The Role of Serum Vitamin and Mineral Levels in Benign Essential Blepharospasm: A Comparative Study

Abstract

Objectives:

This study aims to compare serum levels of folic acid, Vitamin B12, 25-hydroxy (OH) Vitamin D, calcium (Ca), zinc (Zn), phosphorus, and magnesium (Mg) between patients with benign essential blepharospasm (BEB) and healthy controls and to examine their associations with disease severity and frequency.

Methods:

A retrospective study was conducted on 20 patients with BEB (13 females, 7 males) and 25 healthy controls (15 females, 10 males) from our clinic. Serum levels of folic acid, Vitamin B12, 25-OH Vitamin D, Ca, phosphorus, Mg, and Zn, as well as ophthalmologic examination results, were analyzed. BEB severity and frequency were assessed using the Jankovic Rating Scale (0–4).

Results:

Serum levels of Vitamin B12, folic acid, Zn, Ca, phosphorus, and Mg were within normal limits for both groups. However, serum Vitamin D levels were below normal in both groups. No significant differences were found between the BEB and control groups regarding serum Vitamin B12, 25-OH Vitamin D, Ca, phosphorus, Mg, and Zn levels (p>0.05). Notably, serum folic acid levels were significantly lower in the BEB group compared to controls (6.19±2.75 vs. 8.95±4.10, p=0.011). In addition, a significant negative correlation was observed between serum folic acid levels and Jankovic severity (r=−0.378, p=0.011) and frequency scores (r=−0.392, p=0.008).

Conclusion:

These findings suggest that folic acid may play a role in BEB pathogenesis. Further studies are needed to explore the underlying mechanisms and potential benefits of micronutrient supplementation in BEB management.

Introduction

Benign essential blepharospasm (BEB) is a rare neurological condition characterized by involuntary contractions of the orbicularis oculi muscles surrounding the eyes. This results in excessive blinking, eye closure, and visual impairment (1). The spasms can be distressing, making it hard or even unfeasible for those affected to participate in daily activities, such as reading, driving, or sustaining eye contact during conversations (2). Despite being classified as “benign,” BEB can lead to significant morbidity by affecting vision, social interactions, and emotional health.

The low prevalence of essential blepharospasm, with an estimated incidence of 0.10% among individuals, (3) has led to a limited understanding of its underlying mechanisms. The specific etiology of BEB remains unidentified, but increasing evidence suggests the involvement of various factors, including genetic predisposition, environmental triggers, and neurochemical imbalance (4). Conventionally, neurology has defined this condition as a result of neurotransmitter imbalances and basal ganglia dysfunction (5). Recent studies have started to examine the potential impact of micronutrient status, specifically essential vitamins and minerals, on the development of BEB (6-8).

Micronutrients play a critical role in various physiological processes, including cognitive functions, serving as cofactors, and modulating oxidative stress (9). The majority of vitamins and essential minerals are not produced by the body and must be acquired through diet. A deficiency in specific micronutrients leads to several alterations in nervous system development.

Vitamin B12 and folic acid are essential for numerous physiological functions, including neuron function, neurotransmitter regulation, and DNA synthesis. These processes are crucial to the development of movement disorders, such as BEB, and various neurological and neuromuscular problems have been linked to deficits in these vitamins (10).

Calcium (Ca) is an essential component in signal transmission across the neuronal membrane and nerve terminal, and it also participates in several cellular processes, including apoptosis. The discharge of Ca from the sarcoplasmic reticulum is vital for muscle contraction (11). Vitamin D regulates the absorption of Ca and phosphate (P). Hypophosphatemia and Vitamin D insufficiency are both linked to muscle weakness (12). Magnesium (Mg) is vital in numerous metabolic processes due to its involvement in various enzymes. On the contrary, Mg serves as a physiologic Ca channel blocker (13). A notable correlation between serum Mg levels and muscle strength has been documented (14).

Synaptic zinc (Zn) is essential for neuronal transmission, significantly contributing to neurogenesis, cognition, memory, and learning. Recent studies indicate that the disruption of Zn homeostasis is related to several central nervous system diseases (15).

This study aims to compare the serum levels of Vitamin B12, folic acid, 25-OH Vitamin D, Ca, Mg, P, and Zn in patients with BEB to those of healthy individuals and to determine the relationship between these micronutrient levels and the intensity and frequency of BEB symptoms, as evaluated using validated clinical rating scales.

Methods

This retrospective case–control study included 20 BEB patients (13 females and 7 males) who were followed up and treated periodically with botulinum toxin injections for BEB in the department of oculoplastic surgery and 25 age- and gender-matched healthy individuals (15 females and 10 males). The study was conducted in the ophthalmology department of the Haseki Training and Research Hospital, from October 2023, to December 2023. Demographic data, clinical characteristics, and medical history were obtained from the medical records of all participants. We conducted complete neurological exams on all the patients to rule out any underlying neurological conditions. Both patients and controls using supplements, including Vitamin B12, folic acid, Ca, phosphorus (P), Mg, Vitamin D, and Zn, and patients with a history of thyroid and parathyroid surgery were not involved in the study. The blood tests were conducted within 3 months before the ophthalmological examination.

In our laboratory, the normal ranges of serum concentration were between 8.6 and 10.0 mg/dL for Ca, 1.6 and 2.6 mg/dL for Mg, 2.5 and 4.5 mg/dL for P, 15 and 55.5 ng/mL for 25-OH Vitamin D, 197 and 771 ng/L for Vitamin B12, 3.89 and 26.8 g/L for folic acid, and 70 and 114 g/dL for Zn.

The severity and frequency of BEB were evaluated using the Jankovic Rating Scale (JRS), which assigns scores ranging from 0 to 4 (16).

The study was carried out in compliance with the principles stated in the Declaration of Helsinki and obtained clearance from the local ethics committee (173–2023). Informed consent was obtained from all participants before data collection.

Statistical analysis was conducted utilizing the Statistical Package for the Social Sciences version 25. Descriptive statistics involving means and standard deviations were determined for continuous variables. Group comparisons between essential blepharospasm patients and controls were performed using independent t-tests for continuous variables and Chi-square tests for categorical variables. A P-value below 0.05 was deemed statistically significant.

Results

The demographic properties of 20 BEB patients and 25 age- and gender-matched control cases are given in Table 1. The range of age was 44 to 87 for the BEB group and 45 to 84 for the control group. Table 2 summarizes the results of serum Vitamin B12, folic acid, Ca, P, Mg, 25-OH Vitamin D, and Zn concentrations. Serum Vitamin B12, folic acid, Ca, P, Mg, and Zn levels were within normal limits, while 25-OH Vitamin D levels were below normal limits in both groups. There was no significant difference between the BEB and control groups regarding the seeked parameters except for the mean serum folic acid level, which is significantly lower in the BEB group (p=0.011) (Fig. 1).

Table 1.

Demographic properties of study participants

	BEB (n=20)	Control (n=25)	p
Sex (F/M)	13/7	15/10	0.487
Age	59.75±9.80	62.04±9.19	0.204

BEB: Benign essential blepharospasm; F: Female; M: Male.

Table 2.

Laboratory data of study participants

	BEB (n=20)	Control (n=25)	p
Vitamin B12	363.10±188.56	336.16±170.95	0.698
25-hydroxy (OH)-Vitamin D	13.72±7.52	11.68±5.51	0.560
Folic acid	6.19±2.75	8.95±4.10	0.011
Zinc	83.15±17.41	81.66±16.01	0.854
Calcium	9.54±0.37	9.36±0.45	0.181
Phosphorus	3.42±0.72	3.50±0.49	0.499
Magnesium	1.94±0.19	2.01±0.16	0.232

BEB: Benign essential blepharospasm.

Figure 1.

The mean folic acid levels of the benign essential blepharospasm and control groups.

Clinical assessments were conducted to evaluate the severity of blepharospasm symptoms in the patient group in conjunction with serum vitamin measurements. The mean JRS severity and frequency scores were 2.6±0.5 and 2.1±0.4, respectively, for the BEB patients. Serum folic acid levels were negatively correlated with both Jankovic severity and frequency scores (Table 3).

Table 3.

The correlation of serum Vitamin B12, 25-OH Vitamin D, and folic acid levels with Jankovic severity and frequency scores

	JSS		JFS
	r	p	r	p
Vitamin B12	0.050	0.745	0.079	0.606
25-hydroxy (OH)-Vitamin D	0.164	0.282	0.199	0.191
Folic acid	-0.378	0.011	-0.392	0.008

JSS: Jankovic Severity Score; JFS: Jankovic Frequency Score.

Discussion

The findings of this study revealed that the levels of evaluated micronutrients were within normal limits for both the BEB and control groups except 25-OH Vitamin D. While serum folic acid levels were within laboratory normal limits in both groups, BEB patients had significantly lower folic acid levels compared to controls, and there was a negative correlation between the Jankovic severity and frequency score and folic acid levels. This observation suggests there may be a link between folic acid levels and BEB.

BEB is characterized by involuntary contractions of the orbicularis oculi muscles and frequently other protractor muscles. In severe cases, it leads to functional blindness (5). The annual incidence is estimated at approximately 0.1/1,000 individuals, and although it is infrequent, the disease has a significant impact on quality of life (3). The precise etiology of BEB remains unclear. The primary form of BEB typically has a gradual onset and is more common in middle-aged females. In contrast, secondary BEB is linked to lesions in the basal ganglia, brainstem, and thalamus. One of the characteristic features of BEB is focal dystonia, which is characterized by disproportionate muscle contractions that may be isolated or generalized. This neurological movement disorder is associated with repetitive movements, forceful contractions, and, in some cases, painful abnormal postures. Dysfunctions in basal ganglia and cerebellar circuits, as well as disturbances in mitochondrial function, dopamine signaling, and Ca homeostasis, play a role in the pathogenesis of dystonia, including BEB (17,18).

Ca, Mg, P, and Vitamin D are essential for neuromuscular function, significantly involving muscle contraction and neurotransmission. Ca modulates the interaction between excitation and contraction, neurotransmitter release, and muscle contraction by sarcoplasmic reticulum signaling. In contrast, Mg modulates Ca channels, stabilizes neuronal excitability, and facilitates ATP metabolism, which energizes muscular activity. P, an essential element of ATP and creatine P, supports energy-dependent muscular functions, and Vitamin D regulates Ca-P homeostasis by improving intestinal absorption and supporting bone and muscle health (19). Previous studies have highlighted the potential significance of these micronutrients in movement disorders. For instance, Serefoglu Cabuk et al. (7) indicated markedly reduced serum Ca levels in BEB patients compared to controls, suggesting a possible correlation between Ca deficit and dystonic activity. Nevertheless, they did not observe significant differences in Mg, P, or 25-OH Vitamin D levels among the groups. Eroğul et al., (8) observed lower Ca and 25-OH Vitamin D levels in BEB patients in comparison with controls, despite noting the need for further prospective studies to understand these correlations better. Pratty et al. (20) examined the correlation between acute dystonic reactions and serum Ca levels in patients with acute psychosis. They concluded that no association was seen between acute dystonia and serum Ca. The widespread Vitamin D deficiency observed in both groups may be attributed to factors, such as limited sun exposure, dietary habits, or lifestyle common in our population.

Ca channel dysfunctions and intracellular Ca signaling abnormalities have been linked to dystonia, reflecting disturbances in basal ganglia and cerebellar circuits (17). Mg’s function as a Ca antagonist may additionally affect dystonic activity by modulating synaptic transmission and muscle excitability (14). While the present study did not reveal significant variations in serum Ca, Mg, P, and 25-OH Vitamin D levels, localized deficiencies or imbalances in neuronal tissue may still contribute to dystonic mechanisms. This underscores the necessity for advanced imaging and cerebrospinal fluid studies to investigate micronutrient balance in BEB patients. Further research addressing intracellular Ca and Mg modulation, along with the role of Vitamin D in neuromuscular stability, can clarify their contributions to BEB.

Zn is an essential trace element that plays a pivotal role in many neurological functions, including neurotransmitter synthesis, modulation of synaptic activity, and protection of neuronal structure (21). Zn is known for its interaction with glutamatergic and GABAergic systems, which is crucial for motor control. Changes in Zn levels can disturb the excitatory-inhibitory balance in neural circuits, thereby playing a role in the pathophysiology of dystonic movements (15). In addition, Zn’s antioxidant properties reduce oxidative stress, a factor that leads to neuronal dysfunction. In the literature, some studies revealed that Zn deficiency and also accumulation may lead to neurotoxicity and neuronal cell death, both resulting in neurological disorders (21,22). However, to the best of our knowledge, this is the first study that evaluated the serum Zn levels in BEB patients.

Vitamin B12 deficiency has been associated with multiple neurological diseases, such as peripheral neuropathy, myelopathy, and dystonia. The role of Vitamin B12 in dystonic mechanisms is mainly related to its function in lowering homocysteine levels, a neurotoxic molecule that may affect dopamine metabolism, provoke oxidative stress and lead to mitochondrial malfunction (6). Obeid et al. (6) emphasized the contribution of hyperhomocysteinemia, resulting from B12 deficiency, increased oxidative damage, and neuroinflammation, both of which may exacerbate dystonic symptoms (6). Our study found no significant differences in serum B12 levels between BEB patients and controls, indicating that overt systemic B12 insufficiency may not be a primary factor in BEB. Erogul et al. (8) noted markedly reduced B12 levels in BEB patients compared with controls (8). However, since serum 25-OH Vitamin D and Ca levels were also lower in BEB patients, it is difficult to tell which of these components is specifically linked to the disease.

In our study, folic acid levels in BEB patients were found to be significantly lower than in controls, and this finding suggests a potential role in the pathophysiology of the disease. As discussed previously, Vitamin B12 affects homocysteine metabolism by facilitating its remethylation with methionine. Folic acid acts as a critical cofactor in this process, contributing to methylation reactions that are essential for DNA synthesis, neurotransmitter regulation, and myelin maintenance. Folic acid deficiencies can lead to elevated homocysteine levels, which are associated with neurotoxicity through oxidative stress, endothelial dysfunction, and excitotoxicity, all of which may contribute to the neuronal damage and abnormal neuromuscular activity observed in dystonia. High homocysteine levels resulting from folic acid or B12 deficiencies may disrupt dopamine metabolism and basal ganglia function, potentially exacerbating dystonic symptoms (6). Specifically, in patients with BEB, abnormalities in neurotransmitter balance, Ca signaling, and oxidative stress pathways have been suggested as contributing factors. Folic acid deficiency may increase susceptibility to BEB by exacerbating these underlying dysfunctions. The clinical assessment of BEB severity using the JRS revealed a spectrum of symptom severity among patients. This variability underscores the heterogeneous nature of essential blepharospasm, where some individuals experience milder symptoms while others experience more debilitating manifestations. The negative correlation between folic acid levels and BEB severity and frequency warrants further investigation to determine whether lower folic acid concentrations are associated with more severe blepharospasm symptoms.

Although our study provides important information, it has limitations, such as the retrospective methodology, the small sample size, and the limited age range of participants. Further research with a prospective study design and larger study groups should comprehensively examine the processes by which folic acid affects blepharospasm and evaluate the potential of supplementation as a treatment option.

Conclusion

The study indicated that serum levels of Vitamin B12, folic acid, Ca, P, Mg, and Zn were normal in both BEB patients and control subjects. In contrast, Vitamin D levels were subnormal in both groups. While our findings highlight the potential importance of folic acid in BEB, isolating its specific role remains challenging, as Vitamin B12, Vitamin D, and Ca deficiencies have also been observed in BEB patients. Future research should aim to directly assess homocysteine levels, along with the combined effects of Vitamin B12 and folic acid supplementation, to understand their contributions to BEB better. Investigation of methylation patterns, oxidative stress markers, and cerebrospinal fluid metabolite profiles may further clarify the relevant molecular pathways and identify therapeutic targets for intervention.