Higher-Order Cerebral Function

Question 1

Disconnection syndromes

Answer 1

result when a lesion in the white matter disconnects the network. for example, white matter lesion can disrupts connections between the visual cortex and the language processing areas, causing a patient to lose ability to read.

Question 2

Handedness

Answer 2

approximately 90% of the population is right-handed. Although each hemisphere controls simple movements of the contralateral limbs, skilled complex motor tasks for both right and left limbs are programmed mainly by the dominant, usually left, hemisphere. thus, left hemisphere lesions more often result in apraxia, a disorder formulating skilled movements.

Question 3

Left hemispheric dominance

Answer 3

left hemisphere dominant for 95% of right-handers, and in over 60-70% of left-handers. Left handers tend to have significant bilateral representation of language, especially if there is a family history of left-handedness or ambidexterity. thus, they often recover language more quickly following stroke than right-handers.

left does detailed analytic abilities and complex motor planning (praxis).

Question 4

Non-dominant hemisphere specialization

Answer 4

appears to be generally more important for complex visual-spatial skills, for imparting emotional significance to events and language, and for music perception. Both hemispheres are involved in attention to the contralateral environment, but only the right hemisphere is significantly involved in attending to both sides. Lesions of the right hemisphere usually cause marked inattention to the contralateral left side, even in individuals who are right hemisphere dominant for language.

causes impairments in spatial attention and complex visual-spatial abilities, especially those involving spatial orientation and perception of the overall gestalt, or big picture.

Question 5

Dominant vs. Nondominant Hemisphere functions

Answer 5

Left: Language
Right: Prosody (emotion conveyed by tone of voice)

Left: Skilled motor function (Praxis)
Right: Visual-spatial analysis and spatial attention

Left: arithmetic: sequential and analytical calculating skills
Right:Arithmetic: ability to estimate quantity and to correctly line up columns of numbers on the page

Left: Musical ability; sequential and analytical skills in trained musicians
Right: Musical ability: in untrained musicians, and for complex musical pieces in trained musicians

left: sense of direction: following a set of written directions in sequence
Right: Sense of direction: finding one’s way by overall sense of spatial orientation.

Question 6

Posterior parietal and temporal association cortex

Answer 6

more involved in interpreting perceptual data and assigning meaning to sensory information

Question 7

anterior frontal association cortex

Answer 7

more important for planning, control, and execution of actions

Question 8

arcuate fasciculus

Answer 8

subcortical white matter pathway connecting Wernicke’s and Broca’s areas

Question 9

angular gyrus

Answer 9

connections to wernicke’s area to assist in comprehension, but it is also important for written language. when reading, visual information first reaches primary visual cortex in the occipital lobes, is processed in visual association cortex, and then travels anteriorly via the angular gyrus to reach the language areas.

Question 10

Connections with language areas

Answer 10

Language networks have important reciprocal connections with subcortical structures such as the thalamus and basal ganglia. Lesions of the thalamus, basal ganglia, or subcortical white matter in the dominant hemisphere can produce aphasia that can be mistaken for a cortical lesion.

Question 11

Aphasia

Answer 11

a defect in language processing caused by dysfunction of the dominant cerebral hemisphere.

Question 12

Broca’s aphasia

Answer 12

most commonly caused by infarct in the territory of the left MCA superior division.

most salient feature is decreased fluency of spontaneous speech.

Guidelines

• phrase length of fewer than 5 words
• number of content words (nounds) exceeds the number of function words (prepositions, articles, and other syntactic modifiers).
• Word generation tasks, such as FAS can be useful for detecting subtle decreases in verbal fluency.
• Prosody (the normal melodious intonation of speech that conveys the meaning of sentence structure) is lacking in patients with Broca’s.

has a resulting effortful, telegraphic quality, with a lack of grammatical structure and a monotonous sound.

• can have paraphasia, but less common than in Wernicke’s.
• marked naming difficulties

lesions in broca’s causes a disconnection from Wernicke’s area. Therefore, repetition is also impaired. Tend to have most difficulty repeated phrases in a high content of function words, such as no ifs, and, or buts or “If I were here, she would be there.” Comprehension is relatively intact. but one notable exception is impaired comprehension of syntactically dependent structures. for example, when hearing a passive sentence such as “The lion was killed by the tiger,” a patient often incorrectly chooses the tiger as the animal that is dead.

writing and reading aloud in Broca’s have a slow, effortful agrammatical quality that is similar to the deficits in spoken language. Reading comprehension is often relatively spared, except for syntactically dependent structures.

Question 13

Commonly associated features in Broca’s aphasia

Answer 13

• dysarthria
• right hemiparesis of the face and arm more so than the leg, especially when left MCA superior division is the cause.
• normal visual fields
• frustration and depression
• apraxia involving the nonparetic left side of the body and oral-buccal-lingual structures

Question 14

Little broca’s vs. big broca’s aphasia

Answer 14

Big: caused by large lesions, such as MCA superior division, which can involve much of the dominant frontal lobe, as well as subcortical structures. initially a global aphasia that improves during recovery to settle into a broca’s aphasia.

Little: caused by smaller lesions, confined to the region of the frontal operculum, including broca’s area. there is initially broca’s aphasia, which improves during recovery to only mildly decreased fluency and some naming difficulties.

Question 15

Wernicke’s aphasia

Answer 15

caused by a lesion of wernicke’s area and adjacent structures in the dominant temporoparietal lobes. The most common etiology is infarct in the left MCA inferior division territory, although other lesions can also provide markedly impaired comprehension. Patients with severe wernicke’s aphasia do not respond appropriately to questions and follow virtually no commands. Interestingly, a few commands relating to axial muscles, especially “close your eyes” and sometimes “stick out your tongue,” may elicit a correct response despite severe wernicke’s aphasia.

Spontaneous speech has normal fluency, prosody, and grammatical structure. However, impaired lexical function results in speech that is empty, meaningless, and full of nonsensical paraphasic errors. Naming is impaired. Lesions in this area also result in disconnection from broca’s area, causing impaired repetition. Reading and writing show similar impairments to the speech deficits in Wernicke’s aphasia, And consist of fluent, but meaningless, paraphasic renditions.

Question 16

Commonly associated features in wernicke’s aphasia

Answer 16

contralateral visual field cut, especially of the right upper quadrant due to involvement of the optic radiation. Apraxia may be present but it can be difficult to demonstrate because of impaired comprehension. Dysarthria and right hemiparesis are usually absent or very mild. In marked contrast to broca’s aphasia, patients often appear unaware of their deficit (anosognosia), behaving as if carrying on a normal conversation despite their markedly abnormal speech. Angry or paranoid behavior may occur, causing this occasionally to be misdiagnosed as a psychotic disorder.

Question 17

Other names for broca’s aphasia and wernicke’s aphasia

Answer 17

Broca’s: Expressive aphasia, motor aphasia, anterior aphasia, nonfluent aphasia
Wernicke’s: receptive aphasia, sensory aphasia, posterior aphasia, fluent aphasia
Note that these terms are not preferable, because they do not completely or accurately describe the aphasia’s.

Question 18

Global aphasia

Answer 18

Impaired fluency, impaired comprehension, and impaired repetition. Can be seen in large left MCA infarcts that include both the superior and the inferior divisions. It can also be seen in the initial stages of large left MCA superior division in parks that eventually improve to become broca’s aphasia (big broca’s) and in large subcortical infarcts, haemorrhages, or other lesions.

Question 19

Conduction aphasia

Answer 19

Normal fluency and normal comprehension, but impaired repetition. This is caused by an infarct or other lesions in the Peri-sylvian area that interrupt the arcuate fasciculus or other pathways in the vicinity of the supramarginal gyrus that connect wernicke’s area to broca’s area. Speech is fluent, paraphasic errors are common, and naming is often impaired, which can lead to a misdiagnosis of Wernicke aphasia. Unlike the case with Wernicke’s aphasia, however, comprehension is spared.

Question 20

Transcortical aphasias

Answer 20

Resemble broca’s, wernicke’s, and global aphasia’s, except that repetition is spared. The classic calls of transcortical aphasia is watershed infarcts, Which spare broca’s area, wernicke’s area, And their interconnections but damage other language areas in the frontal or temporoparietal cortices. Transcortical aphasia’s are also common in subcortical lesions, such as those involving the basal ganglia or thalamus in the dominant hemisphere. In addition, transcortical aphasia is a common pattern seen during recovery from other aphasia syndromes.

Question 21

Transcortical motor aphasia

Answer 21

Like Broca’s aphasia, but with spared repetition. Possible cause is ACA- MCA watershed infarct. This lesion destroys connections to other regions of the frontal lobe that are needed for broca’s area to function in language formulation. However, Peri-Sylvian connections from posterior to anterior language areas are left intact, enabling repetition.

Question 22

Transcortical sensory aphasia

Answer 22

Like Wernicke’s aphasia, but with spared repetition. MCA- PCA watershed infarcts are one possible cause of this disorder. Connections to structures in the brittle lobe and temporal lobe that are needed for wernickes area to function are destroyed, while the Peri-sylvian area Is left intact. The result is a condition that resembles Wernicke’s aphasia, except that repetition is spared.

Question 23

Mixed transcortical aphasia

Answer 23

Impaired fluency and impaired comprehension, as in global aphasia, but with intact repetition. Also called isolation of the language areas. A possible cause is combined MCA- ACA and MCA- PCA watershed infarcts, although this form of aphasia is often seen in subcortical lesions as well.

Question 24

Anomia or dysnomia

Answer 24

Normal fluency, normal comprehension, normal repetition, but have some naming difficulties and occasional paraphasias. Naming difficulties can be severe or relatively mild. Causes of anomic aphasia are numerous and include subcortical or cortical lesions in the dominant hemisphere and recovery from more severe forms of aphasia.

Question 25

Alexia and agraphia

Answer 25

Alexia: Impairments in reading
Agraphia: Impairments in writing

these can be caused by deficits in central language processing and not by simple sensory or motor deficits. Alexia and agraphia can each occur in isolation, or they can occur together. In patients with aphasia, agraphia is invariably present. This cooccurrence may be due to the fact that normal writing requires intact functioning of the entire language apparatus. When alexia or agraphia occurs as part of an aphasic disorder, the reading and writing abnormalities tend to parallel those of the aphasic syndrome for spoken language. Lesions that cause aphasia are the most common cause of alexia and agraphia

Question 26

Agraphia without aphasia

Answer 26

Can be seen in lesions of the inferior parietal lobule of the language- dominant hemisphere. This may or may not be accompanied by other features of gerstmann syndrome. Writing requires focused attention and is therefore usually severely abnormal in patients with global confusional disorders. In addition, agraphia in the hand ipsilateral to the language dominant hemisphere can occasionally be seen in lesions of the corpus callosum Because of disconnection of language (usually left hemi) from motor function (right hemisphere for left handed).

Question 27

Alexia without agraphia

Answer 27

First described by Dejerine in 1892
Caused by a lesion in the dominant occipital cortex extending to the posterior corpus callosum, often a PCA infarct. The lesion in the dominant occipital cortex prevents the processing of visual information from the right hemifield, including written material. A right hemianopia is therefore usually present. Meanwhile, information about the left hemifield that has reached the right occipital cortex is prevented from crossing to the language areas by the lesion in the posterior corpus callosum. This is a disconnection syndrome.

These patients are able to write normally, but they cannot read even their own writing. They can name words that are spelled out loud to them. Other mild deficits that can be present include some degree of anomia, especially color anomia. However, significant aphasia is not usually present.

Question 28

Agnosia

Answer 28

Defined by Teuber as “a normal percept stripped of its meaning.”

Question 29

Gerstmann’s syndrome

Answer 29

When all 4 sumptoms of agraphia, acalculia, right-left disorientation, and finger agnosia are all present, this strongly localizes to the dominant inferior parietal lobule, in the region of the angular gyrus. It can occur as a relatively pure syndrome, but it is more often accompanied by other deficits localizing to the dominant inferior parietal lobule, such as a contralateral visual field cut, alexia, anomia, or more severe aphasia.

Question 30

ideomotor apraxia

Answer 30

inability to carry out an action in response to verbal command, in the absence of any comprehension deficit, motor weakness, or incoordination. Caused by inability to formulate the correct movement sequence.

can ask: salute the flag, brush hair, light a match and blow it out, etc.

these patients make awkward looking attempts and perform tasks ineffectually. In mild apraxia, they may make body part as tool substitutions.

Apraxia is not a very well localized disorder, and it can be caused by lesions in many locations. However, there is an association between apraxia and aphasia: at least 1/3 of patients with aphasia have some apraxia, and apraxia of the oral and buccal muscles is particualrly common in Broca’s aphasia. Apraxia can affect orofacial, proximal, or distal limb movements differently. They may have particular difficulty puckering their lips or sticking out their tongues on command, while others may have more difficulty with other body movements.

Question 31

Aphemia

Answer 31

severe apraxia of speech articulation without a language disturbance. usually caused by a small lesion of the dominant frontal operculum restricted to Broca’s area. they have normal written language. They have effortful, poorly articulated speech sometimes referred to as foreign accent syndrome. Severe aphemia can cause muteness, with preserved writing ability. Aphemia also occurs as a developmental disorder in children, often without a visible lesion on imaging studies. It is referred to as verbal apraxia in this context.

Question 32

Cortical deafness

Answer 32

caused by bilateral lesions of the primary auditory cortex in Heschl’s gyrus. Patient’s are often aware that a sound has occured but are unable to interpret verbal stimuli and cannot identify nonverbal stimuli such as a telephone ringing or a dog barking.

Question 33

Pure word deafness

Answer 33

AKA verbal auditory agnosia- can identify nonverbal sounds but cannot understand any spoken words. Unlike Wernicke’s aphasia patients, these patients can read and write normally. ALthough a few paraphasic errors may occur early on, speech is usually normal within a few days of onset. The lesion is usually an infarct in the auditory area of the dominant hemisphere that extends to the subcortical white matter, cutting off auditory input from the contralateral hemisphere as well. also a disconnection syndrome.

they can usually sepak normally but cannot understand speech, even their own speech if it is recorded and played back to them. some cases of this have also been reported with bilateral lesions of the superior temporal gyrus.

Question 34

Nonverbal auditory agnosia

Answer 34

patients understand speech but cannot identify nonverbal sounds. The lesion in nonverbal auditory agnosia is usually located in the nondominant hemisphere.

Question 35

Contralateral hemineglect

Answer 35

most often occurs with lesions of the right parietal or frontal cortex.Can also occasionally occur with lesions of the cingulate gyrus, thalamus, basal ganglia, or midbrain reticular formation. It is usually more pronounced and persistent with right hemisphere lesions.

During the recovery period, patients with hemineglect are more prone to injury and falls, and they may inadvertantly bump or injure their contralateral side. Driving should be avoided until patients are able to demonstrate normal attention to both sides.

Associated features include:

1. Sensory neglect: ignoring visual, tactile, or auditory stimuli in the contralateral hemispace
2. motor-intentional neglect, in which patients perform fewer movements in the contralateral hemispace
3. combined sensory and motor neglect
4. conceptual neglect, in which the patients’ internal representations of their own bodies or of the external world exhibit contralateral neglect.

anosognosia for the deficit is common.

Question 36

Tests for sensory neglect

Answer 36

visual, tactile, or auditory extinction on double simultaneous stimulation. must first establish normal primary sensation by testing each side alone. With subtle neglect, extinction may be inconsistent.

Question 37

allesthesia

Answer 37

common with patients with hemineglect, in which they erroneously report the location of a stimulus given to the left side of the body as being on the right.

Question 38

Testing for Motor-Intentional Neglect

Answer 38

observe for akinesia or decreased spontaneous movements on unilateral limbs or trunk, or decreased eye movements towards the neglected side. A marked ipsilateral gaze preference (toward the lesion) is common, especially in acute frontal or parietal lesions. Patients may exhibit motor impersistence, especially of the contralateral limbs. They may appear to have decreased motor power, but upon further prompting can demonstrate normal power. The examiner can demonstrate motor extinction with the patient’s eyes closed by randomly intermixing commands to raise the right arm, left arm, or both.

Tactile response test- can be helpful for those with encephalopathy or difficulty following commands. Pt is instructed to raise whichever limb is touched, obviating the need for them to attend to and interpret the commands “right” “left” or “Both.” Have them close their eyes. this is sensitive to both sensory and motor neglect.

To test motor neglect in isolation, a variant test, called the crossed response test, can be used. The pt. is asked to move the limb opposite the one touched. other tests of motor neglect, or of directional motor bias, include asking the patient to close their eyes and then point to a table while blindfolded. Some patients exhibit spatial akinesia, in which limb movements are impaired when the limbs are located in the neglected hemispace. The examiner can demonstrate this deficit by asking patients to cross their arms during the test.

Question 39

Allokinesia

Answer 39

seen in motor-intentional neglect, in which the patient inappropriately moves the normal limb when asked to move the neglected limb.

Question 40

Combined testing for sensory and motor neglect

Answer 40

tactile response test.

• many pen and paper tests. line bisection test and other cancellation tests.
• drawing: clock drawing. other drawings, such as flower, house etc. or to copy simple or complex figures.
• reading a newspaper or magazine.
• describe a picture/scene
• writing sample (tend to crowd words on one side of the page).

Question 41

conditions in which anosognosia is common

Answer 41

hemineglect, right hemisphere lesions, Wernicke’s aphasia, frontal lobe disorders, amnesia with confabulation (such as in Wernicke-Korsakoff syndrome), and cortical blindness. Also in psychiatric conditions such as schizophrenia and bipolar disorder.

Question 42

Anosodiaphoria

Answer 42

common in patients with right hemisphere lesions and hemineglect, in which they are aware that they have severe deficits yet show no emotional concern or distress about it.

Question 43

hemiasomatognosia

Answer 43

manifestation of hemineglect (conceptual) , in which patients deny that the left half of their body belongs to them. May be distressed that “someone left an arm in my bed.” or may claim that their left extremities belong to someone else or that they are not even limbs at all.

Question 44

Conceptual neglect

Answer 44

may have abnormal internal representations or memories of imagined scenes or experiences. For example, patients with hemineglect who were asked to recall various landmarks from a square in Milan while facing the cathedral could recall details on only the right side of the square. when they were then asked to imagine themselves facing away from the cathedral, the patients were able to describe details on the opposite side of the square.

Question 45

Other clinical features of nondominant hemisphere lesions

Answer 45

most common difficulty encountered by patients with nondominant-hemisphere lesions is in tasks requiring visual-spatial analysis, or constructional abilities, such as drawing pictures or arranging blocks in specific geometric patterns. Pts may also have marked difficulty judging or matching the orientation of lines displayed at different angles. Deficits in these tasks are usually most severe with right parietal lesions, but they can also be seen with lesions in other locations in the right hemisphere, as well as with lesions of the left parietal lobe.

Pts with nondominant hemisphere lesions often have trouble appreciating the gestalt, or overall spatial arrangement, in such tasks.

In contrast, patients with dominant hemisphere lesions tend to understand the overall concept yet omit certain important details.

NDH lesions can result in relatively severe personality and emotional changes. They may appear bland or apathetic and, in addition to hemineglect, they often display an overall decrease in level of alertness and attention, especially if they have acute lesions. Irritability is also a common manifestation.

Right parietal infarcts can cause bilateral ptosis, lying in bed with both eyes forcibly closed and becoming very nasty when one attempts to examine them. Some are overtly psychotic and have delusions and hallucinations.

NDH lesions also cause difficulty comprehending emotional content of others’ speech (receptive aprosody) and conveying appropriate emotional expression in their own speech (expressive aprosody).

Right hippocampal formation lesions, such as mesial temporal sclerosis, can cause deficits in visual-spatial memory. For example, they may be able to copy a picture, but they cannot draw it from memory a few minutes later. Impaired geographic orientation, or sense of direction, was thought to be associated with right temporal lesions, although recent studies have emphasized the importance of the right parietal or right occipitotemporal cortex.

Many patients with right temporal seizures or lesions have increased tendency to experience deja vu and other mystical or religious phenomena. Right hemi lesions may also be associated with rare but intriguing disorders such as Capgras syndrome, in which patients insist that their friends or family members have all been replaced by identical-looking imposters.; Fregoli syndrome, in which patients believe that different people are actually the same person who is in disguise; and reduplicative paramnesia, in which patients believe that a person, place, or object exists in two identical copies.

Question 46

3 functional domains of the frontal lobes

Answer 46

1. Restraint: inhibition of inappropriate behaviors. judgment, foresight, perseverance, delaying gratification, inhibiting socially inappropriate responses, self-governance, concentration
2. Initiative: motivation to pursue positive or productive activities. Curiosity, spontaneity, motivation, drive, creativity, shifting cognitive set, mental flexibility, personality
3. Order: the capacity to correctly perform sequencing tasks and a variety of other cognitive operations. abstract reasoning, working memory, perspective taking, planning, insight, organization, sequencing, temporal order

Question 47

3 main surfaces of the frontal lobe

Answer 47

1. lateral
2. medial
3. orbitofrontal

Question 48

location of the frontal eye fields

Answer 48

in the premotor cortex (which lies just in front of the primary motor cortex on the lateral surface of the frontal lobes) and extends anteriorly.

Question 49

Prefrontal cortex

Answer 49

portions of frontal lobe lying anterior to the motor, premotor, and limbic areas. It is the largest part of the frontal lobes and consists of higher-order heteromodal association cortex.

Question 50

Most important thalamic nucleus with bidirectional connections to the prefrontal cortex

Answer 50

mediodorsal nucleus (although connections with the medial pulvinar and intralaminar nuclei are present as well).

Question 51

Working memory

Answer 51

ability to hold in a limited amount of info in an immediately available store while a variety of cognitive operations are performed. Dorsolateral prefrontal cortex is important for working memory.

Question 52

Dorsolateral prefrontal cortex and role in learning

Answer 52

research shows activation in this region along with teh medial temporal lobe in successful learning of new information (left for verbal and right for visual).

Question 53

Wisconsin card sorting test

Answer 53

requires shifting cognitive set- they must have mental flexibility to infer that the rules for the sorting task they are performing change repeatedly. associated with the dorsolateral frontal cortices.

Question 54

distinction between dorsolateral convexity lesions vs. ventromedial orbitofrontal cortex

Answer 54

dorsolateral convexity lesions tend to produce an apathetic, lifeless, abulic state, while ventromedial orbitofrontal lesions lead to impulsive, disinhibited behavior and poor judgment. In clinical practice, numerous exceptions to this dichotomy exist. Many frontal lesions affect both areas, making the usefulness of the classification somewhat limited.

Question 55

abulia

Answer 55

seen in frontal lobe dysfunction. passive and apathetic, exhibiting little spontaneous activity, markedly delayed responses, and a tendency to speak briefly or softly. In extreme, they may be totally immobile, akinetic, and mute but will continue to appear awake, sitting with their eyes open.

Question 56

disinhibition

Answer 56

seen in frontal lobe dysfunction. silly behavior, crass jokes, and aggressive outbursts.

Question 57

witzelsucht

Answer 57

inappropriate jocularity seen in frontal lobe dysfunction. seeming unconcerned about potentially serious matters.

Question 58

Incontinence related to frontal lobe dysfunction

Answer 58

can be seen in frontal lobe disorders affecting the medial frontal regions. Patients are characteristically unconcerned about their incontinence.

Question 59

verbal fluency and frontal lobe dysfunction

Answer 59

word generation tasks can be used to detect subtle decreases in verbal fluency and are sensitive to dominant hemisphere frontal dysfunction.

Question 60

paratonia

Answer 60

or gegenhalten, seen in frontal lobe lesions, in which tone is increased, but in a manner in which the patient appears to resist the movements of the examiner in an almost willful fashion.

Question 61

Primitive reflexes

Answer 61

grasp reflex. can detect more subtle dysfunction by distracting the patient in conversation.

suck reflex- elicited by touching the patient’s lips with a cotton swab

snout: elicited by tapping the patient’s lips
root: elicited by stroking the patient’s cheek or holding an object near the patient’s mouth.

Question 62

Evaluating frontal lobe function Outline

Answer 62

1. history and behavioral obs
   a. best test is real world; history from family or other contacts may be more revealing than patient exam.
   b. behavioral obs, looking for:
   - abulia
   - inappropriate jocularity (witzelsucht)
   - other abnormalities of comportment or insight
   - confabulation
   - utilization behavior and environmental dependency
   - perseveration, impersistence, and spontaneous frontal release signs
   - incontinence

II. Mental status exam
a. attention
-digit span forward and backward
-months forward and backward
b. memory
c. perseveration and set-shifting ability
-bedside: Luria alternating sequencing tasks (written, manual)
-formal testing: trails b, WCST
d. ability to suppress inappropriate responses
-bedside: auditory or visual go-no-go tests
-formal: Stroop
e. word generation, figure generation
-FAS test or other word generation tests
-figure generation (figure fluency)
f. abstract reasoning
-similarities
-proverb interpretation
-logic problems
g. judgment; influence of future consequences on current behavior
-difficult to test; questions about situations (e.g., fire in theater) are artificial and test mainly general knowledge and reasoning ability
-gambling task
h. language testing
i. testing for hemineglect
III. other exam findings
a. skull shape (hyperostosis may signify a frontal meningioma
b. olfaction (anosmia may signify an orbitofrontal tumor)
c. optokinetic nystagmus testing (impaired saccades occur away from side of lesion)
d. hemiparesis or upper motor neuron signs
e. motor impersistence (stick out tongue or hold up arms for 20 seconds)
f. gengenhalten (paratonia)
g. primitive reflexes or “frontal release signs” (grasp, suck, snout, root)
h. frontal “magnetic” gait disturbance

Question 63

Myerson’s glabellar sign

Answer 63

Myerson’s glabellar sign is associated with movement disorders such as PD. exam finding in which a patient is unable to resist blinking when tapped repetitively on the glabella, the area above the nose and between the eyebrows.

Question 64

Frontal gait abnormalities

Answer 64

shuffling, unsteady, magnetic gait, in which patient’s feet barely leave the floor.

Question 65

Why do disorders affecting the brain diffusely often present clinically as frontal dysfunction

Answer 65

possibly b/c frontal lobes make up a large proportion of the brain, and therefore multifocal disorders have a greater chance of affecting the frontal lobes before other brain regions. In teh case of hydrocephalus, it has been proposed that the dilated ventricles compress frontal subcortical white matter pathways, or possibly the anterior cerebral arteries.

other remote lesions from the frontal lobes may mimic frontal dysfunction due to the frontal lobes forming part of a network of widespread cortical and subcortical connections. Dysruption of certain neurotransmitters, such as dopamine, can also lead to frontal lobe dysfunction.

Question 66

Binding problem

Answer 66

question of how unified percepts are formed in the brain.

Question 67

visual mental imagery

Answer 67

our ability to imagine a scene that is not present. appears to utilize the same visual areas that perceive exogenous visual stimuli; however, there is some controversy over the extent to which primary visual cortex is involved.

Question 68

blindsight

Answer 68

some individuals with lesions of the primary visual cortex are able to perform tasks such as inserting an envelope correctly in a slot, despite having no conscious visual perception of the slot. Blindsight apparently depends on information transmitted to association cortex by extrageniculate visual pathways, bypassing the lateral geniculate nucleus and primary visual cortex. Some studies have also demonstrated small islands of preserved vision in the blind hemifield measuring only a few minutes of degree that are not able to support conscious vision but may influence behavior.

Question 69

Anton’s syndrome

Answer 69

AKA cortical blindness, caused by bilateral lesions of the primary visual cortex.. patients have complete visual loss on confrontation testing, yet they have anosognosia and are completely unaware of the deficit. other exam findings include loss of blink to threat, loss of eye closure in response to bright lights, and loss of optokinetic nystagmus (OKN). some patients may also have blindsight.

Question 70

Syndromes of the inferior occipitotemporal cortex

Answer 70

fusiform gyrus. hits the what stream. lesions here can cause deficits in the recognition of colors, faces, and other objects, as well as other visual phenomena related to color and form. complex formed visual hallucinations resulting from seizures of the inferior occipitotemporal visual association cortex have been described.

Conditions:
prosopagnosia (bilateral involvement), achromatopsia

can cause a generalized visual-object agnosia applying to both generic and specific recognition of all visual objects, including those just described. May be considered a perceptual agnosia because vision is often described as appearing hazy. sometimes patients with these lesions have a so-called visual static agnosia, in which they are able to recognize an object only when it moves.

Question 71

Prosopagnosia

Answer 71

patients are unable to recognize people by looking at their faces. lesion location is usually the bilateral inferior occipitotemporal cortex, also known as the fusiform gyrus. this is a type of associative agnosia, in which they correctly perceive the face and can describe it, but cannot associate it with a familiar person. not limited to people. farmers can have trouble recognizing tehir cows, and bird watchers wtih recognizing specific birds.

can be associated with achromatopsia and with alexia and with upper-quadrant or bilateral upper visual field defects.

Question 72

Achromatopsia

Answer 72

central disorder of color perception. It can be thought of as cortical color blindness and should be contrasted with color agnosia, in which color perception is intact. Patients with this cannot name, point to, or match colors presented visually. they can, however, name the appropriate color for an object described verbally. Usually aware of the deficit. describe the affected vision as appearing in shades of gray. it can occur in a quadrant, a hemifield, or the entire visual field. When the whole field is involved, it is usually accompanied by prosopagnosia and is caused by bilateral inferior occipitotemporal cortex lesions. Hemi-achromatopsia is caused by lesions in the contralateral inferior occipitotemporal cortex. Associated deficits include alexia and upper-quadrant or bilateral upper visual field defects.

Question 73

Color anomia

Answer 73

caused by lesions of the primary visual cortex of the dominant hemisphere extending into the corpus callosum, and it is associated with alexia without agraphia and right hemianopia. also reported with lesions of the medial occipitotemporal association cortex, adjacent to the splenium of the corpus callosum. Patients cannot name or point to colors presented visually. Howeer, perception of colors is preserved, as demonstrated by patients’ ability to match colors presented visually. This is not a true anomia or language disorder because patients can name the appropriate color for an object described verbally, so it should be distinguished from anomic aphasia.

Question 74

micropsia and macropsia

Answer 74

micropsia-objects appear unusually small

macropsia: objects appear unusually large.

in either, it can sometime soccur in only part of the visual field

Question 75

metamorphopsia

Answer 75

more general term describing a condition in which objects have distorted shape and size. also called “alice in wonderland” syndrome and can occur in migraine, infarct, hemorrhage, tumors, or other disorders of the inferior or lateral visual association cortex. occasionally also seen in retinal pathology or toxic or metabolic disturbances.

Question 76

visual reorientation

Answer 76

condition where the environment appears tilted or inverted to the patient. associated with vestibular or lateral medullary dysfunction.

Question 77

Palinopsia

Answer 77

lesions of the visual association cortex cause a previously seen object to reappear periodically. For example, one patient looked at a plant and then a few minutes later, the plant reappeared and seemed to be growing out of her omelet. can also occasionally be caused by medications such as trazodone.

Question 78

Cerebral diplopia or polyopia

Answer 78

patients see two or more images, respectively, of an object. more than two images or monocular diplopia is sometimes seen in psychiatric conditions. however, monocular or binocular double vision, triple vision, and so on can also be seen with occipital lesions, corneal lesions, or cataracts.

Question 79

Erythropsia

Answer 79

visual illusion characterized by gold, red, purple, or other unnatural coloring of the visual field. can also be seen with certain drugs, such as in digitalis toxicity, in which objects may appear to have a yellowish halo.

Question 80

Syndromes of the dorsolateral parieto-occipital cortex

Answer 80

this region is in the “where?” stream and processes motion as well as spatial localization and integration. Lesions of the dorsolateral parieto-occipital cortex can therefore cause deficits in these aspects of visual processing.

Includes Balint’s syndrome

Question 81

Balint’s syndrome

Answer 81

caused by bilateral lesions of the dorsolateral parieto-occipital association cortex, there is a clinical triad consisting of 1. simultagnosia 2. optic ataxia, and 3. ocular apraxia.

Simultagnosia is the core abnormality of Balint’s and consists of impaired ability to perceive parts of a visual scene as a whole. Optic ataxia is the impaired ability to reach for or point to objects in space under visual guidance. Ocular apraxia is difficulty voluntarily directing one’s gaze toward objects in the peripheral vision through saccades. some patients need to move their heads to initiate a voluntary redirection of gaze.

these patients may be diagnosed incorrectly with visual agnosias or alexia, which can be shown not to be present when care is taken to ensure that the visual stimulus is in a region the patient can see. Because this is caused by lesions of the dorsolateral parieto-occipital cortex, associated deficits may include inferior-quadrant visual field cuts, aphasia, or hemineglect. Most often these bilateral lesions of dorsolateral P-O C are caused by MCA-PCA watershed infarcts, although bilateral hemorrhage, tumors, dementia with PCA, or other lesions can also produce this syndrome.

Question 82

Simultagnosia

Answer 82

Simultagnosia is the core abnormality of Balint’s and consists of impaired ability to perceive parts of a visual scene as a whole. Patients can perceive only one small region of the visual field at a time. This region shifts around unpredictably, often causing patients to lose track of what they were looking at. They have particular difficulty scanning a complex visual scene or identifying moving objects (this is the opposite of visual static agnosia). When confronted with a large complex visual stimulus, patients have a tendency to describe small, isolated parts seemingly at random and have no awareness of the overall unified object or scene. This can be thought of as a deficit in visual-spatial binding.

Question 83

Optic ataxia

Answer 83

Optic ataxia is the impaired ability to reach for or point to objects in space under visual guidance. this can be distinguished from cerebellar ataxia because in optic ataxia the ability to point using proprioceptive or auditory cues is intact, and once an object has been touched, a patient with optic ataxia can perform smooth movements back and forth to it even with eyes closed.

Question 84

Auditory Hallucinations

Answer 84

can be caused by disturbances of higher-order auditory processing involving the auditory cortex and adjacent association cortex.

patients with sensorineural deafness can develop elaborate auditory hallucinations (music, voices, etc), which may be a release phenomenon analogous to Bonnet syndrome (visual hallucinations caused by visual loss).

Lesions or ischemia of the pontine tegmentum involving the trapezoid body, superior olivary nucleus, and other auditory circuits can, rarely, cause auditory hallucinations, such as rain on a roof, buzzing, or musical tones like an orchestra tuning up, which are analogous to the visual phenomena of peduncular hallucinosis.

In paracusis, another rare disorder, a sound that is heard once is then heard repeatedly, analogous to palinopsia.

Psychotic disorders are relatively common causes of both simple and elaborate auditory hallucinations. Imaging studies during active hallucination in Sz shows activation of diverse brain regions.

Seizures in primary auditory cortex can cause simple auditory phenomena, such as the sound of a train approaching or of an airplane taking off, often perceived as coming from the side opposite to the involved cortex. Seizures in this area can also cause transiently decreased hearing. Involvement of the auditory association cortex gives rise to more elaborate auditory phenomena such as voices or music. Music hallucinations are more often caused by seizures in the nondominant hemisphere than in dominant, although they can also occur with peripheral or pontine lesions.

Question 85

Tinnitus

Answer 85

a common disorder consisting of a persistent ringing tone or buzzing in one or both ears, usually caused by peripheral auditory disorders affecting the tympanic membrane, middle ear ossicles, cochlea, or eighth cranial nerve.

Question 86

Self-audible bruits

Answer 86

pulsatile “whooshing” sounds that can be associated with turbulent flow in arteriovenous malformations, carotid dissection, or the extracranial-to-intracranial pressure gradient that is produced by elevated intracranial pressure.

Question 87

Two components of consciousness as described by Plum and Posner

Answer 87

1. Content of consciousness– the substrate upon which consciousness acts and includes sensory, motor, emotional, and mnemonic systems acting at multiple levels. It comprises memory, emotion and drives, language, executive function, visual processing, motor planning, and so on. Without normal operation of these systems, completely normal consciousness is not possible.
2. Level of consciousness is regulated by several brain networks that act on this substrate and constitute the consciousness system. Like other major functional systems in the brain (such as motor, somatosensory, etc) the consciousness system consists of cortical and subcortical networks that carry out specialized functions- in this case, regulating the level of consciousness. It can be described in terms of 3 distinct processes that maintain 1. alertness 2. attention and 3. awareness of self and environment (mnemonic AAA).

the consciousness system networks that control these functions include the upper brainstem, thalamic, hypothalamic, and basal forebrain activating systems, along with the medial and lateral frontoparietal association cortex and cingulate gyrus. Other structures such as the basal ganglia and cingulate gyrus may also play a role through their participation in attention mechanisms.

Question 88

2 major functions of attention

Answer 88

1. selective, or directed, attention involving focusing attention on a particular domain above others. this implies attention to certain stimuli, objects, or concepts to the exclusion of others. In selective attention, attention is directed at specific components of the “substrate,” or content of consciousness, described in the previous paragraph. Examples can include:
   
   • attention to a visual, tactile, or auditory stimulus in a particular location in space
   • attention to inputs of a specific sensory modality
   • attention to a specific higher-order aspect of a stimulus (e.g., color versus shape)
   • attention to a particular object, including inputs from various modalities.
   • attention to an object, emotion, plan, or concept that is not physically present but is either remembered or imagined.

imaging studies show these are reflected in activation of specific brain regions, following known anatomical principles. For example, attention to a somatosensory stimulus on the body activates the corresponding somatotopic region of somatosensory cortex, attention to a visual stimulus in a particular location activates the corresponding retinotopic region of visual cortex, and so on. Specific areas of limbic and association cortex are also involved in higher-order processing.

2. sustained attention includes functions such as vigilance, concentration, and nondistractability. sustained attention can be directed at a specific task, object, or modality, or it can involve a more generalized increased level of vigilance- for example, while one is awaiting an anticipated stimulus.

Question 89

declarative vs. nondeclarative memory

Answer 89

declarative: involves conscious awareness and is processed by medial temporal and diencephalic regions
nondeclarative: does not involve consciousness and is processed by other brain regions.

Question 90

resting state activity

Answer 90

in functional imaging, when people are awake but not engaged in a specific task, brain networks show slow (duration greater than 10s) spontaneous fluctuations in activity levels. this resting activity is correlated within distinct functional brain systems such as the motor, visual and other brain networks.

default mode network activity. important role of medial parietal region including the precuneus, along with the posterior cingulate, and retrosplenial cortex (cortex located just behind the splenium of the corpus callosum) in self-reflection, introspection, and self-awareness.

Question 91

tests of sustained attention

Answer 91

digit span. normal span is 5-7+.
backward: 4+ is normal. or 2 less than the patient’s forward span.

ask patients to recite the months of the year forward and backward. backward should take no longer than twice as long as forward. should be done without errors.

world backward and counting backward by 3 form 30 or by 7 from 100. less useful.

Motor impersistence is another useful bedside indication of impaired attention. patient can be asked to stick out their tongue, or hold up their arms for 20 seconds, without subsequent prompting. if they do not persist, this is a form of motor inattention.

Vigilance can be tested with the “a” random letter test, where a random sequence of letters are recited at a rate of about 1 per second, and the patient is instructed to tap for the a

Question 92

Common causes of impaired general attention

Answer 92

• diffuse encephalopathy
• focal lesions, especially of the frontal or parietal lobes or of the brainstem-diencephalic activating systems, but also of many other brain regions
• ADHD
• psychiatric disorders- e.g., depression, mania, schizophrenia

Question 93

encephalopathy

Answer 93

nonspecific term that means simply diffuse brain dysfunction

acute enchepahlopathy (hours to weeks or a few months; AKA acute confusional state, organic psychosis, acute organic brain syndrome, or delirium) is most often toxic or metabolic in origin and is often reversible. prominant inattention, confusing, waxing and waning level of alertness, and difficulty registering new memories due to both inattention and diffuse dysfunction of the memory network. they usually have marked difficulty with writing, calculations, and constructional ability, any of which could be misconstrued as focal deficits if the underlying deficit in attention is not recognized. can often be worse in the evening (sundowning). marked slowing is seen on EEG.

chronic is months to years.
this has poorer prognosis and can represent neurodegenerative dementia such as AD.

Question 94

ADHD

Answer 94

common- affects 1-5% of elementary school children. onset is typically by age 3, although problems do not usually emerge until school is started.

Neuroimaging studies and neurologic evals are essentially normal except for markedly impaired attention, impulsivity, and perhaps some “soft” findings on exam. more likely to cause problems with high-level executive functions, organizational skills, and time management abilities rather than simpler impairments of digit span. Usually cause is unknown. 3-5x more liekly in boys, and siblings are at an increased risk. treated wtih CNS stimulants such as methylphenidate (Ritalin), SSRIs such as atomexetine (Strattera) or other meds, combined with individual and family behavioral therapy.

Many show remission by adolescence. but about 30% continue to have ADHD in adulthood.

Question 95

delirium

Answer 95

often used for acute confusional state in which agitation and hallucinations are prominent.

Question 96

Static encephalopathy

Answer 96

term used to describe permanent nonprogressive brain damage as a result of head injury, anoxia, or congenital abnormalities of the brain.

Question 97

Vitamin B12 Deficiency

Answer 97

causes megaloblastic anemia, along with subacute combined degeneration of the spinal cord (posterior columns more than corticospinal tracts). Subacute combined degeneration can also involve teh cerebral white matter, resulting in dementia. Reversibility depends on how quickly it is treated.

Question 98

Wilson’s disease

Answer 98

important treatable cause of dementia, often presenting in adolescence with hepatic dysfunction, dysarthria, movement disorders, or psychotic manifestations.

Question 99

AD patholophysiology

Answer 99

major changes are cerebral atrophy, neuronal loss, amyloid plaques, and neurofibrillary tangles. changes typically occur initially and are most severe in (descending order): 1. medial temporal lobes, including the amygdala, hippocampal formation (especially CA1), and entorhinal cortex; 2. basal temporal cortex extending over the lateral posterior temporal cortex, parieto-occipital cortex, and posterior cingulate gyrus; and 3. frontal lobes.

Primary motor, somatosensory, visual, and auditory cortices are relatively spared, at least initially.

Cell loss and neurofibrillary tangles are also prominent in the nucleus basalis, septal nuclei, and nucleus of the diagonal band, where cholinergic projections arise, and to a lesser extent in the locus ceruleus (norepinephrine), and raphe nuclei (serotonin).

Senile plaques are composed of an insoluble protein core containing b-amyloid, along with apolipoprotein E, surrounded by a rim of abnormal axons and dendrites called dystrophic neurites. Neurofibrillary tangles are intracellular accumulations of hyperphosphorylated microtubule-associated proteins or paired helical filaments known as tau proteins. Amyloid is a general term for insoluble protein deposits that can occur in various organ systems in different forms of amyloidosis. B-Amyloid is a specific protein associated with AD, derived from proteolytic precursor protein. Cleavage of APP can occur at several different sites, but cleavage at an intracellular location by a protein called y-secretase is thought to promote the formulation of toxic soluble B-amyloid oligomers, which later aggregate into insoluble extracellular B-amyloid plaques.

Question 100

AD clinical features

Answer 100

anosognosia is common.
dominant early feature is usually short-term memory loss. next, they often develop word-finding difficulty, or an anomic aphasia, along with other features of posterior temporoparieto-occipital dysfunction, including apraxia and visuoal-spatial deficits. Typically, behavioral abnormalities occur later in this illness than in FTD. may wander and become lost in the neighborhood; leave home unclothed; become paranoid or accusatory, sexually inappropriate, agitated, or aggressive, fail to recognize family, or perform unusual activities such as placing food in the oven without turning it on, or turning on all the stove burners and then leaving the house.

severe frontal lobe dysfunction can develop later in the course. Motor disturbances are also not usually present early in the course and if abnormal gait is present early, other diagnoses should be considered. Hallucinations do not occur early.

Median time of survival is 8 years but this is age-dependent.