title: Skull base osteomyelitis in otitis externa: The utility of triphasic and single photon emission computed tomography/computed tomography bone scintigraphy.
abstract: BACKGROUND
  Skull base osteomyelitis (SBO) refers to infection that has spread beyond the external auditory canal to the base of the skull in advanced stages of otitis externa. Clinically, it may be difficult to differentiate SBO from severe otitis externa without bony involvement. This study was performed to determine the role of three phase bone scintigraphy (TPBS) and single photon emission tomography/computed tomography (SPECT/CT) in detecting SBO.
  
  
  METHODS
  We retrospectively analyzed records of 20 patients (14 M, 6 F) with otitis externa and suspected SBO. TPBS and SPECT/CT of the skull were performed. Findings were correlated with clinical, laboratory and diagnostic CT scan findings.
  
  
  RESULTS
  All patients were diabetic with elevated erythrocyte sedimentation rate. A total of 18 patients had bilateral and two unilateral symptoms. Cranial nerves were involved in eight patients and microbiological culture of ear discharge fluid positive in seven. Early images showed increased temporal vascularity in nine patients and increased soft-tissue uptake in 10, while delayed images showed increased bone uptake in 19/20 patients. Localized abnormal tracer uptake was shown by SPECT/CT in the mastoid temporal (15), petrous (11), sphenoid (3) and zygomatic (1) and showed destructive changes in five. Thus, TPBS was found positive for SBO in 10/20 patients and changed the management in four.
  
  
  CONCLUSIONS
  Our study suggests that TPBS with SPECT/CT is a useful non-invasive investigation for detection of SBO in otitis externa.
authors.affiliation: Department of Nuclear Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Dhritiman
authors.initials: D
authors.lastname: Chakraborty
authors.forename: Anish
authors.initials: A
authors.lastname: Bhattacharya
authors.forename: Ashok Kumar
authors.initials: AK
authors.lastname: Gupta
authors.forename: Naresh Kumar
authors.initials: NK
authors.lastname: Panda
authors.forename: Ashim
authors.initials: A
authors.lastname: Das
authors.forename: Bhagwant Rai
authors.initials: BR
authors.lastname: Mittal
keywords: Bone scan; otitis externa; single photon emission computed tomography/computed tomography; skull base osteomyelitis