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Hemifacial spasm (HFS) is a movement disorder of facial muscles innervated by the facial nerve. This condition often demands regular utilization of healthcare resources. However, knowledge of the incidence and prevalence of this condition is based on scarce studies. This research aimed to identify the incidence and prevalence of HFS in Finland's largest hospital district.
Methods
This retrospective study was conducted in the largest hospital district in Finland (Helsinki and Uusimaa). The study included consecutive HFS patients who visited the departments of Neurology and Neurosurgery in the Hospital District of Helsinki and Uusimaa between 2014 and 2019. The demographics included sex, side of the spasm, treatment allocations, duration of symptoms before diagnosis, and age at the time of diagnosis.
Results
279 patients were identified from the medical records. 62% of patients were women and had left-sided spasms. The crude mean incidence among women was almost double that of men (1.86 vs. 0.94). The highest crude mean annual incidence among men was in the age group 60–79 years, while among women, it peaked in the age group 80 years and over. The mean annual age-standardized incidence of HFS was 1.53, 1.94 in women, and 1.05 in men. The mean age-standardized yearly prevalence was 10.62, 11.62 among women, and 9.31 among men. The annual age-standardized prevalence of HFS increased steadily from 2014 to 2019.
Conclusions
The incidence and prevalence of women outnumbered men. HFS is typically left-sided. The HFS incidence peaked after 80 years in women and men aged 60–79 years.
Hemifacial spasm (HFS) is a movement disorder that causes progressive paroxysmal synchronous involuntary tonic and clonic contractions of facial muscles innervated by the ipsilateral cranial nerve VII, namely the facial nerve [
]. The contractions of facial muscles lower the quality of life by causing a deleterious impact on activities of daily living (ADL) and stigma concerning the condition. [
] Treating this condition with oral medication, botulinum toxin, and neurosurgical interventions requires regular utilization of healthcare resources and causes high medical costs. Hence, general practitioners and non-specialized neurologists need to recognize a typical HFS patient and know the available treatment options for patients to refer them to the right specialist.
The number of epidemiological studies on HFS is few. An older retrospective population-based study tracked the incidence and prevalence of HFS in Olmsted County, Minnesota, USA, between 1960 and 1984. [
] In 1984, Olmsted County had a population of 96,776. A more recent study was a service-based prevalence study in Oslo, Norway, in 2001, with a population base of 780,000. [
] It is essential to investigate the current prevalence and incidence of the condition as the impact of HFS symptomatology on the quality of life and healthcare utilization is significant.
The Hospital District of Helsinki and Uusimaa (HUS) has the most extensive population base of all the University Hospitals in Finland, with a population of 1.6 million residents. This research aimed to identify the current state and trends in the incidence and prevalence of HFS in a large, consecutive, and hospital-based cohort study over six years.
2. Materials and methods
2.1 Literature review
PubMed was searched on February 7th, 2022, with keywords and Medical Subject Headings (MeSH) related to the epidemiology of HFS. The search yielded 183 articles. The articles and the references connected to them were reviewed. Only two articles concentrated on epidemiology, one retrospective cross-sectional prevalence study, and one retrospective incidence and prevalence study.
2.2 Patient population
All consecutive patients with ICD-10 diagnoses of G51.31, G51.32, and G51.33 were identified from the electronic medical records in this retrospective study conducted in the Departments of Neurology and Neurosurgery of HUS. The cohort included HFS patients who had visits between 2014 and 2019 at HUS. All HFS diagnoses were confirmed by a neurologist, ear-nose-and-throat doctor, or neurosurgeon with a particular interest in movement disorders.
The population of HUS used in the data analysis to calculate the crude values was from Statistics Finland. The database was “11re -- Population according to age (1-year) and sex by area, 1972-2021”. This database recorded the population and age at the end of the statistical reference period, the 31st of December each year[dataset]. [
] The population used included the years 2014–2019, both sexes, all age groups, and municipalities covered by HUS services.
The reference population used in the data analysis was from European Statistical Office (Eurostat). The database was “Population on 1 January by age and sex”[dataset]. [
] In this database, the population was recorded on the 1st of January. The filters used to define the dataset included all age classes, “European union - 28 countries (2013-2020)” as a geopolitical entity, both sexes, and 2019 as the time.
2.3 Data collection
Approval for this study was obtained from the HUS Ethics Committee in November 2019. Informed consent from the patients was not required due to the retrospective nature of this study. Demographic and clinical data were collected regarding sex, side of the spasm, treatment allocations, duration of symptoms before diagnosis, and age at the time of diagnosis.
2.4 Statistical analysis
The statistical analysis was performed using IBM SPSS Statistics v27.0 and Microsoft Excel v2018 software. Counts (N) and percentages (%) were used to describe the nominal variables. The mean with standard deviation (SD) was calculated to demonstrate the distribution and range of continuous variables.
All incidence values presented are cumulative in this study. The crude annual incidence was calculated by dividing the sum of new HFS cases in a calendar year by the population of the HUS area. Similarly, the yearly crude prevalence was established by dividing the sum of individual HFS patients who visited neurology or neurosurgery clinics in a calendar year by the population of the HUS area. In prevalence analysis, the elder duplicate was removed if the patient had visited clinics in two different age distribution groups during the same year. Mean annual crude incidence and prevalence were calculated by dividing the sum of yearly cases by the study years. The age-standardized values were calculated using direct age-standardization to the standard population of Europe in 2019. The database of Eurostat had an “open-ended” age class of which data points were evenly distributed to other age classes to get the standard population of Europe used in the direct age standardizing. All incidence and prevalence rates were expressed as per 100,000.
3. Results
279 patients were included in the study. The clinical features of the cohort are shown in Table 1. The majority were women, the mean age at diagnosis was 56.47 years (SD 14.37), the side of the spasm was left in 62% of the patients, and the condition was rarely bilateral. The most common treatment was botulinum toxin injections in almost 90% of the cases. In addition, 28 (10.04%) patients (14 women, 14 men) had undergone neurosurgical treatment. The mean age of the patients with neurosurgical treatment was 50.15 years (SD 13.65) at the time of diagnosis. All surgical patients had a left-sided spasm. The mean delay from diagnosis to surgery was 5.59 years (SD 6.21).
Table 1Clinical features of patients with hemifacial spasm.
In the cohort, 139 new HFS cases were diagnosed between 2014 and 2019 in the Departments of Neurology and Neurosurgery of HUS. The mean annual age-standardized incidence was 1.53 (1.94 in women and 1.05 in men). The mean age-standardized yearly prevalence was 10.62, 11.61 among women, and 9.31 among men. The age- and sex-specific crude mean annual incidence and prevalence rates of HFS per 100,000 residents between 2014 and 2019 that increased with age are presented in Fig. 1, Fig. 2.The highest crude mean annual incidence among men was in the age group 60–79 years, while among women, it peaked in the age group 80 years and over. The mean crude incidence among women was almost double that of men (1.86 vs. 0.94) Fig. 1. The crude mean annual prevalence was greatest for women and men aged 80 years and over Fig. 2. The age-standardized yearly incidence of HFS decreased from 1.87 to 0.64 between 2014 and 2016 and increased to 2.02 between 2016 and 2019 Fig. 3. The annual age-standardized prevalence rates of HFS increased steadily from 2014 to 2019 Fig. 4.
Fig. 1Age- and sex-specific mean crude incidence of hemifacial spasm 2014–2019.
The current study reports the incidence and prevalence of a hospital-based, consecutive retrospective cohort of HFS patients. This is the third study on the epidemiology of HFS, with the previous reporting from 1960 to the 1980s and 2001.
The mean annual age-standardized incidence of HFS was 1.53 per 100,000, whereas the mean age-standardized yearly incidence in women was 1.94 and 1.05 in men. Compared to Auger et al. (1990) [
], the incidence in the present HFS cohort is higher and over double among women and over 40% higher in men than the incidence of 0.81 in women and 0.74 in men reported by Auger et al. In the current cohort the almost double total crude mean incidence in women over men (1.86 vs. 0.94) is not entirely explained by the demographics of the aging Finnish population, since the ratio exceeds the excess of women even in older age groups. Moreover, the age-standardized yearly incidence of HFS decreased in both sexes between 2014 and 2016. Subsequently, it increased to 2.61 and 1.16 per 100,000 in women and men, and women outnumbered men every year. These higher incidences in the present cohort may suggest differences in diagnostic proficiency and possibly that more Finnish women seek treatment for HFS in the current cohort due to better awareness of treatment possibilities. Indeed, botulinum toxin injections have been applied only since the 1980s in Finland for various conditions, including the treatment of HFS. It can be assumed that over the last two decades, botulinum toxin has been a common practice among specialized neurologists and ear-and-nose specialists to treat HFS, as it was used in almost 90% of patients as treatment in this cohort.
Among facial movement disorders or neurovascular compression syndromes, trigeminal neuralgia is the most common and has been reported with an overall incidence of 21.7 to 26.8 per 100,000 in Europe. [
Epidemiology and clinical features of idiopathic trigeminal neuralgia and glossopharyngeal neuralgia: similarities and differences, Rochester, Minnesota, 1945-1984.
] For comparison, Bell's palsy has an incidence ranging from 23.0 to 107 cases per 100,000 based on the studies conducted in Korea, Italy, and Egypt. [
] 1.53 incidence of HFS in the present cohort represents the rarer end of the spectrum compared to other neurovascular compression syndromes and facial movement disorders.
The mean annual age-standardized prevalence was 10.62 in the present cohort. For women, it was 11.61, and for men 9.31. Compared to the mean prevalences of 11 and 9.8 reported earlier, the prevalence in the current cohort is in a similar range. [
] However, the hospital-based design might underestimate the prevalence due to patients' unwillingness to receive invasive treatment provided in hospitals, let alone neurosurgical treatment. Some patients with mild symptoms may not be referred to specialized health care. Additional skewing may result from patients who choose oral medications as monotherapy; thus, the follow-up continues in primary health care centers. Nevertheless, the age-standardized yearly prevalence of HFS has steadily increased between 2014 and 2019, primarily in women from 2017 to 2019. The largest age group of HFS was patients 80 years and older. In women, HFS was also diagnosed commonly after 80 years of age. Thirty years ago, Auger et al. reported no patients older than 80 in their study. [
The present cohort's mean age at the diagnosis was 56 years (SD 14.37). Other neurovascular compression syndromes are commonly diagnosed around a similar age or younger. For example, the mean ages of trigeminal neuralgia and glossopharyngeal neuralgia at diagnosis are reported to be 51.5 years (SD 17.6) and 54.0 years (SD 5.7 SD). [
] Similarly, compared to common differential diagnoses of facial movement disorders, HFS patients are of similar or older age since the mean age of blepharospasm at the time of diagnosis is reported to be 46.38 years (SD 13.18), oromandibular dystonia 54.1 years (SD 18.4), and spasmodic dysphonia 35 years. [
] 62% of patients were female in the current cohort, similar to what Nilsen et al. reported.4 Likewise, trigeminal neuralgia is more common among women, 71.2% female. In contrast, glossopharyngeal neuralgia patients have equal numbers of men and women. [
] More recently, the left-sided condition has been more common in extensive studies in Asia and Europe. 51.2% of HFS patients had a left-sided spasm in Chinese and 53.3% in Italian cohorts. [
HUS has favorable features for incidence and prevalence studies of HFS despite being a hospital-based joint service district. Firstly, Finland provides comprehensive public general and specialized health care services for Finnish citizens paid by taxes, not private insurance, including HFS treatment. Thus, most HFS patients are treated in public hospitals, not the private sector. Secondly, for HFS patients, public health care services include regular visits to neurologists with a particular interest in movement disorders and botulinum toxin injections. Surgical treatment with microvascular decompression and electrocoagulation are also included in the analysis. In Finland (population of 5.5 million residents), the neurosurgery departments in five university hospitals are the only surgical treatment providers for HFS.
Only 10.04% of patients had undergone neurosurgical treatment, and the mean delay from diagnosis to surgery was over five years. Interestingly, half of the patients referred for neurosurgery were men, yet over 62% of HFS patients are women. The neurosurgical treatment was performed at an average age of around 56 years which is also the mean age at the diagnosis of HFS. This implies neurosurgical treatment for younger patients, despite the referral delay. In Finland, as elsewhere in Europe, conservative invasive treatment with botulinum toxin injections is the first-line treatment option due to its well-recognized effectiveness. [
] One cannot oversee that surgical treatment options might be more unfamiliar among neurologists. Hence, conservative treatment options are often tested years before the patient is referred for surgical evaluation. Patients should be informed about the possibilities of microvascular decompression and facial nerve electrocoagulation soon after diagnosis and referred to surgical assessment if the treatment effect is unsatisfactory with botulinum toxin and per oral medications. [
Efficacy of CT-guided percutaneous stylomastoid foramen puncture through the mandibular angle approach and radiofrequency ablation of facial nerve for the treatment of hemifacial spasm.
] As a future approach, we intend to study further the effect of botulinum toxin and neurosurgical treatment on the quality of life of HFS patients to optimize the patient-related outcome.
To conclude, only one American and one Norwegian study have been published regarding the epidemiology of HFS before the current research. After that, the incidence of HFS has grown, particularly among women, while prevalence has remained at a similar level. HFS is typically diagnosed in a woman in her 80s, and the condition is most probably left-sided.
Funding
The corresponding author (Paula Nurminen) received financial support for conducting and preparing this article from The Department of Research and Development of Helsinki University Neurocenter. The Department of Research and Development of Helsinki University Neurocenter did not influence the study design, writing of the report, or decision to submit the article for publication.
Data availability
The corresponding author's data supporting this study's findings are available upon reasonable request.
Declaration of Competing Interest
Paula Nurminen (corresponding author) has no other conflict of interest. Johan Marjamaa has no conflict of interest relevant to the research subject. Mika Niemelä has no conflict of interest relevant to the research subject. Tiina Sairanen has no conflict of interest relevant to the research subject.
Acknowledgements
We want to thank Ms. Kirsi Weckström for her advice and help with many practical problems behind the scenes and Mr. Harri Palomäki for his help in statistical analysis.
Epidemiology and clinical features of idiopathic trigeminal neuralgia and glossopharyngeal neuralgia: similarities and differences, Rochester, Minnesota, 1945-1984.
Efficacy of CT-guided percutaneous stylomastoid foramen puncture through the mandibular angle approach and radiofrequency ablation of facial nerve for the treatment of hemifacial spasm.
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