Tc-99m TRODAT uptake in an osteoid tumor of clivus.

Tc-99m TRODAT is cocaine analog and binds to the dopamine transporter in vivo. Tc-99m TRODAT single-photon emission computed tomography/computed tomography. (SPECT/CT) is useful for demonstrating presynaptic dopaminergic dysfunction in patients with Parkinsonism. However, few reports have shown extrastriatal uptake of Tc-99m TRODAT. We present the case of a 67-year-old male who underwent Tc-99m TRODAT SPECT/CT for evaluation of Parkinsonism. In addition to tracer binding in the striatum, tracer uptake was noted in an osteoid tumor of the clivus. Integrated SPECT/CT enabled precise localization and characterization of the extrastriatal site of tracer binding and emphasizes the importance of such coincidental findings.

A 67-year-old male patient complained of gait imbalance for the past 1 year. The treating neurologist referred him for ([2-[2-[3-(4-chlorophenyl)-8-methyl-8-azabicyclo [3,2,,1] oct-2-yl] methyl](2-mercaptoethyl)-amino] ethyl] amino] ethanethiolato (3-)-N2, N2', S2, S2']oxo-[1R-(exo-exo)]) (Tc-99 m TRODAT) single-photon emission computed tomography/computed tomography (SPECT/CT). Axial fused SPECT/CT [Figure 1a] showed asymmetric tracer accumulation in the basal ganglia. The corresponding plain CT axial image [Figure 1b] showed an infarct in the right frontal white matter with no lesion in the basal ganglia. Axial fused SPECT/CT image at the level of pons showed increased radiotracer uptake in the clival region [Figure 1c] while corresponding axial plain CT image in the bone window showed a predominantly sclerotic lesion in the clivus [Figure 1d]. On taking a detailed history again, the patient revealed that he had undergone a magnetic resonance imaging 2 years back which had revealed the lesion which was considered as a benign osteoid tumor of the clivus and no active intervention was planned.

Figure 1

Tc-99m TRODAT (a) axial fused single-photon emission computed tomography/computed tomography images showed asymmetric tracer accumulation in the basal ganglia. The corresponding computed tomography axial image (b) showed an infarct in the right frontal white matter with no lesion in the basal ganglia. Axial fused single-photon emission computed tomography/computed tomography image (c) at the level of pons showed increased radiotracer uptake in the clival region, while corresponding axial plain computed tomography image in bone window showed a predominantly sclerotic lesion in the clivus (d)

Dopamine transporter imaging has been widely used in movement disorders including Parkinson's disease.[123] Tc-99m TRODAT, a cocaine derivative, is a neutral lipophilic complex that contains N-(alkylthiolate) tropane, aminobis (ethylthiolate) and a center core of Tc-99m.[4] Although it has high specificity and affinity for dopamine transporter, few studies elucidated uptake in extrastriatal pathology.[56789101112] Osteoid is composed of fibers (type-1 collagen) and ground substance (chondroitin sulfate and osteocalcin). TRODAT uptake in an osteoid lesion has not been described in the literature, and the mechanism of this localization needs consideration.

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