Palpable Pulsatile Mass of the Forehead: A Case Series of Superficial Temporal Artery Pseudoaneurysms

Pseudoaneurysms of the STA are rare. Since the first description by Thomas Bartholin in 1740, only 400 cases of STA pseudoaneurysms, isolated or associated with arteriovenous fistulas, are described in scientific literature [1]. The most common etiology of STA pseudoaneurysms is blunt trauma, accounting for 75% to 95% of cases. Penetrating injury, iatrogenic injury after surgical procedures involving face or head and spontaneous pseudoaneurysms due to atheromatosis or a congenital defect of the arterial wall are other described causes [2,3].

Although lesions of the STA are rare, the STA is unprotected over a long distance. In most case reports the superficial anterior branch is affected. Between the occipitofrontalis muscle and the temporalis muscle, the anterior branch of the STA is most vulnerable to compression against the rigid scull [2,4] (Figure 1). Male and elderly patients with atherosclerotic and/or calcified arteries are especially vulnerable to this type of aneurysm. men are also more likely to be exposed to trauma [5]. 

Figure 1: Anatomy of the ATS in relation to occipitofrontalis and temporalis muscle. Between the occipitofrontalis muscle and temporalis muscle the anterior branch of the STA is most vulnerable to compression against the rigid scull [1,4].

Most aneurysms of the STA are pseudoaneurysms: a trauma to the STA leads to partial trans section and/or contusion of a segment of the artery and causes the lumen of the artery no longer being surrounded by the three layers of the arterial wall [2,4] (Figure 2). This is in contrast to a “real” aneurysm, where the three layers of the arterial wall remain present. Often young patients have a compressible pulsatile mass of 1-1, 5 cm approximately two to six weeks after traumatic injury of the temporal region. Additional symptoms can be throbbing headache, auditorial and visual disturbances, vertigo and rarely facial nerve paresis. The pulsations of the mass can be eliminated or reduced by proximal compression of the STA. A systolic murmur and a palpable ‘thrill’ can be present [2,4].

Figure 2: Schematic demonstration of anatomy of pseudoaneurysm (a) true aneurysm (b) In true aneurysm all layers of the vessel wall are involved [6]. 

 

In the differential diagnosis a lipoma, hemangioma, AV malformation, meningocele, angiofibroma, and supra-orbital neurinoma should be kept in mind. Nevertheless, the correct diagnosis can often be made by detailed history and accurate clinical examination [4]. Diagnosis is frequently confirmed by duplex-sonography and sometimes by classical or CT-angiography [2,7].

We retrospectively created a database of patients on whom an operation of the STA was performed, excluding STA biopsies. Between 2006 and 2016, five patients at our institution have undergone surgery of the STA for a palpable pulsatile mass of the forehead. We provided demographic, histologic, clinical and therapeutic data from these five cases. Finally, we compared our results with current literature and provided a review on pseudoaneurysms of the STA and its treatment. Verbal informed consent for publication of patient information and images was provided by our patients.

Case 1

Case 2

Case 3

Case 4

Case 5

STA-pseudoaneurysms require adequate treatment due to the risk of spontaneous rupture, pain and potential esthetic reasons [4, 9]. However, only three case reports with spontaneous rupture of the STA-pseuodoaneurysm have been described in literature. Surgical resection under general or local anesthesia is considered the standard therapy [1, 2, 4,9]. The pseudoaneurysm is localized with subsequently ligation of the proximal and distal STA; next, the pseudoaneurysm is completely resected [10]. 

Nonsurgical methods include observation and application of continuous pressure over the aneurysm with eventual thrombosis. These methods can be effective in cases of small STA pseudoaneurysms, sometimes associated with arteriovenous fistulas [1,5]. Others suggest that conservative treatment is not appropriate due to the risk of rupture, bleeding and thrombo embolism [5,11].

Nowadays endovasculair approaches for treatment of vascular malformations gain popularity. Endovascular treatment using a microcoil or vascular plug may be used as a therapeutic tool when the STA pseudoaneurysm has a relatively inaccessible localization, such as the proximal STA [1]. In these cases, adequate dissection of the parotid gland and the facial nerve before ligation and resection of the aneurysm may pose a greater threat than the aneurysm itself; justifying endovascular embolization as the first choice of treatment [1]. Compared to surgical resection, coil embolization requires a longer preoperative time but has a shorter recovery time and avoids/minimizes the surgical scar [1, 9].Nikolakopoulos et al., suggest that an endovascular approach should only be performed when angiography is mandatory for diagnosis [5].

Furthermore, percutaneous ultrasound-guided injection of thrombin can be used on chronic or sub acute pseudoaneurysms with a diameter of 4 cm or less [5]. In contrast to coil-embolisation, local injection of thrombine has a higher incidence of complications such as allergic reactions, risk for recanalisation and distal ischemia [5,9]. Other disadvantages are the lag time for resolution of the thrombosed pseudoaneurysm and the need for reexamination with duplex ultrasound to ensure no recanalization of the pseudoaneurysm has occurred [5]. 

The diagnosis is confirmed histo pathologically with loss of normal arterial architecture and an arterial wall that mainly consists of fibrous tissue and organized thrombus.

Our results are concordant with the current literature regarding pseudoaneurysms of the STA. 75% of our patients with a STA pseudoaneurysm are male with a median age of 35 years at diagnosis. For patients with a traumatic event preceding the development of a pseudoaneurysm the median delay was 3 weeks, in contrast to the AV malformation which arised spontaneously. All our patients presented with a pulsatile swelling at clinical examination. Correct diagnosis could be made by detailed history and clinical examination, and confirmed by duplex-sonography in four cases and angio-MRI in one case. In all five cases, surgical resection with ligation of the proximal and the distal vessels of the pseudoaneurysm and the AV malformation was performed. Histo pathologically, the diagnosis of a traumatic pseudoaneurysm of the STA was confirmed in four cases, with a median diameter of 0.86 cm, and an AV malformation of the STA in the remaining case. 

STA pseudoaneurysms are rare and develop in most cases post traumatically. Despite recent advances in endovascular approaches, surgical resection remains the treatment of choice.