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Temporal Bone Osteoradionecrosis


KEY FACTS

Terminology

  • Radiation therapy (RT)-induced injury to temporal bone

Imaging

  • Bone CT findings

    • Moth-eaten destruction of temporal bone and adjacent skull base ± sequestrum

  • T2 MR findings

    • High-signal mucosal injury of external auditory canal (EAC), middle ear cavity, mastoid

    • High signal of adjacent brain → radiation necrosis

    • Meningitis, abscess, dural sinus thrombosis

Top Differential Diagnoses

  • Malignant external otitis

  • Coalescent mastoiditis

  • Aggressive cholesteatoma

  • EAC carcinoma

  • Paget disease

Pathology

  • Avascular bone necrosis from obliterative endarteritis

  • Susceptible to infection, which accelerates ORN

Clinical Issues

  • Presentation: Otalgia, otorrhea, hearing loss after RT

  • Occurs few months to many years post RT (> 60 Gy)

    • Most common in setting of regional RT for parotid, EAC, or nasopharynx carcinoma

  • Treatment options

    • Conservative management: 1st-line option

    • Surgical management and adjuvant therapy as indicated; may require subtotal petrosectomy

    • Pentoxifylline, vitamin E, and clodronate (PENTOCLO) for prevention and treatment

Diagnostic Checklist

  • CT for bone changes, extent of involvement; MR for complications

Axial bone CT reveals abnormal soft tissue
filling the left external auditory canal (EAC) and mastoid air cells with obvious destruction of the posterior EAC wall and mastoid septations
. Note mixed sclerotic and lytic
bone. These findings represent the classic appearance of temporal bone osteoradionecrosis.

Axial bone CT shows radiation-induced necrosis of the bony EAC
and confluent destruction of mastoid air cells. Note "floating" bony sequestrum
, all indicating severe osteoradionecrosis.

Axial bone CT shows diffuse opacification of the middle ear and mastoid in association with permeative-destructive bony changes in this previously radiated patient. Focal bone necrosis is seen in the petrous bone
and lateral mastoid cortex
.

Axial T1 C+ FS MR in a previously radiated patient reveals nonspecific enhancing tissue in the middle ear
, mastoid
, and petrous apex
. Although radiation changes can be suggested by MR, osteoradionecrosis of bone is a diagnosis best made by temporal bone CT.

TERMINOLOGY

Abbreviations

  • Osteoradionecrosis (ORN)

Synonyms

  • Radiation osteitis, radiation necrosis, irradiation osteomyelitis, avascular bone necrosis

Definitions

  • Radiation-induced injury to temporal bone

    • Localized (more common): Limited to external auditory canal (EAC)

    • Diffuse: Involves mastoid septations and middle ear cavity (MEC), possibly skull base

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