sensory disturbances at the level of thalamus and cortex

SENSORY DISTURBANCES AT THE LEVEL OF THALAMUS

AND CORTEX

SENSORY DISTURBANCES

NEUROLOGICAL

• PN, NR,SpC,BS, Thalamus, Cortex

NON NEUROLOGICAL

• HYSTERICAL

SOMATIC SENSATIONSSUPERFICIAL DEEP COMBINED/ CORTICAL

PAIN VIBRATION TWO POINT DISCRIMINATION, TACTILE LOCALISATION

TEMPERATURE POSITION STEREOGNOSIS , GRAPHAESTHESIA

TOUCH PASSIVE MOVT DOUBLE SIMULTANEOUS STIMULATION

PATHWAYS

SPINOTHALAMIC

• ANT- crude touch

• LAT- pain, temperature

DORSAL COLUMN

• Fine touch• Position sense

• Vibration

Figure 26.18 The main somatic sensory pathways.

Downloaded from: StudentConsult (on 5 July 2011 01:13 AM)© 2005 Elsevier

THALAMUS

Forms the lateral wall of 3rd ventricleSupply: POST. CEREBRAL A

SENSORY RELAY CENTRE- ‘HEAD GANGLION OF ALL SENSORY SYSTEMS’

PROCESSING OF SENSATIONS- ‘Fnl gateway of cerebral cortex’

PARTS

1.Ant. Nuclei

2.Med. Nuclei

3.Lat. Nuclei [Largest;neothalamus]4.Intralaminar N

LATERAL NUCLEI

DL VM

ANT INT POST

LAT[VPL] MED[VPM]

VPL VPM

SPINAL,MEDIAL

LEMNISCITRIGEMINAL

LEMNISCI

AREA 3,1,2

THALAMIC LESIONS

C/L loss of all sensationsTHALAMIC SYNDROME:- Lacunar infarction1. c/l sensory loss2. Thalamic/ athetoid hand3. Intention tremor4. Choreoathetosis

5. Thalamic over-reaction eg; DEJERINE ROUSSY SYNDROME- agonizing pain in the affected areaRx: frontal lobotomy6. Amelognosis7. Thalamic phantom limb 8.Mild hemiparesis

CORTEX

PARIETAL CORTEXCORTICAL Br of MCA n ACAPrimary sensory area-3,1,2Sec sens areaSensory assosn area-5,7,40

CORTICAL LESIONS

c/l Cortical sensations are lost Hemi neglect,hemi inattention Simulate paralysis

Pseudothalamic syndrome- Cortical lesion with c/l loss of sensationsAnt. Parietal infarctionSimulate thalamic lesion

LAT MED

Thalamic lesion

Cortical lesion

pain + _

Tingling n numbness + _

Perception of sensation

_ +Loss of discrimination

_ +