The role of 123I-FP-CIT-SPECT in the differential diagnosis of Parkinson and tremor syndromes: a critical assessment of 125 cases

Abstract

(123)I-FP-CIT-SPECT is useful in the differential diagnosis of Parkinson's disease (PD) and tremor syndromes. Recently, there have been reports on normal nigrostriatal uptake of radio ligands in PD patients, referred to as scans without evidence of dopaminergic deficit (SWEDDs). Furthermore, a dopaminergic deficit has been described in some cases of different tremor types. We sought to clarify the occurrence of SWEDDs in PD and a possible association of various tremor types with PD. We performed a retrospective case analysis of 125 patients with diagnostically uncertain Parkinsonian or non-Parkinsonian tremor syndromes with clinical assessments and (123)I-FP-CIT-SPECT. A total of 36/40 (90%) patients with the predominant clinical feature of a postural and/or kinetic tremor showed normal DAT SPECT; 73/85 (86%) with predominant clinical symptoms of PD showed abnormal DAT SPECT with lower overall radio ligand uptake and a significant asymmetry contralateral to the clinically more affected side. In all, 4/40 (10%) of non-Parkinsonian tremor patients had abnormal DAT SPECT, but no corresponding asymmetry of radio ligand uptake. Probable essential tremor was considered clinically in follow-up assessments although final diagnosis of these four tremor cases remains inconclusive. A total of 12/85 (14%) clinically suspected PD patients had normal DAT SPECT (SWEDDs). Clinical reassessment identified two patients with dystonic tremor. Five patients with a positive response to levodopa remained unclear. In four cases of suspected PD with normal DAT SPECT, non-neurologic diseases were identified. One case showed a complete and spontaneous remission of symptoms. DAT SPECT offers an objective method to confirm or exclude a dopaminergic deficit in tremor predominant parkinsonism for clinically inconclusive cases. There was no evidence of a decrease in DAT binding in the majority of patients with postural and/or kinetic tremor. The striatal asymmetry index is a further helpful tool for differentiating PD from non-PD tremor syndromes.

Scan without evidence of dopaminergic deficit: A 10-year retrospective study

“…However, assessments taken in combination allow a greater sensitivity for determination of nigro-striatal impairment. In previous studies, an incorrect initial diagnosis of degenerative parkinsonism seems to account for a significant proportion of SWEDDs [12,13,23] and, in those studies where a second, follow-up scan has been performed, conversion from normal to abnormal was rather uncommon (8.3% in Ref. [13] and 12.5% in Ref.…”

Nigrostriatal Dopamine Terminal Imaging with Dopamine Transporter SPECT: An Update

“…They feature no compromised presynaptic function over years, no progressive decline of presynaptic functions, a lack of a clear positive response to dopaminergic medication (an exception may be some patients with dopa-responsive dystonic tremor), and no patterns of glucose metabolism compatible with classic PD. The prognosis of SWEED subjects is considered to be more favorable than that for classic neurodegenerative PS (32)(33)(34)(35)(36). To the best of our knowledge, histopathologic proof of SWEDD pathology is still lacking; for further clarification, such studies are clearly needed.…”

A role for accelerometry in the differential diagnosis of tremor syndromes

“…At present, the gold standard for diagnosis is based on a combination of validated hallmark criteria, long-term patient monitoring, and response to specific drugs (Deuschl et al, 1998). Use of a dopamine transporter tracer in single-photon emission computed tomography (DAT-SPECT) is also an accepted method for differentiating the tremor of idiopathic Parkinson's disease (PD-T) from essential tremor (ET) or dystonic tremor (DT) (Sixel-Doring et al, 2011). Kinematic analysis is a further means of studying the distinctive features of tremor syndromes.…”