Performing a cerebrospinal fluid (CSF) tap in veterinary medicine can easily be performed as long as you are aware of anatomical locations and have the patient in a deep plane of anesthesia. This VetGirl video shows you how easy it is to perform a cisternal tap.
How to perform a CSF tap at the Atlanto-Occipital location for Cerebrospinal Fluid Collection:
1) The patient should be anesthetized under general anesthesia with endotracheal intubation. A stiff endotracheal tube is recommended to avoid occlusion of oxygen flow during the neck flexure required for the procedure.
2) Typically, the cerebellomedullary cistern (CMC) is the preferred site of collection in dogs and cats for atlanto-occipital cerebrospinal fluid collection. The patient should be placed in lateral recumbency for optimal access to the CMC site.
3) The anatomic location of this preferred site is found at the junction between the lines formed by the occipital protuberance/arch of the axis (C2 vertebrae) and the cranial edges of the wings of the atlas (C1 vertebra).
4) A spinal needle (e.g., 20 or 21 gauge, 1.5 inch needle) is commonly used to reach the CMC site in most dogs and cats. NOTE: Larger dogs > 30 kg may require a longer (e.g., 2.5 inch) spinal needle.
5) Prior to insertion of the needle, aseptic technique is imperative. The CSF area is clipped followed by a surgical scrub.
6) An assistant holds the head in ventral flexion so that the muzzle/nose is parallel to the table. This position is why using a stiff endotracheal tube during general anesthesia is important, to prevent occlusion of the tube with flexion of the neck. It is also important that the assistant monitors respiration during the procedure.
7) Once in the appropriate position, the needle is positioned on the midline, perpendicular to the neck, and advanced slowly 1-2 mm at a time penetrating the skin, and then the dura mater.
8) During advancement through the dura mater and atlanto-occipital membrane, the clinician may feel a slight 'pop'. Following this "pop", and after the dura is penetrated, resistance should decrease.
9) Once through these membranes, the stylet is removed, and CSF flow is visually observed and collected.