Reduced 123I Ioflupane Binding in Bilateral Diabetic Chorea

Abstract

We report a 64-year-old man with diabetic chorea whom we investigated with dopamine transporter SPECT, ¹⁸F FDG PET, ^99mTc ethylcysteinate dimer (ECD) SPECT, and ¹²³I metaiodobenzylguanidine (MIBG) scintigraphy. Dopamine transporter SPECT revealed reduced ¹²³I ioflupane binding in the bilateral striatum. ¹⁸F FDG PET showed metabolic dysfunction in the bilateral striatum, as shown in earlier studies. ^99mTc ECD SPECT revealed reduced brain perfusion in the bilateral caudate nucleus and putamen. ¹²³I MIBG scintigraphy revealed no cardiac sympathetic nerve dysfunction. Our case suggests a possible nigrostriatal presynaptic dopaminergic involvement in diabetic chorea.

FIGURE 1.

We present a 64-year-old man with subacute left-side dominant bilateral choreic movement (diabetic chorea) evaluated using a combination of dopamine transporter SPECT, ¹⁸F FDG PET, ^99mTc ethylcysteinate dimer (^99mTc ECD) SPECT, and ¹²³I metaiodobenzylguanidine (MIBG) scintigraphy. We diagnosed him with diabetic chorea because of poorly controlled diabetes mellitus (HbA1c 13%-18%) and brain MRI showing pathognomonic hyperintensity on T1-weighted imaging in the bilateral caudate nucleus and putamen and right-side external segment of the globus pallidus (A). No significant abnormality on T2- (B) and T2*-weighted images (C) was found in the corresponding area. No significant old infarction or other differential diagnoses for chorea were identified.¹ Dopamine transporter SPECT showed bilaterally and right-side dominant reduced ¹²³I ioflupane binding in the caudate nucleus and putamen (D). The specific binding ratio² was 1.22 on the right and 1.36 on the left side (ELEGP was used as a collimator, and no scatter correction or attenuation correction was applied). The asymmetry dopamine transporter SPECT in diabetic chorea index (AI) of ioflupane binding was 10.7%, revealing a decline predominantly on the right side. This was consistent with the contralateral dominance of the chorea. No confounding medication for the evaluation with dopamine transporter SPECT was identified.³ Brain ¹⁸F FDG PET revealed decreased glucose metabolism (E) in the corresponding area, similar to the dopamine transporter SPECT, suggesting regional dysfunction in the bilateral striatum. There was no significant left-to-right difference in striatal ¹⁸F FDG PET uptake, with an AI of 2.7%. ^99mTc ECD SPECT revealed reduced brain perfusion in the bilateral caudate nucleus, putamen, and thalamus (F). ¹²³I MIBG scintigraphy showed no reduction in the H/M ratio, with 4.95 in the early phase and 5.03 in the late phase (G, late phase). We assumed that a low accumulation in the mediastinum caused this high H/M ratio. Treatment with dopamine antagonist and blood glucose control relieved most choreic symptoms within 4 weeks, and we are now successfully reducing his dopamine antagonist dose. Reduced glucose metabolism was found in the bilateral putamen and caudate nucleus in the ¹⁸F FDG PET in our patient, suggesting regional striatal dysfunction. This was consistent with earlier studies on diabetic chorea.^4–7 Several theories regarding the underlying pathology of diabetic chorea have been proposed, including petechial hemorrhage,⁷ metabolic abnormality because of hyperglycemia,^5,7 patchy striatal necrosis associated with vasculopathy,⁶ and transient ischemia.⁷ No conclusion has been reached to date. The only earlier report using dopamine transporter SPECT with hyperglycemic hemichorea-hemiballismus⁸ revealed decreased ¹²³I ioflupane binding in the striatum as was observed in our case. Cardiac imaging with ¹²³I MIBG scintigraphy in our case revealed normal ¹²³I MIBG uptake by the cardiac sympathetic nerve, suggesting that coexisting Parkinson’s disease, Lewy body disease, diabetic sympathetic nerve dysfunction, or heart failure were unlikely. This suggests nigrostriatal dopaminergic involvement: presynaptic neuronal terminal dysfunction, reduced density of nerve terminals, or reduced density of dopamine transporter is conceivable.^8,9