A rare case of maxillary artery branch pseudoaneurysm

An adult male, with no significant past medical history, presented to Accident & Emergency with episodes of right-sided epistaxis following extraction of the upper right wisdom tooth. Upon initial review, it was felt the bleeding was of nasal origin; however, following repeat episodes, concerns were raised for underlying pathology.

Initial imaging with arterial phase CT sinuses with contrast was performed, evidencing a large defect in the posterior maxilla due to maxillary tuberosity fracture, a known potential sequela of posterior maxillary tooth extraction (Figures 1 and 2). In addition to this, an associated focal area of hyperdensity in the region of the posterior wall of the maxillary antrum was identified (Figure 3). This area was better evaluated on subsequent CT angiogram, and represented a well-defined 14 x 9 x 11mm focus of enhancement with a similar density to the adjacent vascular structures, alluding to a pseudoaneurysm. The position of this enhancing focus suggested that it was arising from the posterior superior alveolar artery (PSAA), a distal branch of the maxillary artery (Figures 4, 5 and 6).

The maxillary artery is one of two terminal branches of the external carotid artery (ECA), further dividing into 3 segments. From the third (pterygopalatine artery), arises the PSAA. This supplies the maxillary teeth and sinus [1].

A pseudoaneurysm is a dilatation of an artery, bound only by the tunica adventitia. Likelihood of incidence and aetiology depends on its location. In the maxillary region, the most likely culprits are trauma, iatrogenic causes and infection [2,3]. Occurrence of pseudoaneurysm in this area is very rare [3].

Pseudoaneurysms may present as a mass (potentially pulsatile), possibly with an audible bruit. Clinical history is important for correlation of signs – recent trauma or surgery in the area should arouse more suspicion [3].

On CT, pseudoaneurysms demonstrate hypoattenuation on non-contrast studies and enhance when contrast is administered. They are usually well-defined, rounded, and communication with the vessel of origin is often seen. They may be surrounded by haemorrhage (often more hyperdense), indicative of rupture [4].

Ultrasound is an alternative non-invasive modality for assessment of superficial pseudoaneursyms; but is highly dependent on the operator’s skill and has low sensitivity in evaluating deeper arteries or vessels of trauma patients with fractures/haematomas [5].

The risk of rupture tends to be greater than that of true aneurysms of the same size, due to weaker support of the aneurysmal wall. Therefore, pseudoaneurysms usually require intervention [2]. Primary methods include surgical management and endovascular therapy. The latter poses less post-treatment complications and eliminates need for general anaesthetic but is not risk-free. The main associated risks include propulsion of embolic material into other arteries, puncturing of the aneurysm wall leading to bleeding, or failure of procedure [3]. Specific risks of ECA branch embolisation include inadvertent embolisation of retinal arterial supply, facial nerve arcade or passage of embolisation material into the brain through arterial connections. Careful mapping of the internal carotid artery and ECA is performed prior to any ECA embolisation to reduce these risks.

Our patient underwent PSAA embolisation with coils and embospheres (Figures 7 and 8), resulting in complete aneurysm occlusion. Apart from minor spotting post-procedure, early recovery has been uncomplicated.

Take home messages

• Pseudoaneurysm of the maxillary artery is a rare, but significant, potential consequence of upper molar extraction.
• Epistaxis can be an atypical presentation of a pseudoaneurysm, and warrants further investigation, especially if a clear cause cannot be found upon initial review.
• Clinico-radiological correlation is crucial in guiding next appropriate investigations and management.

Informed patient consent for publication has been obtained.