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Ear, Nose and Throat Radiology


Selected Disorders of the Ear

External Ear

Squamous or basal cell carcinoma

HRCT

Defines the extent of any bone erosion or destruction

MRI

Allows precise assessment of the soft tissue mass

Necrotizing otitis externa

Definition

An osteomyelitis/necrosis particularly affecting the floor of the external auditory canal ▸ Pseudomonas is a typical initiating organism

  • It typically affects an elderly diabetic patient and is associated with a facial nerve palsy as the diseases spreads to the soft tissues inferior to the skull base

Osteoma of the external ear

Definition

A benign tumour that can arise spontaneously but usually occurs in individuals fond of swimming in cold water ('surfer's ear')

  • They enlarge slowly and present with late conductive deafness (as the tumour fills the external meatus)

CT

A well-defined homogeneous dense tumour ▸ pedunculated, unilateral and lateral to the bone

Middle Ear

Chronic suppurative otitis media and acquired cholesteatoma (keratoma)

Definition

Eustachian tube dysfunction generates a negative pressure within the middle ear (drawing the tympanic membrane inwards) ▸ if any desquamating epithelium from the tympanic membrane cannot be cleared by the natural processes of ear toilet, the desquamated skin accumulates and forms a ball of skin which is known as a keratoma (cholesteatoma) ▸ this can subsequently enlarge and cause bone destruction

  • If the superior tympanic membrane (the pars flaccida) is involved, skin accumulation occurs within the superior Prussak's space (the attic)

CT

A soft tissue mass within Prussak's space with erosion of the scutum ▸ ossicular erosion (commonly affecting the long process of the incus) with medial displacement of the ossicles

MRI

T1WI: low SI ▸ T2WI: high SI ▸ T1WI + Gad: there is little enhancement

  • If the inferior tympanic membrane (the pars tensa) is involved, skin accumulation occurs within the inferior sinus tympani

CT

A sinus tympani-based mass that can fill the middle ear cavity and invade the mastoid bone ▸ it commonly erodes the ossicles with lateral displacement of the ossicles

MRI

T1WI: low SI ▸ T2WI: high SI ▸ T1WI + Gad: there is little enhancement

Congenital cholesteatoma (epidermoid)

Definition

This originates from ectodermal cell rests which may arise within any cranial bone (the petrous temporal bone is the most common)

  • It is usually found within the petrous apex, producing a clearly defined ‘punched-out’ area of bone destruction

  • Cholesterol granuloma: this is an important differential and is a form of granulation tissue ▸ it can be differentiated from a congenital cholesteatoma with MRI

Otosclerosis

Definition

A localized disease whereby the normally dense otic capsule is initially replaced by new vascular spongy bone (with later sclerosis)

  • Acute phase: deposition of islets of osteoid tissue

  • Subacute phase: remodelling and osteoclastic bone resorption

  • Chronic phase: new osteoblast-induced sclerotic bone formation

  • Fenestral: initially starts at the anterior margin of the oval window ▸ it can lead to fusion of the stapes foot plate to the oval window (causing a conductive hearing loss)

  • Retrofenestral (cochlear): this initially starts within the pericochlear bony labyrinth ▸ it can lead to a sensorineural hearing loss

Inner Ear

Glomus tumours

Definition

These are usually benign tumours arising from chemoreceptor cells ▸ glomus jugular tumours arise in the jugular foramen extending into the middle ear cleft ▸ globus tympanicum tumours arise on the medial wall of the middle ear cavity on the cochlear promontory

  • Both present clinically with pulsatile tinnitus and as a mass within the inferior aspect of the tympanic membrane

  • Glomus jugulare (glomus jugulotympanicum) tumour:

CT

A jugular foraminal mass with adjacent destructive and permeative bone changes ▸ it rarely extends below the level of the hyoid bone

MRI

T1WI/T2WI: high SI (due to haemorrhage and slow vascular flow) ▸ T1WI + Gad: there is intense enhancement

  • ‘Salt and pepper’ appearance: this is due to multiple low SI flow voids + subacute haemorrhage

  • Glomus tympanicum tumour:

CT / MRI

An enhancing mass with a flat base located on the cochlear promontory

  • T1WI + Gad: there is intense enhancement

Bell's (facial nerve) palsy

Definition

Typically this describes a sudden facial paralysis which recovers fully or incompletely after 2–3 months

MRI

T2WI: nerve swelling and high SI ▸ T1WI + Gad: pathological nerve enhancement is well described

Trauma

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