The Occipital Emissary Vein: A Possible Marker for Pseudotumor Cerebri

Abstract

BACKGROUND AND PURPOSE: Transverse sinus stenosis can lead to pseudotumor cerebri syndrome by elevating the cerebral venous pressure. The occipital emissary vein is an inconstant emissary vein that connects the torcular herophili with the suboccipital veins of the external vertebral plexus. This retrospective study compares the prevalence and size of the occipital emissary vein in patients with pseudotumor cerebri syndrome with those in healthy control subjects to determine whether the occipital emissary vein could represent a marker of pseudotumor cerebri syndrome. MATERIALS AND METHODS: The cranial venous system of 46 adult patients with pseudotumor cerebri syndrome (group 1) was studied on CT venography images and compared with a group of 92 consecutive adult patients without pseudotumor cerebri syndrome who underwent venous assessment with gadolinium-enhanced 3D-T1 MPRAGE sequences (group 2). The presence of an occipital emissary vein was assessed, and its proximal (intraosseous) and distal (extracranial) maximum diameters were measured and compared between the 2 groups. Seventeen patients who underwent transverse sinus stent placement had their occipital emissary vein diameters measured before and after stent placement. RESULTS: Thirty of 46 (65%) patients in group 1 versus 29/92 (31.5%) patients in group 2 had an occipital emissary vein (P Ͻ .001). The average proximal and distal occipital emissary vein maximum diameters were significantly larger in group 1 (2.3 versus 1.6 mm, P Ͻ.005 and 3.3 versus 2.3 mm, P Ͻ .001). The average maximum diameters of the occipital emissary vein for patients who underwent transverse sinus stent placement were larger before stent placement than after stent placement: 2.6 versus 1.8 mm proximally (P Ͻ .06) and 3.7 versus 2.6 mm distally (P Ͻ .005). CONCLUSIONS: Occipital emissary veins are more frequent and larger in patients with pseudotumor cerebri syndrome than in healthy subjects, a finding consistent with their role as collateral venous pathway in transverse sinus stenosis. A prominent occipital emissary vein is an imaging sign that should raise the suspicion of pseudotumor cerebri syndrome. ABBREVIATIONS: OEV ϭ occipital emissary vein; MDCT ϭ multidetector row CT; PTCS ϭ pseudotumor cerebri syndrome; SCTV ϭ subtracted CT venography

Occipital emissary foramina in human skulls: review of literature and proposal of a classification scheme of the occipital venous anastomoses in the posterior cranial fossa

“…From anatomical point of view, if we refer to the proposed classification system (Figure 3d), an OEV should rarely found having a short course andmaking a direct anastomosis through a complete OEF, which connects a dural sinus with an extracranial vein. In the imaging studies, however, even a longer intraosseous anastomosis is called as OEV, [15] although it should be In (a) the diploic vein is drained to both dural sinus and occipital vein; in our series corresponding IOF+EOF were found in 13.3% of the skulls. In (b) the occipital diploic vein drains only to the occipital vein through EOF (8%).…”

“…In a MRI study on axial images, Cakmak et al [14] reported the OEV in 28% of the cases examined. In another imaging study on subtracted CT venography and contrast enhanced MRI, Hedjoudje et al [15] examined the OEV and reported its presence in 65.2% of the patients with increased pressure in the transverse sinus system versus 31.5% of the patients without pressure signs. Interestingly, however, the whole study is based on an identifiable occipital anastomosing vein connecting the confluence of sinuses or distal part of the superior sagittal sinus with the occipital vein.…”

“…[5][6][7][8][9][10][11][12][13] Additionally, it is demonstrated with much higher incidence in diagnostic imaging studies. [14,15] With the present study, based on examination of human skulls, and after reviewing the literature, we aimed to explain the discrepancies between the reported incidence of the OEF and OEV, which might help radiologists in diagnosing specific pathologies in the dural sinus system [14,15] and also neurosurgeons performing approaches to the posterior cranial fossa. [16]…”

Men Are from Mars, Idiopathic Intracranial Hypertension Is from Venous: The Role of Venous Sinus Stenosis and Stenting in Idiopathic Intracranial Hypertension

“…The link between IIH and venous pressure is further supported by the findings of Hedjoudje et al, who observed an occipital emissary vein in 30 of 46 (65%) patients with IIH versus only 29 of 92 (32%) of healthy controls and found it to be larger on average in patients versus controls. 19 Furthermore, the mean emissary vein diameter was reduced following stenting in 17 patients. These findings suggest that this vein, which connects the torcula with the suboccipital veins, can dilate to serve as a collateral pathway in patients with IIH who have TS stenosis, and that its enlargement may serve as yet another radiological marker of the disease.…”

Variations of the CNS Venous System Mimicking Pathology: Spectrum of Imaging Findings

“…Arteriovenous shunting can produce a similar effect. Emissary veins can also function as collaterals and dilate in individuals with craniosynostosis, particularly when associated with jugular foramen stenosis or atresia, and in cases of pseudotumor cerebri . Occasional anatomic variants, such as diminutive bilateral jugular veins, may cause emissary veins to dilate as they function as collateral venous drainage…”