Question: I’ve reported CPT® code 64999 for an erector spinae pain block for years, but my current employer wants me to use 64461. Which is correct? Washington Subscriber Answer: You are correct that code 64999 (Unlisted procedure, nervous system) is more appropriate for this procedure instead of 64461 (Paravertebral block (PVB) (paraspinous block), thoracic; single injection site (includes imaging guidance, when performed)). Here’s why: Erector spinae plane (ESP) blocks involve injecting anesthetic into the musculofascial plane between the paraspinal back muscles and underlying thoracic vertebrae. The ESP block targets the tips of the transverse processes and is categorized as a paravertebral block, or PVB. A PVB targets the sympathetic chain of nerves and somatic nerves (intercostal and spinal nerves and their branches), from T2 to L1. The erector spinae is a group of muscles and tendons extending the length of the spine (and on both sides). This is not a separately identified spinal nerve or branch, so an injection code specific to a certain nerve or branch of nerves is inaccurate.