Symptoms

• Will help determine whether the character & distribution of pain follow the neuropathic criteria & whether a relevant lesion or disease in the nervous system is probably responsible for the pain

• Can be rated using a valid verbal, numerical or visual analog scale or Numeric Pain Rating Scale such as the Neuropathic Pain Scale & Neuropathic Pain Questionnaire
• Assessed at each visit to monitor therapeutic response

• Quality of pain: burning, sharp, stabbing, cold, allodynia, hyperalgesia, spontaneous, dysesthesia, paresthesia
• Frequent non-painful sensations: pricking, tingling, aching, numbness, hypoesthesia, anesthesia, hypoalgesia, analgesia
• Sensory abnormalities & pain paradoxically co-exist

• Pain usually becomes worse toward the end of the day
• Rule out a neoplastic process if pain progressively increases over the recent months

• Impact on sleep, self-care, daily activities, work, social & sexual dysfunction, mood & suicidal ideas

• Usually resistant to medications (eg Paracetamol, NSAIDs)
• Adequate titrated doses of specific drugs should be determined & documented

• History of dependence disorders can affect decision about prescribing opioids & cannabinoids
• Consider interaction of sedatives & alcohol w/ other substances

• Paresthesias (eg tingling, itching, sensation of something crawling on one’s skin, discomfort of one’s foot “falling asleep”)
• Dysesthesias (eg pricking, electric shock-like, burning or shooting pain)
• Phantom pain

• Allodynia
• Hyperalgesia
• Hyperpathia
• Hypoesthesia/Anesthesia

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Physical Examination

• Allows integration of the patient’s current symptoms & localization of the involved elements of the nervous system
• Identifying pain localization, quality, intensity & pattern is essential
• Reveals the presence of negative (loss of function) & positive (hyperalgesia &/or allodynia) signs for sensory modalities affecting the somatosensory system & relevance to the underlying disease or lesion

• May reveal motor weakness in the distribution of the involved nerve

• May be decreased or absent in the distribution of affected nerve

• Reduced or absent light touch, pin prick, vibration responses & proprioception in the affected nerve territory
• Sensory disturbances can expand outside the area of nerve innervation
• Dynamic allodynia: pain arising from gentle brushing of skin w/ cotton ball
• Thermal allodynia: burning sensation due to an ice cube placed on the skin
• Hyperalgesia to a pin prick test
• Pain on leg lifting: irritation of lumbar nerve roots
• Myofascial trigger points: myofascial pain plus neuropathic pain

• Changes in skin temp, color, sweating or hair growth (complex regional pain syndrome)
• Residual dermatomal scars persisting after herpes zoster infection
• Characteristic skin changes of DM

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Ancillary Tests

• May be conducted to document the presence of a specific underlying neurologic disease or confirm a sensory lesion w/in the pain distribution

• Quantitative means to measure objective response

• Standard neurophysiological responses to an electrical stimulus can identify, localize & quantify damage along peripheral or central sensory pathways
• Pain-related evoked potential: Laser-evoked potentials are the easiest & most reliable methods for assessing function of the nociceptive & A-delta fiber pathways in patients w/ NP
• Electromyography & Nerve Conduction Velocity (EMG/NCV): Provides objective evidence of nerve injury or dysfunction but primarily evaluates the large myelinated fibers thus small fiber neuropathy may not be ruled out if the result is normal
• Microneurography: Provides valuable information on the physiology & pathophysiology of all nerve fiber groups but this is not recommended as routine procedure for assessing patients w/ peripheral NP
• Pain-related reflexes: Diagnostically useful only for facial pains as in trigeminal pain disorders

• Best tool for assessing neuropathies w/ distal loss of unmyelinated nerve fibers
• Recommended in patients w/ painful or burning feet of unknown origin & w/ clinical impression of small fiber dysfunction

• Glucose tolerance test
• Thyroid function
• Vitamin B12 levels
• CD4+ T-lymphocyte counts
• Lumbar puncture

• Psychophysiological measure of perception in response to external stimuli of controlled intensity, which allows documentation of sensory profile
• Appropriate to quantify positive sensory phenomena like mechanical & thermal allodynia & hyperalgesia which may help characterize painful neuropathic syndromes & predict or monitor treatment effects

• Functional neuroimaging studies are encouraged in patients w/ NP

• Facilitates specific diagnosis

• May help in the diagnosis of complex regional pain syndrome

• Measures cerebral blood flow or metabolic activity in defined brain regions

• Can identify small patches of inflammation in peripheral nerves

• Investigate local synaptic changes specifically associated w/ a given task or a particular stimulus by comparing statistically activated & controlled conditions

• The main advantage is to identify potential patients w/ NP, particularly by non-specialists

• Unidimensional scales
• McGill Pain Questionnaire
• Douleur Neuropathique en 4 (DN4) Questions
• ID-Pain
• Pain DETECT
• Leeds Assessment of Neuropathic Symptoms & Signs
• Standardized Evaluation of Pain
• Chinese Identification Pain Questionnaire

• Brief Pain Inventory
• Neuropathic Pain Scale
• Neuropathic Pain Symptom Inventory

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