Localization and bx correlates Flashcards
Hippocampal disfunction
Ex HM:
- anterograde amnesia
- preserved working memory, retrieval of old
- drilled word recall, shapes - can repeat but gone after 20 min
Alzeimers = similar pattern
Overview of cortical networks
Limbic/memory (cingulate, hippo, amyg, mammilary, thalamus)
Language (L temp - parietal)
Visuospatial (R inf parietal)
Face/object recognition (occip - parietal)
Executive function (frontal)
Lesions anywhere in loop cause similar deficits
Transient global amnesia
Stress, Valsalva -> venous congestion -> hippocampal disfx
- retrograde amnesia (months-years) - recovers completely
- new consolidation - period “in hospital” is lost
- difficulty with drilled words
- lasts 2-12 h -> recover most fx
- DDx: stroke, epilepsy
Alcoholic memory
Wernicke’s encephalopathy
- acute dt thiamine deficiency
- confusion, ataxia, nystagmus, ophthalmoplelgia
Korsakoff’s syndrome
- sequelae of Wernicke’s (20%)
- hemorrhagic necrosis of mammillary, mediodorsal thalamus
- difficulty consolidating, confabulation
Goal of treating Wernicke’s is to prevent Korsakoff’s
Classic aphasia syndromes
Broca’s - narrow, defined region
- can’t generate, frustrated, can’t repeat
- transcortical motor (nearby) - can repeat but can’t produce
Conduction - arcuate fasciculus
- can understand and produce, can’t repeat
Wernicke’s - larger, more complex area
- can’t understand, nonsensical speech
- transcortical sensory (nearby) - can repeat but not follow command
Alexia, agraphia
Usually co-occur with aphasia - similar patterns
- Broca’s -> effortful, sparse, aggramatical
- Wernicke’s -> hypergraphic without understanding
Pure agraphia
- Exner’s area - L mid-frontal
- L supramarginal gyrus
Pure alexia
- L fusiform (inf parieto-temp)
L angular gyrus - can be either or combination
Overview of parietal syndromes
Superior (either side) - somatic association
- agraphesthesia (can’t place sensation)
- astereognosia (can’t ID object in hand)
L inferior
- angular - Gerstmann syndrome
- supramarginal - idiomotor apraxia - can’t imitate motions
R inferior
- contralateral neglect (without insight)
- localization and spatial disorders (ex dressing)
Gerstmann syndrome
L angular gyrus
R-L disorientation
Finger agnosia (can’t place sensations)
Agraphia
Acalculia
Overview of occipital pathways
Occip-parietal = WHERE - lesion -> Balint's syndrome Occip-temporal = WHAT - agnosia (can't name object) - prosopagnosia - can't ID faces (R fusiform)
Balint’s syndrome
Disruption of sup occip pathway
- ocular apraxia - “sticky” vision, can’t follow objects
- ocular ataxia - hand-eye coordination
- simultanagnosia - can’t interpret full visual field
Posterior cortical atrophy
Similar to Alzheimers (plaques, neurofibrillary tangles)
-> affects different functions -> vision, reading, comprehesion
- > Balint’s (“where” pathway)
- Gerstmann - spatial orientation, acalculia
- agnosia - “thought his wife was a hat”
- transcort sensory aphasia - difficulty understanding
Overview of frontal lesions
Almost always bilateral damage
Almost always combination of syndromes
Orbitofrontal -> disinhibition
Cingulate (ex ant cerebral infarct) -> abulia, apathy
Dorsolateral -> executive fx, working memory
Pick’s disease = degeneration with lesions
- L -> language aphasia
- R -> social cues and behavior
Overview of hallucinations
Absence of stimuli
Not asleep, no voluntary control
Deafferentiation - Bonnet, musical, phantom limb
- from secondary vs primary cortex
Abnormal stimulation - epilepsy, migraine
Subcortical - peduncular hallucinosis
“Higher order” processing - psychosis
Bonnet syndrome
Loss of visual input (ex chronic vision loss) -> hallucinations
More prevalent in dim lighting
Disappears if they close their eyes
Good insight into problem vs reality
Auditory - similar - musical hallucinosis with hearing loss
- can also be TBI, epilepsy, psychosis
- may have some control (ie “change song”)
Phantom limb
5-10% amputees
Usually painful, often feels malformed
May “move” under volitional control
Central - can’t just fix or block nerves
Peduncular hallucinosis
Subcortical lesion
- usually infarct
- brain stem, cerebellar, pontine, thalamus
- will have other symptoms of lesion (ex ophthalmoplegia)
Visual hallucinations
- vivid, entire visual field, usually nature scenes
- more vivid if eyes closed
Good insight into hallucination vs reality
Epilepsy and behavior
Temporal lobe -> Geschind’s syndrome (type personality)
Forced normalization/alternate psychosis
- treatment of seizures causes hallucinations
- normal EEG -> symptoms
- can last several weeks
Aggression - uncommon during ictal
- post-ictal - immediate, 5 minutes, generalized
- common, more common with R hemisphere?
- interictal - episodic discontrol
- rage episodes, out of proportion, 20 minutes
- L hemisphere, low IQ, depression
Geschwind syndrome
Type personality associated with temporal lobe epilepsy
“Limbic hyperconnection”
Religiousity, profuse writing
Philosophical, hyperemotional (can have rage episodes)
Hyposexual
Vs Kluver-Bucy syndrome = limbic disconnection
- placid, unemotional
- hypersexual
Pariteal association areas
Brodmann area 7 Visual and somatosensory -> spatial - orientation, sense of self/agency - activation proportional to attention Damage -> dec attention -> neglect if non-dom (R)
Working memory
Reverberatory circuits - loss of activity -> loss of information
Localized to type of info
- parietal = objects, spatial
- frontal - explicit
Temporal association cortex
Broadmann 21 and 22
Visual and auditory -> object recognition and language
Deficit -> agnosias (popagnosia = faces - usually non-dom)
- acalculia - usu dominant, inf and angular
Prefrontal association cortex
Dorsolateral = 9, 10, 46 - executive, working memory
Orbitomedial = 11, 12 - impulse control, personality
- mood ant cingulate
Key function = inhibition
Damage -> utilization (grabbing objects), perseveration
Voluntary movement
Begins in supplementary motor - readiness potential
(lesion -> abulia)
-> parietal - illusion/perception of agency
Disrupted connection -> alien hand syndrome (lack of agency)