CPT® Code 88356

The CPT® Code 88356 refers to a specialized laboratory test known as morphometric analysis of nerve fibers. This procedure is specifically designed for the pathological analysis and quantification of intraepidermal nerve fiber (IENF) density and/or sweat gland nerve fiber (SGNF) density obtained from a skin punch biopsy. The primary objective of this analysis is to assist in the diagnosis of peripheral nerve diseases that affect small nerve fibers. Small fiber neuropathy (SFN) is a condition characterized by sensory pain in the extremities, often presenting with normal results on electromyography and nerve conduction studies, indicating that large fiber neuropathic disease is not present. Various medical conditions are associated with SFN, including diabetes, HIV, systemic lupus erythematosus, and neurosarcoidosis. To perform this test, a skin punch biopsy is typically taken from the lower extremity, with the calf being the preferred site. The collected tissue is then processed using a microtome, which slices the tissue into thin sections. These sections are subjected to immunostaining with anti-protein-gene-product 9.5 antibodies, which helps in visualizing the small sensory fibers. The analysis is conducted using either immunohistochemical or immunofluorescent techniques to examine the morphology of the small sensory fibers that innervate the skin. During the evaluation, the number of intraepidermally originating nerve fibers that cross the basement membrane between the dermis and epidermis is counted across several sections. Additionally, the total length of the epidermis is measured, allowing for a calculation of the number of nerve fibers per millimeter. This calculated density is then compared to normative data to either support or rule out a diagnosis of small fiber neuropathy.