Aneurysms in Retrotympanic Internal Carotid Artery: Case Insights

Introduction An internal carotid artery (ICA) that follows a retrotympanic course is a rare but well‐documented anatomical variant. During embryological development, the congenital absence of the cervical portion of the ICA results in formation of this aberrant collateral circulatory pathway (Nicolay et al., 2014; Roll et al., 2003). We present a case series of two patients with aneurysms in the setting of these unilateral variants, specifically located in the portion of the aberrant ICA running through the middle ear. Methods We present two patients who were noted to have ICA aneurysms in the retrotympanic portion of the ICA. Results The first patient is a 69‐year‐old man who presented with unilateral mixed conductive and sensorineural hearing loss. He underwent initial evaluation by otolaryngology during which his left‐sided aberrant ICA and associated aneurysm were detected on computed tomography (CT) of the orbits and sella and confirmed with follow‐up CT angiography (CTA). After discussion with the patient regarding the possibility of a rupture event causing catastrophic bleeding from the middle ear and the possibility that mass effect exerted on the middle ear structures by the aneurysm could be contributing to his hearing loss, the patient elected for treatment of the aneurysm with Pipeline embolization. This procedure was performed without complications and resulted in minor improvement of the left‐sided hearing loss.The second patient is a 66‐year‐old woman who was incidentally found to have a left‐sided aneurysm in the aberrant retrotympanic segment of the ICA. This was identified via diagnostic head CT during workup for migraines and confirmed with follow‐up magnetic resonance angiography (MRA) and digital subtraction angiography (DSA). Given the small size of the aneurysm, lack of symptoms, and patient preference, she elected for conservative management with serial imaging. Conclusions These two cases highlight the potential for aneurysm formation in an unexpected location in the setting of the well‐known anatomic variant of a retrotympanic course of the ICA. Providers should carefully evaluate for the presence of an aneurysm in patients with a retrotympanic course of the ICA to help avoid potential catastrophic inadvertent violation of the aneurysm during procedures of the middle ear. 1.Nicolay S, De Foer B, Bernaerts A, Van Dinther J, Parizel PM. Aberrant internal carotid artery presenting as a retrotympanic vascular mass. Acta Radiol Short Rep. 2014 Nov 26;3(10):2047981614553695. doi: 10.1177/2047981614553695. PMID: 25535568; PMCID: PMC4271713.2.Roll JD, Urban MA, Larson TC 3rd, Gailloud P, Jacob P, Harnsberger HR. Bilateral aberrant internal carotid arteries with bilateral persistent stapedial arteries and bilateral duplicated internal carotid arteries. AJNR Am J Neuroradiol. 2003 Apr;24(4):762‐5. PMID: 12695219; PMCID: PMC8148656.