Below CPT Assistant references would support two facet levels in the lumbar region represented by 64493 as described by the L3,L4 medial branches that innervate the L4-L5 facet joint and 64494 for the L4 medial branch and L5 dorsal ramus innervating the L5-S1 facet joint.
August 2010 CPT ASSISTANT
The L3, L4, and L5 medial branch nerves innervate the L4-L5 and L5-S1 facet joints. Therefore, code 64493,Injection(s), diagnostic or therapeutic agent, paravertebral facet (zygapophyseal) joint (or nerves innervating that joint) with image guidance (fluoroscopy or CT), lumbar or sacral; single level,is reported for the first joint injected or blocked (L4-L5). Code 64493 is reported for a single or initial level treated. Add-on code 64494,Injection(s), diagnostic or therapeutic agent, paravertebral facet (zygapophyseal) joint (or nerves innervating that joint) with image guidance (fluoroscopy or CT), lumbar or sacral;second level (List separately in addition to code for primary procedure),is reported for the second joint or level injected or blocked (L5-S1).
Additionally from September 2004 CPT ASSISTANT
"It should be further emphasized that codes 64475, 64476, 64479, and 64480 refer to the injection of a facet joint either by injection into the joint with one needle puncture or by anesthetizing the two medial branch nerves that supply each joint (two needle punctures). For example, a left-sided L4-L5 intra-articular injection performed with a single needle puncture would be coded as 64475. Injection of the L3 and L4 medial branch nerves supplying the L4-L5 facet joint would also be coded as 64475, even though two separate injections are performed to effect the same result."