The diagnosis of<unk><unk>  neuropathy often requires ancillary testing. Nerve conduction studies and electromyography are commonly used to evaluate large myelinated sensory and motor nerve<unk> s, but are ineffective in diagnosing<unk><unk>  neuropathies. Quantitative sensory testing (QST) assesses<unk><unk>  function by measuring temperature and vibratory sensation. Abnormal QST results can be attributed to dysfunction in the central nervous system. Furthermore, QST is limited by a patient's subjective experience of pain sensation. Electrochemical skin conductance and quantitative sudomotor axon reflex testing (QSART) measures sweating response at local body sites to evaluate the<unk>  nerve<unk> s that innervate sweat glands. Electrochemical skin conductance has been evaluated for both early diagnosis of<unk><unk>  neuropathy and follow-up of treatment efficacy. Skin biopsy A skin biopsy for the measurement of epidermal nerve<unk>  density is an increasingly common technique for the diagnosis of<unk> . Physicians can biopsy the skin with a 3-mm circular punch tool and immediately fix the specimen in 2% paraformaldehyde lysine-periodate or Zamboni's fixative. Specimens are sent to a specialized laboratory for processing and analysis where the<unk>  nerve<unk> s are quantified by a neuropathologist to obtain a diagnostic result. This skin punch biopsy measurement technique is called intraepidermal nerve<unk>  density (IENFD). The following table describes the IENFD values in males and females of a 3 mm biopsy 10 cm above the lateral<unk> eolus (above ankle outer side of leg). Any value measured below the 0.05 Quantile IENFD values per age span, is considered a reliable positive diagnosis for<unk> . Intraepidermal nerve<unk>  density (IENFD) normative values for clinical use Females Males Age in years 0.05 Quantile IENFD values per age span Median IENFD values per age span 0.05 Quantile IENFD values per age span Median IENFD values per age span 20–29 10.9 30–39 10.3 40–49 9.6 50–59 8.9 60–69 8.3 70–79 7.7 ≥80 7.2
Small fiber peripheral neuropathy
Diabetic neuropathy
Proximal diabetic neuropathy
Vasculitic neuropathy
Autonomic neuropathy
Peripheral mononeuropathy
Tropical neuropathy
Giant axonal neuropathy