Sensation & Sensory Loss Flashcards
What is the difference between sensing & sensation?
Sensing: Becoming aware of something via the senses
Sensation: Conversion of environmental stimuli/movement of body parts to an electrical signal. Essential for normal movement
What is perception?
- Result of sensory processing
- Can occur consciously or unconsciously
- Guides the response to the sensation
- Relies on emotion, past experience, memory, cognition
What is loss of sensation?
- Decreased sensitivity to somatosensory stimuli
- Primary impairment
- Less common than loss of strength or dexterity
What primary sensory inputs contribute to movement?
- Visual
- Vestibular
- Somatosensation (tactile & kinaesthetic sensation)
What is the role of vision in movement?
- Recognition (objects, movement, direction speed - conscious & automatic)
- Comparison to memory (posterior parietal lobe for integration of sensory input)
- Cognition response
What are the functions of the vestibular system?
- Provides info about direction & speed of head movement
- Position of the head relative to gravity
- Maintaining eye position (gaze stability)
- Postural adjustments
- Autonomic function & consciousness
What is the function of the semicircular canals?
- Give information about angular acceleration of the head, i.e. rotation in 3 planes (forward/backwards, sideways, rotation)
- Only give information under acceleration
What is the function of the utricle & saccules?
- Contain ossicles
- Sensitive to gravity
- Give information about linear acceleration of the head
What areas of the CNS does the vestibular system transmit afferent information to?
- Thalamus
- Basal ganglia
- Cerebellum
- Primary & secondary motor cortices
- Spinal cord
- ANS
What is Pusher syndrome?
- Push body onto affected side following stroke (normally stroke patients push away from affected side)
- No longer have a correct sense of where upright is
- Cognitive perception problem (not visual or vestibular)
- Visual markers are helpful for re-training
What is somatosensation made up of?
- Tactile sensation
- Kinaesthesia
What are the components of tactile sensation?
- Light touch
- Temperature
- Pressure
- Pin prick
- Tactile localisation
- Bilateral simultaneous touch
What does skills does tactile sensation provide?
- Tactile discrimination (differentiating between different textures)
- Stereognosis (ability to know what an object is just with touch, i.e. without vision)
What are the components of kinaesthesia?
- Sense of position
- Sense of movement
- Sense of heaviness
How does kinaesthesia work?
- Force of muscle contraction activates afferent neurons
- Muscle spindles active through full range of contraction & are modified by spinal mechanisms
- Joint receptors become activated at EOR
- Kinaesthetic info is carried on somatosensory pathways
What are the 4 main types of receptors for kinaesthesia?
- Meissner & Pacinian corpuscles (fast adapting, give info about beginning/end of movement)
- Merkel’s & Ruffini’s endings (slow adapting, give info about intensity/duration of contraction)
How does somatosensory loss affect stroke patients?
- Occurs in 60-85% of stroke patients
- Tactile discrimination usually more impaired than kinaesthetic discrimination
- No sharp area of demarcation (i.e. sensory loss doesn’t follow dermatomal distribution)
What are the consequences of sensory impairments?
- Decreased ability to manipulate objects in the hand
- Inability to sustain an appropriate level of force during grasping without vision
- Poor ability to balance in standing
- Decreased walking speed/inability to walk
- Reduced safety
- Decreased ability to learn new skills
Why do we need to assess & train sensation?
- Differential diagnosis
- Safety
- Ability to learn new motor tasks
- Ability to use hands
- Ability to walk
- Leisure activities
What are the most common clinical sensory measures in stroke?
- Nottingham sensory assessment
- Rivermead assessment of somatosensory performance
What is the evidence for sensation testing?
- Most physios assess light touch & kinaesthesia
- Most of the other components aren’t tested often
- 70% of clinicians don’t measure sensation at all
- Sensation isn’t being tested very well in clinical practice at the moment
What are the important components of training sensation?
Training sensation should:
- Be specific (sensory modality, body part)
- Be repetitive
- Be progressive
- Include vision & visual occlusion
- Incorporate feedback
What is the evidence for training sensation in chronic stroke?
- Chronic stroke patients
- 10 x 60 min sessions over 3 weeks of specific sensory retraining (tactile discrimination, wrist kinaesthesia & object recognition)
- Compared to sham
- Improvements in experiment group compared to control
- Effect maintained at 6 week & 6 month follow-ups
What evidence is there for sensory training in chronic hemiplegic stroke patients?
- Specific sensory training compared with control
- 45 mins 3 x per week for 6 weeks
- Significant improvement in tactile & kinaesthetic discrimination only in patients given specific sensory training
What evidence is there for motor & sensory training in chronic stroke patients?
- 4 weeks motor training vs 4 weeks sensory training, then swapped
- Significant improvement in patient function following 12 hours supervised sensory training
- Improvements paralleled type of training
What evidence is there for the Nottingham sensory scale?
- Review of 2 studies looking at Nottingham use after stroke
- Light touch & pressure most reliable
- Pinprick & temperature least reliable
What does motor training in the presence of visual impairment involve?
- Glasses if appropriate
- Simplifying background
- Instructing patient to scan for features of object/environment
- Instructing patient to scan while walking
- Following a moving object with eye & head movements
How can motor training in the presence of visual impairment be progressed?
- Vary levels of illumination
- Increase complexity of background
- Increase speed of moving objects or of patient moving in environment
What does motor training in the presence of nausea/dizziness involve?
- Initially avoid movements that provoke symptoms
- Start with small, slow movements
- Progress to larger amplitude, faster, more joints moving
- Varying terrain
- Gradually add in moving objects
