light touch sensory testing

Question 1

how to perform

Answer 1

peripheral/central NS - specific/anywhere in body
informed consent, contraindications, position
normal sensation with tough cotton wool on chest, ask if it feels normal, patient closes eyes, touch right > left proximal > distal with wool, circumferential around joints, patient says yes when touched, ask where/how it feels
CNS - use map to correspond area in brain
PNS - use map to correspond spinal root
document

Question 2

contraindications

Answer 2

MSK: fractures, damaged soft tissue, joint stability/dislocation, cancer
CR: general wellbeing, infections, fevers
CV: open wounds
N: pain, hypersensitivity, not conscious, skin allergy

Question 3

purpose

Answer 3

to know whether patient has normal sensation, whether spinal root/somatosensory cortex is damaged

recognise neuropraxia, axonotmesis, neurotmesis

Question 4

how to know if normal

Answer 4

negative/normal - patient says yes when touched, equal sensation on both sides

positive - absent, diminished/reduced, heightened/painful/sensitive

normal/impaired/absent
ask questions
does it feel normal?
does it feel the same as the other side?
what area of the limb am I touching?

Question 5

principles

Answer 5

right > left, proximal > distal
2/3 touches for amount of bones/muscles
test anterior + posterior
patients eyes closed

Question 6

structure

Answer 6

CNS - UL, LL, spinal cord, brain

PNS - dermatome, spinal root, nerve path
femoral nerve - L2-4, medial hip, thigh, knee, calf, heel
median - C5-T1, anterior arm, dorsal + palmar fingers 1-3 1/2
axillary - C5-6, deltoid muscle/shoulder, lateral arm

Meissner corpuscles - a cutaneous nerve ending responsible for transmitting the sensations of fine touch + vibration

pathway: skin, afferent nerve, spinal cord, efferent nerve, muscle