Neglect 2

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Neglect: definition: failure to respond to, report, or orient to novel or meaningful stimuli presented to the side opposite the lesion
Neglect: rule outs: sensory, motor, or memory deficits
Neglect: other terms for: unilateral spatial agnosia, amorphosynthesis, left-sided fixed hemianopia, hemi-inattention, hemi-neglect, hemispatial agnosia
Neglect: first description by: jackson (1978)
Sensory neglect: definition: deficit in awareness of stimuli contralateral to a lesion not involving sensory projection systems or primary cortical sensory areas
Neglect: 2 types OR 2 other types: spatial, personal
OR attentional/sensory and intentional/motor
Spatial neglect: 3 frames of reference: body centered, environmentally centered, object centered
Sensory neglect: associated disturbances: inattentive to stimuli ipsilateral to lesion- but this is less severe, problems with disengaging or shifting attention in contralateral direction
Distinguishing sensory neglect from sensory deficit: increasing instructional cues, using novel stimuli, or using strongly motivational cues
Probes for sensory neglect: tests of extinction, line bisection, covert attentional shifts
Sensory-representational neglect: probes for: have pt close eyes and point to body midline, pt usually points to right of midline
Motor-exploratory neglect: definition: reluctance to scan and explore L hemispace
Motor-exploratory neglect: probes: target detection tasks: more difficult tasks are more sensitive in detection (lines easier than letters, letters easier than complex shapes)
Neglect dyslexia: definition: failure to read words on left side of page
intentional neglect or limb akinesia: definition: reluctance to move limbs on L in absence to damage to corticospinal system
hemispatial akinesia: definition: pt fails to spontaneously use contralateral extremity, but may have good strength when focusing on that part
hypokinesia: definition: milder form of hemispatial akinesia, in which there is a delay in initiating movement
limbic-motivational neglect: definition: pts devalue the L side of space and act as if nothing important could happen on that side; there is no emotional salience for that side of space
Inattention: probes for milder versions: sensory extinction to double simultaneous stimulation: may still occur after hemi-attention improves, pt fails to report stimulation on contralateral side when both sides are stimulated simultaneously
Inattention: behaviors suggestive of: pts will recognize that the limbs are their own, but refer to them as though they were objects
Allesthesia: behaviors suggestive of: disturbance of body schema perception in tactile modailty, in which stimulation of one side of body is perceived as located on other side
4 types of motor neglect: akinesia, hypokinesia, motor extinction, motor impersistence
motor extinction: definition: pts who do not display akinesia when they are moving only one limb may do so when they must move both limbs simultaneously
motor impersistence: definition: inability to sustain a motor activity
spatial neglect: can occur in three dimensions of space: horizontal, vertical, and radial (near, far)
spatial neglect: behavioral manifestations and probes for: line bisection, cancelleation tasks, and drawing
spatial neglect: adaptive behavior manifestations: failure to groom or dress contralateral side
hemispatial neglect: frames of reference (2): body-centered or environmental
Neglect classifications: sectors of space: personal neglect, peripersonal neglect (within reaching space), and far extrapersonal neglect (only when stimuli are out of reach)
anosagnosia: definition: unawareness or denial of deficits or of affected extremities
anosagnosia: behavioral manifestations: if pts are asked to complete a task wtih affected limb, will say they are left handed or claim to have done the task when they haven't
anosodiaphoria: definition: pt will admit to sensory or motor impairment, but be unconcerned about it, may follow a period of anosagnosia
Neglect: which hemisphere?: Much more frequent and severe after R hemi lesions because R hemi specializes in spatial distribution of attention.
Neglect: three cortical regions involved: Parietal (inferior), frontal, limbic
Neglect: subcortical regions involved: thalamus, striatum, superior collliculus
thalamic neglect: deficit attributed to: problem with engaging, not disengaging as seen in parietal lesions
Neglect: parietal component: inferior parietal lobe, key role is in spatial attention as integrating spatial map with motor output channels
small lesions here rarely lead to neglect, need subcortical damage and large parietal lesion
Neglect: frontal component: ? plays critical role in attention network by converting plan and intentions into sequences of motor acts that shift focus of attention
lesions confined to frontal lobe can cause neglect
specific regions possibly frontal eye fields or inferior frontal gyrus
Neglect: limbic component: cingulate is least well understood, but may play role in identifying motivational relevance of events and sustaining effort
can have neglect with only cingulate gyrus lesion, rarely
Neglect: cingulate gyrus two proposed components: anterior- reflecting global attentional engagement
posterior- lateralized shifts of relevance and focal attention
Two hypotheses of mechanisms underlying neglect syndromes: reprsentational hypothesis (one proponent Bisiach)
attentional hypothesis (seems to be more accepted, proponents include Heilman, Posner, Mesulam)
Neglect: representational hypotheses defined: posterior parietal cortex is thought to contain an elaborate spatial representation of the external world, unilateral loss of this representation causes neglect
Representational hypotheses of neglect: classic experiment: Pts were asked to describe a cathedral in Milan; they failed to describe landmarks imagined on left side of scene
Which cathedral was it?: Piazza del Duomo in Milan
Piazza del Duomo experiment could be interpreted...: impaired representation (mental), impaired scanning of representation, inability to attend to contralesional hemispace
Cueing of Piazza del Duomo experiment patients: improved performance, suggesting attentional component, which isn't well explained by representational view
Unilateral Akinesia Hypothesis of Neglect (an Attentional hypothesis proposed by Heilman): defect in orienting to stimuli due to disruption in arousal system in affected hemisphere.
Unilateral Akinesia Hypothesis of Neglect (an Attentional hypothesis proposed by Heilman): Problem: why don't most severe cases of neglect follow damage to RAS?
Covert Orienting Hypothesis of neglect (an attentional hypothesis proposed by Posner): disengage, shift, engage model
neglect results from inability to shift away from intact hemispace
ATtentional network hypothesis of neglect (an attentional hypothesis proposed by Mesulam): neglect is a network syndrome, represents damage to one or more components of a distributed network, represents a domain-specific impairment of spatial attention
Neglect: assessment issues, what to rule out: primary sensory deficits (by varying attentional cues),
motor deficits
unilateral hearing loss: does not occur after unilateral lesions, if pt has unilateral hearing loss, it is neglect
visual field cuts: are not affected by position of eyes in space, neglect is
sensory evoked potentials: are normal in neglect pts
assessment of neglect should include these modalities: auditory, visual, somesthetic
standardized testing for neglect: cancellation: look at omissions and search strategy
line bisection: deviations to ipsilateral side
drawing: copy or draw clock
reading and writing
Neglect: treatment by managing environment: arrange to reduce risk of injury, position important stimuli on R side, reduce competing/distracting stimuli, present some stimuli in neglected field for therapy
Neglect: training: operant techniques can improve exploration of contralesional space, but this might remain task specific and not generalize
Neglect: cueing: attentional cueing may help, bottom up cues include providing novel stimuli, top down cues include providing directions to attend
Neglect: behavioral goals: conscious knowledge of the importance of searching to left hemispace before engaging
kinesia paradoxica: definition: principally, an endo-evoked akinesia, with poor response to internal cues, but normal response to external cues (often seen in parkinson's disease)
endogenously evoked akinesia: definition: poor motor response to internal stimuli
exogenously evoked akinesia: definition: poor motor response to external stimuli
defective vigilance: definition: pt will be able to detect contralesional stimuli initially, but, with repeated stimulation, will eventually fail

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