Foramen magnum variability and occipital dysplasia in the dog
1994
Simoens, P. | Poels, P. | Vyt, P. | Lauwers, H. (Gent Univ. (Belgium). Faculteit Diergeneeskunde. Vakgroep Morfologie)
Size and shape of the foramen magnum were studied in skulls from 80 Pekingese, 12 Doberman Prinschers and 7 German Shepherds. After maceration of the skulls, the total height (H), normal height (h), maximal width (B) and area of each foramen magnum were measured, and skull indices were determined. The basic configuration of the canine foramen magnum is ovoid, with a short dorsoventral axis (h) and longer horizontal axis (B). The mean ratio between normal height and width (h:B) was 77 per cent in small dogs and 75 per cent in larger dogs. The foramen magnum had a dorsal extension with variable length (N) in all but two Pekingese, in 7 Doberman Pinschers and 5 Beagles and in none of the German Shepherds examined. Prolapse of the cerebellum or brain stem through the enlarged opening was prevented in all cases by a fibrous membrane covering the dorsal notch. The degree of dysplasia (N:h), notch index (N:H), occipital index (H:B) and foramen magnum index (B:H) were determined for each case. The size of the foramen magnum presented a large variability and was not significantly correlated with age or gender. The dimensions of the foramen magnum were better correlated with skull size than with the degree of brachycephaly. Comparative anatomic data and the absence of any neurologic problems in the dogs of this study indicate that the dorsal extension of the canine foramen magnum is a normal morphologic variation rather than a pathologic condition.
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