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Recovery in Aphasia

Week 6Feb 17th, 2011

+Spontaneous Recovery

Spontaneous recovery in aphasia

Mechanisms of recovery

Selective variables affecting recovery

Parameters of recovery

Means of examining recovery

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Spontaneous Recovery 1. Related to the natural healing process 2. Improvement of language function which is inevitable in most

cases of aphasia regardless of whether patients receive speech/language treatment

3. This recovery appears to stem from substitution of function and brain reorganization

Spontaneous Recovery 4. Information regarding spontaneous recovery has mostly been

measured by the Western Aphasia Battery (WAB) whereas amount of recovery in treated patients has been measured by the Porch Index of Communicative Ability (PICA), Functional Communication Profile (FCP), or the Neurosensory Center Comprehensive Examination of Aphasia (NCCEA)

Two hypotheses have been advanced at the macroscopic level of brain organization Regression of diaschisis

a functional impairment is present in structurally unaffected brain regions connected to the damaged area.

This phenomenon is often called diaschisis. Regression of intrahemispheric and

transhemispheric diaschisis may be associated with the recovery of a function (i.e., language), that is subserved by an extensive network of regions in both hemisphers.

Two hypotheses have been advanced at the macroscopic level of brain organization Regression of diaschisis

www.fil.ion.ucl.ac.uk/.../aphasia1.html

Two hypotheses have been advanced at the macroscopic level of brain organization “Takeover” of function: Takeover of linguistic functions by the contralateral, undamaged

hemisphere Reorganization of function takes place in undamaged areas within

the same hemisphere

www.fil.ion.ucl.ac.uk/.../aphasia1.html

• There is considerable evidence that both intrahemispheric and interhemispheric reorganization play a role in the recovery process.

• In the first few months after a stroke, when the recovery proceeds at a fast rate, regression of functional depression in ipsi- and contralateral areas is the main mechanism underlying recovery.

• This period is usually associated with a prevalent improvement of auditory comprehension

• The subsequent phase, characterized by a much less steep recovery function, might be related to the process of functional reorganization; the relative contribution of undamaged regions of the left hemisphere and of the healthy right hemisphere remains to be assessed

• A contribution of the healthy hemisphere is probable for lexical retrieval, while speech programming aspects seem to remain strongly lateralized to the left hemisphere.

• Recovery of function involves expanded cortical regions in LH• E.g., further language decline following second stoke in the LH• PET, SPECT results showed increased metabolic activity, or

regional cerebral blood flow in the RH as well as undamaged portions of the language network in the LH

+Selective variables affecting recovery

1. Patient-related variables Age Gender Education Linguistic Background Handedness Motivational and Social factors

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1. Patient-related variables Age:

“Minimal” effect of age on recovery A fast and relatively complete recovery can be expected in children with

acquired aphasia Better prognosis being associated with earlier lesion onset

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1. Patient-related variables Gender

Better recovery in females Possible due to less lateralized pattern of hemispheric specialization in

females

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1. Patient-related variables Education

Education does seem to play a role Other factors: socioeconomic status and general intelligence acquisition of reading skills modulates the clinical picture of aphasia

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1. Patient-related variables Linguistic Background

Differential recovery patterns have been observed in patients who know more than one language

The notion that first acquired language recovers first has been challenged

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1. Patient-related variables Handedness

Better or faster recovery: left-handed patients and patients with “atypical” hemispheric language dominance Crossed right-handed aphasics, crossed and uncrossed left-handers These patients often show unusual dissociation of linguistic

performance

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1. Patient-related variables Motivational and Social Factors

Depression interacts negatively with recovery Depression may be severe in patients with anterior lesions Many of these aspects have been largely neglected

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2. Disease-Related Variables Etiology Lesion Size Lesion Site Clinical Picture Time Post-Onset

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2. Disease-Related Variables Etiology

Negative prognostic factors: progressive disease of the nervous system such as a malignant tumor or a degenerative condition

Aphasia due to TBI recovers better than aphasia due to cerebrovascular lesion

Hemorrhagic strokes tend to be associated with better outcome in comparison with ischemic strokes

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2. Disease-Related Variables Lesion Size

Size of vascular lesions with the help of CT scan Strongest negative predictor of recovery It is closely associated with the variable of aphasia severity

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2. Disease-Related Variables Lesion Site

Role of lesion site on the recovery of several aspects of language function, such as speech fluency or auditory comprehension

Cortico-subcortical lesions of the left precentral gyrus were found in patients who remained nonfluent six months after onset

Extension of lesion toward the basal ganglia or mesial frontal white matter is associated with a negative prognosis for fluency.

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2. Disease-Related Variables Lesion Site

According to Naeser and colleagues, only the lesion extent in the temporal lobe correlated with severity and recovery of comprehension disorder

Kertesz et al 1993: it was lesion extent in the inferior parietal area that predicted comprehension recovery

Aphasias associated with subcortical lesions are associated often with a fast and complete recovery, leaving the patients with a mild residual semantic-lexical disorder

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2. Disease-Related Variables Clinical Picture

Relationship of aphasic syndromes, according to the traditional taxonomy, with recovery.

Initial severity, defined according to global impairment measures, appears to be the strongest predictor of recovery

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2. Disease-Related Variables Time Post-Onset

The rate of spontaneous recovery is maximal in the first 6 months after stroke, with a very steep curve in the first six weeks.

However, significant improvement can be observed in severely aphasic patients up to 2 years post-onset

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In summary There is unequivocal evidence that clinical severity, lesion size, and time

post-onset are negative prognostic factors. Lesion site has predictive value for specific aspects of linguistic recovery. The role of other variables such as gender, age, handedness, and linguistic

background, deserves further investigation

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Recovery of Aphasia: Recovery of Function

A. Parameters of Recovery 1. Amount: usually indicated by difference between 2

assessments in a patient 2. Outcome:

1. Prediction determining whether a level of language function can be predicted given certain information; considered the endpoint of recovery

2. point at which patient is dismissed from speech/language therapy

3. end of recovery is confirmed when language measures no longer show an upward trend across time

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Recovery of Aphasia: Recovery of Function

A. Parameters of Recovery 3. Rate

a. time it takes to reach maximum level of recovery

b. usually reached before occurrence of peak test score/final test score

+Recovery of Aphasia: Recovery of Function

A. Parameters of Recovery 4. Pattern

a. Reflected in different amounts and rates of improvement which occur among different language functions

b. language functions making greatest improvement are usually receptive and imitative functions

+Recovery of Aphasia: Means of Examining Recovery

A. Dichotic Listening 1. Normal individuals demonstrate what is called a right ear

advantage for the LH processing of language 2. Contralateral fibers are stronger than the ipsilateral fibers in the

auditory system 3. Petit and Noll (1979) used the dichotic paradigm with aphasic

patients 4. aphasic patients usually show a left ear advantage for language

processing which is called the lesion effect

+Recovery of Aphasia: Means of Examining Recovery

A. Dichotic Listening 5. Petit et al. continued to use the dichotic paradigm in the same

group of patients as they recovered over time.

6. As recovery occurred the left ear advantage became larger suggesting that the right hemisphere was becoming more involved in the language process with these patients

+Recovery of Aphasia: Means of Examining Recovery

B. Use of the Wada Technique: 1. Injecting sodium amytol (barbituate) into the carotid (right or

left) artery and it anesthesizes that particular hemisphere

2. Kinsbourne (1971, 1984, 1998) used the WADA technique with a group of Broca’s patients who had minimal verbal production

+Recovery of Aphasia: Means of Examining Recovery

B. Use of the Wada Technique: 3. there was no change in their verbal skills when the LH was

anesthesized

4. however, they lost their verbal skills when the RH was anesthesized suggesting that the RH was subserving the language these patients had.

+Recovery of Aphasia: Means of Examining Recovery

C. Time-sharing paradigm: 1. (Kligman & Sussman, 1983, 1995) used the time-sharing

paradigm which is based on the assumption that if one hemisphere has to do two different things at the same time, it won’t do them as well as if they were doing each of these functions in isolation

2. Particularly interested in motor movements of the hand and a speaking task simultaneously

+Recovery of Aphasia: Means of Examining Recovery

C. Time-sharing paradigm: 3. So, in normals, if they were tapping with the right hand

(controlled by the LH) and then started speaking (also controlled by the LH), their tapping behavior would deteriorate

4. However, if they are tapping with the left hand (controlled by the RH) and start speaking, there will be no deterioration in their tapping behavior

+Recovery of Aphasia: Means of Examining Recovery

C. Time-sharing paradigm: 5. With aphasic patients, it was observed that their tapping

behavior deteriorated using either hand when a speech-language task was introduced, suggesting that the RH was participating more now in language functioning.

www.bu.edu/naeser/aphasia/projects.html

Three overt naming fMRIs in a chronic nonfluent aphasia patient treated with 1 Hz rTMS to suppress R posterior Pars Triangularis: pre-rTMS (9 Yr. poststroke), and at 3 and 16 Mo. post-rTMS (11 Yr. poststroke). Note increased L perilesional and L SMA activation (white arrow) on fMRI at 16 Mo. post-rTMS (best naming score, 58%). New Shift to L SMA Activation with Improved Overt Naming fMRI at 11 Years Poststroke in Nonfluent Aphasia after rTMS to Suppress R BA 45.