Parietal lobe

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Parietal lobe

  1. 1. PARIETAL LOBE <br />DR ARUN S<br />
  2. 2. Introduction<br />No independent existence as <br /> anatomical / physiological unit<br />Operates in conjunction with brain <br /> as a whole<br />Strategically situated b/w other lobes<br />Greater variety of clinical manifestations than rest of the hemisphere<br />Dysfunction likely to be overlooked unless special techniques used <br />
  3. 3. History<br />In 1874 Bartholow recorded odd sensation from legs on stimulating post central gyrus through skull wounds<br />Cushing in 1909 --- Electrical stimulation in conscious human beings under LA –– mainly tactile hallucinations<br />
  4. 4. Critchley(1953) –<br /> monograph on “ The Parietal Lobes” <br />Djerine– alexia , agraphia -- angular gyrus lesion <br />Liepmann--- ideomotor & ideational apraxia in (L) sided lesion <br />
  5. 5. Neuroanatomy<br />Occupies middle third of cerebral hemispheres<br />Situated b/w frontal ,temporal ,occipital lobes with anatomical & functional continuity<br />
  6. 6. Boundaries<br />Anterior –Central sulcus & its imaginary continuation over inner paracentral lobule medially <br />Posterior- parieto occipital sulcus on mesial aspect & its continuation (imaginary) to join pre occipital notch inferolaterally<br />Lower- Sylvian fissure & its imaginary extension backwards<br />
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  8. 8. Lateral surface<br /> 2 well defined sulci<br />Post central sulcus –parellel to Fissure of Rolando<br />Inter parietal sulcus- runs AP from post central sulcus to occipital lobe<br />
  9. 9. Lateral surface<br />Gyri<br /> Post central gyrus- primary sensory area(3,1,2)<br /> Superior parietal lobule(5,7)<br /> Inferior parietal lobule ( Ecker’s lobule )<br />Supramarginalgyrus (area 40) arches over Sylvian fissure <br />Angular gyrus (area 39 ) - arches over the superior temporal sulcus<br />
  10. 10. Mesial surface<br />Paracentral lobule- mesial part of post central gyrus<br />Precuneus- behind post central gyrus<br />Subjacent part of cingulategyrus- below sub parietal sulcus<br />
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  12. 12. Vascular supply<br />Lateral - MCA <br />Artery of Rolandic fissure<br />Artery of inter parietal fissure <br />Artery of post parietal fissure<br />Inter opercular parietal artery<br />Artery to angular gyrus<br />Mesial - ACA mainly & PCA to a slight extent <br />
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  14. 14. Venous drainage<br /> Superficial middle cerebral vein –lies in lateral fissure <br />Vein of Trolard (superior anastomotic vein) - connects sup middle cerebral vein to SSS<br />Vein of Labbe’ ( inferior anastomotic <br />vein ) - connects sup middle cerebral vein to Transverse sinus<br />
  15. 15. Post central gyrus<br />Granular cortex<br />Receives most of its afferents from VPL nucleus of thalamus<br />Projects to somatosensory association cortex (area 5)<br />Some parts (except hand & foot ) connected to opposite somatosensory cortex via corpus callosum<br />Representation of C/L side of body<br />
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  17. 17. Postcentral gyrus<br />Superior part represent the LL <br />Middle part -- the trunk & UL and <br />Lower part --the face<br />Amount of cortex devoted to any particular body area – proportional to sensory acuity <br />Tips of fingers & lips larger area of representation<br />
  18. 18. Posterior parietal region<br />Superior & inferior Parietal lobule<br />Connections <br />Post central gyrus<br />
  19. 19. Superior parietal area<br />Area 5b- occupies large portion of Sup parietal lobule <br />Extends over medial surface to include pre cuneus<br />No large pyramidal cells in layer V<br />Granular layer – great depth & density<br />
  20. 20. Inferior parietal area<br />Supra marginal & angular gyrus <br />No pyramidal cells <br />Granular cortex well developed<br />Close proximity to occipital & temporal lobe<br />
  21. 21. Parietal lobe functions<br />Difficult to describe due to bewildering range of symptoms <br />Simple functional division <br />Anterior region- post central gyrus / sensory strip<br />Posterior region – lies behind post central gyrus & is composed of tertiary cortex<br />
  22. 22. Functions of anterior region<br />Somato sensory perception<br />Tactile perception <br />Body sense<br />Visual object recognition<br />
  23. 23. Functions of posterior region<br /><ul><li>Language</li></ul> Reception of spoken language <br /> Reading <br /><ul><li>Spatial orientation & attention</li></ul>Route following <br />L- R discrimination <br /><ul><li>Calculation
  24. 24. Intentional movement
  25. 25. Praxis
  26. 26. Constructional ability </li></ul>Drawing<br /><ul><li>Short term auditory memory</li></li></ul><li>Optic radiation passes to Occipital Lobe via deep region . Lesion ---VF defects<br />Angular & supramarginal gyri of dominant hemisphere – imp in language & related functions<br />
  27. 27. APRAXIA<br /> Definition <br />Difficulty in performing skilled motor acts which can not be explained by an elementary sensory or motor deficit or language comprehension disorder<br />
  28. 28. Apraxia<br />Limb apraxia–<br />Limb kinetic / melokinetic<br />Ideomotor<br />Ideational<br />Disassociation <br />Conduction<br />Conceptual <br />Constructional & dressing –often associated with neglect & visual perceptual disorders<br />
  29. 29. Scattered , fragmentedLoss of spatial relationsFaulty orientation Energetic drawing Addition of lines to make drawing correct<br />
  30. 30. Coherent , simplifiedPreservation of spatial relationsCorrect orientation Slow & laborious Gross lack of details<br />
  31. 31. Tests<br />Pressure sensitivity<br />Two point discrimination<br />Point localisation <br />Position sense<br />Tactual object recognition<br />
  32. 32. Two point discrimination<br />Use a compass / calibrated 2 point esthesiometer<br />1mm tip of tongue<br /> 2-4 mm finger tips<br /> 4-6 mm dorsum of fingers<br /> 8-12 mm on palm<br />20-30 mm on dorsum of palm<br />
  33. 33. Amorphosynthesis<br />Inability to synthesize separate tactile sensations into perception of form <br />Lack of recognition of C/L body & of space<br />Astereognosis<br />Loss of ability to recognize object by touch <br />Unable to name objects, describe or demonstrate their use<br />Primary sensations intact <br />
  34. 34. Asomatognosia <br />Agnosia relates to patient’s own body <br />Types<br />Anosognosia<br />Autotopagnosia<br />
  35. 35. Anosognosia<br />Ignorance of existence of disease <br />More with (R ) PL lesions <br />U/L neglect may co exist<br />Deny weakness /sensory loss of affected limb<br />Extreme cases- disowns limb<br />
  36. 36. Autotopagnosia<br />Impairment in localization / naming of parts of own body<br />Patient unable to point to body parts named by examiner / move them <br />May not be able to identify them on examiner’s body / on diagram <br />
  37. 37. Finger agnosia<br />Inability to recognize , name & point to individualized fingers on self & others – usually middle 3 fingers<br />Form of autotopagnosia <br />B/L lesion<br />Central feature of Gerstmann syndrome<br />
  38. 38. Language dysfunction<br />Dominant PL lesion<br />Defect in reception of spoken language & reading<br />Conduction aphasia<br />
  39. 39. Agraphia<br />Spontaneous writing & writing on command more affected than copy righting<br />Irregular & tremulous script, misspelling , semantic & syntactial errors<br />Site – inferior parietal lobule<br />
  40. 40. Apractic agraphia- agraphia despite normal sensory, motor & visual feed back, word & letter knowledge<br />Lesion- Dom sup parietal lobule<br />Visuo spatial agraphia-neglect of (U) side of paper in writing<br />Lesion -- (R) temp- parietal junction<br />
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  42. 42.
  43. 43. Effects of unilateral disease of the parietal lobe, right or leftA. Corticosensory syndrome and sensory extinction B. Mild hemiparesis (variable), unilateral muscular atrophyin children, hypotonia, poverty of movement, hemiataxiaC. Homonymous hemianopia or inferior quadrantanopia(incongruent or congruent) or visual inattentionD. Abolition of optokineticnystagmus with target movingtoward side of the lesionE. Neglect of the opposite side of external space<br />
  44. 44. Effects of unilateral disease of the dominant (left) parietallobe<br />A. Disorders of language (especially alexia)B. Gerstmann syndrome (dysgraphia, dyscalculia, finger agnosia, right-left confusion)C. Tactile agnosia (bimanual astereognosis)D. Bilateral ideomotor and ideational apraxia<br />
  45. 45. Effects of unilateral disease of the nondominant (right) parietal lobeA. Visuospatial disordersB. Topographic memory lossC. Anosognosia, dressing and constructional apraxiasD. ConfusionE. Tendency to keep the eyes closed, resist lid opening,and blepharospasm<br />
  46. 46. Effects of bilateral disease of the parietal lobes<br />A. Visual spatial imperception, spatial disorientation, andcomplete or partial Balint syndrome<br />
  47. 47. THANK YOU<br />

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