Neuropathic Pain CBM and Oxford Flashcards
Causes / mechanisms of neuropathic pain
- 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
Qualities of neuropathic pain
- Sharp
- shooting
- stabbing
- burning
- paroxysmal
- dermatomal
- Allodynia
- hyperalgesia
- hyperpathia
- sensory changes
- weakness perceived
Chemotherapy induced Peripheral Neuropathy
- 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
Physical exam findings for neuropathic pain
- 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
Spurling’s maneuver
- 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
Horner’s syndrome
- 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
What is neuropathic pain?
Pain arising from injury to peripheral or central nervous system
Tinel’s sign
- tapping over Erb’s point in supraclavicular fossa suggests pathology in brachial plexus
C8-T1
- weakness in finger flexors
- weakness intrinsic hand muscles
- C8-T1 roots or brachial plexus
Lower motor neuron signs
- Pain
- Hypotonia
- Areflexia /hyporeflexia
- weakness
- numbness
- saddle anesthesia
- sphincter dysfunction
- fasciculations
Upper motor neuron symptoms
- pain exacerbated by laying down, cough, sneeze, strain
- Lhermitte’s sign
- spasticity
- hyperreflexia
- weakness
- numbness/paresthesias
- spinal tenderness
Cervical radiculopathy
Sensory and motor
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
Lhermitte’s sign
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…..
Investigations of neuropathic pain
- try to localize as much as possible
- neuro exam
- MRI
- EMG - large nerve function
- nerve biopsy
Pharmacological management of neuropathic pain
- First line
- Gabapentin / other anticonvulsants
- SNRI
- TCA
- Opioids
- Second line
- NMDA antagonists
- methadone
- corticosteroids
- cannabinoids
- continuous infusion of local anesthetic
