By Rahul V. Pawar, MD, DABR; David Dunaway, DO;
and Lyle R. Gesner, MD

History

Seizures (successfully treated with antiepileptic medications)

Description

Persistent drainage pathways that connect the confluence of sinuses with the sigmoid sinus/internal jugular vein bilaterally. Atretic left transverse/sigmoid sinus segments (incidental).

Diagnosis

Persistent occipital sinuses

Discussion

• Aside from understanding the various limitations/pitfalls of MR venography, recognizing anatomic variants of major venous drainage is critical and surgically relevant.

• “Flow gaps” can be seen in up to 30% of normal MR scans typically within the hypoplastic transverse sinus, principally as a function of slow intravascular flow, in-plane flow, and/or complex flow patterns. Hypoplasia of the transverse or sigmoid sinus may be associated with alternative drainage pathways (eg, persistent occipital sinus).

• Occipital sinuses usually communicate cranially at the torcular Herophili and caudally at the foramen magnum, where a multitude of variations may exist.

• Occipital sinuses have been reported in up to 10% of normal subjects and may be associated with atretic transverse/sigmoid sinus segments and internal jugular vein. Correlation with CT may bolster confident diagnosis by demonstrating a smaller caliber sigmoid sinus groove and/or jugular foramen.

• Occipital venous network is believed to regress once most of the venous flow passes through the major dural sinuses when children assume the upright position.

• Relevance: (Accidental) discovery of a persistent occipital sinus during posterior fossa surgery can result in catastrophic hemorrhage and/or occlusion of the occipital sinus that may lead to venous thrombosis/infarction.

— Rahul V. Pawar, MD, DABR, is a radiologist at Saint Barnabas Medical Center in Livingston, New Jersey.
— David Dunaway, DO, is a radiology resident at Saint Barnabas.
— Lyle R. Gesner, MD, is the neuroradiology section head at Saint Barnabas.