Intraobserver and interobserver agreement for results of low-field magnetic resonance imaging in dogs with and without clinical signs of disk-associated wobbler syndrome.

OBJECTIVE: To determine interobserver and intraobserver agreement for results of low-field magnetic resonance imaging (MRI) in dogs with and without disk-associated wobbler syndrome (DAWS). DESIGN: Validation study. ANIMALS: 21 dogs with and 23 dogs without clinical signs of DAWS. PROCEDURES: For each dog, MRI of the cervical vertebral column was performed. The MRI studies were presented in a randomized sequence to 4 board-certified radiologists blinded to clinical status. Observers assessed degree of disk degeneration, disk-associated and dorsal compression, alterations in intraspinal signal intensity (ISI), vertebral body abnormalities, and new bone formation and categorized each study as originating from a clinically affected or clinically normal dog. Interobserver agreement was calculated for 44 initial measurements for each observer. Intraobserver agreement was calculated for 11 replicate measurements for each observer. RESULTS: There was good interobserver agreement for ratings of disk degeneration and vertebral body abnormalities and moderate interobserver agreement for ratings of disk-associated compression, dorsal compression, alterations in ISI, new bone formation, and suspected clinical status. There was very good intraobserver agreement for ratings of disk degeneration, disk-associated compression, alterations in ISI, vertebral body abnormalities, and suspected clinical status. There was good intraobserver agreement for ratings of dorsal compression and new bone formation. Two of 21 clinically affected dogs were erroneously categorized as clinically normal, and 4 of 23 clinically normal dogs were erroneously categorized as clinically affected. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that variability exists among observers with regard to results of MRI in dogs with DAWS and that MRI could lead to false-positive and false-negative assessments.

Transcranial magnetic stimulation in Doberman Pinschers with clinically relevant and clinically irrelevant spinal cord compression on magnetic resonance imaging.

OBJECTIVE: To evaluate the use of transcranial magnetic stimulation for differentiating between clinically relevant and clinically irrelevant cervical spinal cord compression on magnetic resonance imaging (MRI). DESIGN: Validation study. ANIMALS: Clinically normal Doberman Pinschers without (n = 11) and with (6) spinal cord compression on MRI and 16 Doberman Pinschers with disk-associated wobbler syndrome (DAWS). PROCEDURES: After dogs were sedated, transcranial magnetic motor evoked potentials were recorded from the extensor carpi radialis muscle (ECRM) and cranial tibial muscle (CTM). Onset latencies and peak-to-peak amplitudes were measured. Magnetic resonance imaging was performed to identify spinal cord compression. RESULTS: There were significant differences in ECRM and CTM onset latencies between Doberman Pinschers with DAWS and each of the 2 groups of clinically normal dogs, but there were no significant differences in ECRM and CTM onset latencies between the 2 groups of clinically normal dogs. There were significant differences in CTM peak-to-peak amplitudes between Doberman Pinschers with DAWS and each of the 2 groups of clinically normal dogs, but there were no significant differences in ECRM peak-to-peak amplitudes among groups or in CTM peak-to-peak amplitudes between the 2 groups of clinically normal dogs. There was a significant correlation between severity of spinal cord compression and ECRM onset latency, CTM onset latency, and CTM peak-to-peak amplitude. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that transcranial magnetic stimulation may be a useful diagnostic tool to differentiate between clinically relevant and clinically irrelevant spinal cord compression identified on MRI alone.