Sensory system. Pathway, Dematomes, Various lesions of sensory system.

1. Dr. Shalu Jain
MD Scholor
Pt. Khushilal Sharma Govt. Auto. Ayurveda College And Institute, Bhopal (M.P.)

2. Five senses

3. Sensory Pathway

5. Sensory Dermatomes
 Dermatomes :- it is an area of skin that is mainly supplied
by single spinal nerve.
Purpose :- testing of dermatomes is part of the
 Purpose :- testing of dermatomes is part of the
neurological examination looking for rediculopathy as
sensation changes within a specific dermatomes may help
in determining the pahological disc level.

7.  C1 - no cutaneous supply; supplies meninges
 C2 - occiput, earlobe, angle of jaw
 C3 - nape of neck
 C4 - above clavicle
 C4 - above clavicle
 C5 - deltoid; over aspect of shoulder tip
 C6 - radial half of forearm including thinar eminence and
thumb
 C7 - longest spinous process – longest finger (middle finger)
 C8 - little finger, hypothinar eminence and ulnar aspect of
hand

8.  T1 - ulnar aspect of forearm
 T2 - ulnar aspect of arm
 T3 - lies in axilla
 T4 - nipple
 T4 - nipple
 T8,T10,T12 – supply rib margin, umblicus and pubis
respectively
 L1 - inguinal ligament
 L3 - lies at knee
 L4 - medial aspect of leg
 L5 - lateral aspect of leg

9.  S1 - includes little toe, tendo-achilles, strip of skin above
it and sole
 S2 - calf musle and hamstring
 S3, S4, S5 –perianal region
 S3, S4, S5 –perianal region

10. Modalities of sensation to be
tested
 Exteroceptive sensations
 Proproceptive Sensations
 Cortical sensations

11. Exteroceptive Senstion /Superficial sensation
Receptors in skin & mucus membrane.
 Tactile or touch
 Pain Sensation
 Temperature sensation

12. Touch
 fine touch – tested by cotton wool
 Crude touch – by blunt object

13. Temperature
 Two test tubes one
containing hot water and
the other crushed ice is
taken and placed on all the
taken and placed on all the
parts of the

14. Pain
 Superficial pain:- tested with a
pin prick
 Deep pain :- tested by pressing the
calves, tendo achillis or testes

15. Proprioceptive sensation
 Position sense
 Joint sense/ sense of passive movement
Vibratory sense

16. Vibration
Assessment of vibration sense is the best clinical test of
the dorsal column pathway.
A low-frequency (128 Hz) tuning fork is applied to bony
prominences.
prominences.
The patient (with closed eyes) is asked to report when the
vibration starts and stop.

17. s

18. Joint sense
 Fixing the joint, the finger/
toe is moved at terminal
interphalangeal joint ,
interphalangeal joint ,
either up or down by
holding the sides of digits.
 Patient to tell the direction
i.e. either up or down.

19. Position sense
• A part of limb / arm is
placed in definite position
and then he is asked to
and then he is asked to
dente the position or place
the other limb in similar
position.

20. Cortical sensory functions
 Point localisation (tactile location)
 Two point Discrimination
 Tactile extinction
 Sterognosis
 Graphesthesia

21. Sense of localzation test
 Touch a part of patient
body with his eyes closed
 Ask him to open the eyes
 Ask him to open the eyes
and place his finger of that
part

22. Two point discrimination test
 Ability to distinguish the contact of two separate points applied
simultaneously to the skin.
 Finger pulp & lips – 3-5 mm
 Palm – 2-3 cm
 Palm – 2-3 cm
 Sole – 4 cm
 Dorsum of foot -5 cm above
 Legs – 5cm and above
 Back – 5cm above
 If two point discrimination is lost in the presence of intact
posterior column sensations, it indicates a parital lobe lesion.

23. Cont…

24. Tactile extinction
 When two stimuli are applied
simultaneously to two
symmetrical portion of the
body, the patient neglect the
one on the opposite side of the
lesion,.
 Though individually he
appriciates the stimulus on both
side.

25. Graphesthesia
 The ability to recognize a
number or letter written in
the palm with closed eyes.
 This ability is lost in
sensory cortex lesion

26. Stereognosis test
 The abilty to identify a
suitable object after
careful palpation.
careful palpation.
 This ability is lost in
sensory cortex lesion.

27. Sensory Changes
In
Various Diseases
Various Diseases

28. Poly neuropathy
 Symmetrical glove and
stocking anesthesia
(affecting distal parts
(affecting distal parts
more) involving all the
modalities of sensations.
 There is calf tenderness

29. Cauda equina and Conus lesions
 Loss of all modalities of
sensations involving
especially lower sacral
especially lower sacral
segments leading to
perianal anesthesia

30. Multiple roots involvement
 There are varying degrees of impairement of cutaneous
sensations in the distribution of the nerve roots
Pain sensation is more affected than touch.
 Pain sensation is more affected than touch.

31. Complete section of spinal cord
 All sensations are aboished
below a perticular level, with a
narrow zone of hyperesthesia at
the upper margin of the
anesthetic zone
 In some patients with high cord
compression sacral fibres may
be spared resulting in sacral
sparing.

32. Hemi section of spinal cord
 Pain and temperature is
lost a few segmentbelow a
perticular level on the
perticular level on the
opposite side whilst
vibration, position, and
joint senses are affectedon
the same side.

33. Syringomyelia
 Loss of pain temperature
sensation.
 Touch, vibration, joint and
 Touch, vibration, joint and
position senses are normal.
 This is also called
dissociate anesthesia.

34. Anterior spinal syndrome
 Loss of pain, temperature
and touch below a level
on both sides with
on both sides with
preserved position, joint
and vibration sense.
 Eg. Anterior spinal artery
thrombosis

35. Posterior spinal syndrome
 Loss of poosition, joint
and vibration sense below
a level with normal touch,
a level with normal touch,
temperature and pain
senses.
 Eg. Tabes dorsalis

36. Brain Stem Syndrome
 Loss of touch pain
temerature on same side
of the faceand opposite
of the faceand opposite
side of the body due to
involvement of trigeminal
tract or nucleus or
spinothalamic tract.

37. Thalamic syndrome
 Loss of all modalities of
sensations on the opposite
side of body
 Position sense are more
 Position sense are more
affected than the other
sensation.
 There may be spontaneous
pain & discomfort of the
most torturing and disabling
type.