Symptoms

History
  • 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
Pain Intensity
  • 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
Description of Sensory Symptoms
  • 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
Temporal Variation of Pain
  • Pain usually becomes worse toward the end of the day
  • Rule out a neoplastic process if pain progressively increases over the recent months
Functional Impact
  • Impact on sleep, self-care, daily activities, work, social & sexual dysfunction, mood & suicidal ideas
Previous Treatment
  • Usually resistant to medications (eg Paracetamol, NSAIDs)
  • Adequate titrated doses of specific drugs should be determined & documented
Alcohol & Substance Abuse
  • History of dependence disorders can affect decision about prescribing opioids & cannabinoids
  • Consider interaction of sedatives & alcohol w/ other substances
Spontaneous Pain or Sensation
  • 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
Stimulus-Evoked Pain or Sensation
  • 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
Motor Examination
  • May reveal motor weakness in the distribution of the involved nerve
Deep Tendon Reflex
  • May be decreased or absent in the distribution of affected nerve
Sensibility Examination
  • 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
Skin Examination
  • 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
Laboratory Tests
  • Quantitative means to measure objective response
Neurophysiological Testing
  • 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
Skin Biopsy
  • 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
Additional Tests to Identify Other Causes of Neuropathies
  • Glucose tolerance test
  • Thyroid function
  • Vitamin B12 levels
  • CD4+ T-lymphocyte counts
  • Lumbar puncture
Quantitative Sensory Testing
  • 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
  • Functional neuroimaging studies are encouraged in patients w/ NP
Computed Tomography (CT) Scan
  • Facilitates specific diagnosis
Three-Phase Bone Scan
  • May help in the diagnosis of complex regional pain syndrome
Positron Emission Tomography (PET)
  • Measures cerebral blood flow or metabolic activity in defined brain regions
Magnetic Resonance Imaging
  • Can identify small patches of inflammation in peripheral nerves
Activation Studies
  • Investigate local synaptic changes specifically associated w/ a given task or a particular stimulus by comparing statistically activated & controlled conditions
Screening & Assessment Tools
  • The main advantage is to identify potential patients w/ NP, particularly by non-specialists
Screening Tools
  • 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
Assessment Questionnaires
  • Brief Pain Inventory
  • Neuropathic Pain Scale
  • Neuropathic Pain Symptom Inventory

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