NEUROPATHIC PAIN

DR NAEMAH BINTI SHARIFUDDIN

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INTRODUCTION

• Neuropathic pain is defined as 'pain caused by a lesion or disease of the somatosensory nervous system’¹
• Central Neuropathic pain – lesion/disease in the central somatosensory system
• Peripheral Neuropathic pain - lesion to the peripheral somatosensory system
• Management of neuropathic pain is difficult - difficulty in identifying the nature and exact location of a lesion or health condition causing the neuropathic pain

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INTRODUCTION

• No gold standard, or sets of biomarkers that can document neuropathic pain
• High index of suspicion is required for the diagnosis of neuropathic pain as it can develop slowly over time
• Incidences reported:
• 40 per 100,000 for post herpetic neuralgia
• 27 per 100,000 for trigeminal neuralgia
• 15 per 100,000 for Diabetic Polyneuropathy

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DIAGNOSIS

• Usually described as burning, painful, cold or electric shocks
• Maybe associated with tingling, pins & needles, numbness or itching
• Pain will affect function, sleep, mood, work, and family and social life
• Important to assess beliefs about the pain and helpful or non-helpful self management strategies – will influence the pain and its management
• Use of screening tools help diagnosis and useful during follow up

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MANAGEMENT

• Goal of management are:
• To reduce or eliminate pain
• Improve physical functioning
• Reduce physiological distress
• Improve overall quality of life

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DIAGNOSTIC SCREENING TOOLS

• Validated diagnostic screening tools may be useful:
• Leeds Assessment of Neuropathic Symptoms and Signs (LANSS)
• Self reported LANSS (S-LANSS)
• Neuropathic Pain Questionnaire (NPQ)
• Douleur Neuropathique en 4 (DN4) questions
• painDETECT
• ID-Pain

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LANSS PAIN SCALE

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S-LANSS – patient self score

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Score of ≥ 4 indicates neuropathic pain

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Pain DETECT

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EXAMINATION

• Sensory examination – light touch, temperature, painful stimulus, vibration & proprioception
• Compare both sides and grade as normal, decreased or increased
• Motor testing – tone, strength, reflexes and coordination
• Autonomic changes – colour, temperature, sweating and swelling

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INVESTIGATIONS

• Imaging (CT or MRI) – may be required to exclude nerve entrapment and disc pathology
• Nerve conduction studies or electromyography are useful if large myelinated axonal damage is suspected
• Routine blood test to exclude differential diagnoses:
• FBC, ESR, glucose, creatinine, ALT, vitamin B12, serum protein immunoelectrophoresis and thyroid function

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Common Neuropathic Pain seen in Primary Care

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DIABETIC POLYNEUROPATHY (DPN)

• It is estimated 6-51% of diabetics have DPN
• It is not possible to predict which patients will develop DPN
• Affects both autonomic and peripheral nervous system
• Peripheral nerve involvement – tingling & burning in hands and feet, may have ‘electric shock, hyperalgesia or allodynia
• Clinical features– reduced sensation to light touch and vibration, reduced ankle jerks and mild weakness
• ‘glove & stocking’ pattern of sensory loss
• Differential diagnoses – neurotoxicity (meds or heavy metals), nutritional deficiencies, alcohol related neuropathy, thyroid or electrolyte disorders, nerve entrapment or inflammatory/congenital causes

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DIABETIC POLYNEUROPATHY (DPN) - MANAGEMENT

• Primary prevention – early diagnosis, exclusion of underlying causes
• good glycemic control and lifestyle changes to delay progression and prevent complications
• Current evidence for pharmacotherapy supports use of tricyclic antidepressants (TCA), serotonin-norepinephrine reuptake inhibitors (SNRIs) such as duloxetine/venlafaxine, gabapentin, pregabalin, tramadol, morphine and oxycodone
• Appropriate footwear and podiatry care

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POSTHERPETIC NEURALGIA (PHN)

• Pain that last for more that 3/12 after the onset of herpes zoster (HZ) infection
• Pain intensity can be mild, moderate or severe
• Incidence is unknown but is uncommon in those aged less than 50yrs
• Some patients with recurrent HZ infection do not develop PHN
• Symptoms – sharp or burning pain or ache in dermatomal distribution
• Affected skin may be sensitive to light touch or may have shooting pain that can be excruciating
• Examination may reveal past vesicular rash in dermatomal distribution and hyperalgesia or allodynia

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POSTHERPETIC NEURALGIA (PHN) - MANAGEMENT

• Prevention and management of acute HZ infection
• Paediatric vaccination reduces varicella infection with IgG antibody formation
• Adult vaccination stimulates T-cell mediated immunity and may reduce HZ and PHN
• Treating symptoms of PHN
• Early antiviral therapy shown to reduce the severity and duration of acute HZ infection
• Corticosteroid and oxycodone reduce pain during acute infection
• Pregabalin, gabapentin, TCA, lidocaine 5% patch, and capsaicin cream may reduce PHN pain
• Complimentary combinations of pharmacological agents are more effective than monotherapy

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TRIGEMINAL NEURALGIA

• Sudden severe brief episodes of recurrent stabbing pain in the distribution of one or more branches of the trigeminal nerve
• Majority presents unilaterally
• Women twice as likely affected than men and more common in the 50+ years age group
• Can affect 1,2 or all 3 branches mostly affecting the maxillary and mandibular branches – only 2% affecting ophthalmic branch

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TRIGEMINAL NEURALGIA

• Symptoms – jaw pain that maybe aggravated by chewing, swallowing, talking, touch or consuming hot/cold food or drinks
• Pain can be triggered by shaving or wind blowing across face
• Severe paroxysm are described as ‘shooting’, ’sharp’ or electric like.
• Pathognomonic feature – trigger zones in the distribution of affected nerve
• An attack lasts between 10secs to 2 minutes followed by refractory period
• Weight loss, insomnia and reduced functioning may occur
• Examination may see allodynia or hyperalgesia at the area

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TRIGEMINAL NEURALGIA

• Common cause is compression of the sensory ganglion of trigeminal nerve or its branches by a blood vessel
• Management is by using carbamazepine 200-400mg/day, pain relief is seen in one of every 2 cases.
• Gabapentin, pregabalin, topiramate and older anticonvulsant have been used in refractory cases.
• Surgical treatment (decompressive or ablative) may be needed.

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COMPLEX REGIONAL PAIN SYNDROME

• Rarely seen in primary care
• Diagnosis is based on cluster of clinical criteria affecting the somatosensory and autonomic nervous system
• Early recognition in primary care, implementation of treatment and referral to pain service will help minimize function loss, chronicity and disability

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CASE DISCUSSIONS

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CASE SCENARIO 1

• 60 years old lady, complaining of constant burning sensation over both feet past 2 months
• What other history would you want?
• More about the pain (onset, severity, characteristic)
• Past medical history
• Physical examination

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CASE SCENARIO 1

• Pain score is 5/10, disturbing sleep, burning sensation started mildly 2 months ago and increasing in intensity, associated with pins and needles feeling.
• Underlying T2DM past 10 years
• On examination of the feet:
• Dryness of the skin with multiple hyper-pigmented lesions seen
• Reduced sensation to pinprick and light touch up to mid-shin
• Reduced vibratory sense (128 hz tuning fork) and monofilament test

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DIAGNOSTIC TOOL: DN4 NEUROPATHIC PAIN DIAGNOSTIC QUESTIONNAIRE

4

X

X

X

X

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CASE SCENARIO 1

DIAGNOSIS?

• Diabetic peripheral neuropathy

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The goals of management in neuropathic pain are:

• to reduce pain
• improve physical functioning
• reduce physiological distress
• improve overall quality of life

Best results with multidisciplinary approach

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MANAGEMENT

• TREATMENT TO REDUCE PAIN
• First line:
• Tricyclic Antidepressant – T. Amitriptyline 25mg ON
• T. Gabapentin 300mg OD to 300mg tds
• Duloxetine 30mg/day increasing to 60mg bd
• Pregabalin
• Second line:
• Tramadol or oxycodone

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OTHER MANAGEMENT

• Diabetic control – to reduce further development of DPN
• Skin care and foot care to prevent infections
• Footwear may need to be revised indoor and outdoor

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CASE SCENARIO 2

• 65 year old man complains of burning, tingling and itching sensation over his abdomen for the past 1 week
• What other history would you want?
• More about the pain (onset, severity, characteristic)
• Past medical history
• Physical examination

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CASE SCENARIO 2

• He had history of herpes zoster infection a month ago over the same area
• Pain Initially mild but became constant with pain score 6/10
• Burning in nature and pain worst when his skin came in contact with his clothing
• On examination, hyper pigmented scar seen over his right upper quadrant of the abdomen (T9–T10)

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DIAGNOSTIC TOOL: DN4 NEUROPATHIC PAIN DIAGNOSTIC QUESTIONNAIRE

4

X

X

X

X

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CASE SCENARIO 2

• DIAGNOSIS
• Post herpetic neuralgia

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• MANAGEMENT

The goals of management in neuropathic pain are:

• to reduce pain
• improve physical functioning
• reduce physiological distress
• improve overall quality of life

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PAIN RELIEF

• First line:
• Pregabalin 75mg bd up to 300mg bd
• T. Gabapentin 300mg OD up to 1,200mg tds ( titrate up to max tolerated dose)
• Amitriptyline 25mg ON up to 50mg ON

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Other management:

• Explain to patient no ongoing damage
• Relaxation technique

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PROGRESS OF PATIENT

• Pain reduced with gabapentin given
• Pain score 3/10
• Occasionally burning sensation still felt
• Able to wear clothes and continue with normal daily activity

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THANK YOU

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