title: Magnetic resonance imaging findings in spinal tuberculosis: Comparison of HIV positive and negative patients.
abstract: BACKGROUND
  There is an increasing incidence of Human immunodeficiency virus (HIV) and tuberculosis (TB) co-infection. This has led to an increasing number of atypical features on magnetic resonance imaging (MRI). We postulated that the type 4 hypersensitivity response causing granulomatous inflammation may be disrupted by the HIV resulting in less vertebral body destruction. This study compares the MRI features of spinal tuberculosis in HIV positive and negative patients.
  
  
  METHODS
  Fifty patients with confirmed spinal tuberculosis, HIV status and available MRI scans at a single institution from 2003-2009 were identified. HIV status was positive in 20 and negative in 30. Females were predominant (34:16). The HIV positive group was younger at 32.4 versus 46 years (P=0.008). Blood parameters (WCC, ESR, Hb, Lymphocyte count) were not significantly different between the HIV groups. MRI scans were reviewed by a radiologist who was blinded to the HIV status. Site, extent of disease, body collapse, abscess location and volume, kyphotic deformity and cord signal were reported.
  
  
  RESULTS
  There was no difference between the number of vertebral bodies affection with TB involvement, presence of cord signal or incidence of non-contiguous lesions. The HIV negative group had significantly more total vertebral collapse (P=0.036) and greater kyphosis (P=0.002). The HIV positive group had a trend to larger anterior epidural pus collection (P=0.2).
  
  
  CONCLUSIONS
  HIV negative patients demonstrate greater tuberculous destruction in terms of total percentage body collapse and resultant kyphosis. There is no difference in the incidence of cord signal or presence of non-contiguous lesions. HIV positive patients show a trend to a greater epidural abscess volume. This difference may be explained by the reduced autoimmune response of the type 4 hypersensitivity reaction caused by the HIV infection.
authors.affiliation: Department of Orthopaedics, Tygerberg Hospital, University of Stellenbosch, South Africa.
authors.forename: Cameron Michael
authors.initials: CM
authors.lastname: Anley
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Brandt
authors.forename: Robert
authors.initials: R
authors.lastname: Dunn