Tuesday, November 12, 2013

When right is all that is left:  plasticity of right-hemisphere tracts in a young aphasic patient.
L. Zipse, A. Norton, S. Marchina, G. Schlaug
Ann. N.Y. Acad. Sci. 1252 (2012) 237-245.

This article describes the use of a modified Melodic Intonation Therapy (MIT) intervention with an adolescent girl with severe non-fluent aphasia following a large left-hemispheric stroke.  This approach resulted in improvement in trained and untrained speech supported by Functional Magnetic Resonance Imaging (fMRI) revealing increased right hemisphere activity and Diffusion Tensor Imaging (DTI) scans indicating increased white matter volume in the right hemisphere.

To provide context for the article, MIT is an intervention developed by Sparks, Albert, and Helm [1] after noting that following a left hemispheric stroke, some individuals who develop aphasia have a preserved ability to sing.  MIT was developed using melodic contour and rhythm to support speech of short, trained phrases.

The authors used a modified version of MIT, adapted to the needs of the participant, LF.  The goals of the study were to:  “ 1) test the efficacy of our adaptation of MIT for a patient who did not meet the traditional inclusion criteria for this treatment; and 2) to investigate which structural and functional changes might support MIT-induced improvement when no viable left-hemisphere areas remain to support recovery of speech function.”

The participant, LF, experienced a large left-hemispheric stroke at the age of eleven.  As a result, LF’s speech was non-fluent, she had significant word-finding problems, and impaired repetition ability.  Her comprehension ability remained high.   Standard tests were used to measure these areas with results comparable to Broca’s aphasia.

The authors used 3 baselines, measuring improvement in trained and untrained phrases at the midway, conclusion, and one-month-post treatment times. 

Treatment was intense, with five 1.5 hour sessions per week for 16 weeks. Treatment was divided into two phases.  Both phases included two levels of difficulty.  Phase one included target phrases of varying syllable lengths.  Phase two added a focus on syntax.  The authors provide a detailed description of their treatment and measurements.

Results indicated improvement in both trained and untrained phrases.  Improvement was most notable on trained items.   These functional results, and additionally LF’s improved speech fluency, were supported by family observations during treatment. 

fMRI imaging revealed an increase in activity in the right posterior middle frontal and inferior frontal areas from baseline to mid-point of treatment but followed by a return to baseline level.  This reduction in activation may have been a result of increased efficacy of these regions. 

DTI scans revealed white matter increase in the right hemisphere arcuate fasciculus (AF), a fiber track connecting the superior temporal lobe and the inferior frontal gyrus and motor/premotor regions, and in the uncinate fasciculus (UF).  In the left-hemisphere, these tracks are believed to be associated with speech and language processing.

Following treatment LF’s speech continued to include aphasic qualities but with improvement, most notably, in fluency. 


Two main points were significant to me as I read this article. 

First was the strong evidence of the efficacy of music-supported interventions to address speech rehabilitation goals.  Although there is currently a solid research base of this evidence, this article particularly caught my attention due to the results of improved speech in spite of such extensive left-hemispheric damage.  The authors noted in their conclusion that some researchers suggest a greater unilateral injury (rather than a smaller lesion) may more effectively result in hemispheric transfer and therefore potentially increased rehabilitation outcomes. This is noteworthy to me, as my client population is primarily individuals with severe brain injury.  In the face of significant deficits, it is encouraging to note that there remains the potential for response to therapeutic interventions and in this case, particularly ones that are music-based.  This potential for response of course is dependent on many factors, including lesion location, pre-injury condition, intensity of therapy, and other individualized contributors.  Also, the young age of the participant in this study would be a factor in her improvements.  Prior to the modified MIT approach, LF had received 15 months of speech therapy.  It is notable that using a music-based intervention resulted in further improvements evident both in functionally and in neural changes observed in fMRI and DTI imaging.

Secondly, I was intrigued by the neural plastic response of the AF and UF with increased white matter.  The participant’s AF and UF function in the left hemisphere was damaged and this was indicated by her aphasic symptoms.  It was extremely interesting to me that as her speech ability improved, these areas in the right-hemisphere increased in density.  Speech is typically supported by regions in the left hemisphere.  The hemispheric shift to support speech and the increased AF and UF density was quite striking.  The wonder and the potential of neural plasticity begs many questions, yet this article provided me with encouragement as a music therapist working with individuals living with the affects of acquired brain injury. 

1.  Sparks, R., N. Helm & M. Albert. 1974.  Aphasia rehabilitation resulting from melodic intonation therapy.  Cortex 10: 303-316.

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