Parkinson’s disease has always been a clinical diagnosis.
And most patients who present with the typical unilateral rest tremor, associated with cogwheeling and rigidity are easily distinguished from essential tremor on clinical grounds (click here to review the differences).
However, some atypical cases can cause diagnostic uncertainty. A 2009 study from the UK found that almost 50% of patients with tremor who were taking Sinemet (a medication used for Parkinson’s) prescribed by their primary care physicians, when examined by an experienced neurologist actually had essential tremor or some other diagnosis.
Autopsy studies have shown that almost 1/3 of patients diagnosed with Parkinson’s by neurologists during life actually had alternate pathological diagnoses at autopsy such as progressive supranuclear palsy or Cortico Basal Gangionic degeneration.
A new radiological study, may help end some of this diagnostic uncertainty in difficult cases.
The DaTscan uses single-photon emission computed tomography (SPECT) after an injection of Ioflupane I-123 to demonstrate abnormal dopamine uptake in the basal ganglia in patients with Parkinson’s disease:
Here’s a patient we recently saw, with a right sided rest and re-emergent postural tremor. On the right half of the screen we have shown an image from his DaTscan, showing reduced dopamine uptake in the left basal ganglion, and confirming the diagnosis of Parkinson’s.
If you have already received a diagnosis of Parkinson’s from an expert, and are responding well to dopaminergic therapy, a DaTscan would not add any new information and would therefore be unnecessary. However, if 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 may be reasonable for your doctor to recommend a DaTscan.