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Benign Positional Vertigo: Incidence and Prognosis in a Population-Based Study in Olmsted County, Minnesota
Benign Positional Vertigo: Incidence and Prognosis in a Population-Based Study in' Olmsted County, Minnesota
DAVID A. FROEHLING, M.D., Division ofArea Medicine; MARC D. SILVERSTEIN, M.D., * Division ofArea Medicine and Section of Clinical Epidemiology; DAVID N. MOHR, M.D., Division ofArea Medicine; CHARLES W. BEATrY, M.D., Department of Otorhinolaryngology; KENNETH P. OFFORD, M.S., Section ofBiostatistics; DAVID J. BALLARD, M.D., Ph.D., Section of Clinical Epidemiology
A retrospective review of our population-based medical records linkage system for residents of Olmsted County, Minnesota, revealed 53 patients (34 women and 19 men; mean age, 51 years) with newly diagnosed benign positional vertigo in 1984. The ageand sex-adjusted incidence was 64 per 100,000 population per year (95% confidence interval, 46 to 81 per 100,000). The incidence ofbenign positional vertigo increased by 38% with each decade of life (95% confidence interval, 23 to 54%). One patient had an initial stroke during follow-up; thus, the relative risk for new stroke associated with benign positional vertigo was 1.62 (95% confidence interval, 0.04 to 8.98) in comparison with the expected occurrence based on incidence rates for an age- and sex-adjusted control population. The observed survival among the 53 Olmsted County residents with benign positional vertigo diagnosed in 1984 was not significantly different from that of an age- and sex-matched general population. Patients with benign positional vertigo seem to have a good prognosis.
Dizziness was the third most frequent complaint in a recent study of 1,000 medical outpatients. 1 A substantial number of patients with dizziness have true vertigo. 2 Patients with positional vertigo as an isolated symptom are generally *Henry J, Kaiser Family Foundation Faculty Scholar in General Internal Medicine. This study was supported in part by Research Grants AR 30582 and NS 06663 from the National Institutes of Health, Public Health Service. Dr. Ballard is supported in part by a Career Development Award from the Merck, Sharp & Dohme/Society for Epidemiologic Research Clinical Epidemiology Fellowship Program. Address reprint requests to Dr. D. A. Froehling, Division of Area Medicine, Mayo Clinic, Rochester, MN 55905. Mayo Clin Proc 66:596-601, 1991
believed to have a good prognosis and often are classified as having "benign positional vertigo" (BPV). In one dizziness clinic, BPV was found in 10% of the patients with dizziness." The risk of death, stroke, or some other serious disorder ofthe central nervous system after an initial diagnosis of BPV is unknown. Positional vertigo and nystagmus may be the initial manifestations of brain tumors" and cerebellar infarcts.' In one recent study at a neuro-otologic clinic, 12 of 42 patients with strokes of the vertebrobasilar circulation had had prior episodes of isolated vertigo. 5 Studies of outcomes after BPV or vestibular neuronitis have universally been performed at subspecialty clinics.v" where the spectrum of disease and associated
596
Mayo cue Proc, June 1991, Vol 66
prognoses may differ from those in the general population." The population-based study reported herein was undertaken to determine the incidence rate of BPV, to estimate the persistence of this syndrome, and to determine the subsequent risk of death, stroke, and other disorders of the central nervous system in patients who initially had BPV.
METHODS
Definitions.-BPV was defined as transient
episodes of vertigo that occur only with changes in head position and in conjunction with no other neurologic signs or symptoms aside from positional nystagmus. Positional nystagmus, however, was not a requirement for inclusion in the study. Head trauma, if present, was classified as major or minor. Patients who fulfilled previously defined criteria for head trauma.!? including concussion and loss of consciousness, posttraumatic amnesia, neurologic signs of brain injury, and skull fractures, were classified as having major head trauma. All other patients with head trauma were classified as having minor trauma. Study Cohort.-We retrospectively reviewed the population-based medical records linkage system for residents of Olmsted County, Minnesota, 11 to identify cases of BPV newly diagnosed in 1984. To minimize the potential effects of migration to the area because of health status, we included in the study only those patients who had been residents of Olmsted County for at least 1 year before BPV was diagnosed. The records of all 467 residents with a diagnosis of vertigo, dizziness, labyrinthitis, or a similar condition who were examined in 1984 were reviewed by one of us (D.A.FJ; 53 patients fulfilled the criteria for inclusion. The reasons for exclusion were as follows: dizziness or similar diagnosis with insufficient documentation of vertigo to categorize patients in 195; continuous (not positional) vertigo in 75; no vertigo in 65; onset of BPV before 1984 in 49; associated new signs and symptoms in the central nervous system in 10; orthostatic hypotension in 10; Meniere's disease in 4; otosclerosis in 4; streptomy-
BENIGN POSITIONAL VERTIGO
597
cin toxicity in 1; and missing records in 1. The complete medical records ofthe 53 patients who qualified for inclusion in the study were thoroughly reviewed. Statistical Analysis.-An age- and sex-adjusted incidence rate for BPV was calculated by using the estimated 1984 population of Olmsted County'< and the 1980 white population of the United States. Poisson regression was performed to determine whether the incidence of BPV was associated with age or sex.!" A KaplanMeier survival curve was constructed, and observed survival was compared with expected survival based on 1980 Minnesota life tables. 14 For comparison of categorical clinical variables, X2 analysis was used. The expected number of strokes and the relative risk of stroke in this cohort of 53 patients were calculated by using incidence rates for stroke from the Rochester Cerebrovascular Project. 15 P values ofless than 0.05 were considered statistically significant.
RESULTS
Incidence Rates.-The mean age of the 53
patients who fulfilled our criteria for BPV was 51 years (range, 18 to 87 years). The age- and sexadjusted incidence was 64 per 100,000 population per year, with a 95% confidence interval of 46 to 81 per 100,000 per year (Table 1). Poisson regression indicated that age was significantly (P
Symptoms, Signs, and Diagnostic Eualuation.-Vertigo was the chief complaint in
92% ofthe 53 patients. The initial examination was performed in an internal medicine or family medicine outpatient clinic in 41 patients (77%) and in an emergency room in 8 (15%); 4 patients
598
BENIGN POSITIONAL VERTIGO
Mayo Clin Proc, June 1991, Vol 66
Table I.-Incidence Rates for Benign Positional Vertigo Among Residents of Olmsted County, Minnesota, in 1984
(~)
Total
Male
Female
Sex-adjusted incidence/ 100,000 population per year
0-29 30-49 50-59 60-69 70-84 ;::85 Total
12 11 11
7 3 3 3 2 1 19
5 8 8 4 8 1 34
25 42 141 118 193 182 64*
Age
Patients (no.)
7
10 2 53
*Age- and sex-adjusted to the 1980 US white population.
(8%) were self-referred to our Department of Otorhinolaryngology. Most patients were examined and treated in an outpatient setting. A third of the patients had consultations with otorhinolaryngologists, and five (9%) were examined by neurologists, who confirmed the diagnosis of BPV. Two disease characteristics were notable. Rolling over in bed reproduced the symptoms of vertigo in 40% of the 53 patients. Positional nystagmus was observed in 50% of the 26 patients with BPV whose medical records documented that they had been tested for positional nystagmus with a head-hanging maneuver. The examining physicians had ordered various tests to assess the patients with BPV. Computed tomographic scans of the head, obtained in nine patients, showed normal results in four, cerebral atrophy in two, evidence of trauma in two (a subgaleal hematoma and a skull fracture), and cerebral infarct in one. Audiograms showed normal findings in seven patients, a high-frequency sensorineural hearing loss in eight, and a mixed hearing loss in one. Electronystagmograms showed normal results in four patients and a hypoactive labyrinth in one. Prior Morbidity.-Four patients (8%) had had disorders of the central nervous system 2 to 32 years before the onset of symptoms and the diagnosis of BPV in 1984. One patient had had onset of partial complex seizures in 1952, a probable occlusion of the left carotid artery in
1964, and a vertebrobasilar transient ischemic attack in 1976. The second patient had had a vertebrobasilar transient ischemic attack in 1975. The third patient had had a transient ischemic attack that involved the middle cerebral artery in 1981. The fourth patient had had probable bacterial meningitis in 1982, complicated by a stroke of the anterior circulation (right hemiparesis and aphasia). Eight patients reported having prior head trauma (major in four and minor in four). The median interval from the date of head trauma to the onset of symptoms of BPV was 34 days (range, 0 days to 20 years). Duration of Symptoms.-The medical records showed that 49 of the 53 patients (92%) had follow-up for 1 month or more after the diagnosis of BPV. The other four patients were not examined by a physician in Olmsted County beyond 1 month after the diagnosis of BPV. Of the 49 patients who had a medical visit more than 1 month after the initial examination, the presence of symptoms of vertigo was noted in the medical records of 16 (33%). The patient's age, sex, prior head trauma, symptoms with rolling over in bed, and presence of positional nystagmus were not significantly associated with resolution of symptoms. Subsequent Neurologic Disease.-All 53 patients with BPV had the onset of their symptoms in 1984, the year in which BPV was diagnosed. Four patients (8%) subsequently had disorders of the central nervous system. Two patients experienced strokes during follow-up: the patient with previously diagnosed partial complex seizures had a probable occlusion ofthe right internal carotid artery in 1985 and a hemorrhagic stroke that involved the right posterior cerebral artery in 1986; another patient had a fatal subarachnoid hemorrhage in 1986. A third patient had a transient ischemic attack (amaurosis fugax) in 1988. In the fourth patient, a benign essential tremor was diagnosed in 1985. These disorders followed the onset of symptoms of BPV by 12 to 48 months. No subsequent otolaryngologic diagnoses such as Meniere's disease or otosclerosis were made in these 53 patients after the onset of symptoms of BPV.
Mayo Clio Proc, June 1991, Vol 66
Among the 51 patients who had not had strokes before the diagnosis of BPV, only 1 had a stroke during follow-up (the aforementioned patient with the subarachnoid hemorrhage). By using the incidence rates for stroke from the Rochester Cerebrovascular Project,15 the expected number 'of first strokes for these 51 patients was 0.62. This yielded a relative risk of 1.62 for new strokes after a diagnosis of BPV, not significantly different from unity (95% confidence interval, 0.04 to 8.98). Survival.-Our study group had 161 patientyears of follow-up. Three patients died during the follow-up period: one had a fatal myocardial infarction at 2 years, one had a fatal subarachnoid hemorrhage at 2 years, and one had a fatal lower gastrointestinal hemorrhage at 4 years. As shown in the Kaplan-Meier survival curve (Fig. 1), the overall observed survival of this cohort of 53 patients did not differ significantly from the expected survival, based on the 1980 Minnesota white population life tables for ageand sex-matched persons.
DISCUSSION BPV and nystagmus were first described by Barany'" in 1920. The syndrome was further characterized by Dix and Hallpike '? in 1952 and distinguished from Meniere's disease and vestibular neuronitis. The features ofthe syndrome include vertigo that occurs only when certain head positions are assumed and an associated positional nystagmus that usually is rotatory and is characterized by latent onset, fatigue, and habituation.18 Elicitation of positional vertigo and nystagmus with a head-hanging maneuver is not always possible in patients with a history otherwise compatible with a diagnosis of BPV.8,19 In a study of255 cases of BPV, Katsarkas and Kirkham" did not include positional nystagmus as a requirement for diagnosis. For these reasons, we did not require positional nystagmus as a prerequisite for the diagnosis of BPV. The statistical power of our study to detect an increased risk for subsequent stroke was limited by the small number of patients. With the Poisson distribution with a one-sided a of 0.05, this
BENIGN POSITIONAL VERTIGO
599
study had chances ofonly 12%, 27%, and 43% for detecting a doubling, tripling, or quadrupling, respectively, of the relative risk of subsequent stroke. Thus, in reference to the subsequent stroke experience in this cohort, the observation that the risk of stroke was not significantly increased should not be overinterpreted. Referral bias was avoided in this study because of its population-based nature. Nonetheless, several other possible sources of bias existed. Patients who initially had symptoms of BPV and then were found to have a brain tumor, multiple sclerosis, or stroke within a few days or weeks after seeking medical attention might not have been identified as having diagnoses of dizziness or vertigo and thus might not have been included in our retrospective cohort study. We suspect that the number of patients in this category was small. Primary intracranial neoplasms are uncommon-the age- and sex-adjusted incidence rate before death in Rochester, Minnesota, from 1965 to 1977 was 9 per 100,000 population per year.P? Multiple sclerosis is even less common-the stable age- and sex-adjusted incidence rate in Rochester from 1905 to 1964 was 4 per 100,000 population per year."! Strokes are common, with an age- and sex-adjusted incidence rate from 1980 to 1984 of 135 per 100,000 population per year in Rochester. 15 A patient with a stroke, however, will seldom have BPV as the initial manifestation. In a study in Rochester of 980 patients with nonhemorrhagic brain infarctions that occurred from 1960 through 1979, numerous signs and symptoms were noted at the time of initial examination, but vertigo was not one of them. 22 The basis for inclusion or exclusion ofpatients is a more serious source of selection bias. Because ofinsufficient documentation of signs and symptoms in the medical record, 195 patients had to be excluded, some of whom might have had BPV. If BPV were as frequent among the cases with insufficient documentation as among the other cases (19%), the incidence of BPV would have been approximately 107 per 100,000 population per year. Because of the retrospective nature of our study, complete characterization of our patient
600
BENIGN POSITIONAL VERTIGO
Mayo Clin Proc, June 1991, Vol 66
100 I
'#
80
I-
60
I-
40
'-
20
f-
~
>
'>....
::l
Expected Observed
(f)
0
0
I
I
I
I
I
I
I
I
I
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
Years since diagnosis Fig. 1. Kaplan-Meier survival curve for 53 patients with benign positional vertigo and expected survival based on 1980 Minnesota white population life tables for age- and sexmatched persons.
population was difficult. We were dependent on 1982 to 1984;24 however, the Japanese patients the documentation of signs and symptoms by were tabulated only ifexamined by a subspecialbusy clinicians. For example, most or all of our ist or at a referral center. patients may have had symptoms of vertigo Comparison of our patients with those aswhen rolling over in bed, but most clinicians did sessed in subspecialty clinics reveals some siminot seem to have asked this question or at least larities. The mean age of our 53 patients was 51 did not document a "yes" or "no" answer in the years. In the report by Katsarkas and Kirkmedical record. Similarly, it was difficult retro- ham," the mean age oftheir 255 patients was 50 spectively to distinguish new-onset BPV from years; in the 240 patients described by Baloh acute vestibular neuronitis. and colleagues.!" the mean age was 54 years. In Our ability to determine whether a patient's a recent article, Bloom and Katsarkas'" reported symptoms of vertigo had resolved was limited. that the prevalence of BPV in their dizziness Four patients were lost to follow-up. Whether a clinic increased with advancing age. patient's symptoms were recorded as having Of our 53 patients, 8 (15%) reported having resolved depended on whether the patient com- head trauma before the onset of symptoms and plained of vertigo at a subsequent visit and the diagnosis of BPV. Similarly, 17% of the whether the complaint was documented by the patients described by Katsarkas and Kirkham" physician. and 18% of those in Baloh and associates' study'? Two other epidemiologic studies on vertigo had prior head trauma. Our study design, are relevant. Wladislavosky-Waserman and as- however, did not allow us to address the relative sociates-" reported that in Rochester, Minne- risk of BPV associated with prior head trauma. sota, from 1951 to 1980 the incidence of Meniere's disease was 15 per 100,000 population CONCLUSION per year. A study in Japan found an incidence of This study of BPV has several implications for BPV of 11 per 100,000 population per year from clinical practice. Patients with BPV do not seem
Mayo Clin Proc, June 1991, Vol 66
BENIGN POSITIONAL VERTIGO
to have an increased risk for death and probably do not have a clinically important increased risk for stroke. Because in many patients the symptoms resolve, it may be appropriate to recommend a period of observation before further diagnostic evaluation. A larger study with greater statistical power is needed to evaluate the relationship, if any, between BPV and the risk for subsequent stroke.
12.
REFERENCES
16.
1.
2. 3. 4. 5. 6. 7. 8. 9. 10.
11.
Kroenke K, MangelsdorffAD: Common symptoms in ambulatory care: incidence, evaluation, therapy, and outcome. Am J Med 86:262-266, 1989 Drachman DA, Hart CW: An approach to the dizzy patient. Neurology 22:323-334, 1972 Watson P, Barber HO, Deck J, Terbrugge K: Positional vertigo and nystagmus of central origin. Can J Neurol Sci 8:133-137, 1981 Duncan GW, Parker SW, Fisher CM: Acute cerebellar infarction in the PICA territory. Arch Neurol 32:364-368, 1975 Grad A, BalohRW: Vertigo ofvascular origin: clinical and electronystagmographic features in 84 cases. Arch Neurol 46:281-284,1989 Aantaa E, Virolainen E: Vestibular neuronitis: a follow-up study. Acta Otorhinolaryngol Belg 33:401404, 1979 Greisen 0: Vestibular neuronitis: a follow-up study of 16 patients. J Laryngol 0101 88:741-747, 1974 Katsarkas A, Kirkham TH: Paroxysmal positional vertigo-a study of255 cases. J Otolaryngol 7:320330, 1978 Melton LJ III: Selection bias in the referral of patients and the natural history of surgical conditions (editorial). Mayo Clin Proc 60:880-885, 1985 Annegers JF, Grabow JD, Kurland LT, Laws ER Jr: The incidence, causes, and secular trends of head trauma in Olmsted County, Minnesota, 1935-1974. Neurology 30:912-919, 1980 Kurland LT, Molgaard CA: The patient record in epidemiology. Sci Am 245:54-63, October 1981
13., 14. 15.
17.
18. 19. 20. 21. 22.
23.
24.
25.
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Bergstralh EJ, Offord KP: Projected Rochester and Olmsted County Populations for 1981-1995. Technical Report Series, No. 38, Section of Biostatistics, Mayo Clinic, Rochester, Minnesota, February 1988 McCullaghP, NelderJA: Generalized Linear Models. New York, Chapman and Hall, 1983, pp 127-148 Kaplan EL, Meier P: Nonparametric estimation from incomplete observations. J Am Stat Assoc 53:457481, June 1958 Broderick JP, Phillips SJ, Whisnant JP, O'Fallon WM, Bergstralh EJ: Incidence rates of stroke in the eighties: the end of the decline in stroke? Stroke 20:577-582, 1989 Barany R; Diagnose von Krankheitserscheinungen im Bereiche des Otolithenapparates. Acta Otolaryngol (Stockh) 2:434-437, 1920 Dix MR, Hallpike CS: The pathology, symptomatology and diagnosis of certain common disorders of the vestibular system. Proc R Soc Med 45:341-354, 1952 Mohr DN: The syndrome of paroxysmal positional vertigo: a review. West J Med 145:645-650,1986 Baloh RW, Honrubia V, Jacobson K: Benign positional vertigo: clinical and oculographic features in 240 cases. Neurology 37:371-378, 1987 Annegers JF, Schoenberg BS, Okazaki H, Kurland LT: Epidemiologic study of primary intracranial neoplasms. Arch Neurol 38:217-219, 1981 Percy AK, Nobrega FT, Okazaki H, Glattre E, Kurland LT: Multiple sclerosis in Rochester, Minn: a 60year appraisal. Arch Neurol 25:105-111, 1971 Tumey TM, Garraway WM, Whisnant JP: The natural history of hemispheric and brainstem infarction in Rochester, Minnesota. Stroke 15:790-794, 1984 Wladislavosky-Waserman P, Facer GW, Mokri B, Kurland LT: Meniere's disease: a 30-year epidemiologic and clinical study in Rochester, MN, 1951-1980. Laryngoscope 94:1098-1102,1984 Mizukoshi K, Watanabe Y, Shojaku H, Okubo J, Watanabe I: Epidemiological studies on benign paroxysmal positional vertigo in Japan. Acta Otolaryngol Suppl (Stockh) 447:67-72, 1988 Bloom J, Katsarkas A: Paroxysmal positional vertigo in the elderly. J Otolaryngol 18:96-98, 1989
DAVID A. FROEHLING, M.D., Division ofArea Medicine; MARC D. SILVERSTEIN, M.D., * Division ofArea Medicine and Section of Clinical Epidemiology; DAVID N. MOHR, M.D., Division ofArea Medicine; CHARLES W. BEATrY, M.D., Department of Otorhinolaryngology; KENNETH P. OFFORD, M.S., Section ofBiostatistics; DAVID J. BALLARD, M.D., Ph.D., Section of Clinical Epidemiology
A retrospective review of our population-based medical records linkage system for residents of Olmsted County, Minnesota, revealed 53 patients (34 women and 19 men; mean age, 51 years) with newly diagnosed benign positional vertigo in 1984. The ageand sex-adjusted incidence was 64 per 100,000 population per year (95% confidence interval, 46 to 81 per 100,000). The incidence ofbenign positional vertigo increased by 38% with each decade of life (95% confidence interval, 23 to 54%). One patient had an initial stroke during follow-up; thus, the relative risk for new stroke associated with benign positional vertigo was 1.62 (95% confidence interval, 0.04 to 8.98) in comparison with the expected occurrence based on incidence rates for an age- and sex-adjusted control population. The observed survival among the 53 Olmsted County residents with benign positional vertigo diagnosed in 1984 was not significantly different from that of an age- and sex-matched general population. Patients with benign positional vertigo seem to have a good prognosis.
Dizziness was the third most frequent complaint in a recent study of 1,000 medical outpatients. 1 A substantial number of patients with dizziness have true vertigo. 2 Patients with positional vertigo as an isolated symptom are generally *Henry J, Kaiser Family Foundation Faculty Scholar in General Internal Medicine. This study was supported in part by Research Grants AR 30582 and NS 06663 from the National Institutes of Health, Public Health Service. Dr. Ballard is supported in part by a Career Development Award from the Merck, Sharp & Dohme/Society for Epidemiologic Research Clinical Epidemiology Fellowship Program. Address reprint requests to Dr. D. A. Froehling, Division of Area Medicine, Mayo Clinic, Rochester, MN 55905. Mayo Clin Proc 66:596-601, 1991
believed to have a good prognosis and often are classified as having "benign positional vertigo" (BPV). In one dizziness clinic, BPV was found in 10% of the patients with dizziness." The risk of death, stroke, or some other serious disorder ofthe central nervous system after an initial diagnosis of BPV is unknown. Positional vertigo and nystagmus may be the initial manifestations of brain tumors" and cerebellar infarcts.' In one recent study at a neuro-otologic clinic, 12 of 42 patients with strokes of the vertebrobasilar circulation had had prior episodes of isolated vertigo. 5 Studies of outcomes after BPV or vestibular neuronitis have universally been performed at subspecialty clinics.v" where the spectrum of disease and associated
596
Mayo cue Proc, June 1991, Vol 66
prognoses may differ from those in the general population." The population-based study reported herein was undertaken to determine the incidence rate of BPV, to estimate the persistence of this syndrome, and to determine the subsequent risk of death, stroke, and other disorders of the central nervous system in patients who initially had BPV.
METHODS
Definitions.-BPV was defined as transient
episodes of vertigo that occur only with changes in head position and in conjunction with no other neurologic signs or symptoms aside from positional nystagmus. Positional nystagmus, however, was not a requirement for inclusion in the study. Head trauma, if present, was classified as major or minor. Patients who fulfilled previously defined criteria for head trauma.!? including concussion and loss of consciousness, posttraumatic amnesia, neurologic signs of brain injury, and skull fractures, were classified as having major head trauma. All other patients with head trauma were classified as having minor trauma. Study Cohort.-We retrospectively reviewed the population-based medical records linkage system for residents of Olmsted County, Minnesota, 11 to identify cases of BPV newly diagnosed in 1984. To minimize the potential effects of migration to the area because of health status, we included in the study only those patients who had been residents of Olmsted County for at least 1 year before BPV was diagnosed. The records of all 467 residents with a diagnosis of vertigo, dizziness, labyrinthitis, or a similar condition who were examined in 1984 were reviewed by one of us (D.A.FJ; 53 patients fulfilled the criteria for inclusion. The reasons for exclusion were as follows: dizziness or similar diagnosis with insufficient documentation of vertigo to categorize patients in 195; continuous (not positional) vertigo in 75; no vertigo in 65; onset of BPV before 1984 in 49; associated new signs and symptoms in the central nervous system in 10; orthostatic hypotension in 10; Meniere's disease in 4; otosclerosis in 4; streptomy-
BENIGN POSITIONAL VERTIGO
597
cin toxicity in 1; and missing records in 1. The complete medical records ofthe 53 patients who qualified for inclusion in the study were thoroughly reviewed. Statistical Analysis.-An age- and sex-adjusted incidence rate for BPV was calculated by using the estimated 1984 population of Olmsted County'< and the 1980 white population of the United States. Poisson regression was performed to determine whether the incidence of BPV was associated with age or sex.!" A KaplanMeier survival curve was constructed, and observed survival was compared with expected survival based on 1980 Minnesota life tables. 14 For comparison of categorical clinical variables, X2 analysis was used. The expected number of strokes and the relative risk of stroke in this cohort of 53 patients were calculated by using incidence rates for stroke from the Rochester Cerebrovascular Project. 15 P values ofless than 0.05 were considered statistically significant.
RESULTS
Incidence Rates.-The mean age of the 53
patients who fulfilled our criteria for BPV was 51 years (range, 18 to 87 years). The age- and sexadjusted incidence was 64 per 100,000 population per year, with a 95% confidence interval of 46 to 81 per 100,000 per year (Table 1). Poisson regression indicated that age was significantly (P
Symptoms, Signs, and Diagnostic Eualuation.-Vertigo was the chief complaint in
92% ofthe 53 patients. The initial examination was performed in an internal medicine or family medicine outpatient clinic in 41 patients (77%) and in an emergency room in 8 (15%); 4 patients
598
BENIGN POSITIONAL VERTIGO
Mayo Clin Proc, June 1991, Vol 66
Table I.-Incidence Rates for Benign Positional Vertigo Among Residents of Olmsted County, Minnesota, in 1984
(~)
Total
Male
Female
Sex-adjusted incidence/ 100,000 population per year
0-29 30-49 50-59 60-69 70-84 ;::85 Total
12 11 11
7 3 3 3 2 1 19
5 8 8 4 8 1 34
25 42 141 118 193 182 64*
Age
Patients (no.)
7
10 2 53
*Age- and sex-adjusted to the 1980 US white population.
(8%) were self-referred to our Department of Otorhinolaryngology. Most patients were examined and treated in an outpatient setting. A third of the patients had consultations with otorhinolaryngologists, and five (9%) were examined by neurologists, who confirmed the diagnosis of BPV. Two disease characteristics were notable. Rolling over in bed reproduced the symptoms of vertigo in 40% of the 53 patients. Positional nystagmus was observed in 50% of the 26 patients with BPV whose medical records documented that they had been tested for positional nystagmus with a head-hanging maneuver. The examining physicians had ordered various tests to assess the patients with BPV. Computed tomographic scans of the head, obtained in nine patients, showed normal results in four, cerebral atrophy in two, evidence of trauma in two (a subgaleal hematoma and a skull fracture), and cerebral infarct in one. Audiograms showed normal findings in seven patients, a high-frequency sensorineural hearing loss in eight, and a mixed hearing loss in one. Electronystagmograms showed normal results in four patients and a hypoactive labyrinth in one. Prior Morbidity.-Four patients (8%) had had disorders of the central nervous system 2 to 32 years before the onset of symptoms and the diagnosis of BPV in 1984. One patient had had onset of partial complex seizures in 1952, a probable occlusion of the left carotid artery in
1964, and a vertebrobasilar transient ischemic attack in 1976. The second patient had had a vertebrobasilar transient ischemic attack in 1975. The third patient had had a transient ischemic attack that involved the middle cerebral artery in 1981. The fourth patient had had probable bacterial meningitis in 1982, complicated by a stroke of the anterior circulation (right hemiparesis and aphasia). Eight patients reported having prior head trauma (major in four and minor in four). The median interval from the date of head trauma to the onset of symptoms of BPV was 34 days (range, 0 days to 20 years). Duration of Symptoms.-The medical records showed that 49 of the 53 patients (92%) had follow-up for 1 month or more after the diagnosis of BPV. The other four patients were not examined by a physician in Olmsted County beyond 1 month after the diagnosis of BPV. Of the 49 patients who had a medical visit more than 1 month after the initial examination, the presence of symptoms of vertigo was noted in the medical records of 16 (33%). The patient's age, sex, prior head trauma, symptoms with rolling over in bed, and presence of positional nystagmus were not significantly associated with resolution of symptoms. Subsequent Neurologic Disease.-All 53 patients with BPV had the onset of their symptoms in 1984, the year in which BPV was diagnosed. Four patients (8%) subsequently had disorders of the central nervous system. Two patients experienced strokes during follow-up: the patient with previously diagnosed partial complex seizures had a probable occlusion ofthe right internal carotid artery in 1985 and a hemorrhagic stroke that involved the right posterior cerebral artery in 1986; another patient had a fatal subarachnoid hemorrhage in 1986. A third patient had a transient ischemic attack (amaurosis fugax) in 1988. In the fourth patient, a benign essential tremor was diagnosed in 1985. These disorders followed the onset of symptoms of BPV by 12 to 48 months. No subsequent otolaryngologic diagnoses such as Meniere's disease or otosclerosis were made in these 53 patients after the onset of symptoms of BPV.
Mayo Clio Proc, June 1991, Vol 66
Among the 51 patients who had not had strokes before the diagnosis of BPV, only 1 had a stroke during follow-up (the aforementioned patient with the subarachnoid hemorrhage). By using the incidence rates for stroke from the Rochester Cerebrovascular Project,15 the expected number 'of first strokes for these 51 patients was 0.62. This yielded a relative risk of 1.62 for new strokes after a diagnosis of BPV, not significantly different from unity (95% confidence interval, 0.04 to 8.98). Survival.-Our study group had 161 patientyears of follow-up. Three patients died during the follow-up period: one had a fatal myocardial infarction at 2 years, one had a fatal subarachnoid hemorrhage at 2 years, and one had a fatal lower gastrointestinal hemorrhage at 4 years. As shown in the Kaplan-Meier survival curve (Fig. 1), the overall observed survival of this cohort of 53 patients did not differ significantly from the expected survival, based on the 1980 Minnesota white population life tables for ageand sex-matched persons.
DISCUSSION BPV and nystagmus were first described by Barany'" in 1920. The syndrome was further characterized by Dix and Hallpike '? in 1952 and distinguished from Meniere's disease and vestibular neuronitis. The features ofthe syndrome include vertigo that occurs only when certain head positions are assumed and an associated positional nystagmus that usually is rotatory and is characterized by latent onset, fatigue, and habituation.18 Elicitation of positional vertigo and nystagmus with a head-hanging maneuver is not always possible in patients with a history otherwise compatible with a diagnosis of BPV.8,19 In a study of255 cases of BPV, Katsarkas and Kirkham" did not include positional nystagmus as a requirement for diagnosis. For these reasons, we did not require positional nystagmus as a prerequisite for the diagnosis of BPV. The statistical power of our study to detect an increased risk for subsequent stroke was limited by the small number of patients. With the Poisson distribution with a one-sided a of 0.05, this
BENIGN POSITIONAL VERTIGO
599
study had chances ofonly 12%, 27%, and 43% for detecting a doubling, tripling, or quadrupling, respectively, of the relative risk of subsequent stroke. Thus, in reference to the subsequent stroke experience in this cohort, the observation that the risk of stroke was not significantly increased should not be overinterpreted. Referral bias was avoided in this study because of its population-based nature. Nonetheless, several other possible sources of bias existed. Patients who initially had symptoms of BPV and then were found to have a brain tumor, multiple sclerosis, or stroke within a few days or weeks after seeking medical attention might not have been identified as having diagnoses of dizziness or vertigo and thus might not have been included in our retrospective cohort study. We suspect that the number of patients in this category was small. Primary intracranial neoplasms are uncommon-the age- and sex-adjusted incidence rate before death in Rochester, Minnesota, from 1965 to 1977 was 9 per 100,000 population per year.P? Multiple sclerosis is even less common-the stable age- and sex-adjusted incidence rate in Rochester from 1905 to 1964 was 4 per 100,000 population per year."! Strokes are common, with an age- and sex-adjusted incidence rate from 1980 to 1984 of 135 per 100,000 population per year in Rochester. 15 A patient with a stroke, however, will seldom have BPV as the initial manifestation. In a study in Rochester of 980 patients with nonhemorrhagic brain infarctions that occurred from 1960 through 1979, numerous signs and symptoms were noted at the time of initial examination, but vertigo was not one of them. 22 The basis for inclusion or exclusion ofpatients is a more serious source of selection bias. Because ofinsufficient documentation of signs and symptoms in the medical record, 195 patients had to be excluded, some of whom might have had BPV. If BPV were as frequent among the cases with insufficient documentation as among the other cases (19%), the incidence of BPV would have been approximately 107 per 100,000 population per year. Because of the retrospective nature of our study, complete characterization of our patient
600
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Mayo Clin Proc, June 1991, Vol 66
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Years since diagnosis Fig. 1. Kaplan-Meier survival curve for 53 patients with benign positional vertigo and expected survival based on 1980 Minnesota white population life tables for age- and sexmatched persons.
population was difficult. We were dependent on 1982 to 1984;24 however, the Japanese patients the documentation of signs and symptoms by were tabulated only ifexamined by a subspecialbusy clinicians. For example, most or all of our ist or at a referral center. patients may have had symptoms of vertigo Comparison of our patients with those aswhen rolling over in bed, but most clinicians did sessed in subspecialty clinics reveals some siminot seem to have asked this question or at least larities. The mean age of our 53 patients was 51 did not document a "yes" or "no" answer in the years. In the report by Katsarkas and Kirkmedical record. Similarly, it was difficult retro- ham," the mean age oftheir 255 patients was 50 spectively to distinguish new-onset BPV from years; in the 240 patients described by Baloh acute vestibular neuronitis. and colleagues.!" the mean age was 54 years. In Our ability to determine whether a patient's a recent article, Bloom and Katsarkas'" reported symptoms of vertigo had resolved was limited. that the prevalence of BPV in their dizziness Four patients were lost to follow-up. Whether a clinic increased with advancing age. patient's symptoms were recorded as having Of our 53 patients, 8 (15%) reported having resolved depended on whether the patient com- head trauma before the onset of symptoms and plained of vertigo at a subsequent visit and the diagnosis of BPV. Similarly, 17% of the whether the complaint was documented by the patients described by Katsarkas and Kirkham" physician. and 18% of those in Baloh and associates' study'? Two other epidemiologic studies on vertigo had prior head trauma. Our study design, are relevant. Wladislavosky-Waserman and as- however, did not allow us to address the relative sociates-" reported that in Rochester, Minne- risk of BPV associated with prior head trauma. sota, from 1951 to 1980 the incidence of Meniere's disease was 15 per 100,000 population CONCLUSION per year. A study in Japan found an incidence of This study of BPV has several implications for BPV of 11 per 100,000 population per year from clinical practice. Patients with BPV do not seem
Mayo Clin Proc, June 1991, Vol 66
BENIGN POSITIONAL VERTIGO
to have an increased risk for death and probably do not have a clinically important increased risk for stroke. Because in many patients the symptoms resolve, it may be appropriate to recommend a period of observation before further diagnostic evaluation. A larger study with greater statistical power is needed to evaluate the relationship, if any, between BPV and the risk for subsequent stroke.
12.
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