Is Essential Tremor Predictive of Parkinson's Disease?
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MDS-1012-414 VOLUME 16, ISSUE 2 • 2012 • EDITORS, DR. CARLO COLOSIMO, DR. MARK STACY Is Essential Tremor Predictive of Parkinson’s Disease? Yes No — Elan D. Louis MD, MSc, Professor of Neurology and Epidemiology, — Charles H. Adler, MD, PhD, Professor of Neurology, Mayo Clinic College Columbia University, New York, NY, USA of Medicine, Mayo Clinic, Scottsdale, AZ, USA, Co-Principal Investigator, Arizona Parkinson’s Disease Consortium The possible link between essential tremor (ET) and Parkinson’s disease (PD) has been a subject of interest and debate for some The relationship between essential tremor (ET) and Parkinson’s time. Dating back to the first comprehensive clinical review of ET disease (PD) has been debated for years. Whether ET is actually a risk in 1949,1 there has been discussion regarding the possibility of a factor for developing PD, or whether the relationship is merely relationship between these two coincidental remains unclear. A tremor disorders, with clinicians major confounding factor for linking observing that ET patients have a the two is our limited knowledge tendency over time to develop PD. regarding their etiology. Both PD 2,3 Interestingly, the converse does and ET appear to be syndromes and not seem to occur (i.e., PD pa- not diseases with a single cause so a tients developing ET).2,3 The link is difficult to prove. As there is co-occurrence of the two tremor no diagnostic test for either ET or disorders within the same families PD, and the only definitive diagnos- is also well-documented.4 tic finding for either is the presence Three epidemiological studies, of Lewy bodies and neuronal loss in including two case-control studies the substantia nigra (SN) of subjects and one population-based pro- with PD, neuropathologic studies is spective study, each provide the main focus of this presentation. measures of association that Clinically there is overlap between support the notion that there is a link between ET and PD and, ET and PD. Both may have rest, postural and kinetic tremor as well furthermore, that the presence of baseline ET increases the risk of as some degree of bradykinesia and rigidity. However, these clinical developing incident PD during follow-up.5,6 The magnitude of the findings do not guarantee a diagnosis of PD as it is clear that patients increased odds/risks reported in the three epidemiological studies is with all three cardinal features of PD can have normal dopaminergic on the order of 3 to 13.5 Most important of these was the 2010 imaging (so called Scans Without Evidence of Dopamine Deficiency) prospective, population-based study that was conducted to estimate and no evidence of Lewy bodies neuropathologically. From a clinical- the incidence of PD in ET patients vs. normal controls.6 The study pathological standpoint there are two ways one can approach deter- sample was comprised of 3,813 elderly persons (age >65 years) mining whether ET and PD are related: 1) Is there an increased residing in three communities in central Spain. The baseline evalua- occurrence of a-synuclein staining or Lewy bodies in cases of ET, and tion consisted of an initial screening questionnaire followed by an 2) Is there an increase in ET in subjects with Lewy body pathology. in-person neurological examination; a follow-up examination was The number of autopsied cases of ET has been small. In the first few performed after a median time interval of 3.3 years. During that series there was no evidence of Lewy body pathology, even to the time interval, 6 of 201 (3.0%) ET cases vs. 24 of 3,574 (0.7%) point of some cases with ET and parkinsonian features actually not controls developed incident PD (adjusted relative risk [RR] = 4.27, having Lewy bodies and thus any linking of the two disorders would 5,6 95% confidence interval [CI] = 1.72 – 10.61, p = 0.002). Pres- have been erroneous. More recently multiple pathologic series from ently, there are no contrary data, either from case-control or pro- a single group of investigators have proposed a link between ET and 5 spective studies, to refute the model that ET is a risk factor for PD. Lewy bodies. They have published a number of papers building on Moreover, the evidence from three genetic epidemiological studies their case series and while initially the percentage of ET cases with is that ET and PD seem to co-occur in families to an extent Lewy bodies was greater than in the controls, their more recent papers have shown that there is no difference in Lewy body CONTINUED ON PAGE 18 CONTINUED ON PAGE 18 www.movementdisorders.org E DITORIAL inside this issue We hope you will enjoy this edition of Moving Along. Disorders Course” in honor of The Movement Disorder Society continues to grow Leopold Bloom, made famous in through our educational programs, website, journal the classic James Joyce novel, Ulysses. Cover Story 1 and annual congress. This issue focuses particularly on In “My Generation”, Dr. Santiago Controversy: Is Essential our recent meeting in Dublin. Because of the spirited Perez-Lloret, graciously tells us the Tremor Predictive of and academic discussion at the 16th International Parkinson’s Disease? story of his family and its impact on Congress, we have asked Dr. Charles H. Adler and Dr. his training as a physician. Santiago Editor’s Section 2 Elan D. Louis to summarize the arguments that were has been fortunate in his career to Carlo Colosimo, MD Carlo Colosimo, MD and presented regarding the relationship between essential survive fellowship training from two Mark Stacy, MD tremor and Parkinson’s disease. These reports add of our most well-known colleagues, pathological description to the rich debate long held by President’s Letter 3 Dr. Marcelo Merello and Dr. Günther Deuschl, MD, epidemiologists and phenomenologists in the field. Olivier Rascol. We hope you enjoy President A summary of the Dublin meeting is also provided and this section, and celebrate how the International Congress 4-7 reminds of the record attendance (5,100) for the growth of our society can lead to meeting. Congratulations and thanks to organizing such long-lasting friendships. Society Announcements 8-10 Mark Stacy, MD committee for a tremendously successful meeting and We are grateful for the support of My Generation 11 to award winners listed in the issue. The Basic Move- the staff members of MDS, and the Dr. Santiago Perez-Lloret ment Disorders Course, held prior to the MDS Con- continuing growth of our Movement Disorders family. gress, was a great success. Our Dublin course organiz- European Section 12-15 The editors take great pleasure in congratulating Werner Poewe, MD, ers renamed the session, “Bloomsday Basic Movement Moving Along Managing Editor, Elizabeth (Laur) MDS-ES Chair Clausen, on her wedding, July 21, 2012. She has reminded us that the MDS Secretariat has been ex- Asian and Oceanian 16 Section tremely busy with weddings and engagements this Ruey-Meei Wu, MD, PhD year: Jen (McTavish) Wolf, Program Manager; Megan MDS-AOS Chair Daniels, Program Manager; and Kate (Kirchner) Hausner, Meetings Manager celebrated marriages in Pan-American Section 17 Jorge Juncos, MD 2012, while Kate Breckenridge, Senior Education Program Manager, and Kateri Collins, Program Man- ager, plan to join the Milwaukee young married couples club in the summer of 2013. Congratulations also to Pam Fierst, Executive Assistant, who welcomed a baby boy to her family in October. Finally, we must announce the birth of Nora Colosimo, Rome, March 28, 2012; a daughter that has stolen her father’s heart and his sleep cycle! MDS Endorsed Study Groups Benefits for Study Groups are: - To the extent possible, Study Group Chairs will - Official recognition by TheMovement Disorder assign copyright in rating scales to MDS, which Society may license rights for use by others. - Receiving a letter of recommendation from the Study groups can be approved if: MDS President - The topic of the study is of major interest in the - Financial support for telephone conferences field of Movement Disorders - Meeting space during the annual MDS - The membership is open to world-wide Congress participation and should include the major Duties and responsibilities of Study Groups: researchers in the field - Defining the needs in a specific area of research - The members of the Study Group are MDS - Developing a scientific task on a long-term basis members (exclusions are possible on special - Reporting annually on the progress and next request) steps Application process: - Scientific results should be submitted to the - Submission of the project, its objectives and Movement Disorder Journal aims (timelines and deliverables) - List of participants PAGE 2 Moving Along • Issue 2, 2012 P R E SID E NT ’ S L E TT E R The interest in our specialty is As a result of this growing demand for international steadily increasing and I will ad- collaboration and participation, MDS is launching OFFICERS dress two aspects of these develop- MDS Endorsed Study Groups. MDS announced this ments today. At the 16th Interna- new forum to help researchers who are committed to President tional Congress in Dublin, 5,144 cooperative planning, implementation and reporting Günther Deuschl, MD participants from 82 countries met of research studies which need international participa- President-Elect to learn about the latest in Move- tion in order to meet their goals. These groups have Matthew Stern, MD ment Disorders. Due to the interest been created to promote research into causes, preven- Secretary in the Congress this year, MDS increased the number tion and treatment of movement disorders. MDS is Cynthia Comella, MD of travel grants it provided to help young neurologists not and cannot be a funding source for these groups, Secretary-Elect attend the meeting ($154,000 USD in grants was but as the premier international professional society Francisco Cardoso, MD provided).