Here’s the “Ask the Doctor” section of the Fall ’08 CurePSP Magazine, which I received in the mail on 12/1/08: (not yet available on psp.org)
Ask the Doctor
Lawrence I. Golbe, MD
Director of Research and Clinical Affairs, CurePSP
CurePSP Magazine, Fall ’08
Q: I’ve heard that some people with a diagnosis of PSP actually have corticobasal degeneration. Should I worry about that and get another opinion on my diagnosis?
A: No. PSP and corticobasal degeneration (CBD) are very similar and some experts think they’re even two versions of the same basic disease. They are treated similarly, start at the same average age, have the same long-term prognosis and even share a specific genetic variant as a contributing factor. The difference is that in CBD, there is less falling than in PSP but more difficulty in using the limbs for fine movement. CBD also tends to develop minor jerking movements and abnormal postures of the limbs. The limb problems of CBD are typically highly asymmetric — that is, far worse on one side than the other. All of the symptoms of both PSP and CBD are treated “palliatively,” which means that if the symptom appears, the doctor treats it as a symptom. Some day, if we are able to cure or slow the progression of one but not the other, or if the cures for the two disorders are different, then it will be important to differentiate between the two diagnostically.
Q: OK, so are there any diseases that have cures or very useful treatments that can be mistaken for PSP?
Parkinson’s disease (PD) is sometimes mistaken for PSP when it fails to respond to levodopa, a drug that replaces insufficient brain dopamine. Often, this is simply the result of insufficient dosing. Very often patients with PD have difficulty looking in the upward direction. The combination of this with a much greater-then-average need for levodopa can fool an inexperienced physician into diagnosing PD as PSP. But PD would not display difficulty looking down, the cardinal feature of PSP, and differs in most other respects as well.
Another condition that can be mistaken for PSP and requires special treatment is multiple small strokes. Aggressive management of lipids and blood pressure, administration of blood thinners, repair of narrowed arteries feeding the brain and treatment of heart problems can all reduce the risk of future strokes.
Finally, a very rare brain infection called Whipple’s disease can superficially mimic PSP. However, it usually has rhythmic movements of the eyes and jaw that are absent in PSP. It is diagnosed via MRI with contrast and a spinal tap and treated with antibiotics. In 20 years as a PSP specialist, I have never seen a case.