Therapath Testing Instructions

The same biopsy sample can be used for the ENFD and SGNFD.

In patients with suspected neuropathy, skin samples are obtained at standard sites by punch biopsy distally at either the foot or distal leg (calf), and proximally at the thigh. Values are compared to those obtained in normal subjects.

If focal neuropathy is suspected, a biopsy sample in the distribution of the affected nerve can be compared to the corresponding site on the non-affected side of the body.

T = Thigh, 20 cm distal to the iliac spine at the level of the pubis
D = Distal Leg, 10cm proximal to the lateral malleolus
F = Foot, dorsum of the foot over the extensor digitorum brevis muscle

Before performing the procedure, check the expiration date on the fixative vials (transport media) to ensure that it is viable. For more information about fixative and biopsy supplies, visit the Supplies and Shipping page.

Make a 1 cm circle around the biopsy site. Clean the skin with an alcohol swab. Anaesthetize skin with 2% lidocaine with epinephrine, by injecting the edge of the circle, infiltrating but avoiding direct contact with the biopsy site.

The biopsy is performed using a 3 mm circular punch, at a depth of 4 mm, or almost the full distance of the metal head of the punch tool.

Push the tool with rotational motion and even pressure into the epidermis to the midpoint on the head of the punch tool.

Lift the edge of the biopsy with the anaesthetizing needle or forceps and free the biopsy from the attached underlying fatty tissue using forceps or scissors. Forceps should never contact the upper layer of the skin, but only the underlying tissue as it might destroy nerve fibers.

Place one sample in each vial of fixative and verify that the sample is floating before sealing the vial securely.

Label the vials with the appropriate patient identifiers and body site location.