Quantitative motor unit action potential analysis of paraspinal muscles, diagnostic imaging and necropsy findings in 36 horses suspected of cervical impairment

Aims: To determine the relation between quantitative electromyography (QEMG) of the cervical ventral serratus muscle, radiographic findings and post-mortem gross and histopathological examination in order to calculate the ability of QEMG to localize the region of cervical compressive neuropathy and myelopathy in horses. Methods: In this clinical, non-randomised, partially blinded study (QEMG and histology), 36 warmblood horses with clinical suspicion of cervical spine disease were examined with QEMG in different segments of the ventral serratus muscle. Results were compared to normative data. Diagnostic imaging was performed in 28 cases. All horses were euthanized because of poor clinical prognoses and/or recurrent clinical neurological signs despite treatment and underwent necropsy with emphasis on the cervical nervous tissue and vertebrae. Clinical and diagnostic imaging findings, QEMG results and post mortem findings were compared with each other. Results: Overall mean values of duration (9.54 ms), polyphasia, number ofphases (3.6) and size index (0.67) in horses with cervical lesions were significantly (P<0.05) higher than reference data. Clinical examination correlated significantly with several QEMG- and histological changes but not with radiological abnormalities. A reduced neck mobility seems to be a clinically relevant parameter to suspect cervical spine pathology. No significant correlations were found between radiology and any post mortem findings. For QEMG, in two (C5/6 right side and C6/7 left side) out of twelve cervical segments (C1-2, C2-3, C3-4, C4-5, C5-6, C6-7 on both sides) statistically significant relations with histopathological changes could be found. Conclusions and Practical Relevance: In this study, at the level of C5-6-7 QEMG could predict the site of the lesion in the nervous system whereas radiological imaging failed to identify the site of the lesions. Clinical examination correlated significantly with several QEMG- and histological changes but not with radiological abnormalities. QEMG can be added to the examination protocol of horses suspected clinically of suffering from cervical compressive neuropathy and myelopathy.