Answer of December 2012

Clinical History:

A 22 year-old female patient with a history of scalp swelling since young complained of a scalp mass with bony defect at skull vertex. CT, MRI and DSA were performed.

                                    Figure 1. CT Brain.

                Figure 2. MRI Brain (T1W, T2W, T1W post-contrast images).

                                      Figure 3. DSA.

Diagnosis:

Sinus pericranii (closed type)

Discussion:

CT brain showed a bony defect in the left parietal parasagittal area, associated with an extracranial soft tissue lesion. MRI brain revealed a lobulated extra-axial heterogenous enhancing lesion in the left parietal region. DSA demonstrated a venous pouch at the left parietal scalp region in parasagittal location, which is supplied and drained through the superior sagittal sinus. Overall features are suggestive of sinus pericranii (closed type).

Sinus pericranii is an unusual venous anomaly characterized by collection of venous blood vessels adhering to the outer surface of the skull, communicating with dural venous sinus and extracranial venous system (venous varix & venous malformation). The condition is featured as a vascular scalp mass communicating with dural venous sinus via transcalvarial vein, which courses through a well defined bony defect. Most frequently it is at the frontal or parietal region around midline or paramedian in location, with superior sagittal sinus most commonly involved.

Sinus pericranii can be classified as "closed" and "drainer" types based on the venous drainage pattern. Closed type: blood comes from and drains into dural venous sinus. Drainer type: blood comes from dural venous sinus, and drains into scalp veins.

Symptoms are infrequent but include headache, vertigo, feelings of fullness, or local pain. A non-tender fluctuant bluish scalp mass can be detected, which reduces in upright position and distends when lying prone or with Valsalva maneuver.

Most lesions are congenital, but traumatic causes with disruption of emissary veins at outer table are also possible. They can be associated with developmental venous anomalies, systemic venous malformations, blue rubber bleb nevus syndrome and multisutural craniosynostosis.

Treatment options include surgery and endovascular therapy. Surgery is usually done for symptomatic cases with the aim of cosmetic improvement. Removal of extracranial venous component, ligation of transosseous emissary veins with closure of bone holes / cranioplasty are performed. Good prognosis is usually achieved after surgical removal, and recurrence is uncommon. Endovascular therapy can be given with percutaneous injection of sclerosants or coils into the draining scalp veins, and is usually reserved for small or single drainer sinus pericranii. However, treatment is contraindicated if the sinus pericranii serves as a major intracranial venous drainage pathway or drains an underlying developmental venous anomaly.