Case series: Cervical far-lateral and combined cervical far lateral/foraminal intervertebral disk extrusions in 10 dogs

Abstract

Far-lateral intervertebral disk extrusions (IVDEs) have been reported infrequently in dogs in veterinary literature, mostly affecting the caudal lumbar intervertebral disks. We describe the clinical findings, computed tomography (CT) and magnetic resonance imaging (MRI) findings, treatment, and outcome in 10 dogs with cervical far-lateral IVDEs. Patient databases of 3 small animal hospitals and 1 veterinary teleradiology service were retrospectively searched for patients in which imaging studies (CT or MRI) identified the presence of intervertebral disk material outside the limits of the intervertebral foramen. Presenting clinical signs included: episodic signs of cervical pain (6/10, 30%), persistent signs of cervical pain (3/10, 50%), nerve root signature or lameness (5/10, 50%), and abnormal cervical posture only (excluding nerve root signature) (1/10, 10%). Affected IVD spaces (for 11 IVDEs in 10 dogs) included: C3-4 (6/11, 55%), C5-6 (3/11, 27%), and C2-3 (2/11, 18%). Nerve root signature was not reported for C2-3 IVDEs. All cases were managed medically (without surgery). The top 3 used medications were gabapentinoids (10/10, 100%), non-steroidal anti-inflammatory drugs (NSAIDs) (10/10, 100%), and paracetamol (3/10, 30%). Median treatment duration was 25 days (range 10-84). Short-term outcome (<3 months) was recorded in 9/10 (90%) cases. Resolution of clinical signs was reported in 7/9 (78%) cases. Long-term follow-up was available for 6/10 (60%) cases (median 11.5 months, range 5.5-30 months); 5/6 (83%) showed resolution of clinical signs. Recurrence of clinical signs was reported in 1 case (9 months later), managed medically again, with successful outcome. In conclusion, cervical far-lateral disk extrusions are a rare clinical entity in dogs, but can result in severe, persistent or episodic, pain. Medical management is associated with a positive short- and long-term outcome in most cases.

Keywords: chondrodystrophic; herniation; hyperesthesia; nerve root signature; pain.

Figure 1

Possible directions of intervertebral disk extrusions. a: dorsomedian, b: paramedian, c: dorsolateral, d: (intra)foraminal, e: far-lateral, f: ventral. Reprinted with permission and legend adjusted from (13).

Figure 2

Magnetic resonance images of case #7 with a C3-4 left-sided foraminal and far-lateral intervertebral disk extrusion. A: 3D dorsal nerve root/PROSET (water excitation) sequence – dorsal plane at the level of the C3-4 foramina, B: 3D dorsal nerve root/PROSET (water excitation) sequence – reconstructed transverse plane at the level of the C3-4 intervertebral disk, C: T2*-weighted sequence – transverse plane at the level of C3-4 intervertebral disk, D: T2-weighted sequence – transverse plane as C, E: T1-weighted sequence – transverse plane as C. The white arrows point to the extruded disk material in the foramen and far-lateral position at the level of C3-4 that contrasts with the normal, contralateral side for reference.

Figure 3

Magnetic resonance images of case #8 with a C3-4 right-sided far-lateral intervertebral disk extrusion. A: T1-weighted sequence – sagittal midplane, B: T1-weighted sequence – sagittal paramedian right-sided at the level of the right pedicle of C4, C: T2-weighted sequence – transverse plane at the level of C3-4 intervertebral disk, D: T1-weighted sequence – transverse plane as C, E: 3D dorsal nerve root / PROSET (water excitation) sequence – dorsal plane at the level of the vertebral arteries. The white circle in A depicts the intervertebral disk space that is hypointense on T1W sagittal images, indicating mineralization. The white arrows point to the T1W and T2W hypointense far-lateral extruded disk material. The vertebral artery on the left in E is interrupted on the right side by far-laterally extruded material.

Figure 4

Computed tomographic images (with intrathecal contrast medium – myelogram) of case #2 with a C3-4 right-sided far-lateral and foraminal intervertebral disk extrusion. A: sagittal midplane reconstruction, B: right-sided parasagittal reconstruction at the level of the right pedicle of C4, C: transverse plane at the level of the cranial aspect of C4, D: transverse plane at the level of the C3-4 intervertebral disk, E: dorsal plane reconstruction at the level of the transverse foramen of the C4 vertebra, F: dorsal plane reconstruction at the level of the intervertebral foramen. The affected intervertebral disk and hyperattenuating extruded disk material is circled red.