This study evaluates peripheral nervous system function using Multiple Excitability Measures (MEM) to obtain "electrophysiological pain phenotypes"

Using MEM for peripheral sensory and motor axons we want to identify a set of excitability measures that:

1. Correlate with parameters of clinical pain and of pain processing in existing pain patients (cross sectional study), with the aim to obtain an objective Pain Biomarker.
2. Predict development of neuropathic pain in susceptible patients (longitudinal study). Neuropathic Pain Predictor for patients:

i. Undergoing surgical procedures associated with a relatively high risk of developing neuropathic pain such as thoracotomy and hernia repair ii. Planning to start chemotherapy with potentially neurotoxic agents such as vincristine

Inclusion Criteria:

• Chronic peripheral neuropathic pain
• Painless Patient with risk to develop neuropathic pain (post-surgery, chemotherapy-induced)

Exclusion Criteria:

• Minors

1. Painless patients and patients with chronic peripheral neuropathic pain
2. Susceptible patients for developing pain i. Undergoing surgical procedures associated with a relatively high risk of developing neuropathic pain such as thoracotomy and hernia repair ii. Planning to start chemotherapy with potentially neurotoxic agents such as taxol, vincristine, etc.