Contact between the side of the lumbar puncture needle and a spinal nerve root can result in anomalous sensations (paresthesia) in a leg during the procedure; this is harmless and patients can be warned about it in advance to minimize their anxiety if it should occur. A headache that is persistent despite a long period of bedrest and occurs only when sitting up may be indicative of a CSF leak from the lumbar puncture site. It can be treated by more bedrest, or by an epidural blood patch, where the patient's own blood is injected back into the site of leakage to cause a clot to form and seal off the leak.