Association of clinical and magnetic resonance imaging findings with outcome in dogs with presumptive acute noncompressive nucleus pulposus extrusion: 42 cases (2000–2007)

Luisa De Risio, Vicki Adams, Ruth Dennis et al.

Background
Acute noncompressive nucleus pulposus extrusion (ANNPE) occurs when healthy intervertebral disks are subjected to trauma or excessive force, causing the nucleus pulposus to extrude and contuse the spinal cord without compression. This condition, distinct from Hansen type I disk disease, has a variable prognosis. The study aimed to investigate the associations between clinical findings, magnetic resonance imaging (MRI) results, and outcomes in dogs with ANNPE.

Methods
This retrospective study analyzed medical records of 42 dogs diagnosed with ANNPE based on clinical signs and MRI. Inclusion criteria required acute onset of nonprogressive myelopathy after trauma or strenuous activity, MRI performed within seven days, and complete follow-up data. Key variables included neurologic scores, MRI findings (e.g., extent of spinal cord hyperintensity), and outcomes. Statistical analyses examined associations between these factors and recovery.

Results
Clinical Features: Median age was 6.7 years, with affected breeds including Labrador Retrievers, Border Collies, and Whippets. Neurologic signs localized to T3-L3 spinal segments in 67% of dogs.

MRI Findings: Lesions were characterized by focal spinal cord hyperintensity, reduced nucleus pulposus signal, and minimal spinal cord compression. The extent of spinal cord hyperintensity (PCSAL ≥90%) and longitudinal lesion length-to-vertebral length ratio (LL:VL >1.28) were significant predictors of poor outcome.

Outcomes: Successful outcomes (mild deficits or normal function) occurred in 67% of dogs. Poor outcomes (severe deficits, incontinence, or euthanasia) were associated with higher neurologic scores, larger PCSAL, and presence of GRE hypointensity. Recovery was less likely for dogs with severe neurologic dysfunction (score of 5).

Limitations
The study's retrospective nature and small sample size limited its power. Lack of postmortem validation and inconsistent treatment protocols were additional drawbacks. Some euthanasia decisions potentially influenced outcome interpretations.

Conclusions
Neurologic scores and specific MRI findings, particularly PCSAL, are valuable prognostic indicators in dogs with ANNPE. While MRI assists in diagnosis and outcome prediction, recovery depends significantly on initial neurologic severity. Prospective studies are needed to refine treatment protocols and investigate recovery mechanisms.

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