Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Six The Spine 687
Fig. 6-29 An 8-year-old neutered
female mixed breed dog had pain
upon raising the tail and in the lumbosacral
area. The myelogram
reveals an abrupt dorsal displacement
of the ventral subarachnoid
space at L7-S1. The degree of elevation
is too abrupt to be normal.
Diagnosis: Disc extrusion at L7-S1.
Fig. 6-30 A 5-year-old male Maltese with neck pain and mild left lateralizing tetraparesis. The dorsal
subarachnoid space is narrowed. A ventral extradural mass is at C4-5. Close examination revealed
there are two apparent ventral contrast columns, one of which is a great deal more elevated than the
other. This results from extrusion of disc material slightly to one side of the midline but not enough
to be considered truly lateral in location. Incidental findings of slight disc protrusion at C5-6 and C6-
7 as well as slight hypertrophy of the ligamenta flavum at C3-4 and C4-5 are noted. Diagnosis: Disc
extrusion at C4-5.
the spinal canal. This results in displacement of the spinal cord away from the disc on the
ventrodorsal myelogram and results in widening of the spinal cord on the lateral view (Fig.
6-31). Less frequently, disc material will surround the spinal cord completely (Fig. 6-32). In
rare cases, a disc extrusion occurs with such force that it penetrates the dura and either
lodges within the spinal cord or totally penetrates it. 122,123 In these cases, either a swollen
spinal cord suggestive of an intramedullary lesion or an extramedullary intradural lesion
may be observed on the myelogram (Figs. 6-33 and 6-34). Oblique radiographs are helpful
when the disc material is located ventrolateral to the spinal cord. 115,119 In some cases a disc
extrusion will cause ascending-descending myelomalacia. This may result in normal myelographic
findings but usually produces a swollen spinal cord with contrast medium intermixed
within the neural tissue (Fig. 6-35). Extruding disc material may rupture a vertebral
venous sinus and cause extradural hemorrhage. This will cause the spinal cord to be