Selchuk Peker, H.Ibrahim Sun, Serdar Ozgen, Ozlem Kurtkaya, M.Necmettin Pamir
Marmara University Department of Neurosurgery, Marmara University Neurological Sciences Institute, Istanbul, Turkey
Sinus pericranii is an unusual vascular anomaly of the scalp. A case of sinus pericranii on the right frontal area is presented in this report. The pathogenesis is discussed and the literature is reviewed.
Sinus pericranii, surgery, vascular anomaly.
Sinus pericranii is a small circumscribed fluctuating vascular swelling of the scalp. It directly communicates with the intracranial venous system. This pathology is mostly seen in pediatric age group.
According to Marras , this condition probably first reported by Percivall Pott following a skull fracture in 1760. Hecker was first described it in 1845 as "varix spurius circumscriptus venae diploicae frontalis" .
In this report we present a case of a sinus pericranii in a young adult.
This 21-year-old man presented with headache and soft tissue swelling at the right frontal region for one year. There was no history of head trauma.
Clinical examination demonstrated a 5´3cm, soft, compressible, nonpulsatile mass lesion in the right frontal region.The skin over the lesion was normal. The mass was observed to increase in size when the patient performed a valsalva manoeuver. Neurological examination revealed no pathological signs.
Plain radiographs of the skull demonstrated osteolytic area with sklerotic edges on right frontal region (Fig.1). Computer tomography (CT) demonstrated slightly erosion on the frontal bone (Fig.2). Magneto-resonance imaging (MRI) revealed the mass to be hypointense in T1-weighted and hyperintense in T2-weighted images. The lesion demonstrated heterogenous enhancement with Gd-DTPA (Fig.3). The clinical diagnosis of sinus pericranii was made.
Surgery: Under general anesthesia, an arch-shaped skin incision was made behind the hair line. The tumor was visualised below the periosteum (Fig.4). The vascular mass was removed totally (Fig.5). The vascular channels from the mass to the diploe were obliterated with bone wax (Fig.6). It is confirmed by bilateral juguler compression that there is no blood leakege from the skull.
The postoperative course was uneventful and the patient was discharged 5 days later.
Pathological findings: Microscopic examination of the mass revealed many nonmuscular venous vessels and lined by simple endothelial cells. In some areas fibrous tissue was seen within the lesion (Fig.7).
Sinus pericranii is a collection of nonmuscular venous blood vessels or venous hemangioma adhering tightly to outer surface of the skull bone and communicating directly with an intracranial venous sinus by way of diploic veins .
In 1850, Stromeyer reported this anomaly as a "subperiosteum blood-filled cyst of the skull communicating with an intracranial sinus" and proposed the term "sinus pericranii" . There are numerous terms used in the literature to describe this entity; varix simplex, varix racemosus, varix herniosis, cirsoid aneurysm, venous angioma, varix cirsoideus, fistule osteo-vasculaire, venous tumor of the cranial bones and venous varicosities of the skull .
The cause of this malformation remains unclear. In general, sinus pericranii is considered as a congenital abnormality although trauma is believed to be a possible causative factor at least in some cases . Widely accepted criteria for establishing the origin of this anomaly is the type of tissue lining the sac; an endothelial lining is characteristic of a congenital sinus pericranii, whereas the acquired lesion has a connective tissue lining . The pathological examination of the mass in our case revealed endothelial lining and therefore we accepted this patient as a congenital sinus pericranii.
Sinus pericranii is generally found at the neighborhood of intracranial venous sinuses. There are several reported cases of sinus pericranii situated laterally in the frontal or frontotemporal region .
Almost always this malformation is asymptomatic. The mass characteristically enlarges with increased intracranial pressure such as that due to crying, a valsalva maneuver, or dependent positioning . The size of the mass decreases with direct compression or head elevation. This condition can occur in any age but most patients are below 30 years of age. Male to female ratio is about 2:1 .
A diagnosis of sinus pericranii can be suggested from the clinical appearance of a soft, fluctuant mass located near the intracranial sinus which can vary in size with valsalva maneuvers . Plain X-ray of the skull may reveal hypodense area below the mass. On CT using bone windows there will be a well defined osteolytic lesion. CT in our patient demonstrated some erosion on the frontal bone. Additionally a soft tissue swelling can be seen. MRI demonstrates the signal characteristics of the content of the sinus and relationship of the lesion to the subjecent sinus . Sadler  presented a case studied by MR that showed a lesion with mixed intensity signal, caused by a turbulent flow. MR venography can be used to demonstrate the relationship between the mass and the venous sinuses .
Although spontaneous regression of sinus pericranii has been reported , the anomaly has a tendency to grow gradually . Most patients are asymptomatic, so main aim of the surgery is to eliminate cosmetic problems. But excision of the mass will also prevent massive hemorrhage and traumatic air emboli. Surgical treatment is simply removal of the mass and blocking or supression of the communicating veins. The communicating diploic veins are blocked with bone wax in our patient. Some authors have described extensive craniotomy or craniectomy to remove this malformation . The occlusion of this abnormal pathway has not been reported to result in intracranial venous hypertension . The possible complications during surgery are air embolism and hemorrhage.