Neuropathic Pain. Scott Magnuson, MD Pain Management of North Idaho, PLLC

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1 Neuropathic Pain Scott Magnuson, MD Pain Management of North Idaho, PLLC

2 Pain is our friend "An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage." Early warning system

3 Acute vs Chronic Pain Characteristic Acute Pain Chronic Pain Cause Usually known Often unknown Persists after Duration Self-limited healing; >/= 3 months Treatment Resolution of underlying cause Treat underlying cause & pain disorder

4 Impact of Chronic Pain Quality of Life Physical function Ability to do ADLs Work Recreation Social consequences Marital/family Intimacy Social isolation Psychological Morbidity Depression Anxiety, anger Sleep disturbance Loss of self esteem Socioeconomic Consequences Healthcare costs Disability Lost workdays

5 Definition of nociceptive and neuropathic pain Nociceptive = pain caused in response to potentially tissue damaging stimuli Neuropathic = pain caused by a primary lesion or dysfunction in the peripheral or central nervous system

6 Examples of Nociceptive and Neuropathic Pain

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8 Pain Pathways

9 Primary Afferent Axons A-alpha A-beta A-delta C Mechanoreceptors Sensory/ fast pain Multimodal sensory/slow Mechanoreceptors/ proprioception Diameter (um) Speed (m/s) pain

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11 Wind-up

12 Fig. 2: Neuropathic pain arises following nerve injury or dysfunction. Gilron I et al. CMAJ 2006;175: by Canadian Medical Association

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14 Evaluation of The Patient Pain intensity 0-10 scale Repeatable & consistent Track progression/ success of tx

15 Evaluation of The Patient Pain Descriptors Hot Burning Sharp Stabbing Cold Shocking Electric-like Non-painful sensations Tingling Prickling Tingling Itching Pins and needles

16 Evaluation of The Patient Functional impact Effect of pain on sleep, ambulation, self-care, activities of daily living, work, social or sexual function, mood and suicidal ideation Attempted treatments Determine and document adequacy of dose titration for titratable drugs (e.g., dose reached and duration of treatment, drug treatment stopped owing to adverse effects or lack of efficacy)

17 Evaluation of The Patient Alcohol or substance abuse Addiction history will affect decision to prescribe opioids Consider earlier involvement with a mental health counselor, psychologist or psychiatrist Consider safety of sedative analgesics with alcohol or other sedatives

18 Evaluation of The Patient Physical examination Gross motor examination Motor weakness may occur around the involved nerves Attempt to differentiate between true weakness and antalgic weakness Deep tendon reflexes May be diminished or absent around the involved nerves

19 Sensory Evaluation Light touch, pin prick, vibration sense and proprioception may be diminished or absent in the involved nerve territory Sensory disturbance may aberrantly extend beyond a discrete nerve territory Dynamic allodynia (pain due to cotton wool lightly moving across the skin) Thermal allodynia (burning sensation in response to ice cube on skin) Pinprick hyperalgesia (exaggerated pain following pinprick to the skin) Pain when straight leg is raised, suggestive of irritation of lumbar nerve root Elicitation of myofascial trigger points to favor a diagnosis of myofascial pain over neuropathic pain Possible presence of Tinel's sign

20 Skin Examination Alterations in temperature, color, sweating and hair growth suggestive of complex regional pain syndrome Residual dermatomal scars consistent with previous herpes zoster (shingles) infection Characteristic skin changes consistent with diabetes mellitus

21 Causes of Neuropathic Pain Diabetes Traumatic Multiple sclerosis Vitamin deficiencies HIV Medications Herpes Zoster Alcohol Neoplasia Heavy metals

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24 Non-pharmacologic Treatment Options Cognitive-behavioral therapy Meditation Imagery Biofeedback Relaxation therapy Physical Rehabilitation Acupuncture Transcutaneous electrical stimulation

25 Antidepressants Tricyclics Amitryptyline Nortriptyline Desipramine SSRIs Citalopram, escitalopram, fluoxetine, paroxetine, sertraline SNRIs Duloxetine, venlafaxine, desvenlafaxine

26 Topical Agents Lidoderm 5% Capsaicin Topical cream OTC/Rx Qutenza Compounded gels/creams Lidocaine, anti-inflammatories, TCAs, ketamine

27 Anticonvulsants Sodium channel modulators Carbemazepine Phenytoin Voltage dependent Ca++ channel blockers Gabapentin Oxcarbazepine Pregabalin Lamotrigene* Lamotrigene* Topiramate* Topiramate*

28 NMDA antagonists Ketamine Dextromethorphan

29 Opioids Short-acting Hydrocodone Oxyodone Morphine Hydromorphone Oxymorphone

30 Opioids Long-acting Oramorph, MS Contin, Avinza, Kadian Oxycodone SR, OxyContin Fentanyl patch, Duragesic Oxymorphone Methadone

31 Opioids: Evidence for Neuropathic Pain? Opioids for neuropathic pain. Cochrane Database of Systematic Reviews 2006, Issue 3 Opioids only. No adjunct meds. Short term studies (<24 hrs) = equivocal results Intermediate term (up to 8 weeks) demonstrated improvement

32 Other Medications Mexiletine Clonidine Dronabinol

33 Multimodal Analgesia Drug combinations can provide improved analgesia with less side effects Gilron I, Bailey JM, Tu D, et al. Morphine, gabapentin, or their combination for neuropathic pain. N Engl J Med 2005;352: Simpson DA. Gabapentin and venlafaxine for the treatment of painful diabetic neuropathy. J Clin Neuromusc Disease 2001;3:53-62.

34 Trigeminal Neuralgia Carbamazepine Gabapentin Lamotrigene Baclofen

35 Interventional Pain Management Common nerve blocks Ilioinguinal Common peroneal Agents Local anesthetics Steroids Neurolytics (phenol, alcohol)

36 Interventional Pain Management Trigeminal nerve block

37 Interventional Pain Management Sympathetic blocks Stellate Lumbar Superior hypogastric Ganglion impar

38 Interventional Pain Management Sympathetic blocks Useful for sympathetically mediated pain Series can be beneficial Used in conjunction with PT Cancer patients - Neurolytic

39 Interventional Pain Management Epidural steroid injections Cervical, thoracic or lumbar Interlaminar, transforaminal Diagnostic, therapeutic

40 Interventional Pain Management Spinal cord stimulation Useful for radiculopathies/ neuralgias After more conservative therapies have failed No surgical corrective therapies indicated

41 Interventional Pain Management Intrathecal drug delivery systems Useful when refractory to other conservative txs Combination therapies

42 Gilron I et al. CMAJ 2006;175:

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