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56 Section I: Diagnostics and Planning

A B

W

C2 OCP

W

Figure 5.1 Positioning and landmarks for cisternal CSF tap. (A) Patient is in left lateral recumbency with the head flexed and the nose parallel to the plane
of the table. (B) Landmarks: W, widest point of the wings of the atlas (C1); OCP, occipital protuberance; C2, cranial tip of the C2 spinous process. Note the
OCP and C2 are in alignment and represent the mid‐sagittal plane of the patient.

Figure 5.3 Technique for flexion of the head and extension of the neck for
cisternal CSF tap positioning.

Figure 5.2 Supplies for a cisternal CSF tap: sterile gloves, spinal needle again. If free‐flowing blood is observed in the needle, it is likely the
(Quincke point), collection tubes. needle was directed just lateral to the cisterna magna. The needle
should be withdrawn and a new needle used for another attempt at
sample collection [2].
imaginary line drawn transversely between the widest points of the Once CSF flow is visualized, an assistant catches the drops in the
wings of the atlas and a line drawn sagittally along the midline from sample tube(s) (Figure 5.5 and Video 5.1). Sometimes there is a
the external occipital protuberance to the spinous process of C2 small amount of blood associated with minor iatrogenic trauma to
(Figure 5.1). The needle is slowly advanced further, making sure a small meningeal or muscle vessel in the first couple of drops [2].
that it remains on the midline and parallel to the table. The stylet is These first few drops can be collected in a separate tube, and then a
periodically removed if necessary to check for CSF flow. The spinal second tube used to collect the clearer CSF.
needle is stabilized while removing and reinserting the stylet to If the CSF flow is slow, an assistant can carefully occlude the jugu-
avoid needle movement. In some patients, particularly those with lar veins without changing position of the patient to help increase
domed heads, it is helpful to angle the needle at a more caudal flow. It is important that the position of the head and/or needle is
angle, maintaining the needle on the midline. As the needle is not changed. Aspiration of the fluid with a syringe is not recom-
advanced the collector often notes changes in resistance as the nee- mended. Approximately 1 mL of CSF can be safely removed per 5 kg
dle passes through the fascial planes of the muscle and finally of body weight [3]; however, most routine sampling only requires a
through the dorsal atlanto‐occipital membrane and dura into the total volume of 1 mL for any patient.
subarachnoid space [3]. Once the sample is obtained, the needle is carefully removed
If the occipital bone is encountered, the needle is redirected cau- before the holder relaxes the head. It is not necessary to replace the
dally along the sagittal (midline) plane [2]. If CSF is not obtained stylet prior to removing the needle. In cases where only a small
after two redirection attempts, then the needle is completely with- amount of CSF was obtained in the sample tube, the residual vol-
drawn, landmarks reestablished and sample collection attempted ume in the needle is also collected in the tube.