History: 5-year-old boy with a pulsatile mass of the left middle ear discovered during tympanostomy tube placement.
Findings: An axial CT scan of the left temporal bone demonstrates a soft tissue mass on the cochlear promontory contiguous with the carotid canal. Axial CT of the opposite temporal bone shows normal appearance of the carotid canal with intact posterolateral bony wall. A lateral view from a left carotid arteriogram revels an aberrant course of the petrous portion of the carotid artery that extends too far posteriorly.
Diagnosis: Aberrant carotid artery
Discussion: An aberrant internal carotid artery is an unusual anomaly that can present at any age. Symptoms are usually mild although pulsatile tinnitus can occur. On physical examination, a pulsatile middle ear mass may be identified. This lesion can mimic a glomus tympanicum tumor clinically, and multiple cases have been reported of biopsy of this ‘mass’, often with disastrous consequences. The CT appearance of this condition is diagnostic. Catheter of MR angiography, although unnecessary in most cases, is confirmatory. The aberrant internal carotid artery is formed from anastomosis between the inferior tympanic artery and the caroticotympanic artery that occurs when the petrous segment of the internal carotid artery fails to develop normally. Every radiologist must know about this condition and inform the referring clinician when this diagnosis is made.
Aunt Minnie’s Pearls
- An aberrant internal carotid artery is an important cause of pulsatile tinnitus.
- Inform the referring clinician when this diagnosis is made, so a potentially disastrous biopsy can be avoided.