CPT 64490 is for cervical/thoracic facet joint or nerves that innervate the facet joint. What is being described does not appear to support this for treatment of the facet or facet joint nerves. I have not seen a published statement that this code can be reported for a paravertebral block.
http://ultrasoundblock.com/index.php/nerve-block-techniques/new-blocks/pecs-block
Below I found a description of the PECS block and your mention of CPT 64450 seems correct.
"Thoracic wall blocks (PECS I, PECS II and Serratus plane block) are peripheral nerve block alternatives to paravertebral block for providing both surgical anesthesia and postoperative analgesia for breast surgery. All rely on LA placement between the thoracic wall muscles. Thoracic wall blocks are to the chest what the TAP (transversus abdominis plane) block is to the abdomen. Like the TAP block, their introduction has been facilitated by the widespread availability of portable ultrasound. "
Depending on the extent of surgery, anesthesia/analgesia for breast surgery requires blockade of several nerves innervating the chest wall. For example, for the insertion of breast expanders and submuscular prostheses, tissue trauma is generally limited to the pectoralis major muscle, and therefore only blockade of the lateral and medial pectoral nerves is required. For more extensive procedures such as tumour resections, mastectomy and sentinel node dissection, surgical dissection is typically deeper and requires blockade of the thoracic spinal nerves. For even more extensive reconstructions particularly those involving the axilla, blockade of the long thoracic nerve is needed. Blockade of the thoracodorsal nerve is required for lattissimis dorsi flap reconstruction.
Based on this neural innervation, 3 block types are described depending on the target nerves to be blocked (Fig. 4).
1. PECS 1 block (?Original? PECS block) ? 10mL LA injection between pectoralis major and minor at the 3rd rib level to block the lateral and medial pectoral nerves. Appropriate for surgery limited to pectoralis major.
2. PECS 2 block (?Modified? PECS block) ? a PECS 1 block, in addition to a further 20 mL LA injection between pectoralis minor and serratus anterior at the 3rd rib level. By The latter injection blocks the lateral branch of the T2-4 spinal nerves, and possibly the anterior branch if sufficient LA penetrates the external intercostal muscles. By entering the axilla, the long thoracic nerve may also be blocked (Fig 2). Suitable for more extensive excisions e.g. tumour resections, mastectomy, axillary clearance.
3. Serratus plane block ? ? A single 40 mL LA injection between latissimus dorsi and serratus anterior at the 5th rib level in the mid axillary line. This injection blocks the thoracodorsal nerve. Suitable for latissimus dorsi flap reconstruction