123I-metaiodobenzylguanidine scintigraphy in Parkinson's disease and related disorders

Parkinson's disease: acquired frailty of archaic neural networks?

In Parkinson's disease (PD) many motor and non-motor symptoms are difficult to explain in terms of a purely ascending degeneration process as described by Braak. This essay proposes phylogenetic considerations for consolidating the multidimensional elements of PD. Subtle clinical analysis paired with ethological comparisons as well as patho-anatomical data suggests that disrupted automatic gait control, olfactory deficits, selected visual deficits, impaired emotional face recognition, and REM sleep behavior disorder could be due to dysfunction of phylogenetically ancient networks. Neuroanatomical and behavioral findings lead to a reconsideration of the basal ganglia, to be viewed as the nuclear core of a widely distributed neural network that arborizes throughout the primordial core of the neuraxis, including the brainstem. Fragility of the resulting multiple, closed, ancillary loops that link brainstem and forebrain components of the basal ganglia may be a nodal point, pivotal to the pathogenesis of PD. Other primitive neural networks, such as those located at cardiac or gastro-intestinal levels, may share the same vulnerability. Such a network-based hypothesis overrides the need of a fixed temporal ordering of symptoms based on putative caudal-cephalic propagation patterns of pathological lesions. It also creates testable, secondary hypotheses such as differential gene expression in different neural networks, potential early epigenetic influences, concepts of "overuse" or maladaptation of primitive networks to the constraints of adult life, and system frailty due to irreparable mitochondrial "exhaustion" in highly energy consuming postmitotic cells.

The role of dopaminergic imaging in patients with symptoms of dopaminergic system neurodegeneration

Diagnosis of neurological and psychiatric conditions associated with disturbances of dopaminergic functioning can be challenging, especially in the early stages, and may be assisted with biomarkers such as dopamine system imaging. Distinguishing between Alzheimer's disease and dementia with Lewy bodies is a major diagnostic challenge. Clinical diagnosis of Parkinson's disease is straightforward with classic presentation, but accurate distinction among Parkinsonian variants may be difficult; non-Parkinson's disease conditions are commonly misdiagnosed as Parkinson's disease, and ~20% of patients with Parkinson's disease are not clinically diagnosed despite coming to medical attention. Early and accurate diagnosis is desirable to improve management. Imaging of the dopamine transporter using single-photon emission computed tomography may be of particular utility in this regard. Abnormal imaging indicates underlying nigrostriatal neurodegeneration, supportive of a diagnosis of Parkinson's disease, atypical parkinsonism or dementia with Lewy bodies, and identifies patient groups in whom dopaminergic therapy may be beneficial. Normal imaging supports diagnosis of a condition not involving nigrostriatal neurodegeneration such as Alzheimer's disease, essential tremor or drug-induced parkinsonism and hence a different therapeutic approach. In patients in whom there was diagnostic uncertainty between degenerative parkinsonism and non-degenerative tremor disorders, baseline imaging with the dopamine transporter ligand [(123)I]ioflupane (DaTscan™) has shown 78% sensitivity and 97% specificity with reference to clinical diagnosis at 3 years, versus 93% and 46%, respectively, for baseline clinical diagnosis. In a Phase III trial of [(123)I]ioflupane in patients with initial clinical diagnosis of probable or possible dementia with Lewy bodies or non-Lewy body dementia, mean specificity for excluding non-Lewy body dementia (predominantly Alzheimer's disease) was 90.4%. Using clinical diagnosis as a reference against which to assess sensitivity and specificity of dopamine transporter imaging is a limitation, but definitive diagnosis via pathological confirmation is generally not feasible. In a series of patients with post-mortem brain examination, imaging using [(123)I]ioflupane has demonstrated higher sensitivity (88%) and specificity (100%) for differentiating dementia with Lewy bodies from non-Lewy body dementia than clinical diagnosis (75% and 42%, respectively). Dopaminergic system imaging may be particularly valuable in patients with clinically inconclusive parkinsonism or a clinical diagnosis of possible dementia with Lewy bodies; it is not helpful in differentiating between Parkinson's disease and atypical parkinsonism, although postsynaptic dopaminergic imaging may be of utility. Other potential uses of dopamine transporter imaging include identification of patients with premotor Parkinson's disease, monitoring disease progression in testing novel therapeutics, and as an inclusion criterion for entry into clinical trials.

MIBG scintigraphy in differential diagnosis of Parkinsonism: a meta-analysis

OBJECTIVE

Differential diagnosis between Parkinson's disease (PD) and other Parkinsonism using clinical criteria or imaging methods is often difficult. The purpose of this study is to systematically review and meta-analyze published data about the diagnostic performance of myocardial innervation imaging using (123)I-metaiodobenzylguanidine (MIBG) scintigraphy in differential diagnosis between PD and other Parkinsonism.

METHODS

A comprehensive computer literature search of studies published through March 2011 regarding MIBG scintigraphy in patients with PD and other Parkinsonism was performed in PubMed/MEDLINE and Embase databases. Only studies in which MIBG scintigraphy was performed for differential diagnosis between PD and other Parkinsonism were selected. Pooled sensitivity, pooled specificity and area under the ROC curve were calculated to measure the accuracy of MIBG scintigraphy in differential diagnosis between PD and other Parkinsonism.

RESULTS

Nineteen studies comprising 1,972 patients (1,076 patients with PD, 117 patients with other Lewy body diseases and 779 patients with other diseases) were included in this meta-analysis. The pooled sensitivity of MIBG scintigraphy in detecting PD was 88% (95% CI 86-90%); the pooled specificity of MIBG scintigraphy in discriminating between PD and other Parkinsonism was 85% (95% CI 81-88%). The area under the ROC curve was 0.93.

CONCLUSIONS

In patients with clinically suspected PD, myocardial innervation imaging demonstrated high sensitivity and specificity. MIBG scintigraphy is an accurate test in this setting. Nevertheless, possible causes of false-negative and false-positive results should be kept in mind when interpreting the scintigraphic results.

Subthalamic nucleus stimulation for Parkinson disease with severe medication-induced hallucinations or delusions

Object

Subthalamic nucleus deep brain stimulation (STN DBS) improves cardinal motor symptoms of Parkinson disease (PD) and reduces antiparkinsonian medication. Therefore, STN DBS seems to be well indicated for patients suffering from medication-induced psychotic symptoms. However, there are few available data dealing with the effect of STN DBS in this kind of patient. The authors studied the effect of STN DBS in patients with PD and severe medication-induced hallucinations or delusions.

Methods

The authors retrospectively reviewed the clinical course of 10 patients who suffered from severe medication-induced hallucinations or delusions and underwent bilateral STN DBS. Patients whose preoperative thought disorder score (Unified Parkinson's Disease Rating Scale Part I, item 2) was 3 or more were enrolled in this study. All patients underwent cognitive function examination and brain perfusion SPECT preoperatively to exclude dementia with Lewy bodies.

Results

Subthalamic nucleus DBS yielded significant improvement of motor function in all patients. In 8 patients, psychotic symptoms completely disappeared with significant reduction of dopaminergic medication. In 2 patients, hallucinations and delusions deteriorated immediately after surgery despite complete withdrawal of antiparkinsonian medication. However, these psychotic symptoms completely disappeared after a few months with administration of antipsychotics, and no recurrence was observed afterward in either patient.

Conclusions

Subthalamic nucleus DBS is a good treatment option for patients with PD who are suffering severe medication-induced hallucinations or delusion. However, vigilance is needed, because temporary deterioration of psychotic symptoms may occur after surgery.

Accuracy of magnetic resonance parkinsonism index for differentiation of progressive supranuclear palsy from probable or possible Parkinson disease

BACKGROUND

Combined measurements on conventional magnetic resonance imaging (MRI), such as midbrain area/pons area or magnetic resonance parkinsonism index (MRPI) (pons area/midbrain area × middle cerebellar peduncle width/superior cerebellar peduncle width), have been proposed as powerful tools in the differential diagnosis between progressive supranuclear palsy (PSP) and Parkinson disease (PD). In this study, we evaluated the accuracy of MRPI, compared with midbrain/pons ratio, in distinguishing PSP from probable and possible PD.

METHODS

Forty-two PSP patients, 170 probable PD patients, 132 possible PD patients, and 38 control subjects underwent MRI and, for each patient, midbrain/pons ratio and MRPI were calculated.

RESULTS

Midbrain/pons ratio showed low accuracy in distinguishing PSP patients from those with probable PD (92.9% sensitivity; 85.3% specificity; 86.8% diagnostic accuracy) or those with possible PD (88.1% sensitivity, 88.3% specificity, and 88.2% diagnostic accuracy) and control subjects (97.6% sensitivity, 92.1% specificity, and 95% diagnostic accuracy). By contrast, MRPI showed higher accuracy to distinguish PSP from probable PD (100% sensitivity, 99.4% specificity, and 99.5% diagnostic accuracy), from possible PD (100% sensitivity, 99.2% specificity, and 99.4% diagnostic accuracy), and from control subjects (sensitivity, specificity, and diagnostic accuracy of 100%).

CONCLUSIONS

Our study confirms that MRPI is a more accurate measure than midbrain/pons ratio for differentiation of patients with PSP from those with probable and possible PD.

Diagnostic performance of myocardial innervation imaging using MIBG scintigraphy in differential diagnosis between dementia with lewy bodies and other dementias: a systematic review and a meta-analysis

BACKGROUND AND PURPOSE

This study was designed to review the diagnostic performance of myocardial innervation imaging using iodine-123-metaiodobenzylguanidine (MIBG) scintigraphy in differential diagnosis between dementia with Lewy bodies (DLB) and other dementias.

METHODS

A comprehensive computer literature search of studies published through May 2010 regarding MIBG scintigraphy in patients with DLB was performed in PubMed/MEDLINE and Embase databases. Only studies in which MIBG scintigraphy was performed for differential diagnosis between DLB and other dementias were selected. Pooled sensitivity and specificity of MIBG scintigraphy were presented with a 95% confidence interval (CI). The area under the ROC curve was calculated to measure the accuracy of MIBG scintigraphy in differential diagnosis between Lewy body diseases and other dementias.

RESULTS

Ultimately, we identified 8 studies comprising a total of 346 patients with dementia (152 patients with DLB and 194 patients with other dementias). The pooled sensitivity of MIBG scintigraphy in detection of DLB was 98% (95% CI, 94-100%); the pooled specificity of MIBG scintigraphy in differential diagnosis between DLB and other dementias was 94% (95% CI, 90-97%). The area under the ROC curve was .99.

CONCLUSIONS

Myocardial innervation imaging with MIBG scintigraphy demonstrated high pooled sensitivity and specificity in patients with suspected DLB. MIBG scintigraphy is an accurate test for differential diagnosis between DLB and other dementias.

Dopamine receptor agonists for the treatment of early or advanced Parkinson's disease

Dopamine receptor agonists are indicated for the symptomatic treatment of early, moderate or advanced Parkinson's disease as well as for the reduction of levodopa-related motor complications. Ergolinic dopamine agonists, such as bromocriptine or pergolide, were initially developed and marketed, and then non-ergolinic dopamine agonists, such as pramipexole and ropinirole, were introduced, reducing the risk of drug-induced fibrotic reactions. Once-daily, controlled-release oral and transdermal formulations have been developed aiming at providing more stable 24-hour plasma drug concentrations and more convenient administration. A disease-modifying effect of dopamine agonists has not been demonstrated clinically. As with any other drug, dopamine agonists can also cause adverse drug reactions, which can be related or unrelated to dopaminergic hyperactivation. Dopaminergic reactions include nausea, hallucinations, confusion and orthostatic hypotension, among others, which were readily identified in pre-marketing clinical trials. During post-marketing surveillance, important adverse reactions were identified, such as daytime somnolence, impulse-control disorders and heart valve fibrosis. Other issues, including the efficacy of dopamine agonists for the treatment of non-motor symptoms, remain under evaluation.

Role of pramipexole in the management of Parkinson's disease

The non-ergot dopamine agonist pramipexole is currently indicated for the treatment of the signs and symptoms of idiopathic Parkinson's disease and for the treatment of moderate-to-severe primary restless legs syndrome. A new extended-release formulation of pramipexole has now also been launched in Europe and the US to improve ease of use, compliance and provide a more continuous therapeutic effect over 24 hours. Before initiating any treatment, the benefit-risk ratio to the individual patient must be considered. For pramipexole in the treatment of Parkinson's disease, this means taking into account the available evidence regarding its symptomatic efficacy, effect on delaying long-term levodopa-related motor complications, beneficial effect on non-motor symptoms such as depression, and its safety and tolerability profile. Studies have shown that pramipexole is effective as monotherapy in early Parkinson's disease and as adjunctive therapy in advanced disease. Trials further suggest that the benefits of pramipexole may extend beyond the relief of motor symptoms (akinesia, rigidity and tremor at rest) to the amelioration of depressive symptoms in Parkinson's disease. Pramipexole is generally well tolerated; however, compared with levodopa treatment, pramipexole is associated with a higher rate of some dopaminergic adverse effects.