Neuropathic Pain CBM and Oxford

Question 1

Causes / mechanisms of neuropathic pain

Answer 1

• Mechanical nerve injury
• Chemical nerve injury (chemotx)
• Ectopic discharge following injury
• Sodium channel changes on neurons
  
  • greater expression on injured nerves
  • hyperexcitability, increased transmission
• Calcium channels
• nerve sheath pain - distortion
• Secondary central pain
  
  • sensitization of dorsal horn by glutamate
  • activation of NMDA receptors

Question 2

Qualities of neuropathic pain

Answer 2

• Sharp
• shooting
• stabbing
• burning
• paroxysmal
• dermatomal
• Allodynia
• hyperalgesia
• hyperpathia
• sensory changes
• weakness perceived

Question 3

Chemotherapy induced Peripheral Neuropathy

Answer 3

• platinums
• taxanes
• vinca alkaloids
• bortezomib

affects up to 96% of patients. One year post treatment, still affects 50%. Dose dependent

Presentation

• stocking and glove distribution
• spontaneous pain
• paresthesias
• allodynia
• hyperalgesia
• hypesthesia
• impaired proprioception

Question 4

Physical exam findings for neuropathic pain

Answer 4

• affected area:
  
  • tumour extension
  • muscle spasm
  • lymphadenopathy
  • range of motion limb
  • swelling, discolouration
• neurological exam
• provocative maneuvers
  
  • Tinels
  • Spurling
• application of ice in dermatomal distribution
  
  • perception of intense heat –>
  • pathognomic for neuropathic pain

Question 5

Spurling’s maneuver

Answer 5

• Turn patient head to affected side whil extending and applying downward pressure on top of head
• positive if elicits pain that radiates down expected dermatome
• Tests cervical root radiculopathy and causes cervical compression

Question 6

Horner’s syndrome

Answer 6

• Mioisis, Ptosis, Anhidrosis
• ipsilateral sympathetic nerve damage

Anhidrosis of face, arm, trunk

• MS
• Brain
• lateral medullary syndrome

Anhidrosis of face

• cervical rib traction on stellate ganglion
• thyroid ca
• bronchogenic ca on apex of lung (pancoast tumour)
• Tube thoracostomy complications

No Anhidrosis

• carotid artery dissection
• migraine, cluster headache
• middle ear infection

Question 7

What is neuropathic pain?

Answer 7

Pain arising from injury to peripheral or central nervous system

Question 8

Tinel’s sign

Answer 8

• tapping over Erb’s point in supraclavicular fossa suggests pathology in brachial plexus

Question 9

C8-T1

Answer 9

• weakness in finger flexors
• weakness intrinsic hand muscles
• C8-T1 roots or brachial plexus

Question 10

Lower motor neuron signs

Answer 10

• Pain
• Hypotonia
• Areflexia /hyporeflexia
• weakness
• numbness
• saddle anesthesia
• sphincter dysfunction
• fasciculations

Question 11

Upper motor neuron symptoms

Answer 11

• pain exacerbated by laying down, cough, sneeze, strain
• Lhermitte’s sign
• spasticity
• hyperreflexia
• weakness
• numbness/paresthesias
• spinal tenderness

Question 12

Cervical radiculopathy

Sensory and motor

Answer 12

C5

• Motor - Deltoid
  
  • shoulder abduction
  • biceps flexion
• Sensory
  
  • deltoid
• Reflex
  
  • none

C6

• Motor -
  
  • biceps (elbow flexion)
  • wrist extension
• Sensory
  
  • thumb and index finger
• Reflex
  
  • biceps

C7

• Motor
  
  • Triceps elbow extension
  • wrist flexion
  • finger extensors
• Sensory
  
  • middle finger
• Reflex
  
  • triceps

C8

• Motor
  
  • finger flexors and intrinsics
• Sensory
  
  • ulnar aspect hand
• Reflex
  
  • none

T1

• Motor
  
  • finger intrinsics
• Sensory
  
  • ulnar aspects of hand
• Reflex
  
  • none

Question 13

Lhermitte’s sign

Answer 13

uncomfortable “electrical” sensation that runs through the back and into the limbs. The sensation can feel like it goes up or down the spine. Flexion of neck

The sign suggests a lesion or compression of the upper cervical spinal cord or lower brainstem—usually dorsal columns of the cervical cord or caudal medulla.

MS, transverse myelitis, trauma, radiation myelopathy, b12 deficiency…..

Question 14

Investigations of neuropathic pain

Answer 14

• try to localize as much as possible
• neuro exam
• MRI
• EMG - large nerve function
• nerve biopsy

Question 15

Pharmacological management of neuropathic pain

Answer 15

• First line
  
  • Gabapentin / other anticonvulsants
  • SNRI
  • TCA
  • Opioids
• Second line
  
  • NMDA antagonists
  • methadone
  • corticosteroids
  • cannabinoids
  • continuous infusion of local anesthetic

Question 16

Classification of Neuropathic Pain

Answer 16

Peripheral

• mono/polyneuropathy (DM, etoh, HIV, chemo)
• plexopathy
• radiculopathy
• nerve injury
• amputation
• root avulsions
• post herpetic neuralgia
• trigeminal neuralgia
• neoplasma

Central

• MS
• CNS tumours
• spinal cord injury
• SCC
• syringomyelia
• myelopathy
• stroke

Question 17

Oxaplatin induced neuropathy

Answer 17

• acute phase :
  
  • allodynia and pricking dyesthesia
  • pharyngolaryngeal dyesthesias with SOb or dysphagia with cold drinks
• improves over time, resolution over 6 months

Question 18

Central pain

Answer 18

• Stroke
• MS
• Spinal cord injury

Question 19

Bortezemib neuropathy

Answer 19

• mild moderate sensory loss in distal extremities
• painful paresthesias
• autonomic symptoms (orthostatic hypotension)
• diarrhea, constipation

Question 20

Herpes zoster

Answer 20

• reactivation of varicella zoster
• immunocompromised
• post herpetic neuralgia burning
• paroxysmal lancinating pain in dermatome
• allodynia

Question 21

Nonpharmacological treatment of neuropathic pain

Answer 21

• CBT
• physiotherapy
• interventional analgesia
• massage, exercise, acupuncture

Question 22

Trigeminal Neuralgia

Answer 22

• Carbamazepine / oxcarbamazepien first line
  
  • 90% effective
• sudden, severe pain unilaterally along CN V
  
  • V1 opthalmic
  • V2 Maxillary
  • V3 Mandibular
• loss of myelin of CN V
  
  • compression from blood vessel as it exits brain stem
  • MS
  • Stroke
  • trauma
  • tumour

Question 23

Focal peripheral neuropathy

Answer 23

• Topical lidocaine patch