Effective And Efficient Diagnosis Of Parkinsonism: The Role Of Dopamine Transporter Spect Imaging With Ioflupane I
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Am J Manag Care. 2004 20:S97-S109 Parkinsons disease is a common neurological illness associated with significant patient and payer burden. Its accurate diagnosis is challenging and misdiagnosis is common.1-3 Additionally, overdiagnosis of PD has been observed when only clinical symptoms were used to assess uncertain cases.4 Although experts in movement disorders are able to achieve greater diagnostic accuracy than their primary care or general neurology counterparts, they are still uncertain about the diagnosis in many patients. Adding to this, access to experts may be limited, thus further reducing opportunities for diagnosis.5 Imaging technology has improved considerably in recent years. The 2011 approval by the US Food and Drug Administration of the radiopharmaceutical ioflupane I-123 injection for striatal dopamine transporter visualization using single-photon emission computed tomography offers a new biomarker that can assist in differentiating conditions associated with nigrostriatal degeneration from those movement disorders without this degeneration .6 This publication is based on a roundtable discussion involving a multidisciplinary panel of experts with experience in movement disorders, nuclear imaging, managed care, and patient advocacy, and provides clinical criteria and algorithms to help guide managed care organizations and practitioners in the appropriate use of DaTscan imaging.
Overview of Parkinsons Disease
Why Choose Independent Imaging For My Datscan
Independent Imaging has been putting patients first for over 30 years. Our imaging centers in Wellington, Belle Glade, Lake Worth, and Royal Palm Beach, Florida are fully accredited by the American College of Radiology. Our board-certified radiologists are happy to answer any questions you may have, and we offer extended hours six days a week to accommodate our patients and referring physicians.
Before Taking This Medicine
You should not receive DaTscan if you are allergic to ioflupane I-123. Tell your doctor if you have ever had any type of reaction to another contrast agent, or to iodine.
To make sure DaTscan is safe for you, tell your doctor if you have ever had:
a thyroid disorder
if you have ever had an allergic reaction to potassium iodide or Lugol’s Solution.
Older adults may need kidney function tests before receiving DaTscan. Your kidney function may also need to be watched closely after you have received this medicine.
It is not known whether this medicine will harm an unborn baby. Tell your doctor if you are pregnant.
You should not breastfeed within 6 days after using ioflupane I-123. If you use a breast pump during this time, throw out any milk you collect. Do not feed it to your baby.
What Doctors Look For When Diagnosing Parkinsons
Certain physical signs and symptoms noticed by the patient or his or her loved ones are usually what prompt a person to see the doctor. These are the symptoms most often noticed by patients or their families:
Shaking or tremor: Called resting tremor, a trembling of a hand or foot that happens when the patient is at rest and typically stops when he or she is active or moving
Bradykinesia: Slowness of movement in the limbs, face, walking or overall body
Rigidity: Stiffness in the arms, legs or trunk
Posture instability: Trouble with balance and possible falls
Once the patient is at the doctors office, the physician:
Takes a medical history and does a physical examination.
Asks about current and past medications. Some medications may cause symptoms that mimic Parkinsons disease.
Performs a neurological examination, testing agility, muscle tone, gait and balance.
Prepping For The Datscan
After a few minutes, a young and artsy-looking woman appears and invites me to follow her into the bowels of the imaging center, to the prep room. She has short, spiky blonde hair with light pink streaks. We sit down and she asks me a series of questions as she checks boxes and writes short notes on a printed form. At one point I interrupt her.
How often do you do a DaTscan? I ask.
Rarely and were one of the few places in town that has the machine its expensive. You must have good insurance, she says.
She gives me a Xanax tablet to relax me and prepares an injection of a radioactive isotope, iodine 123. It will make my head glow for the camera when she sticks me into a machine that wraps around my head like its the contents of a burrito. Watching her work, I try to absorb the multicolored peace sign tattooed on the inside of her pale wrist. I wonder why she chose it and whether it helps her feel calm. The drug kicks-in and I begin to feel more relaxed. I show her the slight tremor in my index finger, and her forehead wrinkles and her lips puff out. After a moment of silence, she says, They ordered this scan for that?
My head begins to hurt. My scalp burns.
Try not to move, he says.
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Datscan Imaging: A Clearer Picture Of Parkinson’s
Parkinsons disease affects one in every hundred people over the age of 60. Until recently, however, doctors had to rely on a clinical evaluation, combined with blood tests and brain studies, to diagnose this common movement disorder. But the results were often inconclusive because there was no test to distinguish Parkinsons disease and related disorders from other conditions that have similar symptoms. As a result, effective treatment could sometimes be delayed while the patient and physician searched for answers.
Now, a recently introduced nuclear imaging test called DaTscan is helping specialists at Orange Coast Memorial evaluate patients with suspected parkinsonian syndromes, of which PD is the most common. The test is especially important because it helps distinguish PD and allied disorders from a look-alike condition called essential tremora disorder characterized by trembling of the hands, head, and occasionally the arms and legs. Although Parkinsons disease and essential tremor both involve involuntary shaking movements that are similar, these disorders require very different treatments, says Daniel Truong, M.D., a internationally known neurologist and medical director of The Parkinsons and Movement Disorder Institute at Orange Coast Medical Center. DaTscan allows us to rule out essential tremor and other non-parkinsonian conditions, which can help lead to a more accurate and timely diagnosis and treatment.
Changes In The Brain
Is A Dat Scan Or F
No! Not at all!
First, the diagnosis of Parkinsons disease is obvious in most patients.
The proof of the pudding is in the eating. If you improve significantly with levodopa you have parkinsonism.
If this improvement is consistent for many years you probably have Parkinsons disease.
Second, while these scans are useful in differentiating some diseases like Essential tremor from Parkinsons disease, they are not very useful in identifying mimics .
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Conditions That Mimic Shuffling Gait Seen In Parkinsons:
Please read the article on shuffling gait. It describes 5 causes of shuffling of gait.
The most crucial mimic to remember is Normal Pressure Hydrocephalus .
The person with NPH feels like he is stuck to the ground. This is a magnetic gait. It is easy to mistake this for Parkinsons disease.
For example, see this video posted by the Hydrocephalus Association of America on youtube:
NPH can be treated by implanting a small shunt pipe. This shunt drains excess water around the brain into the abdomen.
What To Expect During A Datscan
Before the DaTscan, it is essential to discuss the patients medical history with the doctor. For instance, some medications may interfere with the imaging and may need to be discontinued.
The radioactive agent that is injected into the patients bloodstream before the imaging takes some time to reach the striatum region of the brain where cells carrying DaT are usually found. After injection, the patient may need to wait for three to six hours before receiving the SPECT scan to visualize DaT distribution in the brain. The scan itself can take 45 minutes to an hour.
The radiologist will then send the brain scans to the neurologist who will explain the results to the patient.
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Additional Testing For Parkinsons
Many doctors I know make a confirmatory diagnosis of Parkinsons disease at this stage. If there are no red-flags, then a single office visit is usually enough to confirm the diagnosis.
Some doctors, including myself, do request some simple investigations . These are done to rule out rare causes and Parkinsons Mimics. Usually, these tests do not show an additional problem.
|Simple tests to detect Parkinsons Mimics|
|1. MRI-Brain with size measurements of brain parts called the midbrain and pons. I usually also request a unique picture called SWI, which shows iron inside the brain.
2. Blood tests:
Datscan: A Test To Help In The Diagnosis Of Parkinsons
In 2011, the Food and Drug Administration approved an imaging test to help diagnose PD. In this test, a radioactive tracer, Ioflupane 123I, also known as DaTscan, is injected into the blood, where it circulates around the body and makes its way into the brain. It attaches itself to the dopamine transporter, a molecule found on dopamine neurons. Several hours after the tracer has been injected, special imaging equipment scans the head to detect the presence of DaTscan.
People with PD will typically have a smaller signal in a part of the brain called the striatum, where the ends of the dopamine neurons are meant to be. Here is a normal scan on the left, which would indicate a healthy dopamine system, next to an abnormal scan on the right, which would indicate an unhealthy dopamine system.
It is important to note that conventional MRI imaging will appear normal in PD and is therefore not helpful in confirming the diagnosis. Other atypical parkinsonian conditions, such as vascular parkinsonism however, can have abnormalities on MRI, so the test may be done to rule out other diagnoses.
Other Symptoms Useful For Parkinsons Diagnosis
Now, in addition to these three main symptoms, the patient may also have other features which support the diagnosis of Parkinsons disease.
- Postural instability: Many doctors/guidelines consider this to be a core symptom of Parkinsons disease. The patient is unstable while walking. Falls are not common in the early stages of Parkinsons disease. But the patient may appear wobbly while taking turns, or if given a slight nudge in a crowded place.
- An expressionless face.
- Freezing or getting stuck while walking.
- Problems with thinking or memory .
On The Day Of The Exam
- Drink plenty of fluids and go to the bathroom frequently
- Wear loose comfortable clothing, since you will need to lie still for a period of time.
- Please bring a list of all medications that you are taking name and dosage.
- We want to make your waiting time as pleasant as possible. Consider bringing your favorite magazine, book or music player to help you pass the time.
- Please leave your jewelry and valuables at home.
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What’s Hot In Pd Should I Get A Datscan Or Pet Scan To Confirm My Diagnosis Of Parkinsons Disease
This past month, the FDA approved DaTscan , a radiopharmaceutical agent which is injected into a patients 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 the Parkinson’s Foundation Ask the Doctor forum is whether or not to pursue DaT or PET scanning to confirm a diagnosis of Parkinsons disease. In this months Whats 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 Parkinsons 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 Parkinsons, for example– or where a potentially risky procedure is being considered , 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 Parkinsons disease scans, because experience is important in accurately reading these imaging results.
How Is Datscan Given
DaTscan is given as an infusion into a vein. A healthcare provider will give you this injection about 3 to 6 hours before your radiologic test.
At least 1 hour before you are treated with DaTscan, you will be given a liquid drink that contains medicine to protect your thyroid from harmful radioactive effects of ioflupane I-123.
Drink plenty of liquid before you receive DaTscan, and for at least 48 hours afterward. Follow your doctor’s instructions about the types and amount of liquids you should drink before and after your test. Ioflupane I-123 is radioactive and it can cause dangerous effects on your bladder if it is not properly eliminated from your body through urination.
Expect to urinate often during the first 48 hours after your test. You will know you are getting enough extra fluid if you are urinating more than usual during this time. Urinating often will help rid your body of the radioactive iodine.
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Conditions That Can Cause Tremors Besides Parkinsons:
The tremor of Parkinsons disease occurs even at rest. Hence it is called a rest tremor. Very few other conditions produce rest tremor.
But, many other diseases produce a tremor which is seen only when moving, for example when writing. This is called an Action tremor or posturokinetic tremor. Even these diseases are sometimes misdiagnosed as Parkinsons disease.
|Causes of Rest Tremor|
2. Excessive stress, coffee or smoking
3. Medications such as bronchodilators, valproate and lamotrigine
4. Chromosomal problems such as Fragile-X syndrome
5. Parkinsons disease itself!
And many others
Testing For Parkinsons Disease
There is no lab or imaging test that is recommended or definitive for Parkinsons disease. However, in 2011, the U.S. Food and Drug Administration approved an imaging scan called the DaTscan. This technique allows doctors to see detailed pictures of the brains dopamine system.
A DaTscan involves an injection of a small amount of a radioactive drug and a machine called a single-photon emission computed tomography scanner, similar to an MRI.
The drug binds to dopamine transmitters in the brain, showing where in the brain dopaminergic neurons are.
The results of a DaTscan cant show that you have Parkinsons, but they can help your doctor confirm a diagnosis or rule out a Parkinsons mimic.
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The Real Role Of Datscan As An Aid To Clinical Diagnosis In Parkinson’s Disease
The authors discuss the role of DaTSCAN and paint a rosy picture of clinical diagnostic accuracy in Parkinsons disease . Clinico-pathological studies suggest good diagnostic accuracy in PD yet experience from drug trials suggests a PD diagnosis error rate of up to 15% and community studies an error rate of over 50%. A recent blinded video study showed high false positive and negative error rates in PD diagnosis and poor concordance between movement disorder experts, which illustrates the fragility and subjectivity of clinical diagnosis in tremulous patients. The indication of DaTSCAN is not for diagnosis of PD or parkinsonian syndromes but per US-FDA prescribing information is “for visualization of the dopamine transporter distribution within the striatum… to assist in the evaluation of adult patients with suspected parkinsonian syndromes.” Only a clinician can make a diagnosis. DaTSCAN may enable that diagnosis in challenging patients. Studies show that DaTSCAN improves confidence in diagnosis and management in clinically uncertain parkinsonian syndromes. Cancer risk from any scan cannot be ignored. The 1 in 7500 possible cancer risk has to be compared to the greater chance of psychological trauma of a false positive PD diagnosis or the functional disability that may result from a missed PD diagnosis.
1. de la Fuente-Fern?ndez R. Role of DaTSCAN and clinical diagnosis in Parkinson disease. Neurology 2012 Feb 8. .
4. DaTscan for Intravenous Use. NDA 22454, 2011
Data Extraction And Quality Assessment
Data were extracted by two reviewers independently and were recorded in absolute numbers. Where proportions only were reported the absolute figure was recalculated. Data on clinical utility following imaging with DaTscan, scan technical characteristics ), and baseline characteristics of studied patients were extracted . Change in diagnosis was defined as any change in the patients assigned or suspected diagnosis following disclosure of the results of the imaging scan. Change in management was defined as any changes that the study authors recorded as changes in treatment or further investigations, such as drug changes , referral for counselling or physical therapy following the disclosure of DaT imaging results. Results were compared, and discrepancies between the two reviewers were resolved in a meeting.
Risk of bias assessment was carried out on all studies using an adapted form of the QUADAS-2 checklist amended by the study authors to fit studies of clinical utility, rather than diagnostic accuracy. A copy of the amended QUADAS-2 checklist is provided in Supplementary data . The risk of bias assessment was used independently of the quantitative meta-analysis.
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What Happens During A Datscan
During a DaTSCAN, a very small amount of tracer, specific for the organ or tissue to be scanned, is injected into a vein by a nuclear medicine technologist. Images may be taken during the injection, immediately after the injection, or following a delayed period to allow the tracer to distribute to the organ or tissue of interest. The gamma rays emitted by the tracer are detected by a special camera that is positioned near the organ or part of the body being imaged.
You will need to remain very still for the camera, but it will not touch you. The radiation from a nuclear medicine procedure is comparable to that received during a routine X-ray. The tracer only remains in the body for a short period of time before being eliminated in the urine or stool.