Neuropathic paintx

ALBERTO RIVERA SANCHEZ MD FAAPMR, ABPM, ABDA

PAIN MANAGEMENT SUB SPECIALIST

Managing Neuropathic Pain

Neuropathic pain Prevalence of 2-40% (Harden 2015)

3.75 million with chronic NP in the US (IASP 1997)

The most common studied NP syndromes are: DMPN PHN

Other causes:○ SCI○ Phantom Pain○ CRPS○ Post CVA○ Nerve Injury

Neuropathic pain 33% of pain patients seen in tertiary

facilities have anxiety disorders (Von Korff, et al 1996)

40-60% meet the criteria for depressive disorder (Banks, 1996)

FDA Approved Med’s for NP Carbamazepine Lidocaine patches Gabapentin Pregabalin (PHN, DMPN) Capsaicin Duloxetine (DMPN) Tapentadol ER (DMPN)

Off label Med’s for NP Anti-depressants Anti-epileptics Anti-arrythmic

Evidence for their safety and efficacy is lacking

Benbow 1999, Kost 1996, Karlsten 1997, Carter 1997

Central Sensitization Excitatory neurotransmitters (e.g. glutamate,

substance P, neurokinin A or CGRP) stimulate the dorsal horn neurons

Repeated pain stimuli activate the NMDA receptors (“wind-up”), which induce prolonged postsynaptic action potentials

 Activation of the NMDA receptors raises intracellular Ca++

Expression of c-fos and c-jun genes leading to increased protein synthesis

Peripheral Sensitization

1° afferent nerve terminals (A-delta, C Fibers) hyperexcitability

Bradykinin, histamine, PG’s, cytokines, and substance P lower their action potential threshold

Mediators increase the gain of the inflammatory milieu

Spine 1997N. Harden 2015

Hyperalgesia Increased pain from a stimulus that

normally provokes pain (IASP 2012)

Treatment:Topical lidocaine 2.5% / prilocaine 2.5%Gabapentin (Pain 2002)

IV Lidocaine (Neurology 2000)

Capsaicin (Scholten 2015)

Allodynia Pain due to a stimulus that does not

normally provoke pain (IASP 2012) Treatment

Gabapentin (Eur Neurol 1998)

Pregabalin (J Pain 2008 )

Ketamine (Pain 1994)

IV Lidocaine (J Pain Symp Mgt 1999)

IV Morphine (Neurology 1991)Tramadol (Pain 1999)

Shooting pain Pain that seems to travel like lightning from

 one place to another Treatment:

Amitriptyline (Neurology 1987)

Carbamazepine (Campbell et al. 1966)

Gabapentin (Eur Neurol 1998)

Imipramine (Neurology 2003)

Lamotrigine (Pain 1997)

IV Phenytoin (Anesth Analg 1999)

Venlafaxine (Neurology 2003)

TCA’s and Other Psych Med’s in NP

Help in NP due to Na+ channel blocking Risk of sedation and anticholinergic

effects

Capsaicin Selective stimulator of C-fibers Cause Substance P release Depletes Substance P Apply 3-4 times/day for 4-8 weeks Capsaicin 8% relief may last 12 weeks Start with tramadol or lidocaine cream

(Pain Ther 2014)

GABA, Pregabalin and NP

Pregabalin Side Effects

Infection peripheral edema, Fatigue constipation, weight gain blurred vision ataxia, dizziness headache diplopia

Drowsiness tremor visual field loss xerostomia accidental injury

Gabapentin and Opioids

Gabapentin Increases the concentration of GABA in

the Brain Modifies Ca2+ currents Excreted 95% unchanged in the urine Good for NP No direct anti-nociceptive effect

Gabapentin Side Effects

Sedation Fever Fatigue Ataxia Nystagmus Dizziness Drowsiness Weight gain due to increased apetite

Ketamine

Amantadine and Dextromethorphan are effective for DMPN (Pain 1998, Neurology 1997)

Herbal supplements Cannabis Plant Extract (AAPM&R 2015)

FMS NP RA Spasticity related pain

Side effects Dizziness Drowsiness Fatigue Legal issues

Herbal supplements Alpha Lipoic Acid 600mg daily L-carnitine 1000mg daily Vitamin B complex Vitamin D once a week CoQ10---FMS—150-300mg daily (PMR Journal 2015)

Non pharmacologic Tx PT OT Pain psychology Cognitive behavioral therapy Ergonomic evaluation Aqua therapy Work conditioning/hardening

Interventional Pain Management Spinal Cord Stimulators Intercostal nerve blocks Peripheral nerve blocks Caudal Epidural injections Sphenopalatine Ganglion Blocks Radiofrequency Neurotomy Stellate Ganglion Blocks

Conclusion The best management option is:

• Multimodal Therapy

Consider the patient’s comorbidities Listen to your patient complaints

Thank you

[email protected] (787) 840-1818