An unusual scalp mass in a 29-year-old woman

We presented a case of a 29-year-old woman who noticed a swelling located in her scalp. One centimeter non-pulsatile and fluctuant paramedian mass was observed in the right parietal scalp region. A year ago, the patient had sought another service for the same complaint, a computed tomography (CT) scan was performed and there was no lesions and was discharged. A new skull CT scan with careful examination of the referred site, revealed a bone defect (Figure 1). Brain magnetic resonance imaging (MRI) along with venography was performed and showed an abnormal communication between the intraand extracranial venous drainage pathways thought a cortical vein, characterizing a sinus pericranii (Figure 2). Because of no esthetic prejudice and no neurological symptom, our patient went on to be treated conservatively. The patient has been followed for two years without intercurrences.


CASE REPORT
We presented a case of a 29-year-old woman who noticed a swelling located in her scalp. One centimeter non-pulsatile and fluctuant paramedian mass was observed in the right parietal scalp region. A year ago, the patient had sought another service for the same complaint, a computed tomography (CT) scan was performed and there was no lesions and was discharged. A new skull CT scan with careful examination of the referred site, revealed a bone defect ( Figure 1). Brain magnetic resonance imaging (MRI) along with venography was performed and showed an abnormal communication between the intra-and extracranial venous drainage pathways thought a cortical vein, characterizing a sinus pericranii ( Figure 2). Because of no esthetic prejudice and no neurological symptom, our patient went on to be treated conservatively. The patient has been followed for two years without intercurrences.

DISCUSSION
Painless soft tissue masses on the scalp are commonly encountered in clinical practice and are often underestimated by the primary care provider, since the most likely diagnoses are benign lesions such as epidermoid cysts, sebaceous cysts and lipomas [1,2]. However, clinicians should be alert to other diagnostic possibilities. Sinus pericranii, a rare vascular anomaly of the venous drainage between the intracranial and extracranial systems, is one of the differential diagnoses which should be considered when a physician encounters a patient with a subcutaneous soft scalp mass [3].  A wide variety of scalp lesions are identified as palpable masses (Table 1) [4,5]. They represent a challenge for clinicians and radiologists, and are frequently confounded by their small size and similar appearances on radiologic images, what may lead to diagnostic mistakes [6].
Most scalp and skull lesions in children and young adults are benign. However, in a recent series, the rate of presence of significant clinical pathologies or requiring follow-up was not negligible around 7.8% and the correct diagnosis was made in only 13-27% patients [2]. The same study indicated that diagnostic workup or interdisciplinary consultations were not performed regularly, which may be of concern since the correct diagnosis of a scalp mass may lead to reduced mortality and morbidity and may guide physicians toward the most appropriate management (surgical or nonsurgical) [6].
Sinus pericranii (SP) is a rare extradural venous anomaly in which there is an abnormal connection between the extracranial venous system and the intracranial dural sinuses via a connecting diploic vein [7]. Although the condition is usually asymptomatic, there have also been reports of symptomatic SP causing debilitating headaches, ataxia, nausea, vomiting, hearing loss, epilepsy, bradypnea, and bradycardia [8]. Some clinical clues may assist the physician in the suspicion of SP: lesion near the midline, compressible or changes with patient's position or Valsalva maneuver [9]. Neuroimaging is fundamental in diagnosis. CT is considered the best examination available to characterize bone defects, and MRI is an essential method for defining lesion extension for both the skin and intracranial spaces[10]. Because of its rarity, the exact nature and management of SP have no guidelines or recommendations. Most SP remain stable in size and flow dynamics over years with a relatively low risk of spontaneous or traumatic bleeding. Endovascular embolization and surgical ligature are effective treatment options [11].
We present a typical case of SP where the correct diagnosis was only possible due to the correct recognition of the clinical characteristics of the lesion and indication of neuroimaging investigation.

CONCLUSION
The knowledge of a wide differential diagnosis of scalp masses enables the clinicians to reach a more accurate diagnosis in the majority of sinus pericranii cases.