Agnosias_112345678765443356788899999-.pptx

Agnosia

1. AGNOSIAS

2. INTRODUCTION SIGMUND FREUD introduced the term in 1891 Agnosias (Gnosis- to know) are disorders of recognition and naming of object, in one sensory modality, in the presence of intact primary sensation Normal percept stripped of its meaning.

3. CRITERIA FOR THE DIAGNOSIS Failure to recognize an object Normal perception of the object, excluding an elementary sensory disorder Ability to name the object once it is recognized, excluding anomia as the principal deficit Absence of a generalized dementia

4. Agnosia results from lesions that disconnect and isolate visual, auditory and somatosensory input from higher level processing Defined as profound, modality-specific recognition impairment in the presence of normal primary sensory function that cannot be fully explained by: mental deterioration, attentional disturbances, unfamiliarity with the stimuli used to assess recognition abilities

5. TYPES Visual Auditory Tactile Important : rule out primary sensory disorder- test visual acuity/field, auditory function, aphasia, cognition and somatosensory functions

6. Visual agnosia

7. VISUAL AGNOSIA Cortical Visual Disturbances Cortical Visual Distortions Visual Object Agnosia Balint Syndrome and Simultanagnosia Optic Aphasia Prosopagnosia Klüver-Bucy Syndrome

8. CORTICAL VISUAL DISTURBANCES Cortical Blindness- Bilateral occipital lobe lesion Unaware that they cannot see, even confabulate visual descriptions or blame their poor vision on dim lighting or not having their glasses, describe objects they “see” in the room but walk into wall - ( Anton syndrome ) Perceptual deficit in which there is unawareness or neglect of the sensory deficit

9. CORTICAL VISUAL DISTURBANCES Blindsight or inverse Anton syndrome- preserved ability to react to visual stimuli, despite the lack of any conscious visual perception Deny blindness despite objective evidence of visual loss May react to more elementary visual stimuli such as brightness, size, and movement , whereas they cannot perceive finer attributes such as shape, color, and depth Subjects sometimes look toward objects they cannot consciously see

10. CORTICAL VISUAL DISTURBANCES Bonnet syndrome- Visual hallucinations in blindness Irritative lesions of occipital visual cortex produce unformed hallucinations of lines or spots , & of the temporal lobes produce formed visual images . Cortical blindness diagnosed by absence of ocular pathology, preservation of pupillary light reflexes, and associated neurological symptoms and signs

11. CORTICAL VISUAL DISTURBANCES B/L PCA territory stroke involves occipital lobes, hippocampus, medial temporal lobe- confused, agitated, short term memory loss HIE; PRES; Meningitis; SLE CJD- Heidenhain variant Posterior cortical atrophy syndrome in Alzheimer and other dementia Transient phenomenon in: Traumatic brain injury Migraine Epileptic seizures Complication of iodinated contrast procedures

12. Cortical Visual Distortions Positive visual phenomena- in migraine and visual field defects- NOT AGNOSIA Metamorphopsia – distortion shape Teichopsia - Scintillating scotoma, irregular shapes Macropsia and micropsia Alice in wonderland Syndrome- changes in shape and size

13. Achromatopsia – loss of colour vision Akinetopsia -loss of perception of motion Palinopsia - Perseveration of visual images

14. Allesthesia – spreadof visual image from a normal to a hemianopic field Polyopia – duplication of objects

15. COLOR VISION DEFICIT – Occipital lobe Achromatopsia – complete loss of colour vision occur either B/L or in one hemifield with lesions of visual association cortex areas 18 and 19 Color agnosia- confabulate an incorrect color name when asked color of object; normally perceived color cannot be properly recognized Difficulty naming or pointing to named colors Can match colors, normal color vision on Ishihara charts Lesions of the left occipital

16. VISUAL OBJECT AGNOSIA Fails to recognize objects by sight, with preserved ability to recognize them through touch or hearing, in the absence of impaired primary visual perception or dementia Appreciative visual object agnosia Associative visual object agnosia

17. Visual object agnosia will be unable to name or recognise a picture of a kangaroo The same patient will have no difficulty naming and describing the characteristics of a kangaroo if requested via the auditory modality. Anomia- will be unable to name the picture and may respond, “it’s found in Australia, it jumps…can’t think of its name,” demonstrating intact recognition. Semantic dementia have central loss of knowledge and will be unable to name the picture or demonstrate any knowledge of the object regardless of modality

18. APPERCEPTIVE VISUAL AGNOSIA Intact vision : Acuity, brightness discrimination, color vision, & other elementary visual capabilities Deficits: Abnormal Perception (pictures, letters, simple shapes) unable to access the structure or spatial properties of a visual stimuli and the object is not seen as a whole or in a meaningful way Cannot recognize, copy or match objects Useful tests- Incomplete letters and object decision from silhouettes

19. ASSOCIATIVE VISUAL AGNOSIA Failure of recognition, assign meaning to appropriately perceived objects Patients can copy or match pictures but they cannot name what they have drawn , excludes primary defect of visual perception Can recognize objects by tactile or auditor stimulus and have intact knowledge of objects Visual perception better than in apperceptive agnosia Lesion: bilateral inferior temporo-occipital junction and subjacent white matter

20. APPERCEPTIVE ASSOCIATIVE

21. Simultanagnosia Partial Balint syndrome deficit; described by Wolpert in 1924 Loss of ability to perceive more than one item at a time Sees details of pictures, but not the whole Seen in bilateral parieto-occipital strokes; posterior cortical atrophy and related neurodegenerative involving posterior parts of both hemispheres

22. Balint syndrome Bilateral hemisphere lesions, often involving the parietal and frontal lobes . Triad of deficits: (1) Ocular motor apraxia- inability to voluntarily shift gaze despite the intact function of extra-ocular muscles- psychic gaze palsy. (2) Optic ataxia- lack of coordination between visual inputs and and hand movements (3) Simultagnosia - Inability to identify different items in a visual scene simultaneously These deficits result in the perception of only small details of a visual scene, with loss of the ability to scan and perceive the “big picture.”

23. OPTIC APHASIA/Optic anomia Intermediate between agnosias and aphasias Cannot name objects presented visually but can demonstrate recognition of objects by pantomiming or describing their use Preserved recognition of the objects distinguishes it from associative visual agnosia Information about the object reach parts of the cortex involved in recognition in the right hemisphere, but the information is not available to the language cortex for naming

24. PROSOPAGNOSIA Inability to recognize faces Apperceptive prosopagnosia – inability to even perceive and process the face Associative prosopagnosia- inability to recognize or apply any meaning to face despite perceiving it.

25. KLÜVER-BUCY SYNDROME Visual agnosia Prosopagnosia Memory loss Language deficits Changes in behaviour, altered sexual orientation , placidity and excessive eating Bitemporal damage: Herpes simplex and surgical ablation. Connections appear to be disrupted between vision and memory and limbic structures, so visual percepts do not arouse their ordinary associations

26. Auditory agnosia

27. Cortical deafness Acquired bilateral lesions in Primary auditory cortex- Broadman area 41 and 42 ( HESCHL gyri) Auditory radiations projecting to HESCHL gyri Can hear noises but cannot appreciate their meaning Cannot understand speech or music Unilateral lesions- little effect on hearing

28. AUDITORY AGNOSIA Hear noises but not appreciate their meanings (1) Pure word deafness (2) Pure auditory nonverbal agnosia (3) Phonagnosia (4) Pure amusia

29. PURE WORD DEAFNESS/ Auditory verbal agnosia Inability to comprehend spoken words, with preserved ability to hear and recognize nonverbal sounds Disconnection of both primary auditory cortices from the left hemisphere Wernicke area Deaf hearing Cannot repeat words or write from dictation Spontaneous reading, writing speaking preserved Non speech auditory information processing - normal Comprehension of spokne words Impaired Non verbal sounds Can recognize Reading, writing, spoken speech Inatact

30. AUDITORY NONVERBAL AGNOSIA Inability to identify meaningful nonverbal sounds but have preserved Pure tone hearing and Language comprehension Bilateral temporal lobe lesions chiefly right

31. PHONAGNOSIA Failure to recognize familiar people by their voices ( analogous – prosopagnsoia ) Lesion: Right parietal lobe Difficulty in matching of unfamiliar voices Lesion: Unilateral or bilateral temporal lobe

32. AMUSIA Loss of musical abilities Recognition of melodies and musical tones Right temporal lobe Analysis of pitch, rhythm, and tempo Left temporal lobe Can sing from memory

33. Tactile agnosia

34. TACTILE AGNOSIAS Fail to recognise numbers or letters written on hand and contralateral he not able to recognise - parietal lobe Astereognosis – inability to identify object by touch Agraphesthesia - inability to recognise a written number or letter traced on the skin

35. TACTILE aphasia Inability to name a palpated object despite intact recognition of the object and intact naming when presented in other sensory modality

36. SUMMARY Disorders of sensory perception and recognition. It may be due to primary sensory cortical defects or its connections. Recognition not only requires primary sensations but also association of perceived items and previous sensory experience and associated memories

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