Diagnoses behind patients with hard-to-classify tremor and normal DaT-SPECT: a clinical follow up study

Abstract

The [123I]ioflupane—a dopamine transporter radioligand—SPECT (DaT-SPECT) has proven to be useful in the differential diagnosis of tremor. Here, we investigate the diagnoses behind patients with hard-to-classify tremor and normal DaT-SPECT. Therefore, 30 patients with tremor and normal DaT-SPECT were followed up for 2 years. In 18 cases we were able to make a diagnosis. The residual 12 patients underwent a second DaT-SPECT, were then followed for additional 12 months and thereafter the diagnosis was reconsidered again. The final diagnoses included cases of essential tremor, dystonic tremor, multisystem atrophy, vascular parkinsonism, progressive supranuclear palsy, corticobasal degeneration, fragile X–associated tremor ataxia syndrome, psychogenic parkinsonism, iatrogenic parkinsonism and Parkinson's disease. However, for 6 patients the diagnosis remained uncertain. Larger series are needed to better establish the relative frequency of the different conditions behind these cases.

What do patients with scans without evidence of dopaminergic deficit (SWEDD) have? New evidence and continuing controversies

“…While in 18 patients the diagnosis of PD could be clinically revised, diagnostic uncertainty in the remaining 12 patients led the authors to perform a second DaT scan, again using both visual and semiquantitative analyses. In 4 (13.3%) of the total 30 cases, the second DaT scan result was abnormal and they were finally diagnosed with PD 47. These results support the notion that an initial normal DaT-SPECT cannot always exclude early degenerative parkinsonism 48–50…”

“…Thus, in the aforementioned 22-month follow-up of the PRECEPT study, 6 of 72 patients with SWEDD were subsequently abnormal, 4 in the indeterminate range (ie, 65–80% of age-expected putamen uptake) and 2 clearly abnormal (ie, <65%) 14. Similarly, Menéndez-Gonzáles et al 47 reported on 30 tremulous patients with SWEDD over a 36-month follow-up period. While in 18 patients the diagnosis of PD could be clinically revised, diagnostic uncertainty in the remaining 12 patients led the authors to perform a second DaT scan, again using both visual and semiquantitative analyses.…”

“…Supranigral parkinsonism41 and some forms of secondary parkinsonism, including normal pressure hydrocephalus and vascular parkinsonism,14 47 have in fact been suggested to account for some of the non-tremulous patients with SWEDD. This underlines the importance of performing structural along with dopaminergic imaging studies.…”

Transcranial sonography of the substantia nigra and its correlation with DAT-SPECT in the diagnosis of Parkinson's disease

“…Actually, about 15% early PD were shown normal brain scans, due to the theoretical possibility in the early phase of PD or "false negative" originated from quantitative analysis of SPECT scans [27] . In addition, some of SWEDDs may be misdiagnosed, but others continue to fulfill PD diagnostic criteria.…”

Neuroimaging biomarkers for Parkinson disease: Facts and fantasy

“…7 In fact, longer follow up may reveal that a greater relative frequency of “normal” scans occur in those with neurodegenerative parkinsonian syndromes including potentially treatable idiopathic PD. 52 Thus, if a clinician relies only on this type of molecular imaging to determine whether an individual does or does not have PD, then that clinician may miss a treatable condition.…”