Clinical Application of Somatosensation Flashcards Preview

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Flashcards in Clinical Application of Somatosensation Deck (82):

Somatosensation is essential for what?

The accurate control of movements and protection against injury


What are the 4 pathways necessary to test for somatosensation?

- Discriminative touch
- Conscious proprioception
- Fast pain
- Discriminative temperature


What does quick screening for sensory impairment consist of?

Testing proprioception and vibration in the fingers and toes and testing past pain sensation in the limbs, trunk, and face with a pinprick


Do somatosensory tests test the ability to use somatosensation to prepare for and during movements?

No, they only require that the patient has conscious awareness and cognition


What is one way you can reveal the location of nerve pathologies?

recording electrical activity from nerves


What are 2 methods of examining sensory nerve function?

- Nerve conduction studies (NCSs)
- Somatosensory-evoked potentials (SEPs)


What do nerve conduction studies evaluate?

The function of peripheral nerves


How are NCS and SEP applied?

Electrical stimulation is applied to the peripheral nerve so that all axons are depolarized simultaneously


Nerve conduction studies only measure the performance of ___-diameter axons



Conduction velocity is slowed in what types of nerves?

demyelinated ones


What are the 3 numeric values that are compared in order to determine whether a NCS is normal

- Distal latency
- Amplitude of the evoked potential
- Conduction velocity


What is distal latency?

the time required for the depolarization evoked by the stimulus to reach the distal recording site


What do somatosensory-evoked potentials evaluate?

The function of the pathway from the periphery to the upper spinal cord or to the cerebral cortex


What are SEPs used to verify?

Subtle signs and locate lesions of the dorsal roots, posterior columns, and brainstem


What is ataxia?

Incoordination that is not the result of weakness


What are the 3 types of ataxia?

- sensory
- vestibular
- cerebellar


What test is used to distinguish between cerebellar ataxia and sensory ataxia?

Romberg test


What is neuropathy?

A general term for dysfunction or the pathologic condition of one or more peripheral nerves


What does complete severance of a peripheral nerve result in?

Lack of sensation in the distribution of the nerve, pain may occur, and sensory changes are accompanied by motor and reflex loss


What does compression of a peripheral nerve result in?

Decreased sensation or a feeling of a limb "falling asleep"


Describe the order in which sensory loss proceeds

1) Conscious proprioception and discriminative touch
2) Cold
3) Fast pain
4) Heat
5) Slow pain


What occurs when compression is relieved?

Sensations are returned in the reverse order that they were lost. Thus, aching pain occurs first, then a sensation of warmth, then sharp, stinging sensations, then cold, and finally a return of discriminative touch and conscious proprioception


What are the 3 common causes of dysfunction of the spinal region?

- Trauma to the spinal cord and complete or partial severing of the cord
- Disease that compromises the function of specific areas in the spinal cord
- Virus that infects the dorsal root ganglion


Describe sensory and motor loss following a complete severing of the spinal cord

All sensation is lost at one of two levels below the lesion and all voluntary motor control is lost below the lesion


Describe sensory loss following a hemisection of the spinal cord

- There is reduced sensation of pain and temperature on the contralateral side two to three dermatomes below the level of the lesion
- There is reduced sensation of discriminative touch and conscious proprioception on the ipsilateral side of the lesion
- There is a zone of complete loss of sensation on the ipsilateral side of the lesion, just below it


What sensations are lost in posterior column lesions?

Conscious proprioception, two-point discrimination, and vibration sense are lost below the level of the lesion


What occurs immediately after a posterior column lesion?

Movements are ataxic


What may occur in a posterior column lesion above C6?

The individual may be unable to recognize objects by palpation because ascending information from the hand has been lost


Infection of a dorsal root ganglion or a cranial nerve ganglion causes what?

Varicella zoster (aka shingles)


What is the major symptom of shingles?

severe pain


Do brainstem lesions causes ipsilateral and contralateral signs?

A mix of the two because the axons that carry sensory information from the body and face cross the midline at various levels


A lesion at what point in the brainstem will sensory loss be entirely contralateral?

In the upper midbrain after all discriminative sensation tracts have crossed the midline


A lesion of trigeminal nerve proximal axons or of the trigeminal nerve nuclei causes what?

An ipsilateral loss of sensation from the face


Lesions in the brainstem often cause mixed sensory impairments, affecting the _____ body and ____ face




What do thalamic lesions result in?

Decreased or lost sensation from the contralateral body or face


Do those who experience thalamic lesions (stroke) have severe pain in the contralateral body or face?

They rarely do


What does a lesion of the somatosensory cortex result in?

Contralateral sensory effects that include decreased or loss of discriminate sensations such as conscious proprioception, two-point discrimination, stereognosis, and localization of touch and pinprick (nociceptive) stimuli


When is the only time in which somatosensory cortex lesions are evident?

When symmetrical body parts are tested bilaterally, so that the person neglects stimuli on one side of the body when the other side of the body is stimulated simultaneously (unilateral neglect)


What is pain often associated with?

tissue damage or potential tissue damage, although it can be experienced independently of tissue damage


Even though nociceptors signal injury, their activity is insufficient to cause pain because pain is a ______.



When nociceptors are stimulated by biochemicals released from tissue that is injured or ischemic they become excessively reactive to stimuli, what is this called?

peripheral sensitization


Unlike superficial pain, when does deep pain usually occur?

After the tissue has been damaged


What is the function of deep pain?

To encourage rest of the damaged tissue


What is referred pain?

Pain that is perceived as coming from a site distinct from the actual site of origin


When does referred pain occur?

When branches of nociceptive fibers from an internal organ and branches nociceptive fibers from the skin converge on the same second-order neurons in the spinal cord or in the thalamus, and the central neurons become sensitized


What does the pain matrix consist of?

Brain structures that process and regulate pain information and are capable of creating pain perception in the absence of nociceptive input


What brain structures does the pain matrix include?

parts of the brainstem, amygdala, hypothalamus, thalamus, and areas of the cerebral cortex


What is the experience of pain strongly linked to?

emotional, behavioral, and cognitive phenomena


What does the discriminative aspect of pain refer to?

The ability to localize the site, timing, and intensity of tissue damage or potential tissue damage


What does the motivational-affective aspect of pain refer to?

The effects of the pain experience on emotions and behavior, including increased arousal and avoidance behavior


What does the cognitive-evaluative aspect of pain refer to?

The meaning that the person ascribes to the pain


Describe the gate theory of pain

If low-threshold mechanical afferents are more active than nociceptive afferents, mechanoreceptive information is transmitted and nociceptive information is inhibited.


According to the gate control theory of pain where is pain transmission blocked?

in the dorsal horn of the spinal cord


What theory incorporates findings from research stimulated by the gate theory?

The Counterirritant Theory


What are the 4 states of dorsal horn processing?

- Normal
- Suppressed
- Sensitized
- Reorganized


Describe the mechanism of suppressed sensory processing in the dorsal horn

Touch, pressure, and vibration information is transmitted normally, but pain impulses are inhibited


Describe the mechanism of sensitized sensory processing in the dorsal horn

There are changes in neurotransmitters and receptors


Describe the mechanism of reorganized sensory processing in the dorsal horn

The structure of the dorsal horn has changed owing to cell death, degeneration of nociceptive axon terminals, and the sprouting of new terminals that synapse with neurons in the nociceptive pathways


Of the 4 states of dorsal horn processing, which are neuropathic (pain causing)?

Sensitized and Reorganized


What does neuropathic pain result from?

changes in neuronal activity, thus by neuroplasticity not by stimulation of nociceptors.


What is Antinociception?

the suppression of pain in response to stimulation that would normally be painful


What are the substances that activate antinociceptive mechanisms?



Endorphins bind to what kind of receptor?

Opiate receptors


The phenomenon of antinociception is summarized by a ___-level model



Where does level 1 of antinociception occur?

in the periphery


Where does level 2 of antinociception occur?

in the dorsal horn


What is level 3 called?

The fast-acting neuronal descending system, involving PAG, the rostral ventromedial medulla, and the locus coeruleus


What is level 4 called?

the hormonal system, involving the PVG in the hypothalamus, the pituitary gland, and the adrenal medulla


Level 5 is the _____ level



At what level do superficial heat and high-rate TENS act on?

Level 2


At what level does low-rate TENS act on?

Level 4


What is pronoception?

The biological amplification of pain signals


What is the mechanism of pronoception?

Edema and endogenous chemicals sensitize free nerve endings in the periphery intensifying pain signals


What causes acute pain?

Threat or actual tissue damage


How does a client report acute pain?

They give a clear, description of location, pattern quality, frequency, and duration of pain


What is the function of acute pain?

Acts as warning of tissue damage to enforce rest of healing tissue


What are the causes of chronic pain?

- Continuing tissue damage
- Environmental factors
- Sensitization of nociceptive pathway neurons
- Dysfunction of endogenous pain control systems


How does a client report chronic pain?

They give very vague descriptions


What is the function of chronic pain?

If tissue damage is not continuing, there is no biological benefit, but there may be a social or psychosocial benefit


What is nociceptive chronic pain due to?

continuing stimulation of nociceptive receptors


What is an example of nociceptive chronic pain?

Chronic pain that results from a vertebral tumor pressing on nociceptors in the meninges surrounding the spinal cord


The chemical changes that occur in chronically damaged tissues activates peripheral nociceptors which leads to what?

Primary hyperalgesia which is an excessive sensitivity to stimuli in the injured tissue