Lay descriptions
NOT my area of expertise, but here are the lay descriptions of these new (in 2009) codes. Please note that 61797 is NOT for a single lesion that is over 3.5 cm diameter.
This is a noninvasive procedure that does not require incision of the scalp or drilling into the skull. Report 61796 (no more than once per course of treatment) for stereotactic radiosurgery on a simple cranial lesion. Simple lesions include those that are less than 3.5 cm in maximum dimension and those that do not meet the criteria for a complex lesion. Report 61797 for each additional simple cranial lesion. Report code 61798 (no more than once per course of treatment) for stereotactic radiosurgery on a complex cranial lesion. Complex lesions include those that are 3.5 cm or greater in maximum dimension; those that are within the brainstem or adjacent (5 mm or less) to the optic nerve, optic chasm, or optic tract; schwannomas; arteriovenous malformations; cavernous sinus tumors; glomus tumors; parasellar or petroclival tumors; pineal region tumors; and pituitary tumors. Code 61798 is also reported for procedures such as thalamotomy or pallidotomy that create therapeutic lesions. If multiple lesions are treated and any single lesion is complex, report 61798. Report 61799 for each additional complex cranial lesion; however, codes 61797 and 61799 may not be reported more than four times for the entire course of treatment regardless of the number of lesions treated. Codes for cranial stereotactic radiosurgery include any required computer-assisted planning, dosimetry, targeting, positioning, or blocking by the neurosurgeon. (emphasis added by FTB)
By the way, for skin lesions, each lesion is coded separately, based on the size, location and character of that individual lesion.
Hope that helps.
F Tessa Bartels, CPC, CEMC