Central Modulation and Sensitization, Disease, and Terminology

Question 1

What is descending modulation in the context of the CNS?

Answer 1

Descending modulation refers to mechanisms in the CNS that modulate sensory input as it travels from the tissues to the brain. These mechanisms can suppress or alter sensory experience, including pain, and involve areas of the brain such as the cortex, thalamus, insula, amygdala, and hypothalamus.

Question 2

What are ascending modulation mechanisms?

Answer 2

Ascending modulation involves modifiers of afferent transmission as sensory signals travel from the tissues to the brain, such as local inhibition in the dorsal horn and filtering in the thalamus.

Question 3

Why is descending modulation often discussed in relation to pain?

Answer 3

Descending modulation is commonly discussed in relation to pain because it helps control the intensity of the pain experience. It can suppress or amplify pain perception, often through mechanisms like endogenous opioid release.

Question 4

What is the purpose of sensory experience, and how can it be altered by the CNS?

Answer 4

The purpose of sensory experience is to bring attention to important stimuli that may require a response. However, in the absence of perceived value or due to distraction or other purposes, the sensory experience can be weakened or eliminated by descending modulation.

Question 5

Who first observed the phenomenon of people feeling less pain in stressful situations, and what did they observe?

Answer 5

Dr. H. K. Beecher, a World War II physician, first observed that wounded soldiers often felt little or no pain, especially initially. This phenomenon was also seen in athletes during intense competition.

Question 6

Which brain areas are involved in descending modulation?

Answer 6

The brain areas involved in descending modulation include the cortex, thalamus, insula, amygdala, and hypothalamus.

Question 7

What are the primary chemicals released during descending modulation, and what is their effect?

Answer 7

The primary chemicals released during descending modulation are endorphins and enkephalins (endogenous opioids), which act as the body’s natural pain relievers, similar to morphine or heroin. These chemicals help reduce pain perception.

Question 8

What role does dopamine play in descending modulation?

Answer 8

Dopamine is involved in the descending modulation process, helping to mediate the release of pain-relieving substances such as endorphins and enkephalins.

Question 9

What is the role of the periaqueductal gray (PAG) in descending modulation?

Answer 9

The periaqueductal gray (PAG) in the midbrain is a key area involved in descending modulation. When activated, it communicates with other brainstem regions to initiate the release of pain-modulating substances like serotonin and norepinephrine.

Question 10

What are some neurotransmitters involved in descending modulation, and how do they act?

Answer 10

Neurotransmitters involved in descending modulation include serotonin (5-HT), norepinephrine (NE), and endocannabinoids such as anandamide. These substances act on neurons in the dorsal horn to inhibit pain transmission.

Question 11

How do modulators from descending pathways affect pain transmission at the synapse?

Answer 11

These modulators can:

• Directly inhibit the synapse where C and A-δ fibers attempt to activate secondary spinothalamic tract neurons.
• Activate local inhibitory neurons to “close the gate” and reduce pain signals.
• Inhibit firing of the secondary neurons themselves.

Question 12

Which local neurotransmitters are involved in descending modulation at the spinal level?

Answer 12

Local neurotransmitters involved include GABA and glycine, which play a role in inhibiting pain transmission in the spinal cord.

Question 13

Where can endorphins and enkephalins produce effects in the body?

Answer 13

Endorphins and enkephalins can produce effects in the spinal cord, where they help modulate pain signals by reducing the activation of pain-transmitting neurons.

Question 14

What can impair descending modulation mechanisms in the CNS?

Answer 14

Descending modulation mechanisms can be impaired by traumatic injuries, pathological conditions, or disruptions to the central pathways involved in modulation, leading to abnormal sensory experiences.

Question 15

What types of problems can result from dysfunction in central modulation mechanisms?

Answer 15

Dysfunction in central modulation mechanisms can lead to pathological pain or sensory issues, either due to aberrant nociception (pain perception) or faulty CNS analysis, or both.

Question 16

How do mood states, mental health, and traumatic history affect central modulation?

Answer 16

Mood states, mental health, and a history of trauma or chronic conditions can alter central modulation by changing how the CNS processes and responds to sensory input, potentially amplifying or distorting sensory experiences like pain.

Question 17

How does anxiety affect the perception of pain?

Answer 17

Anxiety increases the intensity of pain experience. The neurochemistry of anxiety, which involves activation of the sympathetic nervous system, enhances pain perception and pain distress (suffering).

Question 18

How does anxiety and stress impact central modulation of pain?

Answer 18

Anxiety and stress reduce the effectiveness of central modulation mechanisms, making it harder for the body to regulate pain and sensory experiences.

Question 19

What factors contribute to the complexity of how anxiety and stress affect pain perception?

Answer 19

The complexity arises from the combination of physical and psychoemotional factors, especially when dysfunctional stress becomes entrenched or when anxiety illness is present, which can amplify pain perception and distress.

Question 20

What happens during central sensitization?

Answer 20

In central sensitization, sensory signals from primary neurons are normal but are amplified at the dorsal horn of the spinal cord. By the time they reach the brain, these signals are perceived as pain, even though they should not have caused pain.

Question 21

Can nociceptive signals be sent to the brain without a stimulus from the peripheral neurons?

Answer 21

Yes, in central sensitization, nociceptive signals can be sent to the brain from secondary neurons in the CNS without any stimulus from the peripheral primary neurons.

Question 22

What factors contribute to central sensitization?

Answer 22

Central sensitization can be caused by a history of physical and/or emotional trauma, leading to hyperfacilitation of pain, reduced descending modulation, and increased distressing symptoms.

Question 23

How does central sensitization become entrenched over time?

Answer 23

Over time, central sensitization causes altered neuron health, dysfunctional synapses, and changes in neurochemical production and function, which reinforce the sensitization process.

Question 24

How is central sensitization related to chronic pain?

Answer 24

Chronic pain syndromes are often interwoven with central sensitization, where pain becomes amplified and persistent due to the changes in the nervous system.

Question 25

What is somatization in the context of central sensitization?

Answer 25

Somatization refers to the expression of mental or emotional distress as physical symptoms, which can complicate central sensitization by adding to the perceived pain and distress.

Question 26

How are anxiety, central sensitization, and depression connected?

Answer 26

Anxiety, central sensitization, and depression are interconnected and often present in varying degrees in the same person over time, creating a complex relationship between these conditions.

Question 27

How do anxiety, pain, and distress contribute to depression?

Answer 27

Anxiety, pain, and distress cause depletion of serotonin, dopamine, endogenous opioids, and norepinephrine in the CNS. These neurochemicals are important for mood regulation, and their depletion can lead to depression.

Question 28

What role does depression play in the depletion of neurochemicals?

Answer 28

Depression itself depletes serotonin, dopamine, endogenous opioids, and norepinephrine, creating a cycle where these chemicals are further reduced, which worsens the symptoms of depression.

Question 29

How does depression affect descending modulation?

Answer 29

Depression reduces the effectiveness of descending modulation because the neurochemicals involved in this process (e.g., serotonin, dopamine, norepinephrine) are depleted. This contributes to the pain and physical discomfort symptoms seen in depression.

Question 30

What is the placebo effect, and how does it work?

Answer 30

The placebo effect involves the reduction or suppression of uncomfortable symptoms, and it is believed to work in large part by enhancing central modulation. It can be triggered by expectations and the therapeutic relationship.

Question 31

How might massage therapy have a placebo component?

Answer 31

Some researchers believe massage therapy’s effects may include placebo components, especially through the therapeutic relationship and possibly through touch effects on the brain, enhancing central modulation.

Question 32

What is the nocebo effect?

Answer 32

The nocebo effect is the negative counterpart to the placebo effect, where expectations of harm or negative outcomes can increase the perception of pain or discomfort.

Question 33

What are the sensory perception challenges that can arise from damage and disease in the nervous system?

Answer 33

Damage and disease can cause sensory perception challenges through factors such as neuron loss, scarring, inflammation, edema, and the release of chemicals from damaged tissue, leading to intense, irritable firing patterns.

Question 34

How can damage to the sensory system cause interpretation difficulties?

Answer 34

Damage in the sensory system can cause difficulties in brain interpretation by promoting proximal depolarization confusion or by affecting the synchrony of transmission patterns, leading to distorted sensory experiences.

Question 35

How does ischemia, compression, and demyelination affect sensory interpretation?

Answer 35

Ischemia, compression, and demyelination can cause asynchronous transmission patterns, resulting in disordered arrival of sensory information to areas like the thalamus, which may lead to dysfunctional sensory experiences.

Question 36

How can damage to a primary neuron’s receptor or axon result in abnormal sensation?

Answer 36

Damage to a primary neuron’s receptor or axon can lead to abnormal signal activation, causing sensation without an external stimulus, resulting in dysfunctional sensation experiences.

Question 37

What is Complex Regional Pain Syndrome II (CRPS II)?

Answer 37

CRPS II (formerly known as Causalgia) is a condition resulting from peripheral nerve damage, often seen in injuries to the median, sciatic, or C8/T1 spinal nerves. It typically presents with intense burning pain, often with a shooting quality, accompanied by erythema and heightened sensitivity to stimuli, particularly heat.

Question 38

What are common triggers or aggravators of CRPS II?

Answer 38

Pressure, temperature (especially heat), and almost any external stimuli can trigger CRPS II. Strong emotional states can also worsen the condition, leading to guarding postures and behaviors.

Question 39

What is the difference between CRPS I and CRPS II?

Answer 39

CRPS I (formerly known as Reflex Sympathetic Dystrophy) differs from CRPS II in that the pain in CRPS I is not localized to the area around the injured nerve, while in CRPS II, the pain is localized to the affected nerve area.

Question 40

What is neuropathic pain?

Answer 40

Neuropathic pain is a common phenomenon that arises when there is irritation or damage to the sensory nervous system, which can affect peripheral nerves, central nervous system (CNS), or both.

Question 41

What are some causes of peripheral nerve damage leading to neuropathic pain?

Answer 41

Peripheral nerve damage leading to neuropathic pain can be caused by trauma, neuralgias, shingles, facet joint issues, amputation, and other conditions.

Question 42

What are some causes of CNS damage leading to neuropathic pain?

Answer 42

Neuropathic pain in the CNS can be caused by conditions like transverse myelitis, spinal stenosis, multiple sclerosis, CNS infections, and stroke.

Question 43

What are some examples of conditions that affect both the peripheral nerves and CNS, leading to neuropathic pain?

Answer 43

Conditions that can affect both the peripheral nerves and CNS include alcoholism, diabetes, and chemotherapy.

Question 44

How does neuropathic pain present itself?

Answer 44

Neuropathic pain can vary greatly, from numbness and tingling to more intense sensations like burning, electric shock, or stabbing pain. It can also be triggered by non-nociceptive stimuli and can be continuous or episodic.

Question 45

What factors can make neuropathic pain worse?

Answer 45

Factors that can exacerbate neuropathic pain include fatigue, illness, intense emotional states, anxiety, and depression.

Question 46

What treatment approaches are commonly recommended for neuropathic pain?

Answer 46

Common treatment approaches for neuropathic pain include anticonvulsant, analgesic, and antidepressant medications, physiotherapy, massage therapy, psychotherapy, acupuncture, and relaxation practices.

Question 47

What are some possible cause factors of neuropathic pain?

Answer 47

Possible cause factors include:

1. Sprouting of sympathetic post-ganglionic nerve fibers on 1° afferent endings and sensory cell bodies.
2. Lowered threshold for firing of C fibers (hyperesthesia) and A-delta fibers (allodynia).
3. Proliferation of alpha adrenergic receptors on 1° sensory afferent endings and sensory cell bodies.
4. Ephaptic afferent activation (cross-talk between neurons).
5. Permanent hyperactivation of wide dynamic range neurons.
6. Glutamate excitotoxic cell death of inhibitory neurons (glutamate storms).
7. Inadequacy of central descending pathways (serotonin, norepinephrine, and opioid peptides) to control nociception.
8. Immobilization by pain, limiting physical therapy to initiate gating.
9. Sprouting of C fibers in the spinal cord.
10. Extension of interneuron dendrites into additional spinal cord laminae.

Question 48

Why is it important for massage therapists to understand clinical terminology related to sensory abnormalities?

Answer 48

It is important because proper use of terminology leads to more effective communication with other practitioners and enhances the ability to read research, articles, and clinical reports.

Question 49

What is Anaesthesia?

Answer 49

Anaesthesia is the absence of any sensation, where the stimulus does not produce any expected sensory response. It can be induced, for example, through a nerve-blocking agent in dental work.

Question 50

What does Hypaesthesia refer to?

Answer 50

Hypaesthesia refers to diminished sensation, where the experience matches the nature of the stimulus but is less strong than expected. It is commonly referred to as numbness.

Question 51

What is the classic sensory loss pattern of Hypaesthesia in diabetes?

Answer 51

In diabetes, the classic sensory loss pattern is often described as a “sock and glove” pattern, where the hands and feet experience anaesthesia (absence of sensation) and the rest of the shading indicates hypaesthesia (diminished sensation).

Question 52

What is Hyperaesthesia?

Answer 52

Hyperaesthesia is heightened or exaggerated sensation. The experience matches the stimulus but results in an unexpectedly strong response, which can be caused by neuronal irritation, damage, or psychoemotional factors.

Question 53

What is Paraesthesia?

Answer 53

Paraesthesia refers to abnormal sensations like “pins and needles,” “prickling,” or the feeling of “bugs crawling on the skin.” This sensation does not correlate with the actual stimulus and is often a result of nerve irritation or skewed perception.

Question 54

What does Dysaesthesia refer to?

Answer 54

Dysaesthesia occurs when a paraesthesic sensation becomes painful. Examples include “hot pokers,” “electric burning,” or “feels like it’s on fire.” These are strange, painful sensory experiences.

Question 55

What is Allodynia?

Answer 55

Allodynia occurs when a normally non-painful stimulus (e.g., a light touch) results in pain. It is caused by a reduced pain threshold, typically due to local nerve damage, CNS circuitry issues, or poor central modulation.

Question 56

What is Hypalgesia?

Answer 56

Hypalgesia is a weak response to a nociceptive (painful) stimulus. It can be seen as a form of hypaesthesia for pain, where the pain sensation is less intense than expected.

Question 57

What is Hyperalgesia (also known as Hyperalgia)?

Answer 57

Hyperalgesia refers to heightened sensitivity to painful stimuli, where the pain intensity is unexpectedly strong compared to the predicted response to the stimulus. It may continue after the stimulus has ceased and can be accompanied by strong emotional responses.

Question 58

How can injury affect the perception of pain?

Answer 58

After an injury, sensations that are normally painful may become more painful (hyperalgesia) and sensations that are usually non-painful may become painful (allodynia).