Cerebral Cortex I and Vascular Territories

Question 1

Location of the primary visual cortex

Answer 1

Question 2

Location of the primary auditory cortex

Answer 2

Question 3

When we say language function is usually in the left hemisphere, what we really mean to say is. . .

Answer 3

. . . language function is usually in the dominant hemisphere

Question 4

The “where” pathway

Answer 4

The connections between the occipital lobe and parietal lobe.

Visual information is processed here to determine where things are in space with respect to the body. Lesions here can cause neglect.

Question 5

Neglect

Answer 5

Caused by damage to the territory linking the occipital and temporal lobes, more commonly in the non-dominant parietal lobe, causing non-dominant-sided neglect.

Examination findings in patients with neglect may include extinction to double simultaneous stimulation, anosognosia, and sometimes unilateral asomatognosia.

Question 6

Angular gyrus

Answer 6

Located in the dominant hemisphere.

Lesions to this area cause Gerstmann’s syndrome: Left-right confusion, inability to count (acalculia), inability to name the fingers (finger agnosia), and inability to write (agraphia).

Question 7

Broca’s and Wernicke’s areas

Answer 7

Located in the dominant hemisphere.

Question 8

Apraxia

Answer 8

• Difficulty performing a complex learned motor action
• Caused by lesions within the parietal lobe, often on the dominant side
• Three types:
  
  • Limb-kinetic apraxia: difficulty performing these movements
  • Ideational apraxia: inability to conceive of the idea of how to accurately perform an action
  • Ideomotor apraxia: inability to convert an idea about how to do something into a motor plan.

Question 9

Ideomotor ataxia explanation

Answer 9

Affected patients may be able to explain the intended action but are unable to perform it normally, making errors in sequencing and/or timing of the component movements of complex learned actions.

Question 10

Amnesia

Answer 10

• Caused by lesions within the middle temporal lobes and hippocampus
• May be retrograde or anterograde

Question 11

Alexia

Answer 11

Caused by lesions to the inferior aspect of the domintant temporal lobe

Question 12

Prosopagnosia

Answer 12

• Inability to recognize faces
• Caused by lesions to the inferior aspect of the non-domintant temporal lobe

Question 13

Inferior frontal gyrus

Answer 13

Houses Broca’s area!

Question 14

Superior temporal gyrus

Answer 14

Houses Wernicke’s area, among other things.

Wernicke’s area is close to the border with the parietal lobe.

Question 15

Transcortical motor aphasia

Answer 15

This is essentially a Broca’s aphasia with preserved repetition

Question 16

The aphasia hierarchy

Answer 16

Question 17

Aphasias in which comprehension is impaired

Answer 17

Receptive aphasias

Question 18

Transcortical sensory aphasia

Answer 18

Essentially Wernicke’s aphasia with preserved repetition

Question 19

Global aphasia

Answer 19

Production, comprehension, and repetition are all impaired.

Question 20

Conduction aphasia

Answer 20

• Aphasia where the only focal deficit is repetition
• Caused by damage to the arcuate fasciculus

Question 21

Sudden-onset aphasia is most commonly due to ___.

Answer 21

Sudden-onset aphasia is most commonly due to stroke in the dominant-sided MCA area.

Question 22

Abulia

Answer 22

• Decreased initiative/motivation in speech, action, and emotion
• Can manifest as inability to make finalized decisons
• Caused by frontal lobe damage

Question 23

The thalamus and basal ganglia are . . .

Answer 23

. . . islands of gray matter in the center of the brain, surrounded by white matter.

Question 24

Thalamus

Answer 24

• A collection of nuclei, most of which project to one or more cortical regions
• Four basic types of circuitry pass through thalamic nuclei en route to the cortex:
  
  • Sensory pathways
  • Motor control pathways
  • Consciousness/arousal pathways
  • Cognition/emotion pathways

Question 25

Ventral posterior lateral nucleus

Answer 25

• Nucleus within the thalamus
• Takes in somatosensory information from the anterolateral and dorsal column pathways and relays it to the post-central gyrus

Question 26

Lateral geniculate nucleus

Answer 26

• Nucleus within the thalamus
• Takes in visual information from the optic tracts (so one visual field each, one on each side) and relays it through the inferior and superior radiations to the occipital lobe

Question 27

The basal ganglia are part of circuits that ___.

Answer 27

The basal ganglia are part of circuits that initiate and coordinate movements, and dysfunction in the basal ganglia leads to movement disorders

Question 28

Brain arterial supply diagram

Answer 28

Question 29

Vascular territories of brain - lateral view

Answer 29

Question 30

Vascular territories of brian - view along longitudinal fissure

Answer 30

Question 31

Brain watershed territories

Answer 31

Question 32

Anatomic and functional regions hit by MCA infarct

Answer 32

• Largest territory of any cerebral artery
• Parts of frontal, parietal, and temporal lobe
• Include the motor and premotor regions, somatosensory cortex, the frontal eye fields, the language areas, as well as parietal regions of spatial attention, and superior and inferior visual radiations
• Full left MCA syndrome causes right hemiplegia and hemisensory loss, aphasia, gaze deviation toward the left, and right homonymous hemianopia.

Question 33

Full left MCA syndrome

Answer 33

Full left MCA syndrome causes right hemiplegia and hemisensory loss, aphasia, gaze deviation toward the left, and right homonymous hemianopia.

Question 34

Full right MCA syndrome

Answer 34

A full right MCA syndrome causes left hemiplegia and hemisensory loss, left-sided neglect, gaze deviation to the right, and left-sided homonomyous hemianopia.

Question 35

M1 segment of the MCA

Answer 35

The MCA’s stem

Gives off the lenticulostriate penetrating branches that supply the basal ganglia and internal capsule before dividing into superior and inferior branches known as the M2 segments.

Question 36

M2 segments of the MCA

Answer 36

• The superior M2 branch of the MCA supplies Broca’s area (most commonly on the left), the motor cortex, and the superior visual radiation,
• whereas the inferior M2 branch supplies Wernicke’s area (most commonly on the left) and the inferior visual radiation

Question 37

Anatomic and function regions hit by ACA infarct

Answer 37

• ACAs supply the anterior, superior, and medial frontal lobes and the superior and medial parietal lobes—essentially all of the frontal and parietal lobes not supplied by the MCAs
• ACA strokes cause contralateral leg weakness and sensory loss more so than face and arm weakness and sensory loss
• ACA strokes can also cause cognitive changes such as abulia

Question 38

MCA, ACA, arms, and legs

Answer 38

One typically learns that the MCA supplies the face and arm areas on the lateral surface of the homunculus and the ACA supplies the leg area, so that MCA strokes cause contralateral face and arm weakness much more so than leg weakness, and ACA strokes cause contralateral leg weakness much more so than face and arm weakness.

This is true for the gray matter on the cortex surface, but of course, if white matter pathways are affected, this can cause a complete contralateral hemiparesis or hemiplegia affecting the face, arm, and leg

Question 39

Anatomic and functional regions hit by PCA infarction

Answer 39

• The PCAs supply the occipital lobes, inferior medial temporal lobes, and the thalami
• Deficits can include contralateral homonymous hemianopia or superior quadrantanopia, impaired short-term memory (with medial temporal or hippocampal involvement), alexia without agraphia (if dominant temporal lobe), prosopagnosia (if non-dominant lobe temporal lobe), and/or changes in cognition and/or level of arousal (if thalamus is involved)

Question 40

Lacunar strokes

Answer 40

• Caused by occlusion of small penetrating arteries affecting the subcortical white matter (internal capsule), subcortical gray matter (basal ganglia, thalamus or anterior pons)
• Syndromes include:
  
  • Pure motor stroke - posterior internal capsule or anterior pons
  • Pure sensory stroke - VPL/VPM nuclei of thalamus\
  • Ataxia-hemiparesis - internal capsule or anterior pons, involving the corticospinal tract and corticopontocerebellar fibers
  • Dysarthria–clumsy hand - internal capsule or anterior pons

Question 41

MCA-ACA watershed stroke

Answer 41

• Infarction in the MCA-ACA borderzone can cause proximal arm and leg weakness with preserved strength distally in the hands and feet

Question 42

MCA-PCA watershed stroke

Answer 42

• MCA-PCA watershed region is at the parieto-occipital junction
• When the MCA-PCA watershed region is affected bilaterally, the patient will often have deficits in visual attention that can include some or all of the elements of Balint’s syndrome: optic ataxia, ocular apraxia, and simultanagnosia

Question 43

ACA, MCA, PCA stroke summary image

Answer 43

Question 44

Lacunar stroke summary image

Answer 44

Question 45

Area of the brain associated with spatial reasoning, calculation, and attention

Answer 45

Question 46

Area of the brain associated with recognition memory

Answer 46

Question 47

Why is it that profound cases of neglect tend to be left-sided or non-dominant sided?

Answer 47

Both the right and left hemispheres can attend to the right, but only the right hemisphere can attend to the left.

Question 48

Limbic system summary image

Answer 48

Question 49

Ataxia vs Apraxia

Answer 49

Ataxia is a neurological sign wherein there is loss of coordination of muscles. It is a type of movement disorder. Apraxia, on the other hand, is the inability to execute complex, purposeful movements which have already been learnt by the person.