Spontaneous regression of extradural intraspinal cysts in a dog: a case report

Abstract

Background: Extradural intraspinal cysts are fluid accumulations that appear to be associated with increased motion at vertebral joints.

Case presentation: We report the spontaneous regression of lumbar and lumbosacral cysts (presumably synovial cysts) and the unusual occurrence of an S1-2 extradural intraspinal cyst in a dog. The dog presented with lumbosacral pain. Six extradural intraspinal cysts were observed on high-field magnetic resonance imaging from L5-6 to S1-S2. The cysts between L5-6 and L7-S1 ranged from 0.12 to 0.44cm² at their largest area. The largest cyst was located at S1-2 (left), measuring 0.84 cm² at its largest view. The dog was medically managed. A follow-up magnetic resonance imaging scan was obtained 3.5 years after the first imaging. All cysts except the one at S1-2 had reduced in size. Mean reduction in size was 59.6% (35-81%).

Conclusions: In summary, we report a case with multiple extradural intraspinal cysts that underwent spontaneous regression of all but one cyst during a 3.5-year follow-up period. Whether this is a single occurrence, or is part of the natural history of these cysts in the lumbosacral region of dogs, remains to be established. Spontaneous regression of intraspinal cysts had not been described in dogs.

Keywords: Juxtafacet cysts; Lumbar; Magnetic resonance imaging; Synovial cyst.

Fig. 1

Initial (a) and 3.5-year follow-up (b) left parasagittal T2-weighted magnetic resonance imaging (MRI) of extradural intraspinal cysts in a German Shepherd dog. Cysts can be seen at L5–6, L6–7, L7-S1, and S1–2. All cysts except the one at S1–2 are smaller on the follow-up MRI

Fig. 2

Initial (a, b, c) and 3.5-year follow-up (d, e, f) T2-weighted magnetic resonance imaging (MRI) of extradural intraspinal cysts in a German Shepherd dog. a: left parasagittal image showing a large extradural cyst at L7-S1 seen at the first lumbosacral MRI. The level at which the transverse images for b and c were obtained is represented by lines identified with corresponding letters. b: transverse image showing bilateral cysts (arrows) at L7. c: transverse image obtained at the level of the endplate of L7 showing the same cysts seen on b. d: left parasagittal image on follow-up showing at which level the transverse images for e and f were obtained (corresponding lines). Note the large cyst seen on a is no longer visible in this location. e, f: transverse images at approximately the same level as b and c. Note there was a reduction in size of both cysts. R, right