Thrombosed mycotic aneurysm of the cervical internal carotid artery mimicking a parapharyngeal abscess in a child: a case report of multimodal imaging diagnosis.

A parapharyngeal abscess, although relatively rare, is a potentially life-threatening deep neck space infection in the pediatric population that carries a risk of serious complications. Mycotic pseudoaneurysm of the cervical internal carotid artery (ICA) is a rare vascular complication in children that can lead to catastrophic hemorrhage if misdiagnosed and attempted for surgical incision. We report a 7-year-old malnourished boy presenting with fever, dysphagia, and neck stiffness. Suboptimal contrast-enhanced computed tomography (CT) suggested a left parapharyngeal abscess, and surgical drainage was planned. A dedicated CT, magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) mapping, magnetic resonance angiography, and three-dimensional CT angiography identified a completely thrombosed mycotic pseudoaneurysm rather than an abscess. This case demonstrates that complete thrombosis transforms a mycotic pseudoaneurysm into a mass that can easily be mistaken for an abscess without the right imaging modalities and high-quality imaging.