Prognostic Utility of F-Waves in Paraplegic Dogs With Absent Pain Perception Secondary to Intervertebral Disc Extrusion

Background

Approximately 50%–60% of paraplegic deep pain negative (DPN) dogs secondary to thoracolumbar intervertebral disc extrusion (TL-IVDE) recover ambulation after surgery. Mean F-wave duration has been associated with injury severity in TL-IVDE in dogs, but the relationship to outcome is unknown.

Objective

Evaluate the prognostic utility of F-waves in DPN dogs secondary to TL-IVDE treated surgically.

Animals

Thirty client-owned, acutely paraplegic DPN dogs secondary to TL-IVDE were managed surgically.

Methods

Multi-center prospective and observational study. F-waves were performed at baseline (within 24 h post-operatively), 2–4 weeks and 3 months post-operatively. Outcome was categorized as successful or unsuccessful, with success defined as independent ambulation at 3 months post-operatively. F-wave variables were compared between dogs with a successful or unsuccessful outcome and over time using generalized estimating equations. Receiver-operating characteristic curves were generated for baseline F-wave variables.

Results

F-waves were well-tolerated in all dogs. Of 30 enrolled dogs, 12 dogs had a successful outcome, 10 dogs were unsuccessful, and 8 dogs were removed from outcome analysis (3 progressive myelomalacia, 1 severe spinal shock, 2 technical error, and 2 unknown outcome). Baseline mean F-wave duration (displayed as median (range)) was longer in unsuccessful dogs (31.7 (11.4–60.8) ms) versus successful dogs (19.6 (10.8–27.3) ms), p = 0.003. Mean F-wave duration > 28.5 ms was 70% sensitive (95% confidence interval (CI): 40%–100%) and 100% specific (95% CI: 100%–100%) in predicting an unsuccessful outcome.

Conclusions and Clinical Importance

F-waves performed shortly post-operatively could aid in predicting outcomes in DPN dogs secondary to TL-IVDE treated surgically.