I performed rather extensive brachial plexus nerve conduction testing on a badly injured patient. Can I use 99354 to indicate that it took much longer than usual or is that code only for use with E&M procedures?

Emily Hill says CPT instructions under code 99354 indicate that it should only be used with E&M services. For procedural services that require additional time or effort, use the modifier -22 (unusual procedural service), and append it to the appropriate procedure code. Most payers require that documentation demonstrating the unusual nature of the service be submitted with the claim.