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Posts Tagged ‘Theodore A Henderson MD PhD’

SPECT Imaging Aids in Parkinson’s disease Diagnosis

Written by childpsychiatristdenver on . Posted in Dr. Ted's Blog

Molecular neuroimaging using single-photon emission computed tomography (SPECT) has allowed for direct visualization of functional systems in the living human brain. DaTSCAN is a radiopharmaceutical approved 2 years ago by the FDA with indications for “striatal dopamine transporter visualization using SPECT brain imaging to assist in the evaluation of adult patients with suspected Parkinsonian syndromes.” In these patients, DaTSCAN may be used to help differentiate essential tremor from tremor resulting from one of the parkinsonian syndromes (IDP, MSA, PSP). DaTSCAN is an adjunct to other diagnostic evaluations.

Dopamine Transporter (DAT) Imaging

DAT imaging offers certain advantages. First, DAT is largely limited to presynaptic membranes which, in the striatum, are predominantly the axonal terminals of substantia nigra neurons. Therefore, DAT allows direct visualization of the integrity of the neurons that appear most vulnerable to degeneration in IPD. Second, a minimum of metabolic processing, and therefore shorter incubation time during imaging, is possible.

Two derivatives are approved in Europe: I 123 beta CIT, marketed as Dopascan, and I123 Ioflupane, marketed as DaTSCAN. The DaTSCAN has been in use in Europe for 12 years, giving our European colleagues extensive experience with making full use of this marker.

The Value of Quantitative Analysis

One observation, based on the extensive experience in Europe, has been the value of quantitative or semiquantitative analysis. Visual interpretation of the DaTSCAN does not make full use of its capabilities. For example, when specific binding ratios relative to the occipital cortex are quantified (such as provided with the Hermes BRASS system), a Z-score derived from a normal database can be calculated. This has utility in differentiating accurately between Parkinson disease, which typically has an asymmetric dopaminergic denervation in the putamen and caudate, and non-parkinsonian causes of tremor, which show nonsignificant Z-scores. Such causes of tremor include medications and essential tremor.

Quantitative DaTSCAN analysis also is critical in the case of the positive DaTSCAN to assist in differentiation of IPD and other parkinsonian syndromes (MSA, DLB, PSP) that tend to have a symmetrical denervation. However, DaTSCAN cannot reliably distinguish these parkinsonian syndromes alone.

 

As published in Neurology Times

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Mild Cognitive Impairment – An Added Value to Patient and Physician

Written by childpsychiatristdenver on . Posted in Dr. Ted's Blog

By Theodore A. Henderson, MD, PhD | February 28, 2012

Dr Henderson is in private practice in Denver, Colorado. He is a board member of the Brain Imaging Council of the Society of Nuclear Medicine and President of The Synaptic Space, a neuroimaging consulting firm, in Centennial, Colorado.

The recent commentary by Dr Ronald Pies concerning the changes in the diagnostic criteria for Alzheimer’s disease (AD) and Mild Cognitive Impairment (MCI), questioned the value of informing a patient early in the course of a dementing illness……

While there are currently no treatments for AD, it is important to examine what we are treating. By the time AD is diagnosed by clinical symptoms, 8 to possibly 15 years of pathological damage has already occurred. Just as in Parkinson’s disease wherein over 80% of the substantia nigra neurons must be lost before symptoms manifest, the AD-related damage to the entorhinal cortex, hippocampus, and parietal cortex are much advanced by the time a drop in the Mini-Mental-Status Examination score occurs. Treatment at this point cannot undo the pathological damage. Therapeutic interventions, to be effective, must be introduced as early as possible in the pathological process.

Perfusion SPECT neuroimaging can identify MCI with an accuracy of as high as 99%.2-5 Amyloid markers can differentiate AD from controls with 85% to 95% sensitivity and 91% to 100% specificity in advanced cases.6-9 But these markers can also identify MCI with 80 % sensitivity and 90% specificity10; however, it must be noted that 10% of controls aged 50 years have a positive amyloid scan. This false positive rate increases by 10% each decade.6 Nonetheless, neuroimaging provides an endophenotype which can be quantified and detected long before the patient begins to show the cognitive dysfunction of AD or MCI. The implications are tremendous, not just in terms of early intervention, but also in terms of speeding clinical trials. Currently, we must wait years to see if a therapeutic intervention is making a difference……

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