Venous malformation of the parapharyngeal space

A 72-year-old asymptomatic female patient underwent a contrast-enhanced Computed Tomography (CT) of the neck to further evaluate an “incidental finding” detected on a previous head CT, performed at the emergency department for head trauma.

CT of the neck showed a lobulated mass occupying the left parapharyngeal space, with no mass effect on the surrounding spaces or invasion of the adjacent structures. It exhibited mild enhancement after contrast injection in the venous phase and contained several rounded calcifications, consistent with phleboliths.

The parapharyngeal space is a deep space of the suprahyoid neck shaped as an inverted pyramid, extending from the skull base to the hyoid bone below and is comprised mostly of fat and neurovascular structures. Parapharyngeal space masses are rare, corresponding to only 0.5% of all head and neck tumours, the majority of which consist of salivary gland tumours, specifically pleomorphic adenomas [1,2].

The International Society for the Study of Vascular Anomalies (ISSVA) divides vascular anomalies into two main groups: vascular tumours and vascular malformations [3]. Venous malformations (VM) are the most common vascular malformation, even though they only correspond to <1% of all parapharyngeal space masses [4].

VM of the parapharyngeal space are usually detected incidentally since they are asymptomatic, and symptoms usually arise from compression of adjacent structures when they are large. The most common symptoms related to parapharyngeal space lesions are otalgia, dysphagia, and facial pain [5].

CT has an important role in evaluating these lesions due to its high sensitivity for detecting phleboliths and looking for the presence of bone involvement [3]. They usually present as lobulated masses of soft tissue attenuation. Even though phleboliths are only present in less than 30% of VM, they are pathognomonic of these slow-flow venous malformations [6].

MRI is the gold standard imaging technique for evaluating VM, due to its inherent superior spatial resolution and soft tissue contrast. VM are exquisitely bright on T2W sequences, with intermediate signal intensity on T1-weighted images, and they usually show progressive enhancement after contrast administration, with contrast filling in on delayed images. Signal voids can be seen in the presence of phleboliths [6].

Pleomorphic adenomas also demonstrate high signal intensity on T2W sequences and can present with calcifications, even though they are more mass-like expansile lesions, have a type A curve of contrast enhancement on DCE perfusion studies, and calcifications are usually more coarse or punctate [6].

Lymphatic malformations are featured by fluid-filled cavities containing fluid-fluid levels showing little or no contrast enhancement depending on the associated presence of a venous malformation [7].

Differential diagnosis should also include neurogenic tumours and other entities that can show calcifications in the PPS as ectopic meningiomas [8].

Treatment is usually reserved for symptomatic cases or when the diagnosis is uncertain and includes surgical resection and sclerotherapy [9].

In this case, the final diagnosis of a VM of the parapharyngeal space was made by the presence of phleboliths, and the patient decided not to proceed to surgery while being asymptomatic.

Written informed patient consent for publication has been obtained.