Corticospinal tract degeneration and possible pathogenesis in ALS evaluated by MR diffusion tensor imaging.
BACKGROUND
MR diffusion tensor imaging (DTI) appears to be a powerful method to investigate the neuronal and axonal fibre distribution in the human brain. Changes in diffusion characteristics of water molecules in the white matter can be estimated as the apparent diffusion coefficient (ADC) and the fractional anisotropy index (FA).


OBJECTIVE
To characterize DTI changes at three different levels in the corticospinal tract (CST) (corona radiata, internal capsule and pons) in order to elucidate if pathogenesis of ALS is due to an anterograde or retrograde axonal degeneration.


METHODS
We studied eight ALS patients with clinical signs of upper motor neuron involvement. The patients were compared with 11 healthy age-matched controls.


RESULTS
ADC was significantly increased in the CST in ALS patients at the level of the internal capsule and also increased in the pons, but without statistical significance. ADC was unchanged at the level of the corona radiata. FA was significantly reduced at the lowest level (pons), only tended to be reduced in the internal capsule, but was also unchanged in the corona radiata.


CONCLUSIONS
Segmentation of the CST into three regions supports the hypothesis of a 'dying back' mechanism in ALS and suggests that ADC is a more sensitive measure than FA to detect pathological changes in ALS.
Karlsborg
Merete
M
Department of Neurology, Bispebjerg Hospital, Copenhagen, Denmark. merete.karlsborg@inet.uni2.dk
Rosenbaum
Sverre
S
Wiegell
Mette
M
Simonsen
Helle
H
Larsson
Henrik
H
Werdelin
Lene
L
Gredal
Ole
O
D000328:Adult; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis* / Q000378:metabolism / Q000503:physiopathology; D000704:Analysis of Variance; D016022:Case-Control Studies; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011712:Pyramidal Tracts / Q000473:pathology*; D013132:Spinocerebellar Degenerations / Q000175:diagnosis* / Q000209:etiology