HRCT imaging of acquired cholesteatoma: a pictorial review

Chronically discharging ear is a common cause of morbidity in developing countries, and it is also associated with intratemporal and intracranial complications. The surgeon is often able to detect the disease. However, cholesteatoma in the “hidden areas” like anterior epitympanic recess and sinus tympani can be missed. Facial nerve involvement and cholesteatomatous erosion of the bony labyrinth are dreaded complications, the extent of which cannot be assessed completely on clinical examination. Adding to the complexity are the various variations in anatomy like high riding jugular bulb and aberrant internal carotid artery which could lead to catastrophic complications during surgery if left undetected preoperatively. HRCT temporal bone is useful to detect the extent of the disease, various complications, and guide the surgeon for pre-operative planning. In this review, we go through the various HRCT imaging features of acquired cholesteatoma, a reporting template, and a few words about imaging of the post-operative ear.

Aberrant internal carotid artery in the middle ear: the duplication variant

Vascular variants concerning the internal carotid artery (ICA) at the skull base level are rare. Correct workup and diagnosis in case of suspicion of such a variant are important as it mimics glomus tumours and could complicate myringotomy or middle ear surgery. We report a case of a 39-year-old woman presented with a 6-month history of right pulsatile tinnitus and aural fullness. Ear microscopy examination revealed a pale red pulsatile mass anterior to the umbo. Radiological assessment using CT and MRI/magnetic resonance angiography confirmed the diagnosis of an aberrant ICA. Interestingly, a duplication of the ICA was demonstrated, in which the enlarged inferior tympanic artery presented as the aberrant ICA, whereas a narrower collateral hypoplastic native ICA was also present. A conservative approach with regular follow-up appointments was recommended.

Pulsatile Tinnitus Due to a Sigmoid Sinus Diverticulum and/or Dehiscence

In 2009, a 52-year-old man presented with a two year history of intermittent right-sided pulse-synchronous tinnitus. He noted that the tinnitus worsened when his blood pressure was elevated. Otologic exam was unremarkable, with no obvious middle ear fluid or mass. There was no neck bruit, and the tinnitus diminished on manual compression of the ipsilateral internal jugular vein. In keeping with the recommendations for clinical imaging at that time, a non-contrast CT of the temporal bone was performed. This was to evaluate for conditions such as : a middle ear glomus, an aberrant internal carotid artery, a jugular bulb variant (e.g. a high-riding jugular bulb), otosclerosis, superior semicircular canal dehiscence syndrome, a persistent stapedial artery, or a hemangioma of the temporal bone.1 No evidence of these conditions was found. An MRI of the brain, with MR angiography and venography of the intracranial vasculature also performed to evaluate for conditions such as: idiopathic intracranial hypertension, a dural arteriovenous fistula, an arteriovenous malformation, vascular loop syndrome, and dural sinus stenosis or thrombosis.2 All of these conditions were excluded. As no definite pathology was identified, no firm treatment reommendations were initiallly made. In 2011, Eisenman reported on a series of 13 patients with pulsatile tinnitus due to a sigmoid sinus diverticulum and/or dehiscence who were successfully treated surgically via an extraluminal transmastoid approach.3 This was the first relatively large series published in the otologic literature. This publication likewise reported on the subtle radiologic signs that signify the presence of a sigmoid sinus diverticulum and/or dehiscence, such as an irregularity of the normal semicircular contour of the bony sinus wall, focal thinning of the calvarial cortex overlying the adjacent sinus wall, absence of the normal thin layer of cortical bone overlying the sinus, and the "air-on-sinus" sign, where mastoid air cells directly contact the sinus wall, without overlying bone.3 In light of this new information, the patient's imaging studies were re-evaluated, and evidence of a right-sided sigmoid sinus diverticulum and/or dehiscence was identified. The images below show the findings on an axial slice of the patient's temporal bone CT study. How significant is this condition ? Sigmoid sinus diverticulum and/or dehiscence is being increasingly recognized as a common cause of pulsatile tinnitus. In fact, a recent study by Schoeff et al. found its prevalence to be 23% in patients with pulsatile tinnitus.4 As such, the identification of this condition is highly relevant, particularly because effective surgical management is available for its alleviation.