Validation of the accuracy of needle placement as used in diagnostic local analgesia of the maxillary nerve for investigation of trigeminally mediated headshaking in horses.

The study confirms the significant role that experience plays in accurately placing needles for diagnostic local anaesthesia of the maxillary nerve in horses, a common practice used when diagnosing headshaking problems believed to stem from facial dysaesthesia.

Objective of the Research

• The research aimed at determining the precision of needle placement during diagnostic local anaesthesia of the maxillary nerve, which is deployed in identifying cases of headshaking in horses, attributed to facial dysaesthesia.
• The researchers further sought to establish whether there was a relationship between the accuracy of this process and the practitioner’s experience.

Methodology

• To test the accuracy of needle placement, a small amount of contrast medium (a substance used to increase the contrast of structures or fluids within the body during medical imaging) was utilized.
• The procedure was conducted bilaterally on 30 horse cadaver heads divided equally among three disparate groups categorizing the operator’s level of experience.
• The precision of the injection and the position of the deposited contrast medium were then examined using computed tomography (CT).

Results

• The findings indicated that the contrast medium was placed around the target area in approximately 53.3% of the procedures.
• Importantly, the success rate of an experienced operator was higher, with 80% accuracy, compared to the 40% achieved by less experienced or inexperienced operators. This difference was statistically significant (p-value <0.05), highlighting the importance of practitioner experience for successful needle placement.

Implications

• The research suggests that a negative response to the diagnostic anaesthesia does not exclude facial dysaesthesia as the origin of headshaking in horses. This is because the anaesthetic might not have been correctly deposited around the target area, resulting in a false-negative outcome.
• The study concludes that a practitioner’s experience significantly reduces the likelihood of false negatives, thus underscoring the need for experienced operators when performing this procedure.