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IMAGE INTERPRETATION · BRAIN IMAGING

Parkinson’s Disease on DaTscan: Loss of the Comma Shape

DaTSCAN (I-123 ioflupane) SPECT — normal striatal uptake
DaTSCAN (I-123 ioflupane) SPECT — normal striatal uptake

Public domain · Wikimedia Commons · source file

Question

In a patient with Parkinson's disease, a DaTSCAN (I-123 ioflupane SPECT) would show which characteristic pattern?

  1. ANormal bilateral comma-shaped striatal uptake
  2. BBilateral increased striatal uptake
  3. CAbsent uptake in the caudate only, with preserved putamen
  4. DAsymmetric reduction of putamen uptake — loss of the comma shape to a period/dot shape
Show the answer and explanation

D. Asymmetric reduction of putamen uptake — loss of the comma shape to a period/dot shape

In Parkinson's disease, the dopaminergic neurons projecting from the substantia nigra to the putamen degenerate preferentially. On DaTSCAN, this produces asymmetric (contralateral to clinically affected side) reduction in putamen uptake, converting the normal 'comma' shape to a 'period' or 'egg' as the posterior putamen loses dopamine transporter density. More advanced PD shows loss of both putamen and caudate uptake bilaterally. Normal DaTSCAN (bilateral full commas) excludes primary Parkinson's disease. Drug-induced parkinsonism typically shows a normal DaTSCAN.

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