Chronic Pain
- Always a
difficult problem to address, however, there are indications for surgical
intervention in selected cases
- Neuropathic pain – does not respond well to opiates
- Dejourine-Roussy – infarction of
posterior-ventral-lateral thalamus à ataxia, contralateral hemianesthesia, develops into increased
pain/affective unpleasant feelings; facilitation of medial thalamic
nucleus with increased reticular formation pain transmission
- Referred pain – visceral pain fibers and cutaneous pain
fibers both synapse in lamina 5 – mixing occurs
- Phantom limb – lamina 5/thalamus needs input
- Complex
Regional Pain Syndrome – can be associated with nerve injury (type 2, causalgia)
or only minor trauma with no lasting nerve injury (type 1, Reflex
Sympathetic Dystrophy)
- incomplete
PNS injury hyperresponsive to sympathetics; injured
nerves sprout axons sensitive to catecholamines
- diffuse
persistent pain usually in an extremity
- often
associated with vasomotor disturbances, trophic changes, and limitation
or immobility of joints
- frequently
follows local injury
- causalgia
(burning sensation), Sudek atrophy of bone/joint/muscle/skin (not nerve)
- can
treat with sympathectomy or antisympathetic medication
- Treatments
for Chronic Pain
- Anatomic
procedures to correct structural lesion responsible for pain (tumor
debulking, decompression, stabilization)
- Medical
therapy
- Analgesics,
NSAIDs, local anesthetics, anti-depressants
- Biofeedback
techniques
- Augmentative
procedures
- Electrical
stimulation
- TENS
(transcutaneous electrical nerve stimulator) units
- Implantable
epidural stimulators (spinal cord stimulation) – better for appendicular
than for axial pain
- Must
have sensation of area where pain relief is desired
- Stimulator
produces parasthesia in painful area that reduces pain
- Intrathecal/Epidural
catheters – allow delivery of narcotic directly to vicinity of roots
allowing small doses, minimizing systemic narcotic needs
- Labor-intensive
follow-up; can be complicated, so generally used as last resort
- Ablative
surgery – rarely used for benign pain
- Alcohol
injections
- Dorsal
rhizotomy – Interruption of dorsal (sensory) roots within spinal canal
- Indications
are neurogenic pain, post-therapeutic neuralgia, painful paraplegia
- Dorsal
root entry zone lesioning – best for nerve root avulsion pain
- Sympathectomy
– interruption of sympathetic ganglia
- Indications
are hyperhidrosis, causaslgia, visceral pain
- Cordotomy
– Interruption of the spinothalmic tract
- Indications
are intractable cancer pain
- Best
with unilateral pain, but efficacy diminished with time and significant
number of patients develop painful dysesthetic pain over time