Prominent Inferior Intercavernous Sinus in Intracranial Hypotension

Background and Purpose: Distension of the intracranial veins including intercavernous sinuses is a common finding in patients with intracranial hypotension (IH). Following four intercavernous venous communications have been described in the literature: the anterior, posterior and inferior intercavernous sinuses, as well as the basilar plexus. A distended inferior intercavernous sinus (IICS) may mimic a focal pituitary lesion on sagittal T1 images. The purpose of this study is to describe the frequency of enlarged inferior intercavernous sinus in patients with IH and controls.

Material and Methods: The diagnosis of IH was defined by the presence of (1) one of the following clinical scenarios: orthostatic headaches or CSF diversion device and (2) at least two of the following imaging signs: dural enhancement, venous distension sign, brain stem sagging, and spontaneous subdural collections.

The sellar region of 29 patients with IH and 52 controls were examined by consensus by two readers to determine the presence of a distended IICS. The chi-squared test was used to compare both the groups. Sensitivity and specificity of IICS distension as a sign of IH were also calculated.

Results: Of the 26 cases of IH, 13 had an enlarged IICS (44.83%) while in the control group, IICS was distended in 2 subjects (3.85%). These percentages were significantly different (p < 0.001). Sensitivity and specificity of enlarged IICS as a sign of IH were 44.83% (95% CI, 26.46–64.30%) and 96.15 (95% CI, 86.76–99.42%). On sagittal T1 images, the prominent IICS showed a crescent shape in eight cases, oval shape in seven cases and a rounded shape in one case.

Conclusion: Enlargement of the IICS is frequently caused by intracranial hypotension although, less frequently, can be found as a normal or incidental anatomic variant. Recognition of this anatomical structure is important to avoid mistaking it for a focal pituitary lesion.