Neuro: 4.8 - Localization Of Cortical Dysfunction

Front 1

What are some examples of dysfunctions of the cerebral cortex?

Back 1

- Seizures
- Metabolic derangements
- Toxins (alcohol, hallucinogens, sedatives, liver/kidney dysfunction)
- Stroke
- Migraine
- Psychiatric disorders
- Trauma
- Tumor
- Neurodegeneration
- Infection

Front 2

What are the levels of consciousness?

Back 2

- Awake state
- Sleepy
- Stupor
- Coma

Front 3

What level of consciousness is characterized by being able to maintain alertness, attention, awareness including awareness of self and environment?

Back 3

Awake state

Front 4

What level of consciousness is characterized by waning alertness after short periods without stimulation?

Back 4

Sleepy

Front 5

What level of consciousness is characterized by severely impaired alertness; attention, awareness only maintained with continued stimulation?

Back 5

Stupor

Front 6

What level of consciousness is characterized by loss of alertness, attention, awareness and arousability?

Back 6

Coma

Front 7

What state is characterized by being alert and aware but attention severely impaired / confused?

Back 7

Delirium

Front 8

What state is characterized by all 3 domains affected (alertness, attention, and awareness), but to a lesser degree than in a coma (some alertness maintained)?

Back 8

Encephalopathy

Front 9

What is similar about most patients with altered consciousness (from delirium to coma)?

Back 9

Either structural or functional abnormalities in one of the following regions:
- Diffuse bilateral cerebral hemispheres
- Bilateral thalami
- Brainstem ARAS (ascending reticular activation system)

Front 10

Why is there altered consciousness in "diffuse bilateral cerebral hemispheres"?

Back 10

- Because both hemispheres involved
- If only half the cerebrum involved, typically will NOT have altered consciousness (although they will have focal deficits)
- MRI: anoxic brain injury bilaterally to cortex and thalami

Front 11

Why is there altered consciousness in "bilateral thalamic lesions"?

Back 11

Because ARAS (ascending reticular activation system in brainstem) projects here on the way to the cerebrum

Front 12

What arteries supply the frontal lobe with blood?

Back 12

- Middle Cerebral Artery
- Anterior Cerebral Artery

Front 13

What are the important cortical areas of the Frontal Lobe?

Back 13

- Primary Motor Cortex
- Frontal Eye Fields (FEF)
- Broca's Area
- Prefrontal Cortex
- Orbitofrontal Cortex
- Mesiofrontal Cortex

Front 14

Primary Motor Cortex
- Functions?
- Symptoms if lesioned?
- Symptoms if activated (seizure)?

Back 14

- Voluntarily controls contralateral movement
- Lesion: contralateral hemiparesis
- Activation: contralateral clonic movements; Jacksonian March (seizures travel along gyrus and activate muscles in order seen on motor homunculus)

Front 15

Frontal Eye Fields (FEF)
- Functions?
- Lesions?

Back 15

- Contralateral saccades - voluntary eye movements to contralateral field (R FEF --> look L)
- Lesion: Ipsilateral gaze preference (think tongue - CN XII)
- E.g., L FEF stroke --> L gaze preference

Front 16

What explains this patient's symptoms?

Back 16

- Hemiparesis on R side --> L primary motor cortex
- Eye movements to L side --> L frontal eye fields (FEFs)
- Both supplied by L MCA

Front 17

Broca's Area
- Functions?
- Location?
- Loss of function?

Back 17

- Fluency of language
- Inferior frontal lobe in dominant hemisphere (for most it is L, but for some L handers it is bilateral) -- supplied by MCA
- Loss of function: Broca's Aphasia - Non-fluent Aphasia (non-fluent, halting, effortful speech, composed of only a few words that make sense)

Front 18

What are the characteristics of a Broca's Aphasia?

Back 18

- Non-fluent Aphasia
- Speech is non-fluent, halting, effortful, composed of only a few words that usually make sense
- Comprehension intact
- Agrammatic
- Repetition impaired

Front 19

Prefrontal Cortex
- Functions?

Back 19

- Provides ORDER
- Mediates personality, executive function, ability to sequence and organize tasks, abstract / problem solving

Front 20

Orbitofrontal Cortex
- Functions?
- Location?
- Injury?

Back 20

- Provides RESTRAINT
- Inhibits socially inappropriate behavior
- Part of limbic system (plays role in memory and emotions)
- 2 most common ways to lesion: head trauma as it rubs along base of skull or meningioma (tumor of meninges at base of skull)

Front 21

What parts of the brain are injured during head trauma?

Back 21

- Anterior tips of temporal poles
- Orbitofrontal cortex
- Occipital poles

Front 22

If a patient has a drastic change in personality, what part of the brain is responsible?

Back 22

Prefrontal cortex (responsible for order)

Front 23

If a patient has poor judgment (change from usual), what part of the brain is responsible?

Back 23

Prefrontal cortex (responsible for order)

Front 24

If a patient has inappropriate behaviors (sex with strangers) (change from usual), what part of the brain is responsible?

Back 24

Orbitofrontal Cortex (responsible for restraint)

Front 25

Case: Symptoms began 12 y ago, when patient became easily irritable, began drinking excessively, had sexual intercourse with homeless men, and became increasingly quarrelsome. After 6-8 years she could no longer hold down a job, neglected her hygiene, and started having crazier behaviors.

What is her diagnosis? Why?

Back 25

Frontotemporal Dementia (Pick's Disease)
- Changes in personality --> prefrontal cortex
- Poor judgment --> prefrontal cortex
- Inappropriate behavior --> orbitofrontal cortex

Front 26

What are the characteristics of Frontotemporal Dementia (Pick's Disease)?

Back 26

- Progressive dementia due to neurodegeneration
- Affects prefrontal cortex first --> personality changes, irritability, mood changes, poor executive function
- Eventually affects other regions of frontal cortex such as orbitofrontal cortex and temporal cortex
- Dementia occurs in mid life (50s) - much earlier than most cases of Alzheimer's
- Shortened lifespan

Front 27

Mesiofrontal Cortex
- Functions?
- Lesion?

Back 27

- Provides INITIATIVE
- Motivation and goal-directed behavior
- Micturition Inhibitory Center
- Lesion: akinetic mutism (no moving/talking), abulia (lack of initiative), and incontinence as seen in hydrocephalus (ventricles enlarge and stretch fibers traveling medially to spinal cord)

Front 28

What are the cortical areas in the Parietal Cortex?

Back 28

- Primary Somatosensory Cortex
- Association Cortex
- Non-dominant Association Cortex (R)

Front 29

Primary Somatosensory Cortex:
- Functions?

Back 29

Contralateral sensation

Front 30

Dominant Parietal Somatosensory Association Cortices:
- Functions?

Back 30

- Mediates higher order sensation
- Graphesthesia (ability to discern what is written on skin)
- Stereognosis (ability to discern object placed in hand)

Front 31

Non-dominant Parietal Somatosensory Association Cortices:
- Functions?
- Lesion?
- Location?

Back 31

- Drives spatial attention on both hemifields (R parietal cortex controls spatial attention on L hemifield >> R hemifield; L parietal cortex controls spatial attn on R hemifield primarily)
** Drives attention to world **
- Lesion: contralateral neglect and apraxia
- Usually on R side

Front 32

What is Graphesthesia? What part of the brain mediates it?

Back 32

- Ability to discern what is written on hand
- Parietal somatosensory association cortices

Front 33

What is Stereognosis? What part of the brain mediates it?

Back 33

- Ability to discern an object placed in the hand based on sensation
- Parietal somatosensory association cortices

Front 34

What is Neglect? What part of the brain mediates it?

Back 34

- Not paying attention to contralateral hemifield
- Right side (nondominant association cortice in parietal lobe) is most important for driving attnetion to the world
- E.g., R parietal lesion --> severe L neglect, ignore L side of world, bump into objects on L side, ignore L side of body

Front 35

How can you assess Neglect?

Back 35

- Have a patient bisect a line in the middle (neglect = off-center)
- Have them bisect all the lines on a piece of paper in the middle (neglect = only bisect on one half)
- Have them circle a certain letter on a page full of letters (only circle letter on one half)

Front 36

When you have a patient draw the face of a clock, put all the numbers in, and put the hands at 10 past 11, what are you assessing?

Back 36

- Neglect (non-dominant association cortex of parietal lobe)
- Executive function (prefrontal cortex)

Front 37

What is Apraxia?

Back 37

- Inability to perform a skilled task (e.g., brushing teeth, combing hair, dressing, tying shoe lace)
- Ability to execute a learned task = PRAXIS

Front 38

What is Gerstmann Syndrome?

Back 38

- Lesion of dominant (L) parietal cortex (angular gyrus)
- 4 components to clinical syndrome:
- Agraphia (inability to write)
- Acalculia (inability to calculate)
- Finger Agnosia (inability to recognize fingers)
- R/L confusion (can't discern between R and L)

Front 39

What are the cortical areas of the Temporal Lobe?

Back 39

- Wernicke's Area
- Medial Temporal Lobe

Front 40

Wernicke's Area
- Functions?
- Location?
- Lesion?

Back 40

- Comprehension of language
- Superior temporal gyrus in dominant hemisphere (usually L)
- Lesion: fluent aphasia - lots of nonsensical gibberish (may or may not be aware that it is not correct despite not comprehending); can't follow commands, impaired repetition
- Small branch of MCA

Front 41

What are the characteristics of Conduction Aphasia? What can cause it?

Back 41

- Inability to repeat
- Arcuate fibers damaged
- Smaller branch of MCA stroke

Front 42

What are the characteristics of Global Aphasia? What artery can cause a stroke in this area?

Back 42

- Impaired comprehension, repetition, and fluency
- Usually no language
- Due to full MCA stroke at its proximal origin (where ICA divides into ACA and MCA)

Front 43

What are the symptoms of Kluver-Bucy Syndrome?

Back 43

- Hyperorality (pt explores environment w/ mouth)
- Inappropriate sexual displays (removing clothes, masturbation in public, inappropriate kissing/flirting)
- Irritability and aggression
- Anterograde amnesia (amygdala)
- Alternating episodes of depression and overactivity

Front 44

What causes Kluver-Bucy Syndrome?

Back 44

Bilateral anterior temporal poles and bilateral amygdala injuries (commonly from head trauma)

Front 45

What issues affect the medial temporal lobe?

Back 45

- Hippocampal atrophy - neuronal degeneration in hippocampus occurs early in Alzheimer's disease
- Hippocampal sclerosis - scarring of hippocampus is thought to cause or be the result of uncontrolled complex partial seizures

Front 46

What are the areas of the cortex in the Occipital Lobe?

Back 46

Primary Visual Cortex

Front 47

What problems are associated with defects in the primary visual cortex of the occipital lobe?

Back 47

- Visual field defects (VFD)
- Monocular VFD --> lesion anterior to chiasm
- Binocular VFD --> lesion posterior to chiasm
- Homonymous = affecting both sides

Front 48

If there is a lesion to the RIGHT occipital cortex, how will vision be affected?

Back 48

- L Homonymous Hemianopia
- Right occipital cortex mediates vision from Left hemifield of both eyes

Front 49

If there is a monocular visual defect, what is likely the cause?

Back 49

Lesion anterior to the optic chiasm (B)

Front 50

What does a homonymous hemianopia tell you about the lesion?

Back 50

- Affects both sides
- E.g., R homonymous hemianopia indicates that R field on both eyes are affected
- Indicates a lesion in the cortex / subcortex

Front 51

What structure connects the lateral geniculate nucleus and the visual cortex?

Back 51

Optic Radiations

Front 52

How does a lesion to the optic radiations affect vision?

Back 52

- Lesion to Meyer's loop (temporal optic radiations) --> contralateral superior quadrantanopia
- Lesion to Parietal Optic Radiations --> contralateral inferior quadrantanopia

Front 53

How does a PCA stroke affect vision?

Back 53

- Homonymous hemianopia with macular sparing
- May occur due to dual blood supply to occipital pole (PCA and MCA)
- Outer tip of calcarine cortex is representative of macular vision
- Inner portions of calcarine cortex represent peripheral vision

Front 54

What are the symptoms of Balint Syndrome?

Back 54

- Simultanagnosia (inability to perceive visual field as a whole)
- Optic Ataxia (inability to point to objects in visual field)
- Ocular Apraxia (inability to look at objects in visual field using saccades)