EQUINE CERVICAL VERTEBRAL STENOTIC MYELOPATHYACCESSION# 139543

Christina Copple, DVMRadiology ResidentNCSU CVM

“HEYOKA” 1YR OLD PAINT GELDING Neurologic deficits – 1 wk

Incoordination Ataxia Spasticity in forelimbs Lower motor neuron signs in hindlimbs

Suspected cervical vertebral instability/malformation (“Wobblers Syndrome”)

“WOBBLERS SYNDROME” Cervical vertebral stenotic myelopathy (CVSM) Cervical vertebral malformation (CVM) Cervical vertebral instability (CVI) Equine sensory ataxia Equine incoordination and spinal ataxia

Narrowing of cervical vertebral canal combined with malformation of cervical vertebrae

Anywhere from C1 to T1 Stenosis intermittent (dynamic) or continuous (static) compression

of spinal cord neurologic dz (ataxia & weakness)

Equine Vet. Edu. (2003) 15(4) 212-223

CERVICAL VERTEBRAL STENOTIC MYELOPATHY Young, well-fed, rapidly growing horses Age of onset varies with type of stenosis

Young horses –dynamic lesions, acute onset ataxia or gait abnormalities, +/- trauma

Older horses – static lesions, chronic progressive ataxia or gait abnormalities

Most common in: Thoroughbreds and Quarter Horses Males

Most common noninfectious cause of equine spinal ataxia

Equine Vet. Edu. (2003) 15(4) 212-223

PATHOGENESIS OF CVSM Unknown though considered multifactorial

Genetic predisposition Hormonal changes Nutrition Exercise Trauma Degenerative joint disease of articular process joints

Osteochondrosis lesions of articular processes instability & malalignment of adjacent vertebrae DJD of articular process joints & hypertrophy of soft tissue structures

Controversial role in young horses Horses >4yrs old CVSM often associated with DJD of caudal cervical

articular processes

Equine Vet. Edu. (2003) 15(4) 212-223

C5

C6C7

C5

C6

C7

Articular Process DJD C5-C6 & C6-C7

C7

C6

Normal Cervical Spine

C7 T1

Malalignment at C7-T1

5 CHARACTERISTIC BONEY MALFORMATIONS THAT MAY BE SEEN ON LATERAL CERVICAL RADIOGRAPHS

1. “Flare” or “ski jumps” of caudal vertebral epiphysis of vertebral body

2. Abnormal ossification of articular processes3. Malalignment between adjacent vertebrae4. Extension of dorsal laminae5. DJD of articular process joints

Intravertebral sagittal ratio: <50% at C4-C6 or <52% at C7 Sensitivity-87%, specificity-94%, PPV-95%, NPV-84% (Mayhew & Green 2000)

Equine Vet. Edu. (2003) 15(4) 212-223Equine Vet. Edu. (2005) 17(1) 34-38

THE FATE OF “HEYOKA”

C6 C7

C6C7

ADDITIONAL IMAGING TO CONSIDER Cervical myelography – antemortem confirmation of

compressiono > 50% decrease in opposing dorsal and ventral aspects of

subarachnoid space compared to mid-vertebral site cranial or caudal to lesiono 20% reduction of dural diameter at C6-C7 in neutral or flexed position –

highly sensitive & specific for CVSMo Reduction in dorsal aspect of subarachnoid space to a thickness <2

mmo Failure of contrast medium to pass by a site of compression

Equine Vet. Edu. (2005) 17(1) 34-38Equine Vet. J. (2004) 36(1) 14-20