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Diffusion anisotropy of the cervical cord is strictly associated with disability in amyotrophic lateral sclerosis
  1. P Valsasina2,
  2. F Agosta2,
  3. B Benedetti2,
  4. D Caputo3,
  5. M Perini4,
  6. F Salvi5,
  7. A Prelle6,
  8. M Filippi1,2
  1. 1MRI Research Group, Scientific Institute Fondazione Don Gnocchi, Milan, Italy
  2. 2Neuroimaging Research Unit, Scientific Institute Ospedale San Raffaele, Milan, Italy
  3. 3Department of Neurology, Scientific Institute Fondazione Don Gnocchi, Milan, Italy
  4. 4Department of Neurology, Ospedale di Gallarate, Gallarate, Italy
  5. 5Department of Neurology, Ospedale di Bellaria, University of Bologna, Bologna, Italy
  6. 6Department of Neuroscience, Dino Ferrari Center, University of Milan, Milan, Italy
  1. Correspondence to:
 Dr M Filippi
 MRI Research Group, Scientific Institute Fondazione Don Gnocchi, Via Capecelatro 66, 20148 Milan, Italy; m.filippi{at}hsr.it

Abstract

Background: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with severe cervical cord damage due to degeneration of the corticospinal tracts and loss of lower motor neurones. Diffusion tensor magnetic resonance imaging (DT MRI) allows the measurement of quantities reflecting the size (such as mean diffusivity) and orientation (such as fractional anisotropy) of water-filled spaces in biological tissues.

Methods: Mean diffusivity and fractional anisotropy histograms from the cervical cord of patients with ALS were obtained to: (1) quantify the extent of tissue damage in this critical central nervous system region; and (2) investigate the magnitude of the correlation of cervical cord DT MRI metrics with patients’ disability and tissue damage along the brain portion of the corticospinal tracts. Cervical cord and brain DT MRI scans were obtained from 28 patients with ALS and 20 age-matched and sex-matched controls. Cord mean diffusivity and fractional anisotropy histograms were produced and the cord cross-sectional area was measured. Average mean diffusivity and fractional anisotropy along the brain portion of the corticospinal tracts were also measured.

Results: Compared with controls, patients with ALS had significantly lower mean fractional anisotropy (p = 0.002) and cord cross-sectional area (p<0.001). Mean diffusivity histogram-derived metrics did not differ between the two groups. A strong correlation was found between mean cord fractional anisotropy and the ALS Functional Rating Score (r = 0.74, p<0.001). Mean cord and brain fractional anisotropy values correlated moderately (r = 0.37, p = 0.05).

Conclusions: Cervical cord DT MRI in patients with ALS allows the extent of cord damage to be graded. The conventional and DT MRI changes found are compatible with the presence of neuroaxonal loss and reactive gliosis, with a heterogeneous distribution of the pathological process between the brain and the cord. The correlation found between cord fractional anisotropy and disability suggests that DT MRI may be a useful adjunctive tool to monitor the evolution of ALS.

  • ALS, amyotrophic lateral sclerosis
  • ALSFRS, ALS Functional Rating scale
  • CNS, central nervous system
  • CSF, cerebrospinal fluid
  • DT MRI, diffusion tensor magnetic resonance imaging
  • ETL, echo train length
  • FOV, field of view
  • TSE, turbo spin echo

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Footnotes

  • Published Online First 27 October 2006

  • Competing interests: None.

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