PT than in the latter groups respectively (p_VOL = 0.005, p'_VOL = 0.000; p_SSD = 0.040, p'_SSD = 0.000). All SSDs in IIH patients with PT were accompanied with SSWD.

The dominant VOL and ipsilateral SSWD with/without SSD may be correlated with the occurrence of unilateral PT in IIH patients.