title: Diffusion tensor imaging observation in Pott's spine with or without neurological deficit.
abstract: BACKGROUND
  Diffusion tensor imaging (DTI) is based upon the phenomenon of water diffusion known as "Brownian motion." DTI can detect changes in compressed spinal cord earlier than magnetic resonance imaging and is more sensitive to subtle pathological changes of the spinal cord. DTI observation in compressed and noncompressed spinal cord in tuberculosis (TB) spine is not described. This study presents observations in Pott's spine patients with or without neural deficit.
  
  
  METHODS
  Thirty consecutive cases of TB spine with mean age of 32.1 years of either sexes with paradiscal lesion, with/without paraplegia divided into two groups: Group A: (n = 15) without paraplegia and group B: (n = 15) with paraplegia were evaluated by DTI. The average fractional anisotropy (FA) and mean diffusivity (MD) values were calculated at 3 different sites, above the lesion (SOL)/normal, at the lesion and below SOL for both groups and mean was compared. Visual impression of tractography was done to document changes in spinal tracts.
  
  
  RESULTS
  The mean canal encroachment in group A was 39.60% and group B 44.4% (insignificant). Group A mean FA values above SOL, at the lesion and below SOL were 0.608 ± 0.09, 0.554 ± 0.14, and 0.501 ± 0.16 respectively. For group B mean FA values above SOL, at the lesion and below SOL were 0.628 ± 0.09, 0.614 ± 0.12 and 0.487 ± 0.15 respectively. There was a significant difference in mean FA above the SOL as compared to the mean FA at and below SOL. P value above versus below the SOL was statistically significant for both groups (0.04), but P value for at versus below the SOL (0.01) was statistically significant only in group B. On tractography, disruption of fiber tract at SOL was found in 14/15 (93.3%) cases of group A and 14/15 cases (93.3%) of group B (6/6 grade 4, 3/3 grade 3 and 5/6 grade 2 paraplegic cases).
  
  
  CONCLUSIONS
  The FA and MD above the lesion were same as reported for healthy volunteer hence can be taken as control. FA increases, and MD decreases at SOL in severe grade of paraplegia because of epidural collection while in milder grade, both decrease. In group A (without neurological deficit), mean FA and MD in patients with and without canal encroachment was similar. On tractography, both groups A and B (with or without neurological deficit) showed disruption of fiber tract at SOL and thickness of distally traced spinal cord was appreciably less than the upper cord. FA and MD could not differentiate between various grades of paraplegia. Although the number of patients in each group are small.
authors.affiliation: Department of Orthopaedics, University College of Medical Sciences and Guru Teg Bahadur Hospital, Dilshad Garden, New Delhi, India.
authors.forename: Sohail
authors.initials: S
authors.lastname: Abbas
authors.affiliation: Department of Orthopaedics, University College of Medical Sciences and Guru Teg Bahadur Hospital, Dilshad Garden, New Delhi, India.
authors.forename: Anil Kumar
authors.initials: AK
authors.lastname: Jain
authors.affiliation: Department of Radio-diagnosis, Institute of Nuclear Medicine and Allied Sciences, Timarpur, New Delhi, India.
authors.forename: Namita Singh
authors.initials: NS
authors.lastname: Saini
authors.affiliation: Department of Orthopaedics, University College of Medical Sciences and Guru Teg Bahadur Hospital, Dilshad Garden, New Delhi, India.
authors.forename: Sudhir
authors.initials: S
authors.lastname: Kumar
authors.affiliation: Department of Orthopaedics, University College of Medical Sciences and Guru Teg Bahadur Hospital, Dilshad Garden, New Delhi, India.
authors.forename: Rajagopalan
authors.initials: R
authors.lastname: Mukunth
authors.affiliation: Department of Orthopaedics, University College of Medical Sciences and Guru Teg Bahadur Hospital, Dilshad Garden, New Delhi, India.
authors.forename: Jaswant
authors.initials: J
authors.lastname: Kumar
authors.affiliation: Department of Radio-diagnosis, Institute of Nuclear Medicine and Allied Sciences, Timarpur, New Delhi, India.
authors.forename: Pawan
authors.initials: P
authors.lastname: Kumar
authors.affiliation: Department of Radio-diagnosis, Institute of Nuclear Medicine and Allied Sciences, Timarpur, New Delhi, India.
authors.forename: Prabhjot
authors.initials: P
authors.lastname: Kaur
keywords: Diffusion tensor imaging; Spine; diffusion; fractional anisotropy; mean diffusivity; paraplegia; tractography; tuberculosis; tuberculosis spine