Accuracy of Parkinson's disease diagnosis in 610 general practice patients in the West of Scotland.

UK-based community studies have found high rates of misdiagnosis in Parkinson's disease (PD). Searches of prescription databases and case records identified 610 patients taking antiparkinson therapy for a PD diagnosis in 92 West of Scotland General Practices. Patients with no documented progression of parkinsonism and/or no increase in antiparkinson medication for 3 years were assessed by two movement disorder specialists. FP-CIT SPECT scanning was performed in clinically uncertain cases. Those considered unlikely to have PD had antiparkinson drugs tapered then stopped, with a minimum of 6 months follow-up. Age, sex and disease duration matched controls were also assessed. 64 of 89 (71.9%) patients meeting selection criteria were assessed, of whom 36 (56.3%) were appropriate for therapy withdrawal. Thirty three of those 36 patients (91.7%) and 3 of 64 (4.7%) controls stopped antiparkinson therapy without deterioration giving an overall total of 36 of 610 (5.9%). The revised diagnoses in this group were mainly essential tremor (ET) (n = 14) and vascular parkinsonism (VP) (n = 10). Patients managed in Primary Care were significantly more likely to complete therapy withdrawal than those attending a specialist clinic (15.3% vs. 2.6%, P < 0.0001). The total annual cost of antiparkinson medication for these 36 patients was 13,400 pounds; the mean duration of diagnosis was 6.8 years (SD 5.6). At least 1 in every 20 patients taking medication for PD is misdiagnosed. Nearly all of these patients can be identified by simple screening of prescription databases and case records in Primary Care, followed by clinical review, which allows withdrawal of unnecessary medication.

High resolution micro-SPECT scanning in rats using 125I beta-CIT: effects of chronic treatment with carbamazepine.

PURPOSE: Carbamazepine (CBZ) is a first-line antiepileptic agent with mood-stabilizing effects in bipolar disorder. It has been reported to influence extracellular concentrations of serotonin and dopamine, suggesting an interaction with monoamine transporters. We have investigated this effect using in vivo single photon emission computed tomography (SPECT) in rats. METHODS: Adult male rats received 3 mg/kg/h CBZ via mini-osmotic pump. After 14 days continuous treatment, animals underwent two consecutive SPECT scans, using 125I beta-CIT as a radiotracer to label serotonin transporter (SERT) and dopamine transporter (DAT) sites in the brain. Pharmacologic distinction was enabled by 125I beta-CIT SPECT imaging in rats acutely exposed to the serotonin and dopamine transporter inhibitors, fluoxetine and GBR12909. The interaction between CBZ and 125I beta-CIT binding to SERT and DAT was investigated using in vitro autoradiography. RESULTS: Carbamazepine (10 microm) did not affect binding of 125I beta-CIT to isolated rat brain slices, thereby excluding a direct effect on ligand binding to SERT and DAT. SPECT studies with fluoxetine and GBR12909 highlighted SERT binding in thalamus, hippocampus, centromedial nuclei, and occipital cortex, and DAT binding in the caudate. Prolonged treatment with CBZ failed to influence 125I beta-CIT binding to either SERT or DAT in any of the brain regions examined. DISCUSSION: This study employed the novel technique of small animal SPECT imaging to investigate the effects of CBZ on monoamine transporters in rat brain. Following prolonged treatment, the drug was without effect on SERT or DAT availability. The mechanism by which CBZ exerts its mood stabilizing effects remains elusive.

Parkinson's disease is overdiagnosed clinically at baseline in diagnostically uncertain cases: a 3-year European multicenter study with repeat [123I]FP-CIT SPECT.

Overdiagnosis of Parkinson's disease (PD) is suggested by specialist review of community diagnosis, and in postmortem studies. In specialist centers 4 to 15% of patients entered into clinical trials as early PD do not have functional imaging support for a PD diagnosis. In a European multicenter, prospective, longitudinal study, we compared clinical diagnosis with functional SPECT imaging using [123I]FP-CIT (DaTSCAN, GE Healthcare). Repeat observations were performed over 3 years in patients with tremor and/or parkinsonism in whom there was initial diagnostic uncertainty between degenerative parkinsonism and nondegenerative tremor disorders. Video-recording of clinical features was scored independently of functional imaging results by two blinded clinicians at 36 months (= gold standard clinical diagnosis). Three readers, unaware of the clinical diagnosis, classified the images as normal or abnormal by visual inspection. The main endpoint was the sensitivity and specificity of SPECT imaging at baseline compared with the gold standard. In 99 patients completing the three serial assessments, on-site clinical diagnosis overdiagnosed degenerative parkinsonism at baseline in diagnostically uncertain cases compared with the gold standard clinical diagnosis (at 36 months), the latter giving a sensitivity of 93% and specificity of 46%. The corresponding baseline [123I]FP-CIT SPECT results showed a mean sensitivity of 78% and a specificity of 97%. Inter-reader agreement for rating scans as normal or abnormal was high (Cohen's kappa = 0.94-0.97).

alpha4beta2-nicotinic receptor binding with 5-IA in Alzheimer's disease: methods of scan analysis.

Five patients with Alzheimer's disease and five healthy volunteers were examined by SPECT with the nicotinic receptor ligand 123I-5-IA-85380. Patients were scanned before and after 6 weeks of treatment with donepezil. Quantification by regions of interest was reliable and the optimal normalisation procedure used cerebellar ratios. We found relative reductions in 5-IA binding capacity in patients in thalamus, frontal and central regions of interest of approximately one standard deviation unit (Cohen's d = 1). Reductions in binding after treatment with the acetylcholinesterase inhibitor donepezil of the same magnitude occurred in the brain stem. The study was clearly too small to confirm group differences, but it suggests that 5-IA can be used to examine both group differences and treatment effects in patients with Alzheimer's disease.

Cholinesterase inhibitor use does not significantly influence the ability of 123I-FP-CIT imaging to distinguish Alzheimer's disease from dementia with Lewy bodies.

BACKGROUND: 123I-labelled 2beta-carbomethoxy-3beta-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (123I-FP-CIT) imaging is a diagnostic tool to help differentiate dementia with Lewy bodies (DLB) from Alzheimer's disease (AD). However, in animals, cholinesterase inhibitors (ChEi) have been reported to reduce radioligand binding to the striatal dopamine transporter. As ChEi are frequently used in people with dementia, it is important to determine whether their use affects 123I-FP-CIT uptake in the striatum. OBJECTIVE: To clarify whether chronic ChEi therapy modulates striatal dopamine transporter binding measured by 123I-FP-CIT in patients with AD, DLB and Parkinson's disease with dementia (PDD). DESIGN: Cross sectional study in 99 patients with AD (nine on ChEi, 25 not on ChEi), DLB (nine on ChEi, 19 not on ChEi) and PDD (six on ChEi, 31 not on ChEi) comparing 123I-FP-CIT striatal binding (caudate, anterior and posterior putamen) in patients receiving compared with those not receiving ChEi, correcting for key clinical variables including diagnosis, age, sex, Mini-Mental State Examination score, severity of parkinsonism and concurrent antidepressant use. RESULTS: As previously described, 123I-FP-CIT striatal uptake was lower in DLB and PDD subjects compared with those with AD. Median duration of ChEi use was 180 days. 123I-FP-CIT uptake was not significantly reduced in subjects receiving ChEi compared those not receiving ChEi (mean percentage reduction: AD 4.3%; DLB 0.7%; PDD 6.1%; p = 0.40). ChEi use did not differentially affect striatal 123FP-CIT uptake between patient groups (p = 0.83). CONCLUSIONS: Use of ChEi does not significantly influence the ability of 123I-FP-CIT imaging to distinguish AD from DLB.

Two-year follow-up in 150 consecutive cases with normal dopamine transporter imaging.

BACKGROUND AND AIMS: Functional pre-synaptic dopamine brain imaging is generally abnormal when parkinsonism is degenerative (such as in idiopathic Parkinson's disease) and normal in patients with non-degenerative movement disorder (such as essential tremor). However, some patients diagnosed as early Parkinson's disease have normal presynaptic dopamine imaging. Follow-up of patients with normal imaging should help determine whether such patients truly have degenerative parkinsonism (and therefore represent false negative imaging results), or emerge as cases of non-degenerative parkinsonism (and therefore represent initial clinical over-diagnosis of Parkinson's disease). METHODS AND RESULTS: One hundred and fifty cases with normal I-FP-CIT SPECT undertaken during routine care over a 3-year period were reviewed 2.4 years (interquartile range, 2.2-3.1 years) after SPECT. Diagnosis after follow-up was non-degenerative parkinsonism or tremor in 146 (97%), who did not progress clinically, and degenerative parkinsonism in four (3%), in whom clinical progression was noted. Anti-Parkinson therapy was used in 36, and withdrawn in 27 with no deterioration in 25. Patients strictly fulfilling Brain Bank criteria (part 1) were more likely to undergo a trial of anti-Parkinson therapy (P < 0.05) but were no more likely to maintain or respond to anti-Parkinson therapy than those not fulfilling criteria. CONCLUSION: The clinical profile and therapy response during follow-up of patients with normal presynaptic dopamine imaging supports the diagnosis of a non-degenerative movement disorder in nearly all cases.

Successful antiparkinsonian medication withdrawal in patients with Parkinsonism and normal FP-CIT SPECT.

Between 4% and 14% of patients diagnosed with Parkinson's disease and entering clinical trials have normal presynaptic dopaminergic imaging. The effects of antiparkinsonian therapy have varied in these studies, and the consequences of stopping treatment are not reported. We present 11 patients who initially fulfilled diagnostic criteria and were treated for Parkinson's disease but in whom emerging diagnostic doubts led to antiparkinsonian therapy withdrawal, which was achieved without deterioration. Such cases represent a nondegenerative form of Parkinsonism, which does not benefit from dopaminergic therapy. Prospective vigilance regarding this category is of importance in clinical practice and clinical trials.

Prospective study of presynaptic dopaminergic imaging in patients with mild parkinsonism and tremor disorders: part 1. Baseline and 3-month observations.

To record prospectively, from early presentation, the clinical features of parkinsonism and tremor disorders, in relation to evidence of dopaminergic deficit shown with [(123)I]-FP-CIT (DaTSCAN, Amersham Health) single photon emission computerised tomography (SPECT). Clinical signs were recorded in 62 patients, of whom 24 failed standard Parkinson's disease (PD) and essential tremor criteria, and 38 fulfilled UK Brain Bank step 1 PD criteria. Striatal radioligand uptake was graded visually as normal or abnormal, and specific:nonspecific ratios were calculated. Bradykinesia and rigidity showed significant overall association with abnormal scans (P < or = 0.003), but rest tremor did not (P = NS). In the 24 patients not fulfilling specific criteria (mean age 63 [SD 9] years, disease duration 3 [SD 4] years), 10 (42%) had abnormal visual SPECT assessment and 14 (58%) had normal scans. Of 38 patients with early PD by clinical criteria (mean age 60 [SD 9] years, disease duration 3 [SD 1.7] years), 33 (87%) were visually abnormal. Baseline clinical diagnosis corresponded with SPECT imaging results in 51 of 62 cases (82%), which increased to 56 of 62 cases (90%) with amendment of seven clinical diagnoses at 3 months (blind to SPECT results). Akinetic-rigid cardinal diagnostic features of parkinsonism associate well with dopaminergic deficit in patients with early and mild clinical features. When these clinical features are uncertain, or the patient fails clinical diagnostic criteria, testing for dopaminergic deficit with [(123)I]-FP-CIT SPECT may assist the diagnostic process.

Acetylcholine muscarinic receptors and response to anti-cholinesterase therapy in patients with Alzheimer's disease.

An acetylcholine deficit remains the most consistent neurotransmitter abnormality found in Alzheimer's disease and various therapeutic agents have been targeted at this. In this study we investigated the action of Donepezil, a cholinesterase inhibitor that has few side-effects. In particular we set out to investigate whether muscarinic acetylcholine receptor (mAChR) availability influences the response to this therapy. We used the novel single-photon emission tomography (SPET) tracer (R, R)[(123)I]I-quinuclidinyl benzilate (R, R[(123)I]I-QNB), which has high affinity for the M1 subtype of mAChR. Regional cerebral perfusion was also assessed using technetium-99m hexamethylpropylene amine oxime. We investigated 20 patients on Donepezil treatment and ten age-matched controls. The results showed a reduction in (R, R)[(123)I]I-QNB binding in the caudal anterior cingulate in patients compared with controls and relatively high binding in the putamen and rostral anterior cingulate, suggesting a relative sparing of mAChR in these regions. The main finding of the study was that mAChR availability as assessed by (R, R)[(123)I]I-QNB binding did not distinguish responders from non-responders. Interestingly, we found that the extent of cognitive improvement showed no positive correlation with (R, R)[(123)I]I-QNB binding in any brain region but was inversely related to binding in the insular cortex. This suggests that, within the advised cognitive performance band for use of Donepezil, response is greater in those patients with evidence of a more marked cholinergic deficit. A larger study should investigate this.