THE ABERRANT INTERNAL CAROTID ARTERY: A RARE AND IMPORTANT ANATOMIC VARIANT

Abstract

Background An aberrant internal carotid artery (ICA) is defined as a collateral pathway resulting from agenesis of the first embryonic segment of the ICA. Misdiagnosis can lead to unnecessary surgery and fatal complications.1 Clinically, they can present as pulsatile tinnitus, hearing loss, or a feeling of aural fullness, or they can be completely asymptomatic.2 We present the case of a 14-year-old female seen by her orthodontist for evaluation of malocclusion and popping of the right temporomandibular jaw (TMJ). Clinical and Radiographic Findings A cone beam computed tomography (CBCT) volume from the frontal bone to the level of C4 for orthodontic evaluation was sent to our department for interpretation. Upon review, we observed a high-attenuation, noncorticated, soft tissue entity appearing to arise from the left carotid canal and traversing through the middle ear. No gross abnormalities were noted in the osseous components of the TMJ complexes. Differential Interpretation The differential diagnoses for soft tissue entities in the middle ear include an ICA aneurysm, glomus tumors, and cholesteatomas.3 Correlation with clinical findings and advanced imaging are needed for the differential diagnosis. Discussion/Conclusions The 4 hallmark radiographic findings for an aberrant ICA are an enlarged inferior tympanic canaliculus (ITC), an enhancing hypotympanic mass, an absent vertical segment of the ICA, and dehiscence of the cortex covering the tympanic portion of the ICA.4 Because of the lack of soft tissue/vascular contrast on a CBCT image, only an enlarged ITC and dehiscence of the cortex were seen in this study. Aberrant ICAs are known to cause tinnitus, which can mimic symptoms of a temporomandibular disorder (TMD).5 Because the patient was lost to follow-up, these findings could not be correlated clinically. However, it is important to note that a normal variant, as in this case, could contribute to the differential diagnosis and surgical intervention for TMDs or other incidental pathologies typically seen on CBCT.