A rare cause of a parotid mass: spontaneous pseudoaneurysm of the superficial temporal artery

Abstract

The authors describe a rare presentation of a spontaneous pseudoaneurysm of the superficial temporal artery which mimicked a parotid neoplasm. The clinical presentation, possible aetiology, diagnosis, and management of this condition are discussed.

It is important that clinicians are aware of all the possible causes of a parotid mass, including conditions that may mimic benign tumours, and use appropriate investigations in diagnosis. Pseudoaneurysms of the external carotid artery and its branches are rare and are usually post-traumatic . An unusual case is described in which a spontaneous pseudoaneurysm relating to the superficial temporal artery presented as a parotid mass.

Case study

A 50-year-old female presented to the Oral and Maxillofacial Surgery Department complaining of sudden onset, painless swelling in her left pre-auricular region, first noticed immediately after performing the Valsalva manoeuvre. There was no history of direct trauma to the area. She was generally fit and well, although there was a history of sinus congestion for which she had been advised by a friend to perform the Valsalva manoeuvre to alleviate the symptoms. She had been undertaking the Valsalva manoeuvre several times a day for the 6 months prior to noticing the swelling.

On examination the patient had a soft, non-tender, non-fixed and non-pulsatile mass overlying the left parotid gland. It measured 2 by 1 cm and a provisional diagnosis of a pleomorphic adenoma was made.

The patient was referred for ultrasound, which confirmed a circumscribed hypoechoic mass measuring 21 by 8 mm in the superficial lobe of the left parotid gland with the lesion lying partly extrinsic to the gland outside the capsule at the upper pole. Colour Doppler flow assessment revealed a large arterialised vessel passing through the lesion within the gland, which branched within the mass with continuation of the vessel more cranially ( Fig. 1 ). Arterialised turbulent flow was seen within the mass. A provisional diagnosis of a pseudoaneurysm was made with a likely origin from a branch of the external carotid artery and magnetic resonance angiography (MRA) was recommended.

Fig. 1
Longitudinal Colour Doppler sonogram of the mass. Large arrow (left) showing arterialised turbulent flow within the mass. Small arrows (bottom) showing external carotid artery just before distal bifurcation. P denotes parotid gland.

MRA confirmed a rounded focus of altered signal ( Fig. 2 ) measuring 20 by 10 mm lying in relation to the upper pole of the left parotid gland in the pre-auricular location. The lesion lay partly outside the gland and was of inhomogenous signal on T1 and T2 weighting. It contained internal serpiginous low signal suggesting a vascular origin and also high signal on both sequences consistent with clotted blood. The angiographic sequence ( Fig. 3 ) confirmed a 10 mm focus of abnormal flow within the lesion correlating with the arterialised flow within the aneurysm lumen seen on ultrasound. The lesion was consistent with pseudoaneurysm, relating to the origin of the superficial temporal artery just distal to the terminal bifurcation of the external carotid artery.

Fig. 2
Coronal short tau inversion recovery (STIR) magnetic resonance image with arrow on serpiginous low signal void within the vessel within the mass, which is seen as mixed/high signal. P denotes parotid gland.

Feb 8, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on A rare cause of a parotid mass: spontaneous pseudoaneurysm of the superficial temporal artery
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