Why have I heard PSP referred to as an“ atypical parkinsonism disorder”? Many people with PSP may be told, prior to a more definitive PSP diagnosis, that they have“ parkinsonism.” They may hear the term“ atypical parkinsonism” used as an umbrella term referring to PSP and other related diagnoses. Parkinsonism is a term that describes a constellation of symptoms similar to Parkinson’ s disease, including tremor, imbalance, slowness of movement, and stiffness of muscles. Sometimes a provider will say someone has“ parkinsonism” in very early stages of symptoms, when it is not yet clear what diagnosis someone has.
“ Atypical parkinsonism” is a term frequently used to refer to diseases that look like Parkinson’ s disease in many ways, and may even be initially diagnosed as Parkinson’ s disease but then have other symptoms not as commonly seen in Parkinson’ s disease. These“ atypical” symptoms may include earlier and more profound changes to vision, balance, and speech as well as a lack of robust response to the Parkinson’ s disease medication carbidopa-levodopa. Other diagnoses that are commonly referred to as atypical parkinsonism diseases include corticobasal degeneration( CBD) and multiple system atrophy( MSA). Because of the similarities of care journeys and needs of PSP, CBD, and MSA, it is not unusual for them to be served by the same healthcare providers, support groups, and organizations, including CurePSP.
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What causes PSP, and what is happening in the brain? The direct cause of PSP is not fully understood. However, we do know that it has to do with the clumps of tau protein. Tau is a normal protein found in brain cells and is currently thought to help maintain the microtubules, which are stiff rods that function as the brain cells’ internal transportation and skeletal system. In PSP, the tau seems to become abnormally folded, which causes it to stick together and become stuck inside the cell. The areas of the brain that have cells with tau inside of them also exhibit impaired neuron function and neuronal death. The clumps’ technical name is neurofibrillary tangles. Alzheimer’ s disease and frontotemporal dementia also involve misfolding of the tau protein.
The symptoms of PSP are caused by a gradual deterioration of brain cells in a few places in the base of the brain. The most important such place, the substantia nigra, is also affected in Parkinson’ s disease; damage to it accounts for the symptoms that PSP and Parkinson’ s disease have in common. However, several important areas that are affected in PSP are normal in Parkinson’ s disease, and vice versa. Additionally, Parkinson’ s disease is caused by the misfolding of a different protein, called alpha synuclein, and under the microscope, the appearance of the damaged brain cells in PSP is quite different from those in Parkinson’ s disease. Instead, it resembles the degeneration in Alzheimer’ s disease and frontotemporal dementia, although the location of the damaged cells is quite different in PSP compared with these other tauopathies.
Genetic differences and exposure to certain chemicals are being explored as possible causes, but ultimately, we are not yet sure why tau misfolds or people get certain brain disorders like PSP. For someone who is personally impacted by PSP, we recognize that not knowing the cause can be extremely frustrating, confusing, and scary. Researchers and doctors are working hard to understand PSP and other related neurodegenerative diagnoses, and we hope their work will lead to more answers and treatment options soon.
Is PSP genetic? PSP very rarely runs in families and is not considered a genetic disease. Fewer than one in 20 people with PSP knows of even one other family member with PSP, and detailed neurological