Fractional anisotropy values detect pyramidal tract involvement in multiple system atrophy.
OBJECTIVE
Pathological studies have shown remarkable pyramidal tract involvement in multiple system atrophy (MSA), while clinical pyramidal signs are relatively rare. We investigated the fractional anisotropy (FA) values to assess the degree of pyramidal tract involvement in MSA, in comparison with amyotrophic lateral sclerosis (ALS) and controls. Furthermore, we compared FA values between MSA patients with or without clinical pyramidal signs and controls, and between MSA patients with or without positive conventional MRI findings and controls.


METHODS
We evaluated FA values in the internal capsule, corona radiate and whole pyramidal tract using visualized tractography of 65 subjects (20 probable MSA patients, 28 age-matched ALS patients, and 17 age-matched healthy controls) using a 3.0T magnetic resonance system.


RESULTS
The FA values in the internal capsule, corona radiate, and whole pyramidal tract were significantly lower in MSA patients than in controls and were at a level similar to those of ALS patients. In addition, low FA values were prominent in MSA patients, even in those with short duration of illness, lacking precentral gyrus hyperintensity in FLAIR images, and without pyramidal signs.


CONCLUSIONS
FA values could identify pyramidal tract degeneration even in patients with early phase MSA and those without clinical pyramidal signs or abnormal MRI findings. More extensive degeneration of the pyramidal tract occurs in MSA than so far believed.
Ito
Mizuki
M
Department of Neurology, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Japan.
Watanabe
Hirohisa
H
Atsuta
Naoki
N
Senda
Jo
J
Kawai
Yoshinari
Y
Tanaka
Fumiaki
F
Naganawa
Shinji
S
Fukatsu
Hiroshi
H
Sobue
Gen
G
D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis; D016880:Anisotropy; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000175:diagnosis*; D011712:Pyramidal Tracts / Q000473:pathology* / Q000503:physiopathology