Wednesday, October 7, 2009
Is anyone assessing epidermal nerve fiber density in skin biopsies?
I recently received an advertising pamphlet from Therapath, a New York company offering to evaluate skin punch biopsy specimens in patients with suspected small fiber neuropathy. The pamphlet trumpets Therapath's proficiency, including "board certified neuropathologists meticulously reviewing cases". Although I have heard of this test, no clients of my practice have yet requested such a test. According to Therapath, the result is "reported as the average number of nerve fibers that cross the basement membrane at the dermal epidermal border, over a length of 1 mm. Making the correct diagnosis explains the symptoms, guides the evaluation for the underlying cause, and helps decide treatment". See the photomicrograph from Therapath's website of normal skin with small fibers (arrow) traversing the basement membrane (arrowhead) and coursing through the epidermis. Accompanying the pamphlet is a letter from "neuropathologist and laboratory director" William Harrington, MD in which he states that the American Academy of Neurology has added a practice guideline to include skin biopsy in the scope of practice when evaluating for polyneuropathies. He goes on to say that "skin biopsy for the determination of epidermal nerve fiber density is the most sensitive test for small fiber neuropathy". Therapath provides the clinician with a kit for biopsy collection and shipping to their facility at no extra charge. Eight to 12 days later, Therapath provides a full-color, quantitative laboratory report with images. If anyone has had experience with evaluating such biopsies, please comment on this post and provide us with your insights regarding the utility and technical requirements of this test. I'm not sure whether I would have to use a service such as Therapath's, or perform the service in-house. Thanks!