Tag Archives: rehabilitation

Speech! Speech!

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Just today a review article on voice and speech in PSP and the other atypical Parkinsonian disorders (APDs) appeared in the journal Movement Disorders – Clinical Practice.  The article is written for neurologists, but it should be comprehensible by educated laypersons, which is why I’m recommending it to you all.  

Two terms used in the article that are probably not familiar to you in this context are “spasticity” and “apraxia.” 

  • Spastic speech has a “rubber-band” quality, with abrupt variations in speed and loudness. It’s very common in PSP. It corresponds to spastic limb movements (rare in PSP), where joints can suddenly flex or extend in response to gentle movement or sensory input.
  • Apraxic speech features reduced ability to make certain sounds or words without a corresponding inability to form their components. It’s common in some of the APDs, but not in PSP. It corresponds to limb apraxia (common in PSP), where power and simple tasks are preserved, while more complex, learned tasks are impaired.

The paper includes videos of people with some of the APDs performing a standardized series of speech tasks, including describing the picture below:

The famous “cookie theft scene” test is designed to assess perception, judgement and language, but it serves as a test of voice and speech as well.  

That brings us to the differences among “voice,” “speech” and “language.” 

  • Voice difficulties include things like hoarseness and low/high volume. 
  • Speech difficulties include things like slurring, slowing/speeding and disordered rhythm of sentences. 
  • Language problems include things like wordfinding problems, word substitutions and reduced grammatical ability.  It’s not discussed in the current paper but may be the topic of a subsequent review by the same group of neurologists. 

A quick-and-easy way to organize this scheme is to consider voice problems as arising from the lungs and larynx; speech problems from the mouth, tongue and lips; and language problems from the brain. 

The paper’s authors are all at institutions within CurePSP’s Centers of Care network.  The leader of the project was Dr. Federico Rodriguez-Porcel of the Medical University of South Carolina.  The other 25 authors, including yours truly, are listed in alphabetical order. So, as a clearly biased contributor, I recommend this paper on voice and speech in the APDs to those interested in understanding the range of such problems and their potential for rehabilitation.

The hindbrain steps forward

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The cerebellum is gradually being understood as a contributor to cognitive and behavioral function in both in health and disease.  A new publication has teased out MRI changes in the cerebellum that differentiate PSP from other dementing disorders early in the disease.  This pattern could be developed into a diagnostic test and as a marker of disease progression and even as a guide to rehabilitation measures.

The cerebellum is classically thought of as a regulator of movement.  In its most simplistic essence, its job is to put a brake on voluntary movement instructions from the cerebrum.  The cerebellum is guided in this task by perception of the position and motion of the trunk, head and limbs, by the effect of gravity, all complemented by visual input.

More recently, the cerebellum has demonstrated a memory function when it comes to movement regulation (making “muscle memory” more than just a metaphorical expression), and damage to certain parts of the cerebellum can cause a behavior disinhibition and cognitive impulsivity similar to the frontal lobe damage seen in PSP. In that sense, the cerebellum still functions as a “brake,” but on behavior and cognition rather than just on movement.

Now, researchers from the University of California San Francisco have carefully analyzed routine MRI scans from people with dementia arising from a variety of neurodegenerative conditions including PSP.  They specifically quantified gray matter damage.  (Gray matter is brain tissue composed mostly of cell bodies — as opposed to white matter, which is mostly axons.  In the cerebellum, unlike the cerebrum, the gray matter is the deeper layer and the white matter is superficial.)

The figure below shows the principal results. Illustration from Chen Y, et al. Alzheimer’s & Dementia, 2023. The senior author is Dr. Katherine Rankin. Each MRI image has been reconstructed by computer from routine scans to show the cerebellum splayed out flat.  The randomly assigned colored areas represent a loss of gray matter relative to non-demented people of similar age (“Controls”).  Note that the pattern for PSP differs in obvious ways from the other diseases, though at present the differences are only between the averages for groups, not individual differences useful for diagnosis in routine care. 

Notes: The small type abbreviations are the sub-areas of the cerebellum.  AD=Alzheimer’s disease; CBD=corticobasal degeneration; LBD=Lewy body dementia; TDP=frontotemporal dementia with TDP-43 protein aggregation.  It comes in 3 types. “Pick’s” is a form of frontotemporal dementia.  LBD is combined with AD because at autopsy, the former is always accompanied by some of the latter.  This paper did not include Parkinson’s disease or multiple system atrophy, as those diseases rarely include dementia early in the course, the focus of the present study.

The authors conclude, “These findings suggest the potential for cerebellar neuroimaging as a non-invasive biomarker for differential diagnosis and monitoring.”  They hasten to add that to understand the reasons for these different patterns of cerebellar loss, future studies will have to image the areas of the cerebrum where brain cell activity has been lost and to correlate that with corresponding loss of activity in the cerebellum.  That’s called “functional neuroimaging” as opposed to the “structural neuroimaging” of the current study.   

These insights, aside from their qualitative and quantitative diagnostic value, could provide guidance for electrical or magnetic transcranial stimulation (i.e., delivered across the scalp and skull rather than by inserting hardware onto or into the brain) as symptomatic treatment for PSP and the other dementing disorders.