sensory exam

this is semester 5 sensory exam (CNS). 

in general, sensory exam has  components; pain, soft touch, proprioception and vibration.

·         General rules

o    Explain  before each test

o    Eyes always closed

o    Compare symmetrical areas

o    Compare distal and proximal (start proximally) except in diabetes specific exams,

o    For vibration and position, start from fingers and toes - since it is GENERALLY accepted that if these normal, proximal areas normal (in polyneuropathy)

o    Map out the sensory loss

·         Inspection

o    Hair loss

o    Dry skin

o    Ulcers

o    Colour of skin

o    Muscle atrophy

·         Components of sensory exam (8)

o    Light touch

§  Use fine whips of cotton, or finger to souch the skin lightly

§  Demonstrate light touch on chest

§  Make a dabbing rather than a stroking stimulus

§  Ask patient to respond id the touch is felt, and tell if there is difference on the either side of body.

o    Pain

§  Use disposable pin

§  Demonstrate pain on the chest/forehead

§  Ask patient to close their eyes and report whether they feel sharp or dull

§  Be sure to apply sharp stimulus to all sites

o    Temperaturue

§  Often omitted if pain sensation is normal

§  Use tunig fork heated or cooled by water, ask patient to identify hot or cold.

o    Vibration

§  Use a low freq tuning fork (128Hz)

§  Demonstrate vibration sense on chest / forehead

§  Place stem of fork over distal interphalangeal joint of patient’s index fingers and big toes.

§  Ask patienr to tell you if they feel the vibration, and when it stopped.

§  If vibration sense is impaired, then proceed proceed proximally. - medial malleous

§  This is often the first sensation to be lost in peripheral neuropathy

o    Position sense "proprioception"

§  Grasp big toe and hold it away from other toes, avoid friction.

§  Show the patienr “up” and “down” by Grasping on the sides to lessen clues by pressure.

§  With patient’s eye closed, ask the patient to identify the direction you move the toe.

§  If position sense is impaired, move proximally to  test ankle joint.

§  Test fingers in a similar fashion.

§  If indicated move proximally

o    2 point discrimination

§  Use calipers or an opened paper clip with 2 parallel ends

§  Demonstrate to patient with eyes open, either one or 2 points of stimulus to the fingerpad.

§  Ask patient to close eyes

§  Deliver stimulus and ask patient whey feel one of two points

§  Normal values over fingerpads are 2-4mm.

o    Graphesthesia

§  With blunt object, draw a large number in patient’s palm.

§  Ask patient to identify the number

o    Stereognosis

§  Use as an alternative to graphesthesia

·         Patterns of sensory loss

o    Peripheral nerve (mononeuropathies)

§  According to the distribution area of the affected nerve

o    Polyneuropathy

§  Classified as

·         Toxic

o    Malnutrition / alcoholism

·         Metabolic

o    DM

·         Inflammatory

o    GBS,

·         Infectious

o    Syphilis, HIV

§  Usually symmetrical

§  Glove-stocking distribution

§  More pronounced distally, more on lower extremes

§  Vibration perception is earliest affected modality

o    Dorsal root ganglia / radiculopathy

§  Common in IVD herniation or pressure from narrowing of the intervertebral foramina due to spondylosis (arthritis of spine)

§  Segmental, localized to dermatomes

o    Spinal cord

§  Characterized by both sensory and motor symptoms

§  Complete cord lesion

§  Hemisection of spinal cord etc

o    Brainstem

§  Ipsilateral cranial nerve abnormality and contralateral long-tract dysfunction

o    Thalamus

·         Specific testing for  early diabetic neuropathy

Foot examination should be performed on all diabetic patienrs to detect sensory loss and gangrene / infection etc.