PSP: SOME ANSWERS( continued)
The most common and characteristic eye movement problem in PSP is an impaired ability to move the eyes up or down. This can interfere with eating or with descending a flight of stairs, among other things. This problem is not usually as vexing for the patient and family as the inability to maintain eye contact or to coordinate eye movements while reading, but is much easier for the doctor to detect. Reduced vertical eye movement is usually the first clue that the diagnosis is PSP. Although other conditions, particularly Parkinson’ s disease and normal aging, can sometimes cause difficulty moving the eyes up, PSP is nearly unique in also causing problems moving the eyes down. This problem often takes the form of eye movement“ apraxia,” where the patient can move the eyes up or down only after several requests or with a delay after initiating the effort. In most people with PSP, the difficulty in downward eye movement starts out as a slowing of that movement. This can also interfere with vision, but can be very difficult for a physician to detect. Another eye movement problem that starts early in the illness is square wave jerks— rapid, involuntary, right-left movements that interfere with the ability to precisely aim the eyes at a target.
Yet another eye problem in PSP can be abnormal eyelid movement— either too much or too little— called blepharospasm. A few patients experience forceful involuntary closing of the eyes for a few seconds or minutes at a time, while others have difficulty opening the eyes, even though the lids seem to be relaxed.
They may try to use the muscles of the forehead, or even the fingers, in an effort to open the eyelids( called apraxia of lid opening). About 20 % of patients with PSP eventually develop one of these problems. Others, on the contrary, have trouble closing the eyes, and therefore, these people blink very little. While about 15 – 25 blinks per minute is normal, people with PSP blink, on average, only about 3 – 4 times per minute.
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This reduced blinking can allow the eyes to become irritated and react by producing extra tears, which in itself can become annoying.
What sort of speech problems occur?
The same general area of the brain that controls eye movement also controls movements of the mouth, tongue, and throat, and these movements also weaken in PSP. Speech becomes slurred in most patients after three or four years, on average, although it is the first symptom in a few patients. In Parkinson’ s disease, the speech problem is characterized by soft volume and rapid succession of words. In PSP, however, the speech may have an irregular, explosive, or rubber-band quality( called spastic speech) or a drunken quality( ataxic speech) or may have the same softening of speech as Parkinson’ s disease. Most commonly, there is a combination of at least two of these three features in the speech of patients with PSP.
The speech difficulty of PSP, in combination with the forgetfulness, slow mental responses, personality change, apathy, and poor eye contact during conversation can create an erroneous impression of senility or dementia. True dementia of a sort does occur in many people with PSP, however, and is discussed below.
What about the swallowing problems?
This is the source of the most important and dangerous long-term complications of PSP. Swallowing tough foods or thin liquids can become difficult because of throat muscle weakness or incoordination. This tends to occur later than the walking, visual, and speech problems, but can become very troublesome if the patient tends to choke on food or if food goes into the breathing passages. Usually, problems managing thin liquids precedes difficulty with solid food because the swallowing muscles have difficulty creating a watertight seal that separates the path to the stomach from the path to the lungs. This is true with many neurological diseases. For non-neurologic conditions, such as stricture of the esophagus, the difficulties start with solid foods. Repeated, minor, often unnoticed episodes of small amounts of food and drink dripping into the lungs can cause pneumonia. Often, it is not apparent to the physician or family that the PSP patient’ s pneumonia is in fact the result of subtle aspiration. But aspiration pneumonia is the most common cause of death in PSP.