Head and Neck ImagingPetrous apex, pathology
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Congenital
cholesteatoma presents as an expansile
lesion in the petrous apex, mostly well demarcated. It cannot be distinguished from
cholesterol granuloma on
CT images. On MR, it shows low to intermediate signal intensity on T1-weighted and relative high signal intensity on T2-weighted images (see
cholesteatoma ).
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Inflammation. When pneumatized, a similar spectrum of inflammatory disease can be seen in the petrous apex as in the
middle ear and mastoid. Active infection may cause acute apical petrositis; when associated with
osteomyelitis, this may cause
Gradenigo's syndrome . In the case of
osteomyelitis,
CT shows destructive bone changes in the petrous apex; on
MRI, meningeal enhancement will be visible (
Fig. 2). Further complications include thrombosis of the cavernous
sinus or other intracranial venous sinuses, or formation of an intracranial abscess.
Inflammation in the petrous apex may trigger the formation of a
cholesterol granuloma .
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Trauma. The petrous apex may be involved by a
transverse fracture, temporal bone ; this may be associated with lesions of the adjacent cranial nerves (facial, trigeminal and abducens nerve).
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Tumour. A variety of
benign and
malignant tumoral lesions may be encountered, either originating in the petrous apex or secondarily growing into this structure (Table 1).
Petrous apex, Table 1. Petrous apex tumours (adapted from J.D. Swartz, H. Ric Harnsberger: Imaging of the
temporal bone. 3 Ed., Thieme, New York, 1998, p. 453).
RH
RH
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Already registered? Enter your e-mail in the window below.Re-registerFig. 01a
Axial T1-weighted spin-echo image of temporal bones. The left petrous apex appears hyperintense (arrow) as it is nonpneumatized and contains fatty bone marrow; the right petrous apex is pneumatized and generates no signal.
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Petrous apex, pathology, Fig. 01a | | Petrous apex, pathology, Fig. 02a | |