Intervertebral Disc Disease-Cats

Basics

Overview

Disc extrusion or protrusion causing myelopathy is more common in dogs; both Hansen's type I and type II disc disease, and acute, non-compressive nucleus pulposus extrusion are reported in cats.
Type I disc disease is secondary to chondroid metaplasia and mineralization of the nucleus pulposus.
Type II disc disease is secondary to fibroid degeneration and protrusion of the annulus fibrosus.
With acute, non-compressive nucleus pulposus extrusion, normal nucleus pulposus is extruded through a tear in the dorsal annulus, resulting in a concussive or contusive injury, with minimal to no ongoing compression of the spinal cord.

Signalment

For all reported cats with myelopathy secondary to disc disease-mean age 8.4 years, range 1.5–17 years.
Cats with mineralized type I disc disease-mean age 7.3 years, range 2–13 years.
Predominantly domestic breeds, several purebred (Oriental) breeds reported. Rare exotic large cat (tiger) reported.
No sex predisposition.

Signs

Majority of cats have thoracolumbar or lumbosacral disc disease: clinical signs are confined to pelvic limbs. Cervical disc disease is also described, in which case all four limbs may be affected.
Signs are frequently acute but may be chronic.
Paresis/paralysis.
Ataxia.
Gait abnormality, lameness, reluctance to jump.
Spinal/back pain.
Urinary/fecal incontinence.
Abnormalities of tail carriage or tone.
Loss of pain perception (if severe lesion).
Hypoventilation (if severe cervical lesion).

Causes & Risk Factors

Majority of cats reported had type I disc degeneration, with extrusion of mineralized nucleus pulposus into the vertebral canal resulting in spinal cord trauma and compression.
Unlike dogs, where chondrodystrophic breeds (e.g., dachshunds) are predisposed to type I disc disease and subsequent extrusion, no obvious risk factors are apparent in cats.
Most cats reported had clinically significant disc protrusions or extrusions between T11 and S1. Similar to dogs, the presence of the intercapital ligament from T1–T10 may make disc protrusions in that region less likely.

Diagnosis ⬆ ⬇

Diagnosis

Differential Diagnosis

CBC/Biochemistry/Urinalysis

Usually normal

Other Laboratory Tests

N/A

Imaging

Vertebral column radiographs-narrowed disc space(s), mineralized discs in situ, mineralized disc material within the vertebral canal or overlying intervertebral foraminae.
Myelography-extradural compressive lesion at the affected disc.
CT-extradural compression; mineralization of compressive material may be apparent.
MRI-T2 hyperintensity within injured cord; mineralized disc material appears hypointense on all imaging sequences; extradural compression may be apparent.

Diagnostic Procedures

Cerebrospinal fluid-unremarkable or contaminated with blood in most cats; neutrophilic pleocytosis noted in three cats.
Histopathology of material removed at surgery-consistent with degenerative disc material (type I or II).

Treatment ⬆ ⬇

Treatment

Surgical spinal cord decompression likely the most effective treatment for compressive disc disease.
Risks of spinal surgery should be discussed with the owner-hemorrhage, iatrogenic injury to the spinal cord, instability.
Hemilaminectomy, ventral slot, lateral corpectomy, and lumbosacral dorsal laminectomy surgeries are described in the cat.
Postoperative care-good recumbent patient care, pain management, bladder management if incontinent cat (indwelling urinary catheter or manual expression), and appropriate physical therapy.
Fenestration of adjacent mineralized discs should be considered to avoid recurrence.
Medical management (cage rest, pain management) may be considered in ambulatory cats, but more aggressive diagnostics and treatment should be considered in non-ambulatory cats and those with progressive neurologic signs.

Medications ⬆ ⬇

Medications

Drug(s)

Follow-Up ⬆ ⬇

Follow-Up

Repeat neurologic examinations (at least 1–2 times/day) during hospitalization to monitor postoperative and medically managed patients for improvement or decline in neurologic status.
Strict cage rest for medically managed and postoperative patients for 4–6 weeks, then gradual increase in activity and physical therapy, as needed.
It is unknown whether long-term activity restriction is beneficial.
Because disc disease is uncommon in cats, possible recurrence rate is unknown, but in one cat that recovered well after hemilaminectomy, an additional mineralized disc extrusion caused paraplegia and necessitated a second surgery (unpublished data).
A few cats had persistent urinary retention in spite of good recovery of ambulation, requiring routine bladder expression by the client.
Majority of cats managed surgically (even two without pain perception) had a good-to-excellent outcome.
Very few cats were medically managed long-term, so prognosis with medical management is unknown.

Miscellaneous ⬆

Miscellaneous

Abbreviations

Suggested Reading

Rayward RM. Feline intervertebral disc disease: A review of the literature. Vet Comp Orthop Traumatol 2002, 15:137–144.

Author Marguerite F. Knipe

Consulting Editor Joane M. Parent

Client Education Handout Available Online