Myasthenia gravis concurrent with Parkinson's disease in a Spanish cohort. Causation or correlation?

BACKGROUND

Comorbidity between myasthenia gravis (MG) and other autoimmune diseases is well-documented. However, concurrent MG and Parkinson's disease (PD) have rarely been described. This concurrence has mostly been considered coincidental in cases reported to date.

MATERIAL/METHODS

We characterized patients with concurrent MG and PD within a cohort of 631 MG patients by gender, age, MGFA class, quantitative MG score at diagnosis, UPDRS score at diagnosis, and the DaTSCAN uptake pattern, to determine the frequency and the phenotype of individuals with these two concurrent entities. Meta-analysis of cases in the literature was used for comparison with our series.

RESULTS

Eighteen cases were identified in which the two diseases were concurrent. The major characteristics of the phenotype are male prevalence, late-onset MG, and frequent initial symptoms of dropped head and oculobulbar involvement. DAT confirmed reduced bilateral uptake in eleven patients and reduced unilateral uptake in the others.

CONCLUSIONS

To our knowledge, this is the largest reported series of concurrent MG and PD. This concurrence is more common than expected (2.85%). Either MG or PD may appear first. We found no iatrogenic relationship for the order of appearance. The overlapping of symptoms sometimes leads physicians to overlook the second disease, instead viewing it as a deterioration of the first. This study describes patients with well-documented diagnoses of both MG and PD, thus providing further indications of a shared etiology of these two diseases. Prospective studies including genetic, immunological, and environmental analysis are necessary to identify possible common pathogenic mechanisms.

[Functional neuroimaging in the diagnosis of patients with Parkinsonism: Update and recommendations for clinical use]

Functional Neuroimaging has been traditionally used in research for patients with different Parkinsonian syndromes. However, the emergence of commercial radiotracers together with the availability of single photon emission computed tomography (SPECT) and, more recently, positron emission tomography (PET) have made them available for clinical practice. Particularly, the development of clinical evidence achieved by functional neuroimaging techniques over the past two decades have motivated a progressive inclusion of several biomarkers in the clinical diagnostic criteria for neurodegenerative diseases that occur with Parkinsonism. However, the wide range of radiotracers designed to assess the involvement of different pathways in the neurodegenerative process underlying Parkinsonian syndromes (dopaminergic nigrostriatal pathway integrity, basal ganglia and cortical neuronal activity, myocardial sympathetic innervation), and the different neuroimaging techniques currently available (scintigraphy, SPECT and PET), have generated some controversy concerning the best neuroimaging test that should be indicated for the differential diagnosis of Parkinsonism. In this article, a panel of nuclear medicine and neurology experts has evaluated the functional neuroimaging techniques emphazising practical considerations related to the diagnosis of patients with uncertain origin parkinsonism and the assessment Parkinson's disease progression.

[Functional neuroimaging with SPECT in Parkinson's disease and Parkinsonisms]

INTRODUCTION

The diagnosis of Parkinson's disease and the different Parkinsonian syndromes is currently determined by applying established clinical criteria. Today, different neuroimaging techniques, such as positron emission tomography and single-photon emission computerised tomography (SPECT), are a valuable aid to further our understanding of both the pathophysiology and the diagnosis of the different Parkinsonian pictures. AIM. To examine the usefulness of the different tools utilised to assess the integrity of the nigrostriatal system by visualising the pre-synaptic dopamine transporters and post-synaptic D2 receptors using SPECT techniques; we also sought to determine the role played by the alteration of the cardiac sympathetic innervation using meta-iodobenzylguanidine.

DEVELOPMENT

We review the usefulness of the different nuclear medicine techniques for the diagnosis and differential diagnosis of the distinct clinical pictures that are accompanied by Parkinsonian symptoms, and we also discuss the possible future perspectives of said techniques.

CONCLUSIONS

A combination of the different nuclear medicine techniques that have been reviewed here is useful in the study and characterisation of Parkinsonian syndromes. In the future they could be used to detect subjects who are possibly at risk of developing Parkinsonism and to be able to assess the effect of therapies that may have a potential modifying effect on the disease.