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

Variations in the venous drainage of the central nervous system can have imaging and clinical findings that mimic pathology, presenting a challenge for neuroimagers and clinicians. Patients with these variants may undergo unnecessary testing, and patients with pathology may receive delayed diagnoses because of overlap with benign findings. Consequently, the accurate identification of venous variations on cross-sectional imaging and angiography and their potential causes are critical for differentiating benign imaging variants from potential pathologic processes requiring further evaluation. For example, in the epidural space, benign dilation of the epidural venous plexus may be mistaken for evidence of a fistula, abscess, or metastasis. Hypoplasia of a dural venous sinus or an arachnoid granulation may mimic venous sinus thrombosis. The superior ophthalmic vein may demonstrate benign dilation in intubated patients, mimicking thrombosis, increased intracranial pressure, orbital varix, inflammatory pseudotumor, or other conditions. Furthermore, certain venous variations, such as the occipital sinus or emissary veins, may complicate surgery or herald pathology and should be reported. In addition, some supposedly benign variations, such as the developmental venous anomaly, can be complicated by pathology. The objective of this review article is to provide a descriptive and pictorial review of common anatomic and physiologic variations in the venous drainage system of the brain, spine, and orbits that can mimic pathology. Neuroimaging findings of related pathologies and differences in clinical presentations will also be discussed to assist in the approach to differential diagnosis.