Localization of Cortical Disorders Flashcards
Describe some possible sources of cortical dysfunction.
Vascular insult (stroke), trauma, tumors, toxins/infections, metabolic “derangements”, as well as both psychiatric and neurodegenerative disorders.
Distinguish between sleepiness and stupor.
What structures are implicated in altered consciousness?
Stupor is a more severe impairment of consciousness. It is associated with declines in attention, alertness, and awareness requiring constant stimulation to maintain.
The cerebral hemispheres, thalami, and the ARAS (ascending reticular activating system).
Name 5+ regions that comprise the frontal lobe.
What are its arterial supplies?
The primary motor cortex, premotor cortex, supplementary motor area, prefrontal cortex, broca’s area, frontal eye fields, and orbitofrontal cortex (arguably a limbic structure).
It is supplied by the MCA (laterally) and ACA (medially).
Primary Motor Cortex
What results from lesioning, or from overstimulation?
What is a Jacksonian march?
Primary Motor Cortex
Lesion causes a contralateral paresis. Activation causes clonic movements as seen in seizures.
A jacksonian march is a type of partial seizure that spreads within the motor cortex, causing spreading symptoms in the contralateral distal limbs and spreading towards the face.
Broca’s Area
Where is it located in L and R-handed people?
Describe the result of a lesion here.
Broca’s Area
It is on the left side for most people regardless of handedness. Some L-handers have bilateral activity.
Broca’s aphasia–lack of fluency, effortful and arduous speech with loss of repetition but full comprehension. Very frustrating for the patient.
Prefrontal Cortex
What is it tasked with?
What results from a lesion here?
Prefrontal Cortex
Sequencing, organizing (providing order), higher executive function, abstraction, problem solving. Also personality (think of Phineas Gage when you hear prefrontal cortex).
Executive dysfunction.
Orbitofrontal Cortex
What are its functions?
How is it usually lesioned?
What role does it play in Pick’s disease?
Orbitofrontal Cortex
Provides restraint–particularly involved in regulating social behavior.
Head trauma, meningiomas.
Pick’s disease (or frontotemporal dementia) involves the prefrontal cortex and the orbitofrontal cortex.
Mediofrontal Cortex
What are its functions?
What results from a lesion here?
Mediofrontal Cortex
It provides initiative for action/goal-driven behavior (think supplementary motor area). And inhibition of micturition???
Akinetic mutism, Abulia, and urinary incontinence.
Parietal Cortex
Distinguish between the consequences of somatosensory and associative cortex lesions.
Which hemisphere is important for spatial attention?
What is “apraxia”?
Parietal Cortex
Contralateral sensory loss vs stereoagnosis/graphesthesia, as well as contralateral neglect and apraxia.
Interestingly, spatial attention is more significant for the non-dominant hemisphere.
Inability to perform a task despite the mental and physical capacity to. Usually a skilled but everyday task.
What is “Gerstmann syndrome”?
A lesion to the parietal lobe and angular gyrus that causes agraphia, acalculia, finger agnosia, and R/L confusion.
What is Kluver-Bucy syndrome?
Bilateral damage to the amygdalas (within the temporal poles), resulting in hyperorality, hypersexuality, aggression/irritability/inappropriate fear responses, and anterograde amnesia.
What results from damage to the hippocampus?
Amnesia (eg atrophy from Alzheimer’s)
Partial seizures (eg from scarring)
Occipital Cortex
What is the significance of a visual defect that is homonymous?
Distinguish between a lesion of the optic nerve, and a lesion of the Meyer’s loop.
Why are many anopias macular sparing?
Occipital Cortex
Homonymous deficits (‘seen in both eyes’) are signs of cortical disruption.
A lesion of the optic nerve will eliminate visual input from one eye. A lesion of a Meyer’s loop will cause loss of a section of input from both eyes (the contralateral upper quartile).
Vascular insult to the occipital lobe tends to spare the occipital pole because of robust collateral circulation there.
Distinguish between Simultanagnosia, Optic Ataxia, and Ocular Apraxia.
Simultanagnosia is an inability to process the visual field as a whole.
Optic ataxia is the inability to point to or reach for objects in the visual field.
Ocular apraxia is the inability to foveate objects using saccades.
These are all part of balint syndrome, caused by Alzheimer’s and PCA/MCA watershed strokes.
