Clinical application for Somatosensation Flashcards
What is the purpose of a sensory exams? (cover conscious relay pathways)
establish whether sensory impairment is present and, if so, the location, type of sensation affected, and severity of the deficit
What are the 6 guidelines to improve the reliability of sensory testing?
- Administer tests in a quiet, distraction-free setting.
- Position the patient seated or lying supported by a firm, stable surface to avoid challenging balance.
- Explain the purpose of the test.
- Demonstrate each test before administering.
- Block the patient’s vision during the tests.
- Apply stimuli near the center of the dermatomes being tested.
What does the quick screening for somatosensation include?
- Testing proprioception and vibration in the fingers and toes
- Testing fast pain sensation in the limbs, trunk, and face with a pinprick
What distribution of losses would be seen in a stroke or neuropathy?
body region
What distribution of losses would be seen in a nerve root or spinal cord injury?
Dermatome
What distribution of losses would be seen in a peripheral nerve injury?
Peripheral nerve distribution
What are the two methods for electrodiagnostic studies?
- Nerve conduction study
2. Somatosensory-evoked potentials
Measures peripheral nerve function; Stimulating in the periphery and recording in the periphery; surface recording electrodes are placed along the course of a peripheral nerve, and the nerve is electrically stimulated
Nerve conduction study (NCS)
Tests peripheral nerves and CNS pathways; Stimulating in the periphery and recording in the CNS
Somatosensory-evoked potentials
What type of nerves are you looking at when doing a NCS?Why are they performed?
Large-diameter fibers; to see if there is a loss of myelination
To determine if an NCS is normal, what three numerical values are compared?
- Distal latency
- Amplitude of the evoked potential - measure of how many axons carry a signal
- Conduction velocity- measure of myelination
What test would you use to localize a peripheral nerve problem (myelination, or compression due to carpal tunnel)?
Nerve Conduction Study
Evaluate the function of the pathway from the periphery to the upper spinal cord or to the cerebral cortex; Potentials are used to verify subtle signs and locate lesions of the dorsal roots, posterior columns, and brainstem
Somatosensory-Evoked potentials
What are the three types of ataxia?
- Sensory
- Vestibular
- Cerebellar
Test that is used to distinguish between cerebellar ataxia and sensory ataxia. How do you distinguish between sensory and cerebellar ataxia?
Romberg test
- cerebellar = unable to perform with eyes open or closed
- sensory = can perform with eyes open, but not closed
What three systems are there to maintain balance?
- Visual
- Vestibular
- Proprioception (sensory)
general term for dysfunction or the pathologic condition of one or more peripheral nerves
neuropathy
What will be there result of a severance of a peripheral nerve?
- Lack of sensation in the distribution of the nerve (pain, touch, proprioception)
- Pain may occur (can’t feel stimuli but changes occurring cause pain or tingling in a body part)
- Sensory changes are accompanied by motor and reflex loss
What is the order of sensory losses that proceed pressure, compression or injury?
Starts with the fastest axons and goes to the slowest:
- Conscious proprioception and discriminative touch
- Cold
- Fast pain
- Heat
- Slow pain
What are common causes of dysfunction in 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
Lesion that results in:
All sensation is prevented at one or two levels below the lesion; Voluntary motor control below the lesion is also lost
Transection of the cord
Lesion that results in:
(Spinothalamic) Complete loss of pain sensation occurs two to three dermatomes below the level of the lesion contralateral to the lesion.
(DCML) Discriminative touch and conscious proprioception are lost ipsilateral to the lesion
Hemisection of the cord (Brown-sequard)
Lesion that results in:
- Conscious proprioception, two-point discrimination, and vibration sense are lost below the level of the lesion.
- Movements are ataxic immediately after the lesion.
- Individual may be unable to recognize objects by palpation if the lesion is above C6
Posterior Column Lesions
causes - untreated syphillis, extension injury
Syndrome that results from:
Disrupts spinothalamic fibers that are crossing the midline
Usually occurs in cervical spinal cord; With small lesion, only pain and temperature sensation are lost at level of injury. what pattern does this create?
Central cord syndrom; cape pattern
What is the region that spinothalamic fibers cross?
Ventral white commissure
What can cause central cord syndrome?
- Syringomyelia
2. Trauma
What side do brainstem region lesions affect?
- Usually cause a mix of ipsilateral and contralateral signs
- Sensory loss may be entirely contralateral only in the upper midbrain after all discriminative sensation tracts have crossed the midline.
- Lesions of the trigeminal nerve proximal axons or of the trigeminal nerve nuclei cause an ipsilateral loss of sensation from the face
AKA Wallenberg syndrome
Sensory effects of a cortical lesion are contralateral and include decreased or loss of discriminative sensations: Conscious proprioception, Two-point discrimination, Stereognosis, Localization of touch and pinprick (nociceptive) stimuli [still feel pain and temp but trouble localizing]
Somatosensory cortex lesions
a form of unilateral neglect because the person neglects stimuli on one side of the body when the other side of the body is stimulated simultaneously; the loss of sensation is only evident when symmetrical body parts are tested bilaterally
sensory extinction
What is pain often associated with?
- Tissue damage or potential tissue damage
Pain is a perception
What sensitizes nociceptors?
When tissue is injured or ischemic, biochemicals are released
-Sensitized neurons can fire in response to normally innocuous stimuli, with slight movements, and spontaneously
Nociceptors that are excessively reactive to stimuli are called
peripheral sensitization
Unlike superficial pain, deep pain usually occurs after tissue has been damaged. What is the function of deep pain?
Encourage rest of the damaged tissue
Pain that is perceived as coming from a site distinct from the actual site of origin; usually from visceral tissues to the skin
Referred pain
-Explanation comes from the convergence and facilitation of nociceptive information from different sources
Consists of brain structures that process and regulate pain information and are capable of creating pain perception in the absence of nociceptive input; Includes parts of the brainstem, amygdala, hypothalamus, thalamus, and areas of the cerebral cortex
Pain matrix
Experience of pain is strongly linked to emotional, behavioral, and cognitive phenomena. Understanding requires the consideration of ______, _______, and ______ components
discriminative; motivational-affective; cognitive-evaluative
_______ aspect refers to the ability to localize the site, timing, and intensity of tissue damage or potential tissue damage
Discriminative
________ aspect refers to the effects of the pain experience on emotions and behavior, including increased arousal and avoidance behavior
Motivational-affective
_______ aspect refers to the meaning that the person ascribes to the pain
Cognitive-evaluative
What happens if you inure the anterior cingulate cortex?
it can block emotional aspects of pain but leave discrimination intact
First scientific explanation of how pressure and other external stimuli inhibit pain transmission (holding your thumb when you hit it with a hammer), proposed by Melzack and Wall in 1965.
Some details are incorrect, but it inspired inquiry into the mechanics and control of pain, such as TENS. theory of suppressed dorsal horn processing
Gate Theory
Theory: explains the inhibition of nociceptive signals by stimulation of non-nociceptive receptors occurs in the dorsal horn of the spinal cord; theory of suppressed dorsal horn processing
Counterirritant theory
What are the four states of dorsal horn processing?
- Normal
- Suppressed (50 come in, 20 go up - perceive less pain)
- Sensitized (50 come in, 100 go up - perceive more pain)
- Reorganized (pathological, changing the underlying structure of connections - can start happening with in 2 days of pain)
the suppression of pain in response to stimulation that would normally be painful
Antinociception
endogenous substances that activate antinociceptive mechanisms
endorphines
What do opiate receptors bind with?
endorphins and opiates
Due to continuing stimulation of nociceptive receptors; Neurons are functioning normally; chemical changes in the damaged tissue awaken sleeping peripheral nociceptors; long-term acute pain; serves a useful biological function as a warning to protect injured tissue
Nociceptive chronic pain
Increased pain response (sensation of pain); painful input is perceived as more painful
primary hyperalgesia
what is essential for two-point discrimination, paresthesia, stereognosis, and simultaneous awareness of stimulation on both sides of the body
primary somatotsensory cortex
What will a proprioceptive pathway lesion result in?
sensory ataxia
What cell bodies do the periaquductal gray synapse with? where are they located? what are the postsynaptic axon tracts called?
- Locus coeruleus - midbrain and pons; ceruleospinal tract
2. Raphe nuclei - medulla, specifically rostral ventromedial medulla; raphespinal tract
What are the different antinociceptive systems? how do they block nociceptive input?
I. Peripheral - block sensitization in nociceptors
II. Dorsal horn - Gate/ counterirritant theory
III. PAG - activate inhibitory interneurons at dorsal horn
IV. Hormonal - Release of ACTH at pituitary; slower but longer analgesia; low frequency TENS activates system
V. Descending cortical inhibition - Cognitive meaning; distraction of pain, expectations of pain
What may cause pronociception?
- edema and endogenous chemicals sensitize free nerve endings
- anxiousness or depression
