Pain Modulations

What is pain?

Pain is an ache or bodily suffering resulting from a derangement of functions, disease, or injuries. It is an uncomfortable feeling that tells you something may be wrong. It can be steady, throbbing, stabbing, aching, pinching, or described in many other ways. (John Hopkins medicine).

THE BODY’S NATURAL MECHANISM FOR THE MODULATION OF PAIN.

Accumulating evidence suggests that endogenous pain inhibition depends on activation of the prefrontal cortex, periaqueductal gray and rostral ventral medulla. Nociceptive signals that are transmitted from the periphery to the brain require integration and processing within the spinal cord, brainstem and brain. Increased pain sensitivity, a characteristic of chronic pain, may develop either through peripheral mechanisms (peripheral sensitization) or as a consequence of neuroplastic changes in the CNS (central sensitization). Pain modulatory signals from the PAG can reach dorsal horn neurons of the spinal cord either directly or indirectly via the rostroventral medulla. Compelling evidence suggests that spinal input to the PAG can elicit pain inhibition through a spinal–supraspinal–spinal loop.

Endogenous pathways for the modulation of pain include;

• The Endogenous Opioid system • Pain Gate Theory • Muscle Guarding

Opioid System: The body possess an opioid system (pain modulating), which soften the blow of pain once the brain receives that information. The body then sends signals to the hypothalamus and pituitary gland, which in turn, release ENDORPHINS, which are the body’s natural painkillers. The name of these hormones comes from the term “endogenous morphine.” “Endogenous” because they’re produced in our bodies. Once the signal from the ascending pathway reaches the somatosensory cortex, it triggers the descending pain modulation pathway. The balance between inhibition and facilitation is dynamic, and can be altered in different behavioral, emotional, psychological and pathological states. Descending pain control pathways plays a critical role in determining the experience of both acute and chronic pain. The goal of this pathway is to allow the organism to function enough to respond to the pain source by reducing the pain signal through neuronal inhibition.

It begins in the periaqueductal gray (PAG), a region of the midbrain that process nociceptive information and relays it to the rostral ventral medulla (RVM). These neurons in the RVM then send a signal down the spinal cord to re-

lease endogenous opioids at neuronal synapses at multiple points in the peripheral nervous system to prevent these pain signaling neurons from sending action potentials.

Additionally, these endogenous opioids are released in parts of the dorsal horn of the spinal cord to further block ascending pain transmission signals.

Hormone as a body’s natural pain modulation mechanism. Hormones are chemical messengers that are secreted from endocrine glands in the body directly into the blood, which carries them to organs and tissues of the body to exert their functions.

Severe pain, (either acute or chronic) is a severe stressor which activates the hypothalamic–pituitary–adrenal–thyroid–gonadal (HPATG) system. The HPATG system. is the major stress control mechanism of the body.

The biologic Importance of this system is to produce additional hormones in the thyroid, adrenals and gonads, and secrete them into the serum as they are needed by the body to perform pain-control functions, they also perform functions which include:protection and regeneration of injured tissue, immunologic activity, and metabolic control. Serotonin (5-HT) and norepinephrine are involved in endogenous pain modulation, they are released through descending pain pathways to modulate painful signaling in the spinal cord. Serotonin performs both pain facilitatory and inhibitory functions. Norepinephrine inhibits pain through 2 adrenoceptors.

The goal of the descending pain pathways is to allow the organism to function enough to respond to the pain source by reducing the pain signal through neuronal inhibition.

PAIN GATE THEORY:

This theory was postulated by Melzacks and wall’s . This Gate Control Theory of Pain is a mechanism, in the spinal cord, in which pain signals can be sent up to the brain to be processed to accentuate the possible perceived pain, or attenuate it at the spinal cord itself. The ‘gate’ is the mechanism where pain signals can be let through or restricted. One of two things can happen, the gate can be ‘open’ or the gate can be ‘closed’.

If the gate is opened, pain signals can pass through and will be sent to the brain to perceive the pain.

OPENED GATE

If the gate is closed, pain signals will be restricted from travelling up to the brain, and the sensation of pain won’t be perceived.

CLOSED GATE.

If someone experiences a painful (noxious) stimulus, the application of a non-noxious stimulus (soothing or light rubbing) for example, ice, heat,massage etc can help activate the gate control mechanism, and reduce the pain.

According to this theory, pain stimulation is carried by small, slow fibers that enter the dorsal horn of the spinal cord; then other cells transmit the impulses from the spinal cord up to the brain. These fibers are called T-cells.

The T-cells can be located in a specific area of the spinal cord, known as the substantial gelatinosa. These fibers can have an impact on the smaller fibers that carry the pain stimulation. In some cases they can inhibit the communication of stimulation, while in other cases they can allow stimulation to be communicated into the central nervous system.

For example, large fibers can prohibit the impulses from the small fibers from ever communicating with the brain. In this way, the large fibers create a hypothetical “gate” that can open or close the

According to the theory, the gate can sometimes be overwhelmed by a large number of small activated fibers.There are 3 factors which influence the ‘opening and closing’ of the gate these include:

• The amount of activity in the pain fibers. Activity in these fibers tends to open the gate. The stronger the noxious stimulation, the more active the pain fibers. • The amount of activity in other peripheral fibers— that is, those fibers that carry information about harmless stimuli or mild irritation, such as touching, rubbing, or lightly scratching the skin. These are large-diameter fibers called A-beta fibers. Activity in A-beta fibers tends to close the gate, inhibiting the perception of pain when noxious stimulation exists. This would explain why gently massaging or applying heat to sore muscles decreases the pain.

Muscle guarding (spasm) is the body’s first response when the pain occurs because it is the brain’s reflexogenic attempt to prevent further injury to injured tissues. Pain, aside from being an unpleasant sensation, acts as a signal for the body that an injury Is present. Our body typically responds to this signal through the use of muscle guarding (a protective mechanism) to prevent further injury. Muscle spasms range in intensity from mild, uncomfortable twitches to significant discomfort to intense, severe pain. Spasms typically last from seconds to 15 minutes or longer, and may recur multiple times before going away. Thermotherapy : comprises a number of physical agents that use superficial heat to increase soft tissue extensibility, reduce pain, improve circulation, and accelerate healing. Thermal therapy is believed to accomplish these goals by increasing blood flow (vasodilation), reducing alpha motor neurone firing rate, increasing pain threshold (gating effect; reduced ischemia), and increasing metabolic activity (increasing the availability of oxygen to tissue).

Heat: By increasing the temperature of the skin/ soft tissue, the blood flow increases by vasodilatation. The metabolic rate and the tissue extensibility will also increase. Heat increases oxygen uptake and accelerates tissue healing, it also increases the activity of destructive enzymes, such as collagenase, and increases the catabolic rate.

Cold

temperature of the skin/ soft tissue, the blood flow decreases by vasoconstriction. It will be followed by a vasodilatation which will prevent against hypoxic damage (hunting reflex: If the cold pack is left on the skin for more than 10 minutes, the blood vessels will dilate). The tissue metabolism will decrease just like the neuronal excitability, inflammation, conduction rate and tissue extensibility. At joint temperatures of 30°C or lower, the activity of cartilage degrading enzymes, including collagenase, elastase, hyaluronidase, and protease, is inhibited. the decreased metabolic rate limits further injury and aids the tissue in surviving the cellular hypoxia that occurs after injury.

Deep heating is thought to lessen nerve sensitivity, increase blood flow, increase tissue metabolism, decrease muscle spindle sensitivity to stretch, cause muscle relaxation, and increase flexibility. Heat stimulates the cutaneous thermoreceptors that are connected to the cutaneous blood vessels, causing the release of bradykinin which relaxes the smooth muscle walls resulting in vasodilation. Muscle relaxation occurs as a result of a decreased firing rate of the gamma efferents, thus lowering the threshold of the muscle spindles and increasing afferent activity. There is also a decrease in firing of

the alpha motor neuron to the extrafusal muscle fibre, resulting in muscle relaxation and decrease in muscle tone. All these promote pain reduction.

Ice Therapy

Ice is great for easing damaged superficial tissue that is hot, red, inflamed, or swollen. The inflammatory process is a natural process; however, it can be painful. Ice is a mild way to dull the pain and reduce swelling.

How Physiotherapy Uses Hydrotherapy to Relieve Pain.

Hydrotherapy (also known as aquatherapy) is any activity performed in water to assist in rehabilitation and recovery from hard training or serious injury. It is a form of exercise in warm water and it is a popular treatment for patients with neurologic and musculoskeletal conditions. The goals of this therapy are muscle relaxation, improving joint motion and reducing pain. Hydrotherapy involves the patient being in a heated pool of water, carrying out specific exercises. The water is usually heated at between 33 and 36 degrees Celsius.

The sensation of being in the heated water helps to interrupt pain signals and therefore also help to relieve pain. This study explains, “Sensory-motor hyper stimulation exerted by the hydrostatic pressure, viscosity, and water temperature increases the triggers of thermal receptors and mechanoreceptors while blocking nociceptors.”

During the hydrotherapy session the warmth and the calming setting promotes relaxation. It’s been proven that during hydrotherapy, levels of stress hormones (such as cortisol and norepinephrine) are reduced. Reducing stress can in turn reduce pain levels.

Some Physiotherapy Modalities that Facilitate the Release of Pain Modulating Hormones

Exercise therapy, Manual therapy {Massage} are useful in inducing relaxation and reducing stress levels in the body by reducing cortisol levels. Among the primary paincontrol functions of these hormones are immune and anti-inflammatory actions, cellular protection, tissue regeneration, glucose control, and modulation of CNS receptors, the blood–brain barrier, and nerve conduction. Given the CNS effects of certain hormones, analgesics such as antidepressants, neuropathic agents and opioids, may not achieve maximal analgesic responses without hormone homeostasis.

Ultrasound exert its antiinflammatory effects by down-regulating proinflammatory genes and up-regulating antiinflammatory genes. A transcutaneous electrical nerve stimulator (TENS) sends electrical pulses through the skin to start your body’s own pain killers. The electrical pulses can release endorphins and other substances to stop pain signals in the brain. TENS can reduce pain.

TENS effects on Hypothalamic-PituitaryOvarian axis. It is suggest that normal E2level is very important in regulation behavioral and physiological events essential for successful procreation.

Manual Therapy In Pain Modulation

Three Paradigms for ManualTherapy Therapeutic Effects

• Physiological: positive placebo response

• Bio-mechanical

• Physical: facilitates repair and tissue modeling

Psychological: pain relief via- stimulates gating mechanism;

muscle inhibition; reduction of nociceptive activity; reduced intraarticular or periarticular pressure

Techniques that primarily target muscles and other soft tissues, such as massage, use mechanical pressure. This pressure is hypothesized to increase tissue extensibility with resulting increases in joint motion. Pressure to the tissues will also help to increase blood flow and therefore promote healing and reduce pain. Manual Therapy- Hands-on manual therapies such as soft tissue and joint mobilization help to combat inflammation by gaining movement while reducing pain and encouraging blood flow. Examples of manual Therapy Techniques include; Massage, Trigger Point Therapy, Active Release Technique ,Assisted Active Range of Motion, Passive Range Of motion, Stretches, Lymphatic Drainage, Joint Mobilization , Thrust Manipulation..

Role of Exercise Therapy in Pain Modulation

Exercise is any bodily activity that enhances or maintains physical fitness and overall health and wellness. It is performed for various reasons, to aid growth and improve strength, develop muscles and the cardiovascular system, hone athletic skills, weight loss or maintenance, improve health, or simply for enjoyment.

EXERCISE-BASED MODULATION OF PAIN.

Exercise is a key component of a healthy lifestyle as it helps maintain a healthy body weight and reduces the risk of various morbidities and co-morbidities. Exercise is an acute physiological stress that initiates a multitude

of processes that attempt to restore physiological homeostasis and promote adaptation. A component of the stress response to exercise is the rapid release of hormones from the adrenal gland including glucocorticoids, the catecholamines and aldosterone. While each hormone targets several tissues throughout the body, skeletal muscle is of interest as it is central to physical function and various metabolic processes. Indeed, adrenal stress hormones have been shown to elicit specific performance benefits on the muscle. Exercise can reduce pain sensitivity in painfree participants, also known as exerciseinduced hypoalgesia (EIH). Hypoalgesia is a reduced sensitivity to pain. Physical activity and exercise reduces excitability of central neurons, measured by phosphorylation of the NR1 subunit of the NMDA receptor, alters neuroimmune signaling in the central nervous system, and increases release of endogenous opioids and serotonin in the brainstem pain inhibitory pathways. Regular physical activity can keep the muscles around affected joints strong, decrease bone loss and may help control joint swelling and pain. Regular activity replenishes lubrication to the cartilage of the joint and reduces stiffness and pain. Exercise reduces levels of the body’s stress hormones, such as adrenaline and cortisol. It also stimulates the production of endorphins, chemicals in the brain that are the body’s natural painkillers and mood elevators. Exercise pumps up your endorphins. Physical activity may help

By Woke-Bankole .O. Ifeloluwa Okunoye Mercy Oladele Monijesu Adebiyi shallom Gold Enioluwafe Oluleye Oyetunde Grace Mayowa Akinbodu Sharon Oluwatisheyifunmi