Monthly Archives: May 2023

It’s that pedunculopontine nucleus again. (5CP, part 2)

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My last post described the first two of five new (as of yesterday) publications on PSP to suddenly appear on my routine PubMed search.  The third one is sufficiently interesting and complicated to deserve its own post.

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Falls are perhaps the earliest-appearing and most disabling feature of PSP, but we don’t yet fully understand which of the many brain areas involved in PSP deserves most of the blame.

A PSP-like illness endemic to the islands of Guadeloupe and Martinique is called Guadeloupean tauopathy or Caribbean Parkinsonism (CAP).  It may be the result of consuming two fruits, sweetsop and soursop, which have high levels of a mitochondrial toxin called annonacin.  Injected into rats in a lab, annonacin produces a PSP-like illness complete with abnormal tau accumulation.  However, the human CAP illness includes multiple aggregating proteins in addition to tau.  

The new article from neurologists in Paris and on Guadeloupe and Martinique reports on careful measurements of atrophy of specific brain regions on MRI in 16 patients with CAP, 15 with PSP-Richardson syndrome and 17 healthy, age-matched control participants.  They correlated the results with 11 standard scales assessing gait, general movement and cognitive function and also with electronic measures of gait and eye movement.  The group’s senior leader was Dr. Annie Lannuzel of INSERM, France’s equivalent of the NIH.  She has a long record of research in CAP.  The first author was Dr. Marie-Laure Welter, also of INSERM.

The results were that PSP and CAP differed in their anatomical patterns of brain atrophy.  Although their overall average disease severity was similar, CAP had more cognitive loss with correspondingly more atrophy of cerebral cortex.  On the other hand, the PSP group had more gait instability with correspondingly greater involvement of the midbrain and cerebellum.

The overall statistical comparisons showed that the main source of the gait and balance problem in PSP is damage to the supplementary motor area – pedunculopontine nucleus (SMA-PPN) network.  In CAP the gait/balance problem includes the SMA-PPN but with a major contribution from areas serving general attention and self-awareness.

The SMA is an area of frontal cortex just in front of the primary motor cortex.

The PPN is a complex nucleus at the pons-midbrain junction (PMJ, below):

Here’s why this paper’s results could be important: 

The SMA, as you can see from its superficial location, is an easy target for non-invasive magnetic or electrical trans-cranial stimulation.  TCS is still in its infancy but is starting to show some modest benefits for some movement and cognitive disorders.

The PPN has long been known to be important to the balance issue in PSP and Parkinson’s.  This new research result focuses attention on that nucleus as a potential target for deep-brain stimulation or as a target for surgically implantable stem cells or viral vehicles of genes for depleted enzymes.  Dr. Stuart Clark and colleagues at The State University of New York, Buffalo have already created an experimental model of PSP in rats by altering the function of the PPN.  The results from Welter et al tend to validate the relevance of that model to PSP.  

Five complicated pieces – part 1

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Every day I search PubMed on the term “progressive supranuclear palsy.”  In fact, the PubMed bookmark on my browser is set to that search term as the default.  I’m used to seeing about three new articles appear per week, but over the past 10 days or so, nothing. 

But today, just as I was I wondering if some human being critical to this process at the National Library of Medicine had been downsized, five new articles appeared, and they’re all pretty interesting.  To celebrate the event, I thought I’d share elevator explanations of each, starting here with the first two:

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G. Meduri et al. / FKBP52 Decrease is an Early Feature of Different Tauopathies

A group at France’s equivalent of the NIH (called “INSERM”) discovered in 2010 that a protein called FKBP52 plays a role in the normal degradation of the tau protein.  Now, (links: abstract; full pdf) some of those same researchers have found that levels of FKBP52 are reduced in the brain cells with highest levels of abnormal tau.  They used mouse models and also frontal cortex brain tissue from autopsies showing Alzheimer’s, familial frontotemporal lobar degeneration, Pick’s disease, corticobasal degeneration and PSP.

Furthermore, they found those reduced levels even before any damage had taken place.  This suggests that the direction of causation proceeded from reduced FKBP52 to excessive tau to brain cell damage.  This in turn suggests that a hypothetical imaging procedure showing FKBP52 in the brain could serve as a pre-symptomatic or very early-stage diagnostic test.

The most important implication of this insight is that increasing FKBP52 production (or slowing its rate of loss) could prevent, slow or halt the disease process.  Just as important, it found the same thing in all of those tauopathies, suggesting that they could share the same treatment.

All the more reason for researchers and drug companies interested in Alzheimer’s disease to start out by looking at PSP, which for several reasons is easier to do research on.

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Calisi D et al / Case report of FSH dystrophy Obscuring PSP

Facio-scapulo-humeral dystrophy (FSHD) is a common form of slowly-progressive muscular dystrophy that can start anywhere from childhood to late middle age.  It can eventually cause major disability, but does not shorten lifespan or affect cognition or behavior.

Neurologists in Chieti, Italy report a man in his early 60s with FSHD since childhood confirmed by genetic testing and muscle biopsy.  (Here’s the abstract.) About 5 years before, he had begun to develop more general difficulty with movement that progressed rapidly.  It was diagnosed as atypically rapid progression of FSHD until a neurologist noticed specific signs of PSP that do not occur in FSHD such as vertical gaze palsy, rigidity in the neck, trouble swallowing liquids, impairment of “executive” cognitive abilities and compulsive behavior.  Brain MRI showed atrophy of the midbrain, as is typical for PSP. 

The point is that while PSP is not currently curable, receiving an accurate diagnosis can help in one’s residential, healthcare and financial planning, avoid useless diagnostic tests and treatments, and allow participation in clinical trials.  Once we have a way to slow or halt the progression, an accurate diagnosis could be lifesaving. 

Thanks to this modest case report, physicians taking care of people with FSHD and other chronic, relatively benign disorders affecting movement now know to consider a second diagnosis of PSP in someone with an unusual rapid progression and new neurological features related to the brainstem and frontal lobes.