Lecture 27: Sensation testing C2 Flashcards
When is examination of sensation done
End of neurological exam, largely directed by history.
How is light touch sensation and pain examined and what instruments are used to determine the extent of numbness?
Using cotton wool and safety pin
- Set patient in anatomical position
- With patient’s eyes closed, demonstrate the stimulus over a part where you know it will be normal. Map sensory loss by moving from area of reduced sensation to area of normal sensation
- Ask them to say when they feel it
- Apply stimuli at irregular intervals and irregular place so they cannot predict it.
How is vibration sense examined and what instrument is used to determine the extent of numbness?
128Hz tuning fork
- Start at the great toe, placing hit fork on the toe
- Time how long it takes for patient to say they stop feeling it- 8 seconds is normal
- If it is not felt distally, test bony sites moving proximally at the malleoli, tibial tuberosity, ASIS, rib margin - similar in the upper limb
How is position/proprioception sense examined and what instrument is used to determine the extent of numbness?
- Patient eyes closed
- Start with distal interphalangeal joint of index finger
2.
Grasp the distal phalynx with one finger one each side of the phalynx - not above or below - Make quick movements and cue the patient time “up or down”. start with wide ranged movements and progressively decrease the range of movement
- If impaired, move to MCP, wrist, elbow, lower limb.
How is discriminatory sensory function examined : 4 related tests
- Accurate light touch sensation
- Graphaesthesia: number writing on skin
- Sterognosis: object identification by feet
- Bilateral simultaneous stimulation: to find sensory inattention (affected side sensation lost when stim. bi.
What are the 4 locations of lesions that can cause sensory loss
Periphery:
- Mononeuropathy, mononeuritis multiplex, polyneuropathy
Spinal cord:
- Complete, anterior cord, central cord, hemicord,
Sensory pathways in the CNS above the foramen magnum: Thalamus: hemisensory loss, Corona radiata
Sensory cortex: stroke, tumour,
What are mononeuropathies caused by and how do they manifest - give eg
Due to a lesion in an individual peripheral nerve leading to sensory loss in skin supplied by nerve and weakness in its supplied muscles.
eg. Carpal tunnel syndrome: compression of median nerve: thumb + 2 fingers
What are mononeuritis multiplex caused by and how do they manifest - give eg
Due to a disease that affects peripheral nerves: focal patches of numbness and muscle weakness on different parts of the body.
eg. Vasculitis of arteries supplying the nerves caused by micro polyangitis
What are peripheral polyneuropathies caused by and how do they manifest - give eg
Due to disease of the peripheral nerve that affects longer nerves - eg sensory and/or motor nerves to the distal feet, hands.
Different pathologies cause different sorts of nerve fibres to be involved.
a) Axonal damage due to diabetes/alcohol of small unmyelinated fibres. Oversensitization or numbness start in feet->lower limbs->hands (glove and stocking)
b) Demyelinating neuropathy: large myelinated fibres, myelin layers themselves due to autoimmune Guillain Barre syndrome.
What is peripheral plexus lesion vs radiculopathy cause and manifestation
Plexus lesion: diseases that only affect particular plexuses (brachial, lumbar, sacral …). Symptoms seen in the groups of muscles supplied/ sensation from those areas
Radiculopathy: lesion in a single nerve root/compression by disk hernia. Symptoms seen in
-sensory dermatome loss
-weakness in muscles supplied by that nerve root
-loss of reflexes supplied by that nerve root
How do you find the spinal cord level of sensory loss
Test with the pinprick for spinothalamic pathways, there will be loss of pain and temp below the level of the lesion
What is the pattern of sensory loss caused by an anterior cord lesion- what is a cause
Anterior spinal artery occluded
- Spares the dorsal column discrim and proprioceptive
Lose: pain + temp
What is the pattern of sensory loss caused by an central cord lesion- what is a cause
Dilation of the central canal can put pressure on fibres crossing at the level of spinal cord:
- Spares the dorsal column discrim and maybe motor strength.
Lose: pain + temp
What is the pattern of sensory loss caused by an Hemicord (brown sequard syndrome) lesion- what is a cause
Tumour
On the same side of the tumour: position, vibration (and motor strength) is lost. On the other side Pain and temp is lost (pin prick abnormal).
Dissociative sensory loss.
What is Multiple Sclerosis- what parts does it affect and what is onset like
Autoimmune disorder of the CNS that affects the SC, white tracts in brain, optic nerve via demylination in plaques.
- Focal neurological deficit, subacute onset
- Sensory symptoms often present first
