neuropathy and pain

Neuropathy and

pain

NEUROPATHY

• Neuropathy means disease of one or more

nerves.

• Neuropathies can be sensory, motor or

autonomic.

• Sensory nerves tell us how things feel.

• Motor nerves stimulate muscle contraction

and initiate movement.

• Autonomic nerves control functions that our

bodies don’t consciously regulate, such as

breathing and heart rate.

IASP DEFINITION

• The IASP International Association

for the Study of Pain, defines pain

as an “unpleasant sensory and

emotional experience associated

with actual or potential tissue

damage, or described in terms of

such damage".

PREVALENCE

• The prevalence of neuropathic pain : 6% and 8%.

• Painful diabetic neuropathy : 16% and 26% of people with diabetes.

• Postherpetic neuralgia : 8% to 19% of people with herpes zoster when

defined as pain at one month after rash onset, and 8% when defined as

pain at three months after rash onset.

• The development of chronic pain after surgery is also fairly common, with

estimates of prevalence ranging from 10% to 50% after many common

operations. This pain is severe in between 2% and 10% of these patients,

and many of the clinical features closely resemble those of neuropathic

pain.

NICE clinical guidelines nov 2013

PATHOPHYSIOLOGY

K Bhanu management of neuropathic pain indian perspective chap 125

SYMPTOMS • Numbness

• Burning

• Tingling

• Pain (shooting, sharp, cramping, deep, dull, pin/needle pricking)

• Weakness

• Muscle wasting

• Allodynia (Pain from a stimulus that does not normally evoke pain )

• Hyperalgesia (Exaggerated response to a normally painful stimulus)

CAUSES OF NEUROPATHIC

PAIN

1. Nutritional deficiency (vitaminB12 mainly)

2. Diabetes

3. Alcohol

4. Smoking

5. Infections

6. High BP

7. Post-traumatic spinal cord injury

8. Cancer neuropathy

9. Exposure to toxin

10. Multiple sclerosis

PERIPHERAL CAUSES

Mononeuropathies and multiple

mononeuropathies:

• Diabetic mononeuropathy and amyotrophy.

• Trauma: painful scars, compression, transection

of a nerve, post thoracotomy.

• Neuralgic amyotrophy.

• Connective tissue disease.

Polyneuropathies:

• Metabolic/nutritional:

• Diabetic.

• Alcoholic.

• Amyloid.

• Pellagra.

• Beriberi.

Drugs/toxic:

• Nitrofurantoin.

• Isoniazid.

• Vincristine, cisplatin, arsenic.

• Disulfiram.

Infective:

• Acute inflammatory polyneuropathy (Guillain-

Barré syndrome).

• Chronic inflammatory demyelinating

polyneuropathy (CIDP).

• HIV.

Hereditary

Malignancy

Scadding J; Advances in Clinical Neuroscience and Rehabilitation 2003;3(2)

CENTRAL CAUSESSpinal root/dorsal root ganglion:

• Prolapsed disc.

• Root avulsion.

• Trigeminal neuralgia., Postherpetic neuralgia

(herpes simplex or varicella zoster).

• Tumour

• Arachnoiditis.

Spinal cord

• Trauma

• Multiple sclerosis.

• Vascular: infarction, haemorrhage,

arteriovenous malformations.

• HIV and syphilis.

• Neural tube defect.

• Vitamin B12 deficiency.

Brainstem:

• Lateral medullary syndrome

• Multiple sclerosis

• Tumours

• Tuberculoma

Thalamus:

• Infarction.

• Tumours.

• Haemorrhage.

• Surgical lesions.

Subcortical and cortical:

• Infarction.

• Trauma.

• Arteriovenous malformation.

• Tumour.

Scadding J; Advances in Clinical Neuroscience and Rehabilitation 2003;3(2)

DIAGNOSTIC METHODSA standardized examination of NP should include the following:

• Touch can be assessed by gently applying cotton wool to the skin

• Pain assessed by the response to sharp pin prick stimuli

• Deep pain by gentle pressure on muscle and joints

• Temperature: Cold and heat sensation—by measuring response to thermal

stimulus (metal objects at 20°C or 40°C)

• Vibration can be assessed by determining response to a tuning fork

• Abnormal temporal summation is the clinical equivalent of increasing

neuronal activity after repetitive noxious C fiber stimulation of more than 0.3

Hz.

• The responses should be graded as normal, increased or decreased.

• The stimulus evoked pain types are classified as hyperalgesic or allodynic.


PAIN MEASUREMENT SCALES

Unidimensional scales

• Numeric rating scale (NRS) ]

• Visual analog scale (VAS)

Multidimensional scales

• Initial Pain Assessment Tool

Brief Pain Inventory (BPI)

• McGill Pain Questionnaire

(MPQ)

MECHANISM OF NEUROPATHIC

PAIN

• Uncontrolled neuronal firing after nerve injury is largely attributed to

increased expression of sodium channels.

• In addition to sodium channels, expression of voltage-gated calcium channels

is also increased following nerve injury. Calcium entry through voltage-gated

calcium channels is necessary for the release of substance P as well as

glutamate from injured peripheral nerves.

• Increased expression of the alpha-2-delta subunit of voltage-gated calcium

channels correlates with onset and duration of pain.

• Reduction in GABA, down regulation of GABA and Opioid receptors at dorsal

horn neurons occurs.

DIABETIC NEUROPATHY

American Diabetes Association (ADA) definition "the presence of

symptoms and/or signs of peripheral nerve dysfunction in people

with diabetes after exclusion of other causes"

Diabetic peripheral neuropathy and its evaluation in a clinical scenario: A review Dixit S, Maiya A - J Postgrad Med 2014

CAUSES

• Metabolic factors, such as high blood glucose, long duration of

diabetes, abnormal blood fat levels, and possibly low levels of

insulin

• Neurovascular factors, leading to damage to the blood vessels that

carry oxygen and nutrients to nerves

• Autoimmune factors that cause inflammation in nerves

• Mechanical injury to nerves, such as carpal tunnel syndrome

• Inherited traits that increase susceptibility to nerve disease

• lifestyle factors, such as smoking or alcohol use

Diabetic Neuropathies: The Nerve Damage of Diabetes NIH 2009

CLASSIFICATION OF DIABETIC

NEUROPATHY

I. Peripheral neuropathy, the most common type of diabetic neuropathy, causes

pain or loss of feeling in the toes, feet, legs, hands, and arms.

II. Autonomic neuropathy : changes in digestion, bowel and bladder function,

sexual response, and perspiration. It can also affect the nerves that serve the

heart and control blood pressure, as well as nerves in the lungs and eyes.

Autonomic neuropathy can also cause hypoglycemia unawareness, a condition

in which people no longer experience the warning symptoms of low blood

glucose levels.

III. Proximal neuropathy : pain in the thighs, hips, or buttocks and leads to

weakness in the legs.

IV. Focal neuropathy : sudden weakness of one nerve or a group of nerves,

causing muscle weakness or pain. Any nerve in the body can be affected.

Diabetic Neuropathies: The Nerve Damage of Diabetes NIH 2009

CLINICAL SYMPTOMS OF DPN

• Sensory symptoms are usually worse at night when the patient is

trying to sleep.

• Often, patients with diabetic neuropathy state that movement,

walking, or standing lessens the pain.

• Balance problem is also increasingly common among people with

neuropathy.

MANAGEMENT OPTIONS

NONPHARMACOLOGICAL

THERAPY

• Transcutaneous electrical nerve stimulation, spinal

cord stimulation,

• Aromatherapy

• Acupuncture


FDA APPROVED

MANAGEMENT


RECENT ADVANCES IN

MANAGEMENT

BOTULINUM TOXIN:

• A potent neurotoxin used for the treatment of focal muscle

hyperactivity, may have analgesic effects possibly by acting on

neurogenic inflammation.

• Recent studies reported long-term efficacy of a series of

subcutaneous injections of BTX-A (100-200 units) injected into the

painful area in patients with mononeuropathies (mainly of traumatic

origin) associated with mechanical allodynia, and in patients with

diabetic painful polyneuropathies.

• The drug had an excellent safety profile with no systemic side effect


RECENT ADVANCES IN

MANAGEMENT

LACOSAMIDE

• It is a antiepileptic medication that acts at voltage-gated sodium

channels.

• It has been studied extensively in painful DPN in addition to

epilepsy. Evidence of the efficacy of lacosamide in patients with

painful DPN has been provided in various controlled trials.

• So far Food and Drug Administration (FDA) has not approved this

drug for treatment of painful DPN.


RECENT ADVANCES IN

MANAGEMENT

The various combinations found to be effective in several

controlled trials

• Extended release oxycodone and pregabalin

• Topical 5% lidocaine and pregabalin

• Sodium valproate and glyceryl nitrate therapy

• Moreover, analgesics can be combined with any of the first-

line medications.


neuropathy and pain

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