Should I get a DaTscan or PET scan to confirm my diagnosis of Parkinson’s disease?

You can find out more about NPF's National Medical Director, Dr. Michael S. Okun, by also visiting the NPF Center of Excellence, University of Florida Center for Movement Disorders & Neurorestoration.

This past month, the FDA approved DaTscan (Ioflupane I 123 injection, also known as phenyltropane), a radiopharmaceutical agent which is injected into a patient’s veins in a procedure referred to as SPECT imaging. DaTscan is an important addition because it is anticipated to be more widely available than other techniques and it has received several major endorsements from leading scientists.

One of the most frequently asked questions about Parkinson’s disease on NPF’s “Ask the Doctor” web-based forum is whether or not to pursue DaT or PET scanning to confirm a diagnosis of Parkinson’s disease.  In this month’s What’s Hot column, we offer a review of the subject in light of the recent FDA approval.

If you have already received a diagnosis from an expert, and are responding well to dopaminergic therapy, in most cases of Parkinson’s disease, PET and SPECT scans would not add any new information and therefore likely to be unnecessary. In cases where the expert is not sure of the diagnosis – is it essential tremor or Parkinson’s, for example-- or where a potentially risky procedure is being considered (e.g. deep brain stimulation surgery), it is reasonable for your doctor to recommend a PETscan or DaTscan.  It is important to keep in mind that PET and SPECT scans should be performed only by experienced neurologists who have executed a large volume of Parkinson’s disease scans, because experience is important in accurately reading these imaging results.

Here is how it works:    First, the person receives an injection of the imaging agent. After injection, the compound can be visualized by a special detector called a gamma camera.  This so-called scan measures something called the dopamine transporter (DaT), and it can help a doctor determine if patients are suffering from essential tremor, vs.  Parkinson’s disease or another parkinsonism (i.e., other problems affecting dopamine systems that have symptoms of Parkinson’s disease). . The side effects are minimal (e.g. headache, dizziness, increased appetite and creepy crawly feeling under the skin). PET scans and DaT/SPECT scans examine the "function" of the brain rather than its anatomy. This is an important point because unlike in strokes and tumors, the brain anatomy of a Parkinson’s disease patient is largely normal. These scans can show changes in brain chemistry, such as a decrease in dopamine, which identify Parkinson’s disease and other kinds of parkinsonism. There are several compounds available for use in both PET and SPECT scanning; however PET scans typically focus on glucose (sugar) metabolism, and DaT/SPECT scans focus on the activity of the dopamine transporter. 

The new DaT scans use a substance that "tags" a part of a neuron in the brain where dopamine attaches to it, showing the density of healthy dopamine neurons.  Thus, the more of the picture that "lights up", the more surviving brain cells. If the parts of the brain where dopamine cells should be remain dark in the scan, an expert reader may diagnose early brain degeneration.  This could mean either Parkinson’s disease or parkinsonism.

In Parkinson’s disease, people will lose cells in a part of the brain associated with movement referred to as the basal ganglia.  There is a common pattern seen in people with Parkinson’s, with the cell loss starting on just one side, towards the back of the basal ganglia, and deep down.  Over time, the affected area spreads across the basal ganglia.  However, as part of the normal aging process, it is completely normal to lose some of these cells—therefore it takes an expert to read these scans and figure out if the changes are due to normal aging or due to disease.  There are typical scan patterns that may emerge. The more widespread the decrease in uptake on the scan, the more advanced the degeneration.

Interpretations can, however, be tricky.  The first determination is whether the scan is normal or abnormal.  Next, the expert will determine if the scan follows the pattern of Parkinson’s disease.  Finally, a determination will be made as to the severity of the brain cell loss.  There are only a few centers that regularly perform very high quality PET scans for Parkinson’s disease, and these centers usually have experts in interpretation.  Two centers with leading reputations include Long Island Jewish Hospital in New York (North Shore) and Washington University Hospital in St. Louis, although there are others.

PET scans are FDA-approved for the diagnosis of dementia, but not for the diagnosis of Parkinson’s disease. However, if you or your relative has cognitive impairment, the scan can be ordered to examine for the presence of Alzheimer’s changes as Parkinson’s disease often co-occurs with Alzheimer’s. The cost can range from $2,500-5,000.  Many expert centers perform PET scans for free under research protocols.

Recently, in studies that have attempted to diagnose Parkinson’s early in its course, researchers have found that a subset of patients thought to have Parkinson’s disease have turned up with negative PET or SPECT scans.  These patients do not seem to develop the progressive symptoms of Parkinson’s disease.  These findings are humbling, and they lend credence to the importance of following patients over long periods of time to ensure both accurate diagnosis, and also appropriate treatment. 

An example DaTscan is shown below and it demonstrates essential tremor on the left (normal DaT), and a parkinsonian syndrome on the right (decreased DaT).   

Brain scan


An example of a PET scan is below and it reveals: in the top panel a normal scan, in the middle panel abnormalities in the putamen (red uptake in the figure) in a patient with Parkinson’s disease, and in the lower panel a return to an almost normal scan following the introduction of levodopa.  

Brain scan


In conclusion, in cases where the diagnosis is uncertain (e.g. Parkinson’s disease versus essential tremor), a DaT or PET scan can be very useful.   But patients and their families need to be aware that in general, these scans cannot reliably separate Parkinson’s disease from parkinsonism (multiple system atrophy, corticobasal degeneration, progressive supranuclear palsy), and thus if you seek a scan you will still need an expert to sort out your clinical picture and diagnosis. If you have already been diagnosed, if your symptoms are progressing, and you have an adequate response to medications, most likely a PET or DaTscan would add little new information and therefore not be necessary.

Selected References:

Okun, M.S., Fernandez H.H. Ask the Doctor About Parkinson's Disease. Demos Medical Publishing, 2009.

Kägi G, Bhatia KP, Tolosa E. The role of DAT-SPECT in movement disorders. J Neurol Neurosurg Psychiatry. 2010 Jan;81(1):5-12. Review.

Booij J, Knol RJ. SPECT imaging of the dopaminergic system in (premotor) Parkinson's disease. Parkinsonism Relat Disord. 2007;13 Suppl 3:S425-8. Review.

Stoessl AJ. Positron emission tomography in premotor Parkinson's disease. Parkinsonism Relat Disord. 2007;13 Suppl 3:S421-4. Review.

Scherfler C, Schwarz J, Antonini A, Grosset D, Valldeoriola F, Marek K, Oertel W, Tolosa E, Lees AJ, Poewe W. Role of DAT-SPECT in the diagnostic work up of parkinsonism. Mov Disord. 2007 Jul 15;22(9):1229-38. Review.

Images:

1) http://www.aragoninvestiga.org/tag/parkinson/, Google Images

2) http://www.suite101.com, Google Images

Posted: 2/1/2011 5:39:16 AM by Cathy Whitlock


Browse current and archived What's Hot in PD? articles, the National Parkinson Foundation's monthly blog for people with Parkinson's written by our National Medical Director, Dr. Michael S. Okun. 

August 2014
Everything You Need to Know About Medical Marijuana and Parkinson’s Disease

July 2014
The End for Levodopa Phobia: New Study Shows Sinemet is a Safe Initial Therapy for Treatment of Parkinson's Disease

June 2014
Is light therapy a potential treatment modality in Parkinson’s disease?

May 2014
How does the most common genetic cause of Parkinson’s Disease (LRRK2) cause Parkinson’s disease and could it be used to help develop a better therapy?

April 2014
An Update on DAT Scanning for Parkinson’s Disease Diagnosis

March 2014
Could Northera (Droxidopa) Be an Alternative Treatment for Low Blood Pressure and Passing Out Symptoms?

February 2014
The Dream of a Pill Free Existence and the Continuous Dopaminergic Pump for the Treatment of Parkinson's Disease

January 2014
Should I take Inosine to Raise my Uric Acid Levels and Treat my Parkinson’s Disease?

December 2013
Could Fungus and Mold be an Important Contributor to Parkinson’s Disease?

November 2013
Pimavanserin and the Hope for a Better Drug for Hallucinations and Psychosis in Parkinson’s Disease

October 2013
Halting of the Creatine Study

September 2013
The Importance of Identifying and Treating Caregiver Strain

August 2013
Putting Parkinson’s Disease Information into the Palm of Your Hand: Parkinson’s Enters the Smartphon

July 2013
What Parkinson’s Disease Patients Need to Know about H. Pylori Gastrointestinal Infections

June 2013
A2A Receptor Antagonists and Parkinson’s Disease Treatment

May 2013
Another Setback for Trophic Factor Treatment in Parkinson's Disease

April 2013
IPX066 and What Patients Really Want in New Carbidopa/Levodopa (Sinemet) Formulations

March 2013
The Weather Forecast for Parkinson’s Disease Calls for Worldwide Economic Storm

February 2013
Defeating the Barriers to Implementing Exercise Regimens in Parkinson’s Disease Patients

January 2013
When should you start medication therapy for Parkinson’s disease?

December 2012
Neurologist Care Reduces Hospitalizations in Parkinson's Disease

November 2012
A Victory in Court for Parkinson's Disease Patients who Require Ongoing Rehabilitative Therapies

October 2012
Given the recent FDA announcement about Mirapex (pramipexole), should I be worried about dopamine agonists?

September 2012
What about the new Parkinson’s Disease Vaccine? What should I know?

August 2012
Caffeine as a Potential Treatment for Parkinson’s Disease

July 2012
Time to Consider GPi DBS for Parkinson’s Disease: A Shift in the Practice of Patient Selection for DBS

June 2012
A New Treatment for Parkinson’s Disease-Related Constipation

May 2012
Too Many Pills: Improving Delivery Systems for Parkinson’s Disease Drugs

April 2012
Measuring Quality and Assessing Depression in Parkinson's Disease

March 2012
Watch out for Unexpected Obstacles if You Use a Cueing Strategy to Break Freezing of Gait in Parkinson’s Disease

February 2012
Pill Color, Generic Medications and Insurance Issues: Important Medication-Related Tips for the Parkinson’s Disease Patient

January 2012
Are Blood Tests for Parkinson’s Disease on the Horizon?

December 2011
Placing Stem Cells in Animal Models of Parkinson’s Disease: Another Important Step

November 2011
Important News for the Parkinson’s Disease Community: More Evidence that Sinemet and Madopar are Not Toxic and do Not Accelerate Disease Progression

October 2011
The Case for All Parkinson’s Disease Patients to be Co-managed by a Primary Care-Neurologist Team

September 2011
Scientists say Research on Brain Proteins Involved in Parkinson’s Disease is “Shaping” Up

August 2011
Who Actually Takes Care of Most of the Parkinson’s Patients Worldwide: The Need for Education and the Parkinson’s Toolkit

July 2011
If you are Dizzy or Passing Out, it could be Your Parkinson’s Disease or Parkinson’s Disease Medications

June 2011
How Will Group Visits for Parkinson’s Disease Fit into the Future of Parkinson’s Disease Care?

May 2011
Why Patients Should be Wary of Chelation Therapy for Parkinson’s Disease

April 2011
Opening the Door to Gene Therapy in Parkinson’s Disease: The Need for Refinement of the Technology and Approach

March 2011
Does it Matter if I Can’t Get Brand Sinemet?

February 2011
Should I get a DaTscan or PET scan to confirm my diagnosis of Parkinson’s disease?

January 2011
A Critical Reappraisal of the Worst Drugs in Parkinson’s Disease

December 2010
Environmental Risks for PD: Manganese, Welding, Mining, and Parkinsonism

November 2010
Calling for the FDA to Revise the Eight Sinemet a Day Rule

October 2010
Dry Cleaning Solvents and Potential Environmental Risks for Developing Parkinson’s Disease

September 2010
Maintaining the Balance: Why Parkinson’s Disease Patients Need to Understand Drug Recalls, Withdrawals, and Safety Alerts

August 2010
Shining a Light on Parkinson’s Disease: Optogenetics Has a Bright Future in Research

July 2010
Poor Medication Management of Parkinson's Disease During Hospital Admissions: Patients and Families Can Improve Their Hospital-Based Management

June 2010
Why Are Patches and Continuous Release Technology a Big Deal to Parkinson's?

May 2010
Is the PD SURG Trial Another Surge Forward for DBS Therapy?

April 2010
Cycling in PD in Those Who Can’t Walk: Is it Possible?

March 2010
New iPS Stem Cells for PD: What Does it Mean?

February 2010
Time for Comprehensive Care Networks for PD

January 2010
Is Parkinson's Disease a Prion Disease?

December 2009
Parkinson's Disease Linked to Gaucher's Disease

November 2009
Brain Cells Keep Time Stamps: Implications for Parkinson's Disease Therapies

October 2009
Is it Safe to Have an MRI with a DBS in Place?

September 2009
Take Care of Your Bones as They Are Affected in Parkinson's Disease (Even in Men)

August 2009
Is it Time to Start Paying Attention to Pain Symptoms in Parkinson's Disease Patients?

July 2009
Glutathione Fails to Demonstrate Significant Improvement in PD Symptoms

June 2009
Keeping an Eye on Trials Important to the Parkinson's Disease Patient

May 2009
Increased Risk of Melanoma in Parkinson's Disease

April 2009
Finally a DBS Expert Consensus Statement Aimed at Their True Customers: The Patients

March 2009
Pesticides and Environmental Exposure in Parkinson's disease: Should We Stay Away From the Stink Truck?

February 2009
Is Exercise Effective Treatment and Protection Against PD?

January 2009
Why are Transplant Trials Struggling to Succeed in the Treatment of PD?

December 2008
Are Monoamine Oxidase Inhibitors Disease Modifying or Neuroprotective in PD?

November 2008
Update on Gene Therapy for Parkinson's Disease

Currently: 3.8 (4 ratings)

Print

Each month, we will feature a new column by NPF's National Medical Director, Dr. Michael Okun, on the latest developments in Parkinson's disease research. Read the latest "What's Hot in PD?" below.

Subscribe to this blog

RSS