Association between idiopathic intracranial hypertension and sigmoid sinus dehiscence/diverticulum with pulsatile tinnitus: a retrospective imaging study

The mechanism of occurrence of sigmoid sinus dehiscence/diverticulum (SSDD) in pulsatile tinnitus (PT) patients remains under debate. Its association with idiopathic intracranial hypertension (IIH) lacks evidence, which is important for therapeutic planning and improving the clinical outcome. This study aimed to evaluate the association between SSDD and IIH by comparing the prevalence of several established imaging features of IIH between PT patients with SSDD and healthy volunteers. Thirty-three unilateral PT patients with SSDD identified on CT images and 33 age- and sex-matched healthy volunteers underwent T1-weighted volumetric magnetic resonance imaging (MRI). The optic nerve, pituitary gland, transverse sinus, and ventricles were assessed. The prevalence of established IIH imaging features was compared between the two groups. Furthermore, the PT patients were divided into two subgroups: PT patients with dehiscence only and PT patients with diverticulum. The same statistical analysis was performed on each pathophysiologic entity respectively. The PT patients with SSDD showed a significantly higher prevalence of empty sella (P < 0.001), flattened posterior sclera (P = 0.001), vertical tortuosity of the optic nerve (P = 0.001), protrusion of the optic nerve (P = 0.006), transverse sinus stenosis (P = 0.011), and distension of the optic nerve sheath (P = 0.000). There were no significant differences between the PT and control groups in the maximum widths of the third and fourth ventricles and the lateral ventricle size. In contrast to controls, the imaging findings persisted in both of pathophysiologic entities, except for transverse sinus stenosis. Several IIH imaging features occur more frequently in PT patients with SSDD than in healthy individuals, which suggests a potential correlation between SSDD with PT and IIH.