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Tawk, Karen MD; Abouzari, Mehdi MD, PhD; Martin, Elaine MD; Djalilian, Hamid R. MD
From left: Dr. Karen Tawk is a postdoctoral fellow in otolaryngology at the University of California Irvine, where Dr. Mehdi Abouzari is a translational physician-scientist and a postdoc fellow of otolaryngology, Dr. Elaine Martin is an otolaryngology-head and neck surgery resident, and Dr. Hamid R. Djalilian is the director of neurotology and skull base surgery and a professor of otolaryngology and biomedical engineering.
A 39-year-old male patient presented to the clinic with a history of left-sided hearing loss, ear fullness, and tinnitus. In 2009, an outside otolaryngologist placed pressure equalization (PE) tubes for ear effusion twice, and the patient was placed on steroids and antibiotics, but had no improvement. In 2014, he had serial aspirations of the middle ear with immediate relief. In addition, he reported left-sided ear pain and dizziness. He had no history of previous ear infections but had a car accident with head trauma 15 years prior. Microscopic examination of the left ear showed evidence of middle ear effusion. The right side was normal. The patient had had an MRI previously ordered which the patient brought in and was read as normal. (See Figure 1.)
In adults, a unilateral middle ear effusion, with no history of Eustachian tube dysfunction (ETD), warrants a complete head and neck examination, audiogram, and imaging on the part of the clinician. Most commonly, ETD is due to upper respiratory infections, allergic rhinitis, and gastroesophageal reflux (usually underrecognized). Worrisome conditions that can also cause ETD include nasopharyngeal masses (from benign tumors such as sinonasal polyps to malignancies such as nasopharyngeal carcinoma or clival chordoma) occluding the Eustachian tube. Wegener’s granulomatosis should be considered in adult patients with chronic serous otitis media or acute otitis media. Finally, a condition that can mimic or acute otitis media is the presence of middle ear mass such as glomus jugulare, middle ear adenoma, or aneurysm of the internal carotid artery (ICA). Subsequently, nasopharyngoscopy is warranted to rule out nasopharyngeal carcinoma, particularly in Asians (who have a higher risk of nasopharyngeal carcinoma), and a computerized tomography (CT) scan of the skull base to evaluate for occult masses or evidence of cerebrospinal fluid leak.
The MRI that was read as normal does not appear symmetric (Fig. 1). The carotid artery on the left is larger than the one on the right (left side of the image). Despite the normal radiology reading, this raised our suspicion for a possible abnormality of the carotid artery versus a petrous apex lesion. CT scan of the temporal bones showed complete opacification of the middle ear and mastoid air cells and an enlargement of the carotid canal. In addition, there was a smooth bony remodeling of the left petrous apex likely secondary to a possible aneurysmal dilatation of the petrous segment of the left ICA. The carotid canal wall was dehiscent into the middle ear cavity and had obliterated the Eustachian tube opening (Figs. 2 and 3). A magnetic resonance angiography (MRA) was obtained and showed that there is a fusiform dilatation of the left petrous internal carotid artery, consistent with a pseudo-aneurysm of the carotid artery (Figs. 4 and 5).
It is important to know the anatomical relationship between the ICA and surrounding neuro-otological structures to comprehend the symptoms of pathologies arising from this area. As described by Bouthillier classification, the ICA has seven segments: cervical (C1), petrous (C2), lacerum (C3), cavernous (C4), clinoidal (C5), ophthalmic (C6), and communicating (C7). 1 At the base of the skull, the ICA enters the petrous temporal bone anteriorly to the internal jugular vein and medially to the styloid process. Deeper within the temporal bone, the horizontal segment of the petrous ICA lies medially to the tensor tympani and ET. The genu of the petrous ICA is situated anterior to the cochlea. As the ICA turns anteromedially to exist the petrous apex over the foramen lacerum, it is limited superiorly by the cochlea and tympanic cavity. 2
Aneurysms of the petrous segment of the ICA are rare, as the segment is protected by the bony walls of the carotid canal. Most cases are considered congenital and arise from a weak area in the arterial wall that was the site of origin of regressed embryologic arteries (caroticotympanic and the pterygoid arteries). Other etiologies include traumatic blunt injuries-between the fixed petrous ICA and mobile cervical ICA-and mycotic (fungal) infection due to the proximity of petrous ICA with the middle ear and Eustachian tube. Histologic examination reveals degeneration of the internal elastic lamina and media of the carotid artery. Petrous ICA aneurysms are usually asymptomatic and found incidentally on imaging as fusiform lesions. Nevertheless, they can be associated with a range of symptoms that present in the third decade of life. Symptoms include headaches, facial numbness and/or palsy, nasal congestion, and Horner syndrome (no sweating, ptosis of eyelid, and myosis on same side of face, since the carotid canal contains postganglionic sympathetic nerves). Otologic manifestations include pulsatile tinnitus, dizziness, and progressive hearing loss as a result of a lateral extension of the lesion into the middle ear. In fact, the invasion of the middle ear is due to the erosion of the posterior wall of the carotid canal. The dehiscence of the thin bone plate separating the Eustachian tube from the vertical segment of the petrous ICA can result in symptoms due to ETD. Aneurysm rupture can result in life-threatening hemorrhage with subsequent neurologic deficits, otorrhagia, and epistaxis. It is not associated with subarachnoid hemorrhage because of its extradural location. Further, imaging should generally be obtained before biopsy of any middle ear mass if unknown in origin as the mass could represent the carotid artery, a glomus tympanicum tumor, or a facial schwannoma and can cause devastating consequences. 2,3
Managing ICA aneurysms remains a challenge, particularly in asymptomatic patients. Current treatment options include close observation, endovascular balloon embolization, and surgical trapping. Endovascular balloon embolization consists of inflating a balloon in the ICA immediately proximal to the aneurysm. Then, a second balloon is released proximally as a backup, in case the first balloon deflates. Instead of the second balloon, some surgeons use coil embolization. In some cases, ischemic complications may occur as a result of hypoperfusion. Practically, three case scenarios can present to our clinic/emergency department: asymptomatic patient, symptomatic patient, and patient with a ruptured aneurysm. In the case of an asymptomatic patient, recommending close serial imaging is a reasonable approach. If during follow-up imaging, the aneurysm increases in size, treatment should be considered. For symptomatic patients, the treatment includes endovascular therapy by balloon occlusion, stent placement with or without coil occlusion, and high-flow bypass. Finally, in patients with ruptured aneurysm, urgent care such as endovascular balloon occlusion is required. 2
Thromboembolic strokes associated with petrous ICA aneurysms are rare. Hemorrhage usually occurs in 25% of cases with patients seeking treatment in a timely manner. Therefore, our asymptomatic patient was recommended by neurovascular surgery to repeat the MRA in six months for progression.
Video 1. Axial (horizontal) CT of left temporal bone showing fluid in middle ear and mastoid and obstruction of the Eustachian tube with the carotid artery.
Video 2. Coronal (vertical parallel to face) CT of left temporal bone showing carotid anatomy around the Eustachian tube.
Video 3. Axial post-gadolinium T1-weighted MRI IAC showing dilation of the left carotid artery compared to the right.
Video 4. Coronal post-gadolinium T1-weighted MPR (1mm cuts) MRI IAC showing and dilation of the left carotid artery compared to the right.
Video 5. Coronal MRA source images showing the dilation of the petrous carotid consistent with aneurysm
Video 6. MRA of neck showing the left petrous carotid aneurysm
Read this month’s Clinical Consultation case, then watch the accompanying videos from Hamid R. Djalilian, MD, to review the patient’s imaging for yourself.
Watch the patient videos online at thehearingjournal.com.
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