Time for my occasional, highly selective roundup of recent research. But this time, it’s not about molecules or images. Instead, it’s three clinical things of possible immediate importance in our understanding or everyday management of PSP.
“Neuropathy” means problems with nerves outside the brain and spinal cord, sometimes causing numbness, tingling, imbalance, pain or weakness. Dr. Yumkham Devi and colleagues at the All India Institute of Medical Sciences in Rishikesh have performed one of the few studies to date of neuropathy in PSP. Using both subjective symptoms and nerve conduction testing, they found some degree of damage to the nerves in the limbs in 65% of their patients with PSP and 51% of those with Parkinson’s. The nerves were affected symmetrically, as typically occurs with the neuropathy of diabetes or malnutrition. In contrast, problems with individual nerves are more typical of compressive causes like carpal tunnel syndrome or sciatica. The authors hypothesize that the abnormal tau of PSP could be damaging the Schwann cells, which provide the insulating coat around most nerve fibers. Other research has suggested that Parkinson’s can cause neuropathy through nutritional disturbances such as poor absorption of vitamins by the intestine.
Editorial comment: With only 15 people in this trial with PSP and neuropathy, clear conclusions about the relationship with levodopa use were impossible. However, the high frequency (65%) of neuropathy in PSP and the previous results on nutrition as a likely cause of neuropathy in Parkinson’s are instructive. They provide an important reason for those with PSP to maintain nutrition carefully despite their swallowing problems and to avoid the constipation that PSP often causes. Both issues are very manageable causes of nutritional disturbance that could cause neuropathy.
Dr. Éadaoin Flynn and colleagues of Trinity College, Dublin have reviewed the literature of the dysphagia – the swallowing difficulty – of PSP. Only 20 of 932 published studies of the topic met their rigorous criteria. The most common issues occurred in the mouth, with difficulty coordinating the tongue. The single most common problem was transferring the food from the front of the mouth to the back, with incomplete swallows in 98%. Less common problems occurred in the pharynx and esophagus. Penetration of food into the airway above the vocal cords occurred in 40% and actual aspiration, penetration past the vocal cords, in 24%.
Editorial comment: All PSP experts I know advise an evaluation by a speech/swallowing professional early in the course of the disease. Some even feel it should be done immediately upon diagnosis even if there is no subjective difficulty swallowing. All agree that it should be repeated at least annually or if the symptoms worsen significantly. The most common cause of death in PSP is pneumonia caused by aspiration, where chewed food irritates the lung tissue, making it hospitable to the growth of any bacteria subsequently inhaled from the air. This is low-hanging fruit for those with PSP, as the various modification to diet and eating methods really can make a difference in life expectancy.
Dr. Michał Markiewicz and colleagues at the Medical University of Warsaw, Poland, have reviewed the literature on what we know about the quality of life in PSP and how it should influence everyday management. They discuss the strengths and weaknesses of the PSP-QoL Scale and cite data showing that items on depression and daytime sleepiness correlate best with overall reported quality of life.
Editorial comment: Depression and daytime sleepiness are actually caused by the PSP process itself at work in the areas of the brain controlling emotion and sleep; they’re not just indirect results of other PSP-related symptoms. Therefore, direct treatment of these two symptoms with medication, exercise, or psychological intervention may usefully improve one’s quality of life.
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