05-Lect.-4 Sensory Lesions Dr.Zahoor.ppt
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Transcript 05-Lect.-4 Sensory Lesions Dr.Zahoor.ppt
Sensory Lesions
Dr. ZAHOOR ALI SHAIKH
Peripheral Neuropathy 1
Polyneuritis or Polyneuropathy
(When many peripheral nerves are affected)
All forms of sensations are impaired in distal
parts of limbs (Glove & stocking
anesthesia)
Usually symmetrical
Polyneuritis or Polyneuropathy 2
Causes : Diabetes Mellitus, Vit. B
deficiency (B1, B6, B12) Drugs e.g. INH
(anti T.B.)
Patient complaints of, numbness,
sometimes pain in the feet
On examination: loss of position &
vibration sense.
Herpes Zoster
This disease results from reactivation of the
varicella virus which has lain dormant in
posterior root ganglia following chickenpox
infection earlier in life .
Why reactivation? Usually when body resistance
is decreasd.e.g. Steriod therapy, Leukemias,
The first symptom is severe , continuous pain in
the dermatomal distribution of the affected nerve
root . (nerve root distribution.)
After 3-4 days the skin becomes red and vesicles
appear in the affected area .
These vesicles dry up in 5-6 days , and the pain
subsides .
Sometimes small scars and anesthesia remains
in the affected segment
Dermatomes of
Spinal roots &
Divisions of
Trigeminal (V)
nerve
Tabes Dorsalis (1)
Is a form of Neurosyphilis ( syphilis is a sexuallytransmitted disease , STD).
It can cause damage to the dorsal root, and
dorsal ( posterior ) columns . Consequently ,
there will be :
(1) impairment or loss of proprioception
( vibration , position senses ) and two-point
discrimination sense .
(2) Absent tendon jerks . Explain why ?
Tabes Dorsalis (2)
(3) Sensory ataxia ( ataxia means loss of coordinated
muscular contractions required for the production of
smooth movements) . Expalin why ?
Q: How do we ascertain the presence of sensory ataxia ?
A : By performing Romberg’s Test .
In a patient with damaged psterior columns of the spinal
cord we get a +ve Romberg Test .
A positive Romberg’s Test (Sign) : means that
keeping the feet together , the patient can stand steadily
with the eyes open ; but if he closes his eyes he become
unsteady and tends to fall .
Explain why ?
Gait : wide based & stamping gait. Why?
Brown –Sequard Syndrome (1)
(Hemisection of spinal cord)
Causes: due to stab injury , gunshot ( bullet ) wound,
or tumor .
The example shown here is a lesion on the left side at
the thoracic level of the spinal cord :
Ipsilaterally ( on the same side of lesion )
(1) At the level of the lesion : Loss of all sensations.
(2) Below the level of the lesion : loss of vibration ,
position and two-point discrimination . Why ?
Contra laterally (on the opposite side ) : loss of pain
and temperature sensibility Why ?
BrownSequard
Syndrome
Site of Lesion
Brown –Sequard Syndrome (2)
There is motor weakness ( lower motor neuron
type at the level of the lesion.
Below the lesion- Spastic lower limb (with upper
motor neuron type of lesion on the same side).
Why ?
Syringomyelia (1)
This disease is due to presence of one or more
cysts ( fluid-filled cavities , called syrinx ) near
the central canal of the spinal cord.
The expanding cysts damage second-order
spinothalamic fibers which cross directly in front
of the central canal , affecting pain &
temperature fibers on both sides at the affected
segment
The loss of pain and temperature sensations
extends to several segmental levels . Therefore ,
we get Segmental Loss of pain and temperature
sensations .
Syringomyelia (2)
However , the patient retains
touch and pressure sense as
well as vibration and position
sensations (why are they
spared ?)
This selective loss of pain and
temperature while sparing
touch and proprioception is
called Dissociated sensory Loss
( or Dissiciated Anesthesia)
Loss of
pain and
temperature
sensation
The Parietal Lobe is an Essential Component of
the Somatosensory System
And because its post-central gyrus receives afferent
pathways for perception (appreciation ) of body position
and touch , damage to S1 leads to loss of :
(1) Ability to accurately localize light touch
(2) Two-point discrimination
(3) Ability to appreciate size , shape , texture and weight
of objects (without looking at them) Stereognosis
Sensory inattention ( & hemineglect ) Amorphosynthesis
occur due to damage to somatosensory association area,
as this area plays important role in interpreting the
meaning of sensations perceived by main sensory area S1
(a) Thalamic
(b) Mid-brainstem
Weak
(UMN)
(c) Central Cord
(d) Unilateral cord lesion
(Brown-Sequard)
(e) Transverse thoracic
spinal cord
(f) Dorsal column
T5
C6
L4
(g) Sensory roots
(h) Polyneuropathy
Principal patterns of loss of sensation
-- T5
- C6
- UMN
--- L4
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(a) Thalamic lesion: sensory loss throughout opposite side.
(b) Brainstem lesion (rare): contralateral sensory loss below face and ipsilateral loss on
face.
(c) Central cord lesion, e.g. syrinx: ‘suspended’ areas of loss, often asymmetrical and
‘dissociated’, i.e. pain and temperature loss but light touch remaining intact.
(d) ‘Hemisection’ of cord or unilateral cord lesion=Brown-Sequard syndrome: contralateral
spinothalamic (pain and temperature) loss with ipsilateral weakness and dorsal column
loss below lesion, UMN, upper motor neurone.
(e) Transverse cord lesion: loss of all modalities below lesion.
(f) Isolated dorsal column lesion, e.g. demyelination: loss of proprioception, vibration and
light touch.
(g) Individual sensory root lesions, e.g. C6 (cervical root compression), T5 (shingles), L4
(lumbar root compression).
(h) Polyneuropathy: distal sensory loss.
Thanks to Dr. Taha for his help.