IPHREHAB : PAIN MODULATION AND MECHANISM

IPHREHAB
PAIN MODULATION

• Variability of pain caused by similar injuries.
• Psychological variability.
• Even suggestions of pain relief helpful.
• Existing brain circuits modulate pain transmission pathways.

• One of these circuits has links with hypothalamus, midbrain, medulla oblongata.
• This pathway selectively controls spinal pain transmission neurons through descending pathways.
• Attention, suggestion and opiods work and modulate pain through this pathway.
• Endogenous opiod peptides such as enkephalins and endorphins work through this pathway. 

• Prolonged pain and fear are the most  reliable activating factors for endogenous opiod pathway.
• Released during surgical procedures and even by placebo.

Pain modulating circuits can suppress and enhance pain.

• Both pain-inhibiting  and pain-facilitating neurons in the medulla project to and control spinal pain transmission. Hence pain can be generated without any peripheral nocuous stimuli.
• Increased activity of these circuits is seen during migraine.
• Pain can also be induced by suggestions-psychological factors contribute to pain.

NEUROPATHIC PAIN:

1. Lesions in central and peripheral pathways results in loss or impairment of pain sensation.
2. Paradoxically the damage may also produce pain- diabetic neuropathy, herpes zoster.
3. Also damage to spinothalamic tract or thalamus can also produce pain.
4. Severe and notoriously intractable to standart treatment.
5. Unusually burning, tingling or electric shock like quality.
6. Examination-Sensory deficit in the area of pain.
7. Hyperpathia/allodynia.
8. Topical preprations (5% lidocaine) helpful.

Mechanisms

• Sensitized primary afferent neurons.
• Damaged primary afferent neurons.
• Sensitized nociceptors.-generate impulses in absence of stimulus.
• Increased concentration of sodium channels.
• Sensitivity to norepinephrine.

Sympathetically Maintained Pain

• Causalgia in peripheral nerve injury.
• Pain often begins after a delay of hours to days or even weeks.
• Pain accompanied by swelling of extremity, periarticular osteoporosis and arthritic changes in distal joints.
• Pain relief by sympathetic blockages.

Similar events- reflex sympathetic dystrophy- without nerve damage including fractures, soft tissue injuries, MI, stroke.

Treatment :

• History, Evaluate, examine.
• Remove cause.
• Analgesics NSAIDS, Opiods