New to me, also. But My reseasrch just now, I'll cut & paste
Rare Disease
In CBD, abnormal levels of tau accumulate in the brain cells, eventually leading to their deterioration and causing symptoms of the condition. Exactly why this happens is unknown. [3] Tau also appears to play a role in other neurodegenerative diseases such as Alzheimer disease , progressive supranuclear palsy , and frontotemporal dementia
NHS
People with corticobasal degeneration (CBD) develop a range of difficulties with movement, speech, memory and swallowing. The condition tends to develop gradually, which means it can be mistaken for another condition at first – such as Parkinson's disease, dementia or a stroke.. The symptoms typically become more severe over several years, although the speed at which they worsen varies.
Mayo Clinic
Corticobasal degeneration is a rare disease in which areas of your brain shrink and your nerve cells degenerate and die over time. The disease affects the area of the brain that processes information and brain structures that control movement. This degeneration results in growing difficulty in movement on one or both sides of your body.
UCSF
A person with the disease often becomes immobile five years after symptoms emerge. Within 10 years, pneumonia or other bacterial infections may lead to life-threatening complications. Significant advances in the understanding of CBD have been made and the UCSF Memory and Aging Center is actively involved in researching the cause and course of
"Could someone help me or comment on whether what works for idiopathic Parkinson's is also effective against corticobasal degeneration?"
PD drugs aren't effective. Sorry. Nothing is effective because this disease can cover the entire spectrum of neuro degenerative problems and progresses very rapidly.
Life expectancy is about 10 years maximum with the CBD disease unlike PD.
Some neurologists consider CBD to be a form of PD and hence prescribe PD drugs to no avail because they think the person will respond since it is nothing more than "atypical PD". It isn't.
If you think of the development of the covid-19 virus using "gain-of-function" technology, the toxic tau functions in a similar manner in a person's brain with CBD. A no-win situation and different from PD.
"idiopathic" PD is a somewhat dated term and potentially misleading in many cases.
I'm pretty sure you are already aware that there is no real treatment for Corticobasal Degeneration (CBD). I feel bad for your friend or anyone else having to face CBD with its known outcome.
Some things that almost always come up in neurodegenerative diseases, as you are well versed in are excess oxidative stress, neuroinflammation, mitochondrial dysfunction, decreased melatonin and melatonin receptor production, gut dysbiosis and neuron death.
Since the cause of the disease is unknown, the rarity of CBD makes specific research a very quick study in futility, you are left to choose these as your targets to try and reverse or slow the rapid disease progression that is CBD. You have already named some of the best options to attempt to ameliorate or reverse this damage.
To your list of things to consider, I would add FMT, Short Chain Fatty Acids (SCFA) producing bacteria, fermentable fiber, Albert/wriga's broccoli seed protocol, high dose melatonin, earthing, Photobiomodulation and HDT. These will go a long way in controlling the issues that are likely to allow CBD to progress The issues that will come up along the way will have to be dealt with accordingly.
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