Reference
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.
Reflections
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.
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