Ultrasound-guided atlanto-occipital puncture for cerebrospinal fluid analysis on the standing horse.

The atlanto-occipital site (AO) is convenient for retrieving an adequate volume and quality of cerebrospinal fluid (CSF) in the diagnosis of neurological disease in horses. However, general anaesthesia is not always possible for horses displaying severe neurological signs, or for economical reasons. The objectives of the present work were to determine the feasibility and safety of ultrasound-guided CSF puncture at the AO site on the standing horse. Seven horses (six healthy and one mildly ataxic) were sedated with acepromazine (0.02 mg/kg bodyweight intravenously or 0.04 mg/kg bodyweight intramuscularly) and detomidine (0.01 mg/kg bodyweight intravenously), and placed in stocks or in a recovery stall with the head kept on a headstand. Puncture was performed by ultrasonographic guidance with a parasagittal technique, as previously described, using a 20 g, 3.5 inch spinal needle. In all horses, no adverse reaction was observed when crossing the dura mater and 20 ml of CSF was rapidly retrieved without any blood contamination. Ultrasound-guided CSF puncture can be performed easily at the AO site on a healthy standing horse. Regarding the potential risk of this procedure, safety measures and close observation are essential. Further studies on a larger amount of ataxic horses are also required before considering this technique as an alternative option for CSF puncture.