Lumbar puncture.

(a) For a lumbar puncture, the needle is inserted into the subarachnoid space where there is cerebrospinal fluid. (b) This patient is having a lumbar puncture. In this case, an upright position is being used, but this older patient does not have much flexibility of the spine and is only able to flex the head and shoulders forward. One physician is helping the patient to maintain this position while the other physician inserts the spinal needle. A white sterile drape covers the patient’s back except for a round opening in the drape where the needle is inserted.