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Relevance of 123I-FP-CIT SPECT brain scans in routine clinical settings

Published online by Cambridge University Press:  02 January 2018

Elizabeta B. Mukaetova-Ladinska
Affiliation:
Newcastle Liaison Team for Older Adults, Northumberland, Tyne and Wear NHS Foundation Trust, Newcastle upon Tyne, and Institute for Ageing and Health, Newcastle University, Wolfson Research Centre, Campus for Ageing and Vitality, Newcastle upon Tyne NE4 5PL, UK. Email: Elizabeta.Mukaetova-Ladinska@ncl.ac.uk
Ann Scully
Affiliation:
Newcastle Liaison Team for Older Adults, Northumberland, Tyne and Wear NHS Foundation Trust, Newcastle upon Tyne, UK
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Abstract

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Copyright © Royal College of Psychiatrists, 2015 

The findings from Walker et al's study Reference Walker, Moreno, Thomas, Inglis, Tabet and Rainer1 do not come as a surprise. The high sensitivity and specificity of 123I-ioflupane injection (123I-FP-CIT) single photon emission computed tomography (SPECT) in diagnosing dementia with Lewy bodies (DLB) relate to a highly selected group of individuals, where underlying vascular pathology, severe mental and physical illness (including delirium) as well as medication interference were excluded. The working group also based their findings on a large group of patients with DLB, in comparison to rather modest size groups previously reported.

How relevant is this study to those of us working in a routine clinical setting? What is the sensitivity and specificity of the 123I-FP-CIT SPECT brain scan in differentiating DLB from other dementia syndromes – and pseudodementia in our patients with more advanced age – with polypharmacy, polycomorbidity or recovering from a prolonged spell of acute confusion? Our own clinical experience working with older people with mental and medical health problems suggests that patients can be easily misdiagnosed as having DLB based on their 123I-FP-CIT SPECT scans, and this includes individuals with major depression, severe brain trauma accompanied by widespread vascular white matter changes and small vessel disease, HIV encephalopathy, and even an older adult with mild intellectual disability with frontal lobe syndrome and extensive hypoperfusion as demonstrated on the SPECT brain scan. This is another confirmation of the clinician's gullibility when faced with 123I-FP-CIT SPECT altered scans, as confirmed by Walker et al. Reference Walker, Moreno, Thomas, Inglis, Tabet and Rainer1

With the availability of 123I-FP-CIT SPECT scans, it is unclear what we have learned from the use of this imaging technique: do we use them for DLB diagnosis – based on their abnormal findings alone – or do we put them in the wider context of our patients' clinical symptomatology and medical history? There is a well-documented inverse relationship between vascular lesions and Lewy body pathology; Reference Fukui, Oowan, Yamazaki and Kinno2 30% of patients with frontotemporal lobe dementia have abnormal scans and a significant reduction in uptake in the putamen and the caudate Reference Morgan, Kemp, Booij, Costa, Padayachee and Lee3 (also highlighted by Walker et al Reference Walker, Moreno, Thomas, Inglis, Tabet and Rainer1 ). About 5% of people diagnosed with DLB in fact have vascular dementia Reference Kemp, Clyde and Holmes4 and altered suspected 123I-FP-CIT SPECT are also found in Creutzfeldt–Jakob disease. Reference Ragno, Scarcella, Cacchiò, Capellari, Di Marzio and Parchi5 It is of note that the influence of antipsychotic Reference Barrou, Boddaert, Faucounau, Habert, Greffard and Dieudonné6 and antidepressant medication Reference Booij, de Jong, de Bruin, Knol, de Win and van Eck-Smit7 in older adults has largely been neglected in research studies in the public domain. The evidence from a limited number of animal Reference Nikolaus, Antke, Kley, Beu, Wirrwar and Müller8 and human Reference Ziebell, Holm-Hansen, Thomsen, Wagner, Jensen and Pinborg9 studies clearly indicates that medication (e.g. haloperidol, citalopram, sertraline) reduces 123I-FP-CIT dopamine binding to the dopaminergic transporter. However, there is an overwhelming lack of evidence for the most frequently used drugs in the older population, including a number of dopaminergic antagonists, the influence of polypharmacy, the effect of chronic administration of these drugs and modifying effects of advanced age. Until such data are available, it is not surprising that clinicians would be inclined to diagnose and/or accept the diagnosis of DLB based on the evidence of a dopaminergic abnormality. Even in their strictly controlled study, Walker et al Reference Walker, Moreno, Thomas, Inglis, Tabet and Rainer1 report 5.4% mismatch between 123I-FP-CIT SPECT scan findings and clinical DLB diagnosis. It is now the responsibility of the DLB research community to provide us with further clarification of clinical situations and exclusion criteria when using 123I-FP-CIT SPECT scans to diagnose DLB in busy clinical settings.

References

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