in postmortem studies , dementia with lewy bodies ( dlb ) accounts for 1020% of all cases of dementia and can therefore be regarded as the second most common cause of dementia after alzheimer 's disease ( ad ) . for a definite diagnosis , autopsy is required .
however , confirmation of the diagnosis during the patient 's lifetime is both reasonable and important , since patients with dlb respond to acetylcholine esterase inhibitors   and furthermore demonstrate a hypersensitivity to antipsychotic treatment . clinical consensus criteria from 1996 possess a fairly high specificity with 8090% , but only a low sensitivity , decreasing to 30% according to some studies .
an improvement in clinical accuracy  particularly when ad is part of the differential diagnosis  seems to be worthwhile . in postmortem studies , a 5790% loss of presynaptic dopamine transporters could be demonstrated in dlb but not in ad .
the presence a dopaminergic abnormality in dlb including striatal dopaminergic transporter loss was outlined in vivo with positron ( pet )   and single - photon emission computed tomography ( spect ) . on the grounds of these observations , a positive , i.e. abnormal , fp - cit - spect was included as a feature suggestive of dlb in the revised clinical consensus criteria from 2005 .
sensitivity could thereby be increased up to 81.3% . moreover , in a follow - up study over a period of 1 year , it was shown that in case of clinical suspicion , an fp - cit scan may be helpful .
of 19 patients initially diagnosed as having possible and after 1 year as having probable dlb , 12 patients ( 63.2% ) had pathological fp - cit - spect , while the remaining 7 cases that were assessed as non - dlb at the 1-year follow - up had normal datscan ( 100% specificity ) .
another challenge in differential diagnosis resides in the distinction between parkinson 's disease and dementia ( pdd ) .
it is still an open question whether the underlying neurobiological changes result from one and the same mechanism in both entities .
fp - cit - spect is abnormal in both dlb and pdd , possibly with a lower dopamine transporter uptake in pdd than in dlb .
regarding the current clinical criteria , an agreement was reached that the diagnosis of dlb is not possible when extrapyramidal features are present for > 12 months before the diagnosis of dementia . in the following ,
we describe 3 cases who had no extrapyramidal signs , and thus dlb was the only possible diagnosis ( table 1 ) .
an 80-year - old male complained of progressively decreasing memory over the previous 2 years .
orientation in time and place was reduced , and he developed difficulties in finding the treatment rooms during hospitalization .
neurological examination was completely normal , and , in particular , there were no signs of rigidity , hypokinesia or tremor .
clinical chemistry did not reveal any significant abnormality apart from slightly elevated homocysteine ( 16.1 mol / l ) .
mini mental state examination ( mmse ) was within normal limits ( 28 of 30 points ) , but extensive neuropsychological testing revealed significant abnormalities regarding attention , visuospatial capabilities , short - term and working verbal memory , verbal episodic memory and naming . orientation and executive functions were preserved ( table 3 ) .
cerebrospinal fluid ( csf ) was normal with respect to basic parameters , but phosphorylated tau at threonine 231 was elevated and -amyloid ( a142 ) was decreased .
cerebral magnetic resonance imaging ( mri ) revealed no significant vascular lesions , but frontotemporal atrophy was noted , with relative preservation of hippocampal formation ( fig .
1 ) . according to dsm iv   criteria , dementia was diagnosed and according to nincds - adrda criteria   probable dementia of the alzheimer type was assumed : symptoms were progressive and were demonstrated in more than one cognitive domain .
although only one core feature ( fluctuation ) was present , fp - cit - spect was performed and revealed a diminished dopamine transporter uptake in the basal ganglia ( fig .
in conclusion , following the revised consensus criteria for dlb from 2005 , probable dlb was diagnosed .
an 82-year - old male with ad diagnosed 1 year previously was admitted to the inpatient neurological department due to uncontrolled visual hallucinations . on neurological examination , there were no abnormalities , particularly no extrapyramidal signs .
mmse was only slightly decreased ( 24 of 30 points ) , but apart from orientation all other cognitive domains were at least 1.5 sd from age - corrected means ( attention , executive function , verbal short - term , working and episodic memory , naming and visuoconstruction ; table 3 ) .
csf analysis was normal ( including tau and a142 ) . due to the neuropsychological findings and at least one core feature of dlb ,
on the basis of all the findings , a diagnosis of probable dlb was made .
a 72-year - old male was admitted to the neurology outpatient clinic with subjective memory complaints .
finally , completion of planned actions , e.g. handling of the coffee machine , were reported to be impaired .
updrs - iii motor score was 0 . only upon further inquiry , he admitted fluctuations and to some degree visual hallucinations although the latter more resembled misperception , were only of short duration and were not very well formed .
neuropsychologically , mmse was almost within the normal range with 26 of 30 points , but deficits were found in visuospatial capabilities , executive function and verbal episodic memory , while orientation and naming were spared . thorough assessment of attention was not performed ( table 3 ) .
mri of the head revealed some global atrophy but the mesiotemporal region , including the hippocampus , was spared ( fig .
to be able to offer optimal therapeutic treatment , an accurate diagnosis during a patient 's lifetime is important since dlb patients respond to therapy with acetylcholine esterase inhibitors .
in addition , in dlb patients the sensitivity to antipsychotics is increased , with a 2- to 3-fold increase in mortality .
treatment with these drugs has to be rational and should be restricted to carefully selected substances .
although the clinical diagnosis offers a high specificity , sensitivity with respect to dlb is only very low , leading to an important role of supplemental imaging techniques . in particular
differentiating between dlb and pdd does not require further investigation since they are distinguished by an anamnestic criterion : whether or not dementia has developed within 1 year of onset of extrapyramidal signs .
dementia onset during that period suggests a diagnosis of dlb , whereas a later onset of dementia is suggestive of pdd .
differentiation between dlb and ad is less clear . since there is a huge overlap of clinical criteria , distinction is not feasible in most cases .
the increase in tau and phosphorylated tau and decrease in a142 sometimes found in ad is less pronounced in dlb .
mesiotemporal structures seem to be more affected in ad , whereas in dlb mesencephalic regions are atrophied .
another imaging technique , perfusion scintigraphy of the brain with tc - bicisate ( neurolite ) , has been investigated for its possible role as a diagnostic tool .
the patterns of hypoperfusion slightly deviate between dlb and ad , with more occipital involvement in dlb , while in ad the characteristic finding is a temporoparietal hypoperfusion , but differences are not sufficient   or at least inferior to those found using fp - cit - spect .
hence depiction of the dopaminergic system using ligands such as fp - cit offers the greatest potential for accurate diagnosis during a patient 's lifetime .
furthermore , spect is readily available , analysis is easily adapted to the diagnosis of dlb , and the procedure is not too time consuming .
reduction in fp - cit is clearly and evidently associated with a fundamental neurobiological alteration recognized in dlb , namely dopaminergic loss .
the above - mentioned reasons explain the increased implementation of fp - cit - spect in routine diagnostics to support a diagnosis of dlb .
the question of the utility of the fp - cit - spect in the distinction between dlb and ad then arises , especially for an early diagnosis . in ad ,
thus , whether there are extrapyramidal signs or not has a substantial impact on the diagnosis made .
although parkinsonism is one of the core features of dlb and occurs frequently in the course of the disease , in up to 7580% of cases   it is not required for a probable diagnosis of dlb . in a review of histopathologically confirmed cases from a brain bank and the current literature , parkinsonism was only found as a first sign of dlb in about 50% of the 239 study patients .
it remains to be clarified how often an fp - cit - spect will be abnormal in the absence of parkinsonism , and what criteria should be met before a datscan is performed in case extrapyramidal signs are absent .
our 3 case reports indicate that a fp - cit scan may indeed be abnormal in the absence of extrapyramidal signs .
an overview of the current literature is difficult because in most of the cases there are no detailed clinical descriptions of the patients and their association with datscan findings . from the literature ,
furthermore , an abnormal datscan was found in the presence of only minor motoric abnormalities in 78 of 11 patients ( updrs < 15 ) in a further study . in the light of these observations , it is interesting that even when extrapyramidal motor signs are present , an abnormal fp - cit - spect is rarely found in ad , possibly pointing to an extrastriatal mechanism in the development of parkinsonism in ad .
we conclude that to increase diagnostic accuracy fp - cit - spect should be readily available once the criteria of possible dlb are met . as demonstrated in our cases , attention should be focused on neuropsychological findings , namely preserved orientation , fluctuating levels of attention and visuoconstructive deficits .
the latter two have been shown to be sensitive to and predictive of dlb even in the early stages of mild cognitive impairment .
 clinically , alzheimer 's disease ( ad ) is by far the most common cause of dementia . 
 criteria for the diagnosis of dementia with lewy bodies ( dlb ) are highly specific but not at all sensitive , which is reflected by the higher number of dlb cases detected histopathologically at autopsy . 
 imaging of dopamine transporter with fp - cit spect is one possibility to increase sensitivity . 
 pathological confirmation was also included in the revised consensus criteria for the diagnosis of dlb . 
 however , in the absence of parkinsonism , one of the core features , a clinical diagnosis of ad is more likely . 
 the role of fp - cit spect in dlb diagnosis remains to be clarified . 
 based on our 3 case reports and a review of the literature , the utility of this imaging method in the differential diagnosis of ad and dlb is highlighted . 
Introduction
Case 1
Case 2
Case 3
Discussion
Conclusion