Evaluation of prognostic factors in patients with Bell's palsy

Abstract Background Bell's palsy is a common neurological problem that leads to peripheral palsy of the facial nerve. Most patients have a favorable response with or without treatment while some are left with significant facial deformity. Identification of factors which influence the outcome in patients with Bell's palsy may help clinicians counsel better. Methods A prospective cross‐sectional study was carried out in the Department of Neurology Nobel Medical College, Biratnagar, between February 2020 and February 2021 after obtaining ethical clearance from the institutional review committee. Patients were assessed at the time of presentation to hospital and followed up at 1 week, 1 month, and 3 months after the onset of illness to evaluate for recovery. Results Sixty‐two (61.4%) of 101 patients had a favorable outcome at the follow up on the third month, achieving H‐B grade 2 or lower, while 33 (32.7%) had moderate dysfunction and 6 (5.9%) had severe dysfunction. The following factors were associated with favorable outcome: younger age of onset (p < .001), lower initial H‐B grade of III or IV (p = .001), lesser degree of amplitude reduction on affected side as compared to unaffected side (p = .001) and absence of hypertension and diabetes. The following factors did not influence outcome at three months: duration of Bell's palsy (p = 0.142), side of face affected, and gender (p = .09). Conclusions Most of the patients with Bell's palsy have favorable outcomes. Age, hypertension, initial H‐B grade, and extent of facial nerve degeneration as recorded by nerve conduction studies are important predictors of outcome.

We conducted this study to evaluate if facial nerve conduction study findings, treatment modality, gender, age of onset, hypertension, and diabetes mellitus influenced the outcome.

METHOD
This was a prospective cross-sectional study carried out at the Department of Neurology, Nobel Medical College, Biratnagar, Nepal between February 2020 and February 2021.
All the patients with Bell's palsy who were presented to the hospital were included in this study.
Patients in whom the cause of facial paralysis (e.g., neoplasm, trauma, otitis media, Ramsay-Hunt syndrome) was known were excluded from the study.
All the patients included in this study had a total of four visits. The first visit was when the patient was first seen by us. House-Brackmann facial nerve grading scale has been commonly used to assess the severity of facial weakness (6), where grade 1 indicates normal power while grade 6 indicates complete paralysis of the facial nerve. Nerve conduction study was done on day 4 or 5 after the onset of facial paralysis. As nerve conduction study can be affected by room temperature, a constant temperature of the examination room was maintained with the use of an air conditioner. The amplitude reduction of the affected side was compared with the unaffected side and was expressed as percentage reduction. A poor nerve conduction study result was defined as a loss of amplitude greater than 90%, whereas loss of 90% or less was classified as a good outcome (21).
Patients were treated with either prednisolone alone, or a combination of acyclovir 400 mg five times a day and prednisolone 1 mg/kg per day for 5 days and were gradually tapered over the next 5 days.
Facial physiotherapy was offered to all patients irrespective of severity of facial weakness.

RESULTS
Majority of the study population was adult with a mean age of 42 ± 18.
Almost equal number of patients had either left or right side of the face affected as shown in Table 1.
Most of the patients were adults mainly in the age range of 20 to 40.
Patients less than 20 years and more than 80 years of age constituted 13 (12.86%) as shown in Table 2. Age was an important determinant of outcome, with advancing age having worse outcome than younger patients (p < .001).
House-Brackmann grading system was used to assess the severity of facial weakness as shown in Table 3. Lower H-B grade at the time of presentation to hospital was associated with favorable outcome while higher H-B grade was associated with worse prognosis (p < .001).
Nerve conduction study was done in all the patients with Bell's palsy which showed reduction in the amplitude of the compound muscle action potential as shown in Table 4. We found that a greater degree of amplitude reduction was associated with worse outcome (p = .001).
There was no statistically significant difference in recovery of facial function between patients who were treated with steroid combined with acyclovir and facial physical therapy, and those who were treated with steroid combined with physiotherapy (p = .07).

DISCUSSION
We We assessed blood pressure in all the patients at the time of initial examination and during each visit to the hospital, and determined if it affected the outcome. We found that hypertension at the time of onset of Bell's palsy measured during initial presentation to hospital was significantly associated with worse outcome (p = .03). In three adult case studies in patients with known hypertension, facial palsy was found to occur during episodes of raised blood pressure due to non-adherence to medicine (2; 5; 10). Bell's palsy resolved when the blood pressure was brought under control, suggesting an association between controlled blood pressure and recovery of Bell's palsy. Lee et al. (11) had shown that initial severity of Bell's palsy and control of blood pressure were factors associated with good outcome. When hypertension was detected, medications to control blood pressure was initiated as indicated.
In patients with Bell palsy, diabetes was found to be associated with a poor outcome (p = .007). In patients with diabetes mellitus, Takemoto et al. (22) found worse outcomes than those who did not have diabetes.
Chronic hyperglycemia in patients with diabetes mellitus affects the facial nerve fibers with negative effects on outcome in patients with Bell's palsy.
In our study, both left and right sides were almost equally affected.
However, the side of the face affected did not alter the ultimate outcome in patients with Bell's palsy. Similarly, duration of Bell's palsy before presentation to hospital also did not have a significant effect on the outcome. Patients had a longer duration of illness before coming to the hospital because Nepal is a mountainous country with difficulty in traveling from remote areas.
Twelve (11.9%) patients had previous history of facial palsy, either on the same or opposite side. This figure is higher than that mentioned in other studies.
We used the H-B grading system in our study as it is the most fre- Nerve conduction study test has been used to evaluate the severity of facial nerve damage that quantifies the facial nerve function indirectly by recording motor unit action potential (MUAP) and compound muscle action potentials (CMAP) (12). By comparing the maximum amplitude of the compound muscle action potential of the affected side with the amplitude from the unaffected side, the amount of the degenerated nerve can be assessed. We found that greater degree of amplitude reduction was associated with worse outcome (p = .001). A study done by Prakash and Raymond (17) found that about 65% of those with <50% facial nerve degeneration had complete clinical recovery within a month and more than 90% of those with <75% degeneration had complete recovery within 2 months.
In our study, there was no statistically significant difference in recovery of facial function between patients who were treated with steroid combined with acyclovir and facial physical therapy and those who were treated with steroid combined with physiotherapy (p = .07).
According to the American Academy of Otolaryngology guideline, treatment of patients with Bell's palsy with oral corticosteroid within 3 days of facial weakness is likely to be very effective in patients with or without the use of concurrent antiviral therapy (3).

CONCLUSIONS
Bell's palsy is a common neurological problem which causes a lot of anxiety to patients. A good history and examination help to differentiate peripheral cause of facial palsy from central cause. Age, diabetes mellitus, hypertension, initial H-B grade, and extent of facial nerve degeneration as recorded by nerve conduction studies, affect clinical outcome of Bell's palsy at 3 months after its onset. Our study helps to identify specific factors in the patients which may influence outcome.

DATA AVAILABILITY STATEMENT
Data supporting the findings of this study are available upon reasonable request to the author.