[doi 10.1159%2f000151701] d. savadi-oskouei; a. abedi; h. sadeghi-bazargani -- independent role of...

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Original Paper

Eur Neurol 2008;60:253–257

DOI: 10.1159/000151701

Independent Role of Hypertension inBell’s Palsy: A Case-Control Study

Daryoush Savadi-Oskouei

a Ali Abedi

b Homayoun Sadeghi-Bazargania, c

a Neuroscience Research Center, Faculty of Medicine, Tabriz University, Tabriz, b Physiology Department,

Faculty of Medicine, Ardabil, Iran; c PHS Department, Karolinska Institute, Stockholm, Sweden

Introduction

Ever since Sir Charles Bell in 1821 established that themuscles of facial expression were under the control of aseparate cranial nerve, his name has been associated withall forms of facial palsy.

Bell’s palsy is an acute, unilateral paresis or paralysisof the face in a pattern consistent with peripheral nervedysfunction, without detectable causes [1].

Bell’s palsy accounts for almost three quarters of allacute facial palsies, with the highest incidence in the 15-to 45-year-old age group [2]. It causes considerable loss ofself-esteem among patients. The annual incidence of thisidiopathic disorder is between 11 and 40/100,000, orabout 1 in 60 persons in a lifetime [3]. Men and womenare equally affected, although the incidence is higher inpregnant women (45 cases/100,000) [4].

The cause is unclear. Viral infection, vascular isch-emia, autoimmune inflammatory disorders and heredityhave been proposed as the underlying cause. A viral causehas gained popularity since the isolation of the herpes

simplex virus 1 genome from facial nerve endoneurialf luid in people with Bell’s palsy [1].

Focusing on specific diseases underlying Bell’s palsy,diabetes is the best known. Regarding hypertension’s in-dependent role, methodologically acceptable studies arehardly available. In this case-control study, our aim wasto check for the possible independent role of hyperten-sion in increasing the risk of developing Bell ’s palsy.

Key Words

Facial palsy Bell’s palsy, etiology Hypertension Diabetes

Abstract

Background/Aim: In this case-control study, our aim was to

check for a possible independent role of hypertension in in-

creasing the risk of developing Bell’s palsy.Methods: All pa-

tients diagnosed as having Bell’s palsy referred to a neurol-ogy clinic were enrolled as cases. Controls were selected

among other patients referred to the same clinic. Data were

analyzed using the Stata 8 statistical software package. To

detect the independent effect of exposure variables, a mul-

tiple logistic regression test was used. Results: Bivariate

analysis showed an increased risk of Bell’s palsy for patients

with diabetes or hypertension. Logistic regression results

stratified for patients younger than 40 years of age and oth-

ers showed that diabetes was the independent predictor of

Bell’s palsy in both age groups. Logistic regression results

showed that hypertension could not independently predict

the occurrence of Bell’s palsy among patients younger than40 years but for older ones it could. Conclusion: Hyperten-

sion may increase the risk of Bell’s palsy among those aged

above 40 years. Researchers should be very cautious when

declaring an independent role of hypertension as a cause of

Bell’s palsy. Copyright © 2008 S. Karger AG, Basel

Received: August 29, 2007

Accepted: March 12, 2008

Published online: August 29, 2008

Homayoun Sadeghi-BazarganiKarolinska InstitutePHS Department, Norrbacka, 2nd floor

SE–171 76 Stockholm (Sweden)Tel./Fax +46 8 669 3582, E-Mail [email protected]

© 2008 S. Karger AG, Basel0014–3022/08/0605–0253$24.50/0

Accessible online at:www.karger.com/ene

http://dx.doi.org/10.1159%2F000151701

http://dx.doi.org/10.1159%2F000151701



Savadi-Oskouei/Abedi/Sadeghi-Bazargani

Eur Neurol 2008; 60:253–257254

Materials and Methods

This case-control study was conducted in Ardabil, a moun-tainous province in the northwest of Iran. All the patients diag-nosed as having Bell ’s palsy referred to a neurology clinic from2001 to 2004 were enrolled as cases . A complete medical exam-ination was done and the medical history taken for all patients.Patients with a positive history of stroke were excluded. Finally201 cases who agreed to participate and met the criteria wereincluded in the study. Computerized tomography, magnetic res-

onance imaging and audiometric tests were used to excludeknown causes of facial palsy, and, in cases of ambiguity, ENTconsultations were also requested. The main information gath-ered by a structured questionnaire included e.g. age, sex, clinica lsigns and symptoms or blood pressure. Controls were selectedamong other patients referred to the same clinic. These weremainly patients suffering from headache and idiopathic epilep-sy visiting for the f irst time. The headache patients who had usedantiheadache drugs other than routine tranquilizers were notentered into the study. Those controls with a recent history ofusing corticosteroids or long-term corticosteroid usage were ex-cluded. Based on current medical service delivery and medicalconsult behaviors, headache and Bell’s palsy have similar refer-ral levels. The source populations for controls and cases were

considered reasonably similar. A current stroke or correspond-ing medical history was the exclusion criterion for the controlgroup too.

Blood pressure was measured using a standard method by astandard sphygmomanometer. Hypertensive patients were con-sidered those with a blood pressure equal or more than 140/90mm Hg or a positive history of hypertension currently treated byantihypertensive drugs. The blood pressure of those patients wholacked any of these criteria for hypertension but had a blood pres-sure above 130/90 mm Hg at the first visit was measured again

after 1 month, and the mean blood pressure was calculated. Fast-ing blood sugar and if needed 2-hour postprandial blood sugarwere measured for all case and control group patients. Based onthese data, diabetic patients were distinguished. Also those pa-tients who declared being diabetic and those who received anti-diabetic treatment were considered as being diabetic. Others whohad fasting blood sugar above 126 mg/dl and postprandial sugarabove 200 mg/dl were diagnosed as diabetic, but if they were us-ing corticosteroids, the tests were repeated 1 month after with-drawing them.

Data were entered into the computer and analyzed using theStata 8 statistical software package. To compare the means andproportions, t and 2 tests were used, and odds ratios were cal-culated along with 95% confidence intervals (CI). The statisticalsignificance level was considered at 0.05. To detect the indepen-dent effect of exposure variables, a multiple logistic regressiontest was used. The dependent variable (having a diagnosis ofBell’s palsy) as well as independent variables (being diabetic orhypertensive) were coded as 0 for lacking disease and 1 for hav-ing it. The maximum likelihood approach was used to estimateweights of logistic parameters. Those variables that perfectly pre-dicted the outcome were omitted from the model as well as vari-ables with no statistical or trivial statistical but no clinical sig-nificance.

Results

Basic Information about Control and Case GroupsThe mean age 8 SD in the control group was 40 8

17.8 years. That of patients in the case group was 42.98 21.1 years (fig. 1). Further details of demographic charac-

0

0

0.01

0.02

0.03

D e n s i t y

50

Control Cases

100

Age (years)

0 50 100

C

o l o r v e r s i o n a v a i l a b l e o n l i n e

Fig. 1. Age distribution in the control andcase groups.



Hypertension in Bell’s Palsy Eur Neurol 2008; 60:253–257 255

teristics are given in table 1. 84.6% of controls were head-ache patients. The medical history and current medicalinvestigations of the controls did not confirm any comor-bidity of importance related to Bell’s palsy other than hy-pertension or diabetes. The distribution of Bell’s palsyoccurring in different months of the year is given in fig-ure 2. There was a history of facial palsy in 21.9% of thepatients. None of the cases or controls used drugs whichcould be related to Bell ’s palsy.

Determinants of Bell’s Palsy

Bivariate analysis showed an increased risk of devel-oping Bell’s palsy for patients having diabetes or hyper-tension. 37.3% of Bell’s palsy patients had hypertensioncompared to 14.9% of controls, and 29% of Bell’s palsypatients had diabetes compared to 2% of the controls. Lo-gistic regression results stratified for patients youngerthan 40 years of age and others showed that diabetes wasthe independent predictor of Bell’s palsy in both agegroups. At ages below 40 years, due to perfect predictiondiabetes was omitted from the model, and for the secondage group the odds ratio of diabetics developing Bell’spalsy was calculated to be 15.9 (95% CI: 5.4–46.8). As for

hypertensive patients, logistic regression results showedthat hypertension could not independently predict theoccurrence of Bell’s palsy in patients younger than 40years but for older ones the odds ratio of hypertensivepatients developing Bell’s palsy was calculated to be 4.5(95% CI: 2.5–8.1).

Discussion

In our study, 29% of Bell ’s palsy patients were diabeticwhile in another case-control study it was reported to be24.8% [5]. The frequency of diabetes mellitus reported in

subjects affected by Bell’s palsy varies widely. Many stud-ies have discussed diabetes as a risk factor or predispos-ing factor of Bell’s palsy or stated an association betweendiabetes and Bell’s palsy. However, because of method-ological limitations, conclusions drawn in some of thesestudies do not seem to be quite rational. Most of thesestudies are simple descriptive or even case studies [5–18].Even considering case-control studies, an independent

Table 1. Demographic characteristics of study participants

Patients Mean age8 SDyears

Sex Job

frequency percent frequency percent

Cases Diabetic 51.6819.9 male: 31 52.5 farmers: 17 28.8female: 28 47.5 others: 42 71.18

Nondiabetic 39.31820.6 male: 79 55.6 farmers: 49 34.5female: 63 44.4 others: 93 65.49

Controls Diabetic 63.7816.6 male: 1 25 farmers: 1 25female: 3 75 others: 3 75

Nondiabetic 39.6817.5 male: 86 43.6 farmers: 57 28.93female: 111 56.3 others: 140 71.06

Total 41.5819.6 male: 197 49 farmers: 124 30.84female: 205 51 others: 278 69.15

0

Feb M ar

O c c u r r e n c e ( n )

Apr May Jun Jul Aug Sep Oct NovJan

5

10

15

20

25

30

35

Dec

Fig. 2. Occurrences of Bell’s palsy over the year.

C o l o r v e r s i o n a v a i l a b l e o n l i n e



Savadi-Oskouei/Abedi/Sadeghi-Bazargani

Eur Neurol 2008; 60:253–257256

role of suspected risk factors was not evaluated properly,and no published cohort study was found in the Medlinedatabase [5, 14]. Our study showed that diabetes has anindependent role in increasing the risk of Bell ’s palsy forboth age groups.

Contrary to the available literature and our findings,

some studies have not found any difference in the preva-lence of diabetes between Bell’s palsy patients and thegeneral population [19]. It is a controversy also if facialnerve degeneration is associated with diabetes and if dia-betic patients are more vulnerable to treatment failure[19–24].

Considering the fact that taste involvement is uncom-mon in Bell’s palsy among diabetic patients in older stud-ies, a vascular rather than metabolic mechanism has beensuggested for facial nerve palsy in diabetics [5, 17, 25].

Although it is accepted that diabetes increases the riskof Bell ’s palsy, there is some doubt whether recombinant

human insulin-like growth factor 1 used along with in-sulin may give rise to Bell’s palsy or not [26, 27].

Facial paralysis in a hypertensive patient was first de-scribed more than 100 years ago. We did not find any in-dependent role for hypertension to cause Bell’s palsyamong patients younger than 40 years, but hypertensionhad an association – although not a very strong one –with Bell’s palsy among older patients. Contrary to dia-betes there is less evidence in the literature for hyperten-sion to cause or predispose to Bell’s palsy in the generalpopulation [5–7, 12–15, 28–30]. There has been more at-tention on hypertension in Bell’s palsy among children

and pregnant women [31–37]. The incidence of Bell ’s pal-sy is significantly higher during the last trimester of preg-nancy and the puerperium. Suggested explanations forthis association include fluid retention, hypertension,compromise of the vasa nervorum, infection (particular-ly with herpes simplex virus) and an autoimmune process[33]. Aynaci and Sen [35] stated that as hypertension isone of the rare causes of peripheral facial paralysis in chil-dren, the nonawareness of this association at presentationmay cause serious medical errors and result in delays inthe diagnosis of hypertension which may worsen withcorticosteroid therapy given for Bell’s palsy.

Our findings were consistent with those of a study inNigeria which stated that hypertension was associatedwith Bell’s palsy in patients above 50 years of age [38].However, that was only a cross-sectional study, and noother case-control or prospective study was found tostrongly defend the role of hypertension in causing Bell ’spalsy. This shortage of evidence may be caused by over-looking an interaction between age and hypertension in

studies conducted without age limitations or by not usingmultivariate analysis; as well, in some studies the effectsize and strength of observed association were not con-sidered as focus of analysis.

A variety of physiological theories to explain the rela-tionship between facial paralysis and hypertension have

been published. Although the true etiology remains un-known, there seems to be an adequate explanation to sup-port a probable association between hypertension andBell’s palsy as well as its dependence on age. Small hem-orrhages into the facial canal and neural partial necrosismay be a possible explanation, and there is evidence forthe first mechanism in 2 autopsies reported in the litera-ture. To discuss the role of age in the association of hy-pertension and Bell’s palsy, there may be the followingconsiderations: (1) hypertension has a cumulative andlong-term effect predisposing to Bell’s palsy; (2) increased vascular pathology at higher ages explains the associa-

tion present at higher ages; (3) a severe uncontrolled hy-pertension which is common at higher ages may lead toBell’s palsy; (4) a pathological and even idiopathic hyper-tension (which is more common in hypertensive chil-dren) can lead to Bell’s palsy, and (5) the higher physio-logical susceptibility in children and pregnant womenmay be the cause of an association between hypertensionand Bell ’s palsy.

Any of the explanations mentioned above or other un-known mechanisms may explain the effect of age on theassociation of hypertension and Bell’s palsy. Althoughbased on our design, methods and findings we may not

accept or reject any and further research is needed, re-garding the f irst 3 mechanisms we tend to focus more onthe second. Most of the child cases go to the pediatricclinics instead of a neurology clinic in our area. So ouropinion on the fourth and fifth mechanisms is mainlybased on reports in the literature.

Conclusion

Hypertension may increase the risk of Bell’s palsyamong those aged above 40 years.

More specifically designed case-control or prospectivestudies are needed to clearly investigate the associationbetween hypertension and Bell’s palsy. Researchersshould be very cautious when declaring an independentrole of hypertension in the etiology of Bell’s palsy.

As for the limitations and strengths of the study, likein other case-control studies, unknown confounding fac-tors may possibly modify effects. Unlike some other case-



Hypertension in Bell’s Palsy Eur Neurol 2008; 60:253–257 257

control studies, based on the definition and natural prog-ress of Bell’s palsy, its association with hypertension anddiabetes is not much affected by reverse causality andtemporality problems. A future cohort study with cardi-ology researchers as coinvestigators or at least a larger-scale age-stratified case-control study is suggested to fur-

ther clarify the observed associations.

Acknowledgements

We are thankful to Ardabil University of Medical Scienceswhich supported this research project as well as Alavi UniversityHospital physicians and nurses who helped in conducting thestudy.

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[doi 10.1159%2f000151701] d. savadi-oskouei; a. abedi; h. sadeghi-bazargani -- independent role of...

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