CT of the feline middle ear

Why the middle ear is worth imaging in cats

Middle ear disease is a common cause of vestibular signs in cats. In 196 cats with peripheral vestibular syndrome that all had CT or MRI of the head (Caldero Carrete et al., Veterinary Record, 2025), the diagnoses were:

• otitis media/interna alone (91 cats)
• otitis media/interna with aural polyps (49)
• idiopathic vestibular syndrome (47)
• middle ear neoplasia (7)
• congenital vestibular syndrome (2)

Otitis media/interna was associated with younger age, a longer duration of signs, a history of otitis externa or upper respiratory signs, facial nerve paralysis and Horner syndrome. Most cats with otitis media/interna or idiopathic vestibular syndrome recovered at least partially.

Anatomy that shapes the choice of imaging

The feline tympanic bulla is divided by a septum into a ventromedial and a dorsolateral compartment (Chan et al., Veterinary Dermatology, 2025). Any technique that sees only one compartment can miss disease in the other. Cross-sectional imaging shows both.

CT compared with radiography, ultrasound and MRI

Modality	What the evidence shows
Radiography	Relatively low accuracy for soft-tissue opacification in the bulla. The rostrocaudal open-mouth view is technically difficult; a rostro-10°-ventral–caudodorsal oblique view performed as well in cadavers and may be possible without general anaesthesia (Hammond et al., Veterinary Radiology & Ultrasound, 2005).
Ultrasound	In cadavers, more accurate than radiography for fluid in the bulla, though CT remained the most accurate (King et al., The Veterinary Journal). In 32 cats (64 ears), mostly awake, ultrasound of the ventromedial compartment had 92% sensitivity and 100% specificity against CT or MRI. False negatives came from scant fluid, and it cannot image the dorsolateral compartment.
CT	Reference standard for bulla content in the three studies above. More sensitive than MRI for involvement of the bulla wall and for abnormal content, and often easier for guiding sampling (Ludewig et al., Tierärztliche Praxis Ausgabe K: Kleintiere/Heimtiere, 2024).
MRI	Superior for the soft tissues of the head, the meninges, brain and nerves. Essential to characterise the material inside the bulla and to show central spread of otitis media.

In short: ultrasound is a quick screening test for fluid, CT answers the bony and content question, and MRI is the choice when neurological signs suggest spread beyond the middle ear.

Middle ear CT protocol at a glance

Because polyps can be present in the ear and the nasopharynx at the same time, and can develop in the opposite ear (MacPhail et al., Journal of Feline Medicine and Surgery, 2007), CT needs to include both bullae and the nasopharynx. Contrast enhancement of the bulla lining is part of the reading, as the study of early otitis media below shows. When a cat is anaesthetised for middle ear CT, it is worth discussing whether the nasal cavity, nasopharynx and thorax should be included.

What the radiologist looks at

• Effusion and early otitis media. In 322 cats (644 bullae) (Lee et al., Veterinary Radiology & Ultrasound, 2025), effusion was present in 105 bullae. Contrast enhancement of the bulla lining was seen in 68 of the 105 bullae with effusion, but in only 5 of the 539 without. Focal enhancement of the dorsal bulla wall was the most frequent pattern and the only one seen with mild or moderate effusion. Ventral, lateral, complete-rim and internal patterns appeared with severe effusion. The authors suggest focal dorsal enhancement may be an early indicator of otitis media.
• Inflammatory polyps. These non-neoplastic masses are thought to arise from the lining of the tympanic bulla or Eustachian tube. Cats present with otitis externa and media, or with upper airway obstruction.
• Neoplasia. Middle ear neoplasia is uncommon but was found in 7 of 196 cats with peripheral vestibular syndrome. In a case of middle ear B-cell lymphoma (Takahashi et al., Veterinary Sciences, 2023), both bullae were filled on CT.
• Beyond the ear. In 549 cats that had CT of the head, neck and thorax (Wetzels et al., Veterinary Radiology & Ultrasound, 2025) for inflammatory upper airway disease or otitis media, otitis media was an independent risk factor for lower airway disease. The odds ratio for concurrent lower airway disease was 1.46 with otitis media and 2.27 with otitis media plus rhinitis.

What your report will include

Every Veheri case is read by a radiologist or neurologist, and when you order you can choose Diplomate-only reporting or the full specialist panel. You can chat directly with the specialist assigned to your case, and a simplified pet owner report helps you explain the findings to the owner.

When you take the report forward:

• Keep lymphoma in mind in cats with otitis media signs, particularly those that respond to corticosteroids.
• Neurological signs that suggest spread beyond the middle ear make MRI the better next test.
• Polyps can affect both sides: they can develop in the opposite ear.
• Otitis media with rhinitis raises the odds of concurrent lower airway disease.
• Talking to the owner: most cats with otitis media/interna or idiopathic vestibular syndrome recovered at least partially.

What to include when you request a middle ear CT report

• signalment: age, breed and sex
• signs: head tilt, nystagmus, ataxia, facial nerve paralysis, Horner syndrome, stertor or nasal discharge
• otoscopic findings, including the state of the tympanic membrane
• history of otitis externa or upper respiratory disease
• previous treatment, especially corticosteroids and the response
• any previous surgery, such as polyp traction or ventral bulla osteotomy

How Veheri can help

Veheri’s radiologists report veterinary CT studies remotely for clinics, and we offer expert support for CT protocols, positioning and acquisition. For the canine version, see CT of the middle ear in dogs, and for polyps and other nasopharyngeal disease, see CT of the nasopharynx in cats.