MIBG or fluorodopa scan of the heart, which images
postganglionic adrenergic innervation, is typically defective in
PD and normal in MSA.13,14 However, denervation can occur in
25-30% of MSA patients.14 Another useful test is the TST. TST
is either normal or shows very distal anhidrosis, typically affecting
the toes (Fig. 3). In Fig. 3, the PD case showed very
distal anhidrosis, affecting only parts of the toes, and did not
progress over time. In contrast, MSA causes widespread anhidrosis.23
If both QSART and TST are performed,