Volume 39, Issue 12 , Pages 1234-1236, December 2010
A rare cause of a parotid mass: spontaneous pseudoaneurysm of the superficial temporal artery
Article Outline
- Abstract
- Case study
- Discussion
- Funding
- Competing interests
- Ethical approval
- Acknowledgment
- References
- Copyright
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.
Keywords: Pseudoaneurysm, Superficial temporal artery, Parotid
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-traumatic7. 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 8mm 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 10mm 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 10mm 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.
Fig. 3.
Oblique magnetic resonance angiographic image showing the external carotid artery (ECA), the superficial temporal artery (STA) with the arrow showing the abnormal flow within the aneurysm lumen.
The patient was referred to a vascular surgeon for further assessment. Treatment options were discussed with the patient and as the lesion had not grown in size over 2 months, and there were no associated symptoms, it was decided that the pseudoaneurysm would be treated conservatively with clinical and imaging surveillance initially.
Discussion
A pseudoaneurysm, also known as a false aneurysm, is a dilation of a blood vessel with the rupture of at least one layer of its wall, which is contained by the surrounding tissues. These lesions differ from true aneurysms which involve blood filled dilation of all three intact layers of the vessel wall.
Pseudoaneurysms of the extra-cranial carotid arteries are uncommon and are most commonly post-traumatic, involving the internal carotid artery5. There are only 13 cases in the literature involving the external carotid artery. Pseudoaneurysms of the superficial temporal artery are well described in the literature but are nearly always post-traumatic or iatrogenic2, 3. It is extremely rare for a pseudoaneurysm of the superficial temporal artery to arise spontaneously.
Intra-parotid pseudoaneurysms may present as parotid masses. There are only 7 cases described in the literature: 4 involved the intra-parotid external carotid artery; 2 the superficial temporal artery; and 1 the posterior auricular artery8.
The clinical presentation of the lesion in this case mimicked a parotid tumour. Lack of pulsatility of the mass was a misleading clinical sign. This case highlights the importance of accurate imaging diagnosis, usually in the form of ultrasound, before needle or surgical biopsy of parotid lesions is undertaken. Modern high field strength magnetic resonance imaging systems or multislice computed tomography scanners are capable of producing highly detailed anatomical and angiographic sequences allowing precise lesion delineation and characterisation1.
The cause of the pseudoaneurysm in this patient cannot be known with certainty but it seems likely that that repeated use of the Valsalva manoeuvre played a significant role in its development. It is possible that the repeated sudden changes in arterial blood pressure caused by the Valsalva manoeuvre may have led to weakening of the vessel wall and subsequent pseudoaneurysm formation4. This proposed mechanism of vessel damage is speculative. One case reported in the literature describes rupture of a carotid vessel following a Valsalva manoeuvre during sexual intercourse6. The vessel affected was the common carotid artery and it was repaired surgically with a saphenous vein patch.
Management options for extra-cranial pseudoaneurysms include observation, surgical excision, pressure dressings and embolisation3, 5. This patient was managed conservatively with close observation. The factors influencing this decision were the fact the mass had not enlarged over many weeks, the proximity of the pseudoaneurysm to other important structures, the absence of any associated symptoms and patient choice.
Funding
None.
Competing interests
None declared.
Ethical approval
Not required.
Acknowledgment
The authors would like to thank Nick Taylor for his assistance in putting together this case report.
References
- . Pediatric salivary gland imaging. Pediatr Radiol. 2009;39:710–722[Epub 2009 March 27. Review]
- . Iatrogenic false aneurysm of the superficial temporal artery. Case report. Plast Reconstr Surg. 1977;60:457–460
- . Pseudoaneurysms of the superficial temporal artery: treatment options. Laryngoscope. 2004;114:1000–1004
- . Effects of hypovolemia and posture on responses to the Valsalva maneuver. Aviat Space Environ Med. 1996;67:308–313
- . Pseudoaneurysm of the external carotid artery—review of literature. Head Neck. 2009;31:136–139[Review]
- . Spontaneous rupture of the common carotid artery with pseudoaneurysm formation. Ann Emerg Med. 1997;30:230–233
- . Traumatic pseudoaneurysm of the external carotid artery with parotid mass and delayed facial nerve palsy. Otolaryngol Head Neck Surg. 1999;121:158–160
- . Vascular lesions of parotid gland in adult patients: diagnosis with high-resolution ultrasound and MRI. Br J Radiol. 2004;77:600–606
PII: S0901-5027(10)00287-0
doi:10.1016/j.ijom.2010.06.010
© 2010 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.
Volume 39, Issue 12 , Pages 1234-1236, December 2010
