Description of a regional anaesthesia technique for the dorsal cranium in the dog: a cadaveric study.

Objective To identify landmarks and to describe a technique for nerve blockade of the dorsal cranium in dogs. Study design Anatomic cadaveric study. Animals A total of 39 dog cadavers, weighing 18.0 +/- 9.7 kg ( mean +/- standard deviation). Methods The study was performed in three parts. In the initial part, cadavers were dissected to determine the location of the frontal, zygomaticotemporal, and major occipital nerves, and to identify prominent landmarks for their blockade. In the second part, one technique was developed to block each of the frontal and zygomaticotemporal nerves, and two techniques, rostral and caudal, were developed to block the major occipital nerve. Injection solution was 0.05% methylene blue in 0.5% bupivacaine. In the third part, cadavers were used to test the techniques developed in the second part with 0.04 mL kg(-1) of the same injectate administered at each site ( maximal volume 0.5 mL per site). The length of nerve stained was measured, with a length >= 6 mm considered successful. Confidence intervals were calculated using Fisher's exact test. Results Success rates (95% confidence interval) for the frontal, zygomaticotemporal, and rostral and caudal locations for the major occipital nerve were 94% (80-99%), 91% (76-98%), 74% (58-86%) and 77% (59-89%), respectively. With a combination of both locations, the success rate for the major occipital nerve was 100% (90-100%). Conclusion and clinical relevance This study describes a simple regional anaesthesia technique using palpable anatomical landmarks that may provide analgesia for dogs undergoing craniotomy.