Epidemiology of Focal and Generalized Dystonia in Rochester Minnesota - Needs OCR

8/3/2019 Epidemiology of Focal and Generalized Dystonia in Rochester Minnesota - Needs OCR

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.Mdvemefr tDisordersVol. 3, No.3, 1988,pp, 188-194 1988Movement Disorder Society

.. .Epidemiology of Focal and GeneralizedDystonia in Rochester, MinnesotaJohn G.Nutt, "Manfred D. Muenter, *Arnold Aronson,"Leonard T. Kurland, and *L. Joseph Melton, III

Oregon Health Sciences University, Portland, Oregon, U.S.A.; "MayoCiinic,Rochester, Minnesota, U.S.A.

Summary: The epidemiology of generalized and focal dystonias was investi-gated in the Rochester, Minnesota, population over the period 1950-1982. Thecrude incidence of generalized dystonia was 2 per million persons per year,andfor all focal dystonias combined, 24 per million per year. The crude prevalencerate was 34 per million persons for generalized dystonia and 295 per minionpersons for all focal dystonias. Torticollis was the most common focal dysto-nia; essential blepharospasm, orornandibular dystonia, spasmodic dysphonia,and writer's cramp were less common and had roughly equal incidence and -,prevalence rates. Key Words: Generalized dystonia-Focal dystonia=-Epi- .demiology.

Focal dystonias (blepharospasm, oromandibular dystonia, spasmodic dyspho-nia, torticollis, writer's cramp) have recently been recognized as constituting thesecond largest diagnostic group of patients to attend movement disorder clinics."Large clinical series have defined the clinical features of the focal dystonias (1-8)and have suggested associations with autoimmune disease (3), thyroid disorders .:',(9,10), antihistaminic and sympathomimetic usage (11,12), and brainstem and di-encephalic structurallesions (B), However, no formal epidemiologic studies havedefined the frequency of focal dystonias in the general population nor systemat-ically evaluated possible risk factors for the various disorders.The medical records linkage system of the Rochester Epidemiology Projectoffers a unique opportunity to investigate the epidemiology of the focal and gen-eralized dystonias. The medical records of all individuals residing within the citylimits of Rochester, Minnesota, U.S.A., and seeking outpatient or inpatient med- ..ical care locally are available through the resources of the Rochester Epidemiol-ogy Project and the Mayo Clinic. Furthermore, in addition to the Mayo Clinic'sPresented in part at the Second International Dystonia Symposium, New York, New York, June

1986.Address correspondence and reprint requests to Dr. J. G. Nutt at Oregon Health Sciences Univer-sity, 3131 Southwest Sam Jackson Park Road, Portland, OR 97201, U.S.A.

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EPIDEMIOLOGY OF DYSTONIA" 189. .,

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. .lOl1gtradition of excellence in neurologyv.several Mayo Clinic staff physicians -.have had a special interest in various focal dystoniasvThus, it is likely that these. disorders would be recognized and properly diagnosed in the Rochester popula-tion. .' .... ... .We have used these medical records to estimate the incidence and prevalence'.".of generalized and focal dystonias and to examine some suggested associationsbetween focal dystonias and other medical conditions. An independent study oftorticollis in this population was conducted simultaneously by Drs. Drake Duane .' ..and David Claypool, and some of the preliminary results of that investigation are .included in this report as a personal communication. .

METHODS. . ....Population-based epidemiologic research is possible in Rochester, Minnesota,......ecause medical care is virtually self-contained within the community and isby a handful of providers. Most care is provided by the Mayo Clinic,'which has maintained a common medical record system with its two largeaffili- .~ted hospitals over the past 80 years. This dossier-type medical record containsinpatient and outpatient data and is easily retrievable for review. The diag- ..noses and surgical procedures entered into these records are indexed. The index ..

'includes the diagnoses made for outpatient office or clinic consultations, emer-gencyroom visits, nursing home care, hospitalizations, autopsy examination, arid" death certification. The medical records ofthe other medical care providers in the.:area who had served the local population are also indexed and retrievable through .the medical records linkage system of the Rochester Epidemiology Project. Thus, . ...he details of all medical care provided locally to the residents of Rochester are

available for study.'.... Access to this record system was obtained by a protocol approved by the Mayo'. Clinic Institutional Review Board. All charts coded for diagnoses that might in- '... elude blepharospasm, Meige syndrome or cranial dystonia, spasmodic dysphonia, .writer's or occupational cramp, other focal and segmental dystonias, and gener-alized dystonia for patients residing within the Rochester city limits between theyears 1950 and 1982 were reviewed by the first author. Duane et al. reviewed all ..'cases coded as torticollis for the years 1960through 1979. The diagnostic category..of tardive dyskinesia, which could conceivably contain cases of "spontaneous .:dyskinesia," was not reviewed. Cases were defined as "definite" if the chart

..description was typical for dystonia; as "probable" if the patient had many fea-.' .turesof dystonia but atypical features were present or descriptions by chart were'not definitive; as "possible" if the information from the chart indicated somefeatures consistent with a dystonic disorder but inadequacy of description or other .features raised significant questions about the diagnosis; and as "not dystonia" ifthe patient's symptoms were clearly not those of a chronic dystonia. The dystoniahad to have been present a minimum of 6 months. Essential blepharospasm wasdefined as forceful involuntary closure of both eyes not caused by lid or ocularpathology and not accompanied by involvement of other cranial muscles. Oralmandibular dystonia (Meige syndrome or cranial dystonia) was defined as abnor-

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RESULTS

J. G.NUTTETAL.

mal movements or spasms of facial, masticatory, lingual, or pharyngealIature and could also include blepharospasm. Spasmodic dysphoniaas abnormal phonation caused by involuntary irregular movement or spasmlarynx and was differentiated from vocal tremor (but this could also beWriter's cramp (occupational cramp) was defined as abnormal posture or itremor induced by handwriting or other specific fine motor tasks.dystonia was dystonia affecting one or more limbs as well as axialTorticollis was defined as noncongenital, involuntary, usually asymmetrical,tractions of the cervical muscles producing semirhythrnic, arrhythmic, Ormovement of the head on the cervical spine.Dystonias were categorized by the most prominent dystonic feature(s) andclassified as primary (idiopathic) and secondary (dystonia caused byrologic injury or disease process or as a feature of a systems degeneration).Inpatient and outpatient records of all patients classified as "possible"probable," or "definite" dystonia by the principal investigator wereby Dr. Muenter, and all patients with "possible," "probable," or 'spasmodic dysphonia were reviewed by Dr. Aronson. Consensus wascases to be accepted as "definite" dystonia. The charts of an cases werefor evidence of thyroid disease, prior drug use (specifically neuroleptics, _thornimetic, antihistaminics, and other drugs affecting central _autoimmune disorders, other neurologic disease, and family histories of neurO-,logic disorders. Patients with a history of 2 or more months of neuroleptic expo-sure prior to the onset of the dystonia were excluded.For calculating incidence and prevalence rates, the entire population of -'-"-VvU-_ester, Minnestoa, was considered to be at risk; the denominator

were derived from decennial census figures (14). Prevalence was calculated forJanuary 1, 1983, except for torticollis, which was calculated for January 1, 1The denominator was the Rochester population determined by the 1980 census ofby extrapolation of census data to 1983 (14). Although rates could not be agead-justed due to the small numbers of patients with each condition, the Rochester.population is somewhat younger, on average, than United States whites generally;consequently, age adjustment would have had the effect of increasing the cruderates by a small margin.

Six hundred ninety-seven medical histories were reviewed and 23 cases wereaccepted as representing idiopathic dystonia. Eleven cases of torticollis were'found in a review of 917 patients indexed between 1960 and 1979 (D. Duane,personal communication).A major difficulty in selecting patients was related to differentiating idiopathic -.and secondary dystonia. Two of the cases of generalized dystonia had onset inchildhood, and the question of static encephalopathy related to perinatal injurywas raised in both. One was the product ef a breech delivery, but had normalmilestones and intelligence (IQ 121). At age 3, he developed a dysarthria, and atage 6, dystonic gait. A brother had an uncharacterized speech difficulty , The

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EPIDEMIOLOGY OF DYSTONIA 191child also had normal milestones and' developed aprogressived ystonia in,'the arms at age 9. As both had had normal milestones for several years of lifebefore dystonic symptomatology appeared, they were classified as idiopathic dys-tonia.Further difficulties in classification included two patients with oromandibular

dystonia and evidence of extensive cerebrovascular disease whose dystonia may. been related to vascular lesions in the midbrain or thalamus (13). Another'.case of oromandibular dystonia also had ataxia and peripheral neuropathy raisingthe question of some type of system degeneration. Nevertheless, these threepatients were included as idiopathic cases.Torticollis was the most common focal dystonia. Essential blepharospasm, oro-mandibular dystonia (Meige syndrome), spasmodic dysphonia, and writer'scramp were less frequent (Table O . Each focal dystonia had a greater incidence,and all but blepharospasm had a greater prevalence than generalized dystonia inthe Rochester population (Table 1). The overall crude incidence of focal dystonia,24/106 persons/year (95% c.r., 16.4-34.3) was 12 times as great as that of gener-alized dystonia. The prevalence of all focal dystonias in the Rochester population,295/106 persons (95%) C.l., 172--479),was ~9 times that of generalized dystonia.The demographics of the affected patients are of limited value because of thesmall numbers. However, as in previous clinical series, the average age of onsetof blepharospasm (56 years) and oromandibular dystonia (66 years) was older thanthat for the other focal dystonias (spasmodic dysphonia, 35 years; torticollis, 45years; writer's cramp, 49 years), although any of the focal dystonias could appearin later life (Table 1). Only generalized dystonia had onset in childhood in ourseries; childhood onset of focal dystonias has been uncommon in other series aswell (1-8). There was not the marked preponderance of females among patientswith blepharospasm and cranial dystonia noted in other series (1-3). No familialclusters of focal or generalized dystonia were identified in this material, but familyhistories recorded in the charts were generally sketchy .. Dystonia in body areas other than that of the major involvement was seen in

Frequency and demographics of Rochester, MN, residents diagnosed withdystonia, 1950-1982Incidence Prevalence Age of onset Sex ratioDisorder Cases Ratea 95% CI Cases Rateb 95% CI Mean (range) (M:F)

7 4.6 1.8-9.5 1 17.2 0.5-95.8 56 (32-77) 4:35 3.3 1.1-7.7 4 68.9 18.7-176 66 (40-86) 1:4Spasmaticdysphonia 4 2.7 0.7-6.9 3 51.7 10.7-151 35 (16-4J7) 2:2Torticollis" 11 10.9 5.4-19.5 5 88.6 28.7-207 45 (19-76) 2 : 9Writer's4 2.7 0.7-6,9 4 68.9 18.7-176 47 (30-69) 4:03 2.0 0.4-5.8 2 34 4.1-124 20 (3-49) 3:0

a Crude incidence per 1,000,000 person-years.b Crude prevalence per 1,000,000 persons.c Orornandibular dystonia.d Preliminary data (D. Duane, personal communication).

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i.G.NUTTETAL.patients with blepharospasm, o"romandibuhird.ystonia, and spasmodicbut not the patients with torticollis ".orwriter's cramp (Table 2);was present in many of the patients with focal dystonias, with the exwriter's cramp (Table 2), as has been noted in other reports (3,4,7,8)~neurologic features in the patients with orornandibular dystonia: included a t-'~'.~u.~ .. ,with ataxia and a peripheral neuropathy, possibly suggesting system __, . . , _ U " " .tion, such as olivopontocerebellar atrophy. Two other patients had e .......u' .cerebrovascular disease; one of those two came to postmortem and had' "', u"''-'.':..of lacunar infarcts in the .basal ganglia, thalamus, subcortical.white matterv.a ...."dence of focal vascular lesions of the midbrain and thalamus were present inpatients with oromandibular dystonia (these two patients were not the patients-.with possible autoimmune disorders) (Table 3).

DISCUSSION .The prevalence of generalized dystonia in the Rochester pOPulation(~4' .....million persons) is greater than the 11 per million described for the Jewish .'


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EPIDEMIOLOGY OF DYSTONIA:-', .. . : " ... . .'." '" ," . "

3; Possible etiologic associations among Rochester, MN,residents diagnosed. with dystonia, 1950..:..1982.Adrenergicdrugs Autoimmune Focallesions

Disorder % n % n %2 9 060 : 2 40

046 NA_ . 00

nBlepharospasm (7)a>OMDb (5)Spasmotic dysphonia (4)Torticollis" (11)Writer's cramp (4)Generalized (3)

oo1NAoo

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a Total number of cases in parentheses; NA, not available.b Orornandibular dystonia. .C Preliminary data (Drake Duane, personal communication).

()f cases in our study is small, so that the confidence limits ~f our estimates arelarge. .There are no previous studies with which to compare our estimates for preva-lence and incidence of focal dystonias. It is striking that these, until recently,commonly unrecognized forms of dystonia were approximately 9 times as prev-alent as generalized dystonia and had a 12 times greater incidence rate in Roch-ester. Furthermore, our estimates of the incidence and prevalence of focal dys-tenias may be low. These syndromes are often not brought to medical attention,and if so, are frequently not recognized and documented by non-neurologists,even in medically sophisticated communities such as Rochester. Even diseasesthat are generally recognized by health care providers, such as Parkinson's dis-ease, may be grossly underreported as suggested by a door-to-door survey inCopiah County, Mississippi, U.S.A. (18). That study found that over 40% of theidentified cases of parkinsonism were diagnosed by the survey physicians; boththe patient and the patient's physician being unaware of the diagnosis. Regardless,the dystonias taken together are more common than a number of other neurologicComparison of prevalence of generalized and focal dystonias to that of otherneurologic disorders" in the Rochester, MN, population

Disorder Prevalence"Generalized dystoniaFocal dystoniaMyotonic dystrophyMyasthenia gravisMuscular dystrophyAmyotrophic lateral sclerosisHuntington's diseaseParkinsonismCerebrovascular diseaseConvulsive disorders

3429 530386064671,5696,1206,500

a Prevalence rates for disorders other than dystonia are from reference 19.b Crude prevalence per 1,000,000 persons.

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REFERENCES

J. G. NUTT ETAL.

disorders that constitute a small but consistent portion of neurologicRochester and of most neurologists' practices (Table 4).Thyroid disease, autoimmune disorders, and sympathomimetic drug use nT

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Epidemiology of Focal and Generalized Dystonia in Rochester Minnesota - Needs OCR