Petrous apicitis, also known as apical petrositis, is infection with involvement of bone at the very apex of the petrous temporal bone.
Petrous apicitis is less common than it once was, on account of the widespread and early use of antibiotics for acute otomastoiditis 3-4.
Clinical presentation depends on whether petrous apicitis is isolated or (as is more common) is a complication of acute otomastoiditis. In the later, symptoms will be those of a middle ear infection, superimposed on symptoms specific to petrous apicitis 2:
- deep facial pain due to inflammation of the adjacent dura and trigeminal nerve in Meckel's cave
- abducens nerve palsy (see Gradenigo syndrome) due to involvement of Dorello's canal
Gradenigo syndrome is the classical presentation of petrous apicitis, but it is not present in all patients 3,5. Extension of infection to involve the petrous apex should be suspected when all patients with signs and symptoms of acute otomastoiditis and deep ipsilateral pain 3,5.
Presentation may also be due to extension of inflammatory/infective changes beyond the petrous apex.
- dural venous sinus thrombosis
- intracranial extension
There is debate as to whether it represents osteomyelitis in non-pneumatised bone, or whether (and more generally accepted) a form of osteitis developing from infected and obstructed air cells in a pneumatised petrous apex (analagous to coalescent mastoiditis) 5. Approximately 30% of the population has a pneumatised petrous apex 2, but it is frequently asymmetric.
CT is the modality of choice to evaluate bony changes in the temporal bone, which in the setting of petrous apicitis are erosive lysis with ill-defined irregular edges. Contrast enhanced scans may demonstrate peripheral enhancement as well as dural thickening and enhancement, although these are better appreciated on MRI.
Findings are those of fluid signal with the petrous apex often with peripheral enhancement, which presumably represents a combination of residual mucosa, granulation tissue and adjacent dura/periosteum 5. Thus:
- T1: fluid signal (low to intermediate)
- T2: fluid signal (hyperintense)
- T1 C+ (Gd): peripheral enhancement.
Thickening of the dura of Meckel's cave and the cavernous sinus should be sought, as well as for the findings of cavernous sinus thrombosis.
Treatment and prognosis
In many instances treatment with appropriate intravenous antibiotics suffices. In more severe cases surgical drainage may be required 4.
- 1. Imaging of the temporal bone. Joel D. Swartz, H. Ric Harnsberger. New York : Thieme, 1998. ISBN:0865777004 (find it at amazon.com)
- 2. Vazquez E, Castellote A, Piqueras J et-al. Imaging of complications of acute mastoiditis in children. Radiographics. 23 (2): 359-72. doi:10.1148/rg.232025076 [pubmed citation]
- 3. Mafee MF, Singleton EL, Valvassori GE et-al. Acute otomastoiditis and its complications: role of CT. Radiology. 1985;155 (2): 391-7. Radiology (abstract) [pubmed citation]
- 4. Temporal Bone Imaging. Ellen Hoeffner (Editor), Suresh Mukherji (Editor), Dheeraj Gandhi (Editor), Diana Gomez-Hassan (Editor). Thieme ISBN:1588904016 (find it at amazon.com)
- 5. Head and neck imaging. Ed. by Peter M. Som, Hugh D. Curtin. St Louis (Mo.) : Mosby-Year Book, 2003. ISBN:0323009425 (find it at amazon.com)