Parotid venous malformation - a good radiological interpretation can prevent unnecessary intervention

A 17-year-old male patient presented with facial asymmetry and painless swelling of the parotid gland for five months. On clinical examination, there was a soft and compressible mass and the overlying skin showed a bluish tinge.

The patient was directly transferred to MRI, no prior ultrasound was performed.
Findings:
MRI of left parotid gland showed a heterogeneous signal intensity lesion in the left parotid space, which was involving the superficial as well as the deep lobe of the parotid gland. It showed internal septations with multiple signal voids representing phleboliths and cystic formations with fluid fluid levels. Anteriorly it was abutting the masseter muscle and extending up to the floor of the mouth with minimal infiltration and anterior displacement of the left submandibular gland. Posteriorly it was abutting the sternocleidomastoid muscle. Medially it reached the parapharyngeal space and abutted the carotid sheath and hyoid bone. Inferiorly it extended up to the previsceral space and was abutting the strap muscles. (Fig. 1) No abnormal signals or periosteal reaction was identified in the adjacent mandible. It showed heterogeneous post-contrast enhancement. (Fig. 2)

DISCUSSION:
Vascular anomalies have been subdivided into two main types A) vascular tumours B) vascular malformations. The classic example of vascular tumours are infantile haemangiomas which are further subdivided into 1) congenital haemangioma 2) epitheloid cellular haemangioendotheliomas 3) tufted angiomas 4) pyogenous granulomas, and other rare vascular tumours.
B) vascular malformations are subdivided into low flow lesions which are further subdivided into low flow lesions like venous, capillary, lymphatic and mixed types and high flow lesions divided into arterial and arteriovenous malformation. [1]
Haemangiomas are partly rapidly growing benign vascular tumours present in infants and they never re-appear in adolescence nor in adults.

Clinical Perspective:
Venous malformations are considered the main type of low-flow malformation of the head and neck. By definition venous malformations are present since birth. Patients present with slow-growing masses in adulthood. Histologically, venous anomalies are dysplastic, abnormal, venous vessels. Venous malformations have a tendency to increase in size with patient‘s age and appear as bluish compressible tumours when seen in a superficial location. Intralesional blood stasis can cause recurrent painful thrombophlebitis. On ultrasound venous malformation are hypoechoic serpegenious tubular structures with slow flow pattern showing increased surrounding fatty tissue [2]. Phleboliths within a venous malformation represent remnants of thrombophlebitis. CT also plays an important diagnostic role in venous malformations which show potential bone involvement. Venous malformations of the head and neck showing involvement of the aerodigestive tract, neural and vascular structures, multiplanar dynamic contrast enhanced MRI still is the imaging modality of choice [3]. On T2-weighted images venous anamolies appear as bright hyperintense lesions, if partial thrombosis has occurred in the lesion it shows signal alteration.

Outcome:
Minimally invasive percutaneous sclerotherapy is established for treatment of venous malformations. In large venous malformations, pain relief due to recurrent thrombophlebitis and size reduction can successfully be achieved in more than 90% of patients with Polidocanol or Sodium tetradecyl sulphate foam (STS) [4, 5]. As a result sclerosis of the venous endothelium and induction of fibrosis results in devascularisation of the venous malformation. Depending on location and extension of the Venous malformation, sclerotherapy should be repeated in 8 to 12 weeks intervals for pain management and size reduction of the venous malformation.

Take Home Message, Teaching Points: A good radiological diagnosis can prevent unnecessary intervention.