Extra-striatal Uptake of 99mTc-TRODAT-1 in Meningioma Detected on SPECT/CT: Diagnostic Clue or Mere Coincidence?

Incidental observation of extra-striatal uptake of 99mTc-TRODAT-1 has been reported previously in multiple space-occupying lesions of the brain. We present here a SPECT/CT scan of a 60-year old female with parkinsonism, with normal presynaptic dopaminergic transporters expression and with an intense tracer uptake in a large right-sided frontoparietal meningioma.

A 60-year-old female presented with complaints of gradually progressive asymmetric lower limb weakness (left > right, proximal > distal), rest tremor, rigidity, and postural instability. 99mTc-TRODAT-1 scan was done for evaluation of clinically suspected Parkinson's disease (PD). Serial transaxial single photon emission tomography (SPECT) images ([Figure 1], caudal to cranial) show the normal tracer uptake in bilateral basal ganglia (long thin white arrow) and the incidental focal increased tracer uptake in the right frontoparietal region (dashed white arrow). Transaxial computed tomography (CT) images [Figure 1b] show a large extra-axial, dural-based soft tissue mass in the right frontal-parietal region with calcification, mild peritumoral edema, and minimal midline shift (small bold white arrow)—most likely to be meningioma. The fused serial transaxial SPECT/CT image [Figure 1b] shows an intense tracer uptake in the right frontoparietal mass. The patient was started on levodopa, but did not show any improvement. The patient was later advised excision of frontoparietal mass lesion; however, she refused the surgery.

Figure 1

(a) Serial trans-axial SPECT images showing normal TRODAT uptake in bilateral basal ganglia and extra-striatal uptake in the right fronto-parietal region, better characterized on (b) serial trans-axial CT images and (c) trans-axial SPECT/CT images

A normal functional neuroimaging of the pre-synaptic dopaminergic system as per the new movement disorder society (MDS) criteria excludes a diagnosis of PD. One of the other exclusion criteria is demonstration of alternative conditions (such as tumors) that are known to cause parkinsonism.[1] Meningiomas are the most common intra-cranial tumors associated with parkinsonism. Disruption of the post-synaptic output circuits from basal ganglia to cortex or impairment of tissue perfusion by edema (especially by tumors in frontoparietal region) is the probable mechanism of tumor-induced parkinsonism.[2] These cases usually are unresponsive to levodopa, and only surgical removal of the menigioma has been associated with complete recovery in symptoms.[2345] The coincidental extra-striatal uptake of 99mTc-TRODAT-1 has been reported previously in meningioma, metastasis, subdural hematoma, clival tumors, and oligodendrogliomas.[678910] Identification and characterization of these incidental space-occupying lesions on SPECT/CT with normal symmetric striatal uptake not only can avoid misdiagnosis of idiopathic PD, but can also be useful in planning early and appropriate treatment.

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