Do I Have Parkinson's Disease? Article 1: The Basics

"Do I have Parkinson's" That's about the most common search phrase related to the disease that the Google search engine gets from worried net-surfers. I know that because I checked after reading a book on search engines while waiting in the interminable DMV line yesterday. The book was boring and it made me wonder if anyone is actually enjoying what I write. I figure that if you're going to give me your valuable time to read this, I absolutely need to make it interesting. Neurology is not exactly the subject from whence romantic comedies arise. Oh wait, what about "Love and Other Drugs"? Well if Hollywood can spawn an even half-interesting saga based on a neurological degenerative disease of the brain, I can at least try and keep your valuable attention in discussing this most important question.

In his recent book, "Always Looking Up: The Adventures of an Incurable Optimist," Michael J. Fox describes his first encounter with Parkinson's. In 1990 he says he woke up with a hangover and noticed a twitching in his left pinky finger. Worried, he consulted a neurologist who appropriately told him it was probably nothing serious, maybe a consequence of being hit in the shoulder playing ice hockey.

What tests could that neurologist have done on Mr. Fox so that he'd have known Fox had a more serious long-term illness? Nothing. Unfortunately what was true back in 1990 is still true today in 2010. No blood test, spinal tap, EEG, CT or MRI scan can confirm that someone has Parkinson's disease(PD). Not even DNA testing which can tell whether or not you're kind of more likely to get it, can make the diagnosis. The only tool left standing here is a knowledgable and skilled neurologist.

Even with a thorough exam and interview, diagnosis can still be difficult the way the disease starts showing up and slowly revealing itself varies a great deal from person to person.

Research on finding better ways to answer the question earlier and with absolute certainty has not yet yielded anything yet. Recently a blood protein, EGF, was found to predict who is at risk for mental impairment down the road, but it's only good for patients who already have Parkinson's.

But you say, "Is there not a specific brain area that degenerates? Why then not just look at that area with a very powerful MRI scanner? " Even the latest generation of MRI brain scanners rarely reveal anything abnormal. Unfortunately we're not talking about a big chunk of brain here. The actual area affected is only about 5 millimeters thick and just slightly longer. Small as that is, it can be seen on MRI but there's another problem: in most patients with the disease it remains about the same size, the important dead cells getting replaced by other scar-like brain cells. The area still has the same appearance on a scan.

Maybe if we know a bit more about the disease ourselves: what causes it, what areas of brain get sick, what results from these areas being sick, etc. we could think through our own situation and see the big picture. Maybe not, but at least it could get us thinking about the situation a bit more like a neurologist. Let's see:

OK, as I said there's a tiny center of special brain cells that make lots of the brain chemical dopamine on each side of the brain. This area, the substantia nigra, the one that I said was 5mm thick starts losing its dopamine cells. They start dying off and usually for no apparent reason. Doctors call that an "idiopathic" disorder which is just lingo for, "we have no idea what causes it." This "idiopathic" death of nerve cells in this tiny area ends up having effects all over the brain.

The dying cells when they're still good, manufacture lots of dopamine and like an array of microscopic perforated sprinkler garden hoses, they branch out and send dopamine-squirting projections all over the brain. They make so much dopamine that only about 10,000 cells on each side are enough to supply a brain of about 100 billion active cells with more than enough dopamine. There are two of these miniscule substantia nigra regions, with each one located very deeply within each brain-half.

Dopamine-producing nerve cells in the Substantia Nigra send dopamine-squirting branches to other regions.

One area of the brain that has a huge role in controlling movement needs a lot of dopamine to function adequately. Made up of smaller movement-control centers, and collectively known as the basal ganglia, it relies heavily on this dopamine supply to function normally. This rather complicated control region also sits deep within the brain has new functions still being discovered every day. Keeping it simple, let's for now assume it has only two essential jobs assigned to itself: the initiation of body movements and the maintenance of smooth movements once they have been initiated. Both these jobs become severely compromised when there's not enough dopamine around..

The basal ganglia neurons normally take orders from the higher brain and feedback from the body and from that, they send out coordinated signals to the muscles of the body. When dopamine is in short supply they start to send out more and more disorganized and even random impulses to the muscles of the body, usually beginning on one side only. The results include twitching, tremor, weakness, freezing or halting of movement (akinesia), slowing of movement (bradykinesia), loss of control resulting in uncontrolled spontaneous movement (dyskinesia), cramping, and a gradual loss in the ability to initiate movement.

There's normally so much extra dopamine made that the abnormal movements start to appear only after 80 percent of the sufferer's dopamine cells have died. Even with losing this many brain dopamine cells, the substantia nigra still it appears intact on MRI scan.

Parkinson's however does not just involve disordered movement;Many other abnormal things occur in the body and the mind. That's because these dying dopamine-producing cells from the substantia nigra also send dopamine-squirting projections to other important brain regions. These other regions also need a regular supply of dopamine to do their jobs correctly. One area called the hypothalamus regulates autonomic functions of the cardiovascular system, other organs and cycles of sleep. Another dopamine-dependent area, the limbic system presides over emotions, desires and motivated behavior. Thus, symptoms of PD involve many more abnormalities than just disordered-movement.

The dying dopamine-producing cells of the substantia nigra send dopamine to many brain regions.

All these different potential malfunctions occur in a different sequence and to a different degree in individual patients so that you or I would present very different pictures to a neurologist evaluating us even if we both had the same disease.

In an attempt to make the diagnosis easier in the early stages of its course, the National Parkinson Foundation has outlined the ten most common early warning signs that suggest that you or I might have Parkinson's.

Here they are in summary: Tremor or shaking greater on one side; Small handwriting; Loss of smell; Trouble sleeping; Trouble/stiffness in moving or walking; Constipation, Soft or Low Voice, Loss of facial expression, "masked facies"; Dizziness and fainting; Stooping or hunching over.

Notice that only five of the ten early symptoms involve disorders of movement. Two additional symptoms frequently associated with early PD include excessive daytime sleepiness (EDS) and new psychiatric disturbances. Anxiety and depression can appear as early as 3-5 years before any movement problems show up. For a more detailed and excellent review of the "other" symptoms of PD that don't involve movement, I suggest the following link:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2654529/

Marshall Davidson MD, aka. "Dopadoc" runs the online journal "Dopadoc's Parkinson's Journal" at http://www.dopadoc.com/

NEXT in Article 2: How neurologists make the diagnosis