Spinal Ataxia in Zebras

74 MONTALI et al.
Fig. 7. Cross-section of cervica l spinal co rd (C6) frcm ataxic zebra A2 . Advent itia
fibrosis of small blood vessels. Ma llory's trichro me.
Pathological Findings
Th ere were no gross lesion s in any of the spina l cord s from the three
atax ic zebras (A I, A 2, A 3). In Weiger t-stain ed sectio ns, eac h co rd showed
bilaterally symmet rical demyelinati on in the lat eral and ventral funi culi
(fig.2a) . Both asce nding and descendin g tr acts ap pea red to be affected in th e
lateral funiculi, a nd tracts (descending) adjacent to th e ventral median
fissure were involved in ventra l funi culi . Myelin sheaths varied in width,
and some were dilated a nd empty (fig. 3). Bodi an- stain ed sectio ns showed
a deficit ofaxons and man y were disrupted or fragmented (fig. 4). Occasiona
lly, there were lipid-lad en macrophages within the dilated sheaths
(fig. 5), a nd numerou s astrocytic nuclei and glial" fibers occurred in the
degenerated a reas (fig. 6).
Th ere was advent itia l fibrosis of sma ll blood vessels throu ghout the
ventra l a nd lateral funiculi of white matter (fig. 7). This was most prominent
in zeb ra A 2, but occ ur red in A I and A 3 to a lesser degree.
The pattern a nd inten sity of th e degeneratio n of neu ron al fiber s were
similar in each of the ataxic zebras . In th e zebras in wh ich the entire spina l
co rds were exa mined (A I and A 3) lesion s were prese nt thr ou ghout the
cerv ical, th oracic, lumba r, and sac ra l regions . Dorsal funi cul i and gray
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