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Corticospinal tract degeneration and possible pathogenesis in ALS evaluated by MR diffusion tensor imaging.
Merete Karlsborg1, Sverre Rosenbaum, Mette Wiegell
1Department of Neurology, Bispebjerg Hospital, Copenhagen, Denmark. merete.karlsborg@inet.uni2.dk
Summary
Diffusion tensor imaging (DTI) reveals increased water diffusion (ADC) in the corticospinal tract (CST) of ALS patients, supporting a "dying back" axonal degeneration mechanism. ADC is more sensitive than FA for detecting these pathological changes.
Area of Science:
- Neuroimaging
- Neurology
- Biophysics
Background:
- Diffusion tensor imaging (DTI) is a key MR technique for assessing white matter microstructure.
- Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) quantify water molecule diffusion, reflecting axonal integrity.
Purpose of the Study:
- To investigate DTI changes within the corticospinal tract (CST) at three distinct levels in Amyotrophic Lateral Sclerosis (ALS) patients.
- To determine if ALS pathogenesis involves anterograde or retrograde axonal degeneration.
Main Methods:
- Studied 8 ALS patients with upper motor neuron involvement and 11 age-matched healthy controls.
- Analyzed DTI metrics (ADC, FA) in the corona radiata, internal capsule, and pons segments of the CST.
Main Results:
- Significantly increased ADC in the CST of ALS patients at the internal capsule and pons.
- ADC remained unchanged in the corona radiata; FA was significantly reduced in the pons and tended to decrease in the internal capsule.
Conclusions:
- Findings support a "dying back" axonal degeneration model in ALS.
- ADC is a more sensitive DTI biomarker than FA for detecting early pathological changes in ALS.