Bell’s palsy with abnormal findings in the ipsilateral parotid gland

Abstract

Bell’s palsy (BP) can be caused by acute or chronic inflammation-related demyelination. We describe a pediatric case of BP in which a concomitant ipsilateral parotid gland anomaly of unknown etiology was observed. A 7-year-old boy was admitted to the hospital with a 5-day history of left facial paralysis and swelling of ipsilateral parotid gland. Ultrasonography revealed hypoechoic masses, and T2-weighted magnetic resonance imaging revealed heterogeneous hyperintensity in the left parotid gland. After treatment with prednisolone combined with valacyclovir, the facial paralysis improved; however, the abnormal imaging findings in the left parotid gland remained unchanged five months after the onset. Further investigations were not performed because the patient was completely asymptomatic. Hence, the association between BP and parotid gland lesions was not determined in this case, which warrants further investigation in future research to elucidate the association in relevant cases.

Keywords:

• Bell’s palsy
• facial paralysis
• parotitis
• pediatrics
• recurrent parotitis

Introduction

The diagnosis of Bell's palsy (BP) is usually established clinically based on careful exclusion of other potential etiologies of facial paralysis. Facial paralysis in children can occur due to a wide range of idiopathic, congenital, infectious, traumatic, and neoplastic etiologies. However, BP accounts for approximately half of these cases [1]. Facial paralysis associated with non-bacterial parotitis is rarely observed. We encountered a pediatric case of BP in which abnormal imaging findings were simultaneously observed in the ipsilateral parotid gland.

Clinical presentation

A 7-year-old boy without a significant medical history presented to the emergency department with a left facial paralysis and swelling of the ipsilateral parotid gland that had progressed for 5 days. He had no history of parotid gland swelling and had received one dose of the mumps vaccine at 2 years of age. On admission, a physical examination revealed facial asymmetry at rest without forehead movement on the left side. He was unable to close his left eye completely and had an obvious drooping of the left corner of his mouth. The left tympanic membrane was intact with no periauricular rash. Mild, non-tender swelling was noted in the left parotid gland (Figure 1(a)). Blood examination revealed a white blood cell count of 7.88 × 10⁹/L (normal range: 3.30–8.60 × 10⁹/L), a C-reactive protein level of 0.1 mg/L (normal range: 0–1.4 mg/L), and an amylase level of 104 U/L (normal range: 44–132 U/L). The hearing test demonstrated no laterality; however, the stapedial reflex was absent on the left side. Ultrasonography revealed hypoechoic masses in the left parotid gland (Figure 1(b)). T2-weighted magnetic resonance imaging (MRI) revealed heterogeneous hyperintensity in the posterior part of the left parotid gland (Figure 1(c)). Serological test results for mumps, herpes simplex virus type 1, varicella-zoster virus, Epstein-Barr virus, and cytomegalovirus were negative.

Figure 1. Clinical images of the case. (a) Image of the patient’s face on admission showing left parotid gland swelling and incomplete closure of the left eye. (b). Ultrasonographic images of the left parotid gland showing multiple hypoechoic lesions. (c) T2-weighted MRI showing multiple hyperintense lesions in the left parotid gland (white arrowheads).

The patient was provisionally diagnosed with BP based on the House-Brackmann scale of grade IV [2]. Accordingly, prednisolone (1 mg/kg/day), valacyclovir (75 mg/kg/day), and vitamin B₁₂ (75 μg/kg/day) were administered. Prednisolone was tapered from day 10 and oral administration was completed on day 14. Although the patient did not complain of any pain due to a parotid gland abnormality, recurrent parotitis was suspected based on imaging findings. Two months later, the facial paralysis improved; however, five months after the onset, the abnormal ultrasonographic and MRI findings in the left parotid gland remained unchanged. We did not perform further investigations, such as parotid gland biopsy, because the patient became completely asymptomatic, and the parotid swelling did not worsen. His family agreed to our decision, and we instructed the patient to visit our hospital if there was any change in condition. After more than 2 years, the patient had not developed any recurrent symptoms requiring further evaluation, which was confirmed by a telephone interview follow-up.

Discussion

BP is an acute peripheral facial nerve palsy of unknown etiology. Five major hypotheses have been proposed to explain the etiology of BP: anatomical anomaly, viral infection, ischemia, inflammation, and cold stimulation [3]. However, numerous supporting evidences have suggested that BP could be caused by acute or chronic inflammation-related demyelination. Regarding the histopathology of BP, small round lymphatic cell infiltration around the nerve and myelin sheath collapse by macrophages could be seen, which may be exacerbated by viral infection, triggering autoimmune responses [4].

Parotitis can be caused by bacterial or viral infections, sialoliths, or autoimmune diseases [5]. Although immunodeficiency, allergies, upper respiratory tract and mumps infections may be involved, the cause of recurrent parotitis remains largely unknown [6]. Diagnosis of recurrent parotitis can be made based on the criteria of recurrent symptoms, suppurative inflammation, and petechial shadows seen on parotid ductography or MR sialography, along with the exclusion of mumps or bacterial parotitis [5,6]. Ultrasonography shows multiple small circular hypoechoic lesions in the gland. Moreover, T2-weighted-MRI shows parotid swelling with multiple dot-like hyperintense lesions. The imaging findings in our case were consistent with those of recurrent parotitis. However, the absence of pain and failure of this abnormality to resolve within a short period of time could not be explained. Theoretically, further investigation, such as fine-needle biopsy, might be warranted because malignant lymphoma could be a differential diagnosis.

In this pediatric case, ipsilateral parotid gland lesions of unknown etiology were observed during the evaluation of BP. Cases of bacterial parotitis and parotid abscesses complicated by facial nerve palsy have been reported [7]. However, the association between mumps or other non-bacterial parotitides and facial paralysis is extremely rare. In this case, we could not demonstrate a direct association between facial nerve palsy and parotitis because the absence of the stapedial reflex should have indicated a more proximal nervous system location of the causative lesion of the palsy than the parotid gland. Hence, this observation could not be a complication of facial nerve palsy but was a coincidence. Nonetheless, ipsilateral parotid gland lesions occur simultaneously with facial nerve palsy, and both conditions are relatively rare in children. Therefore, the association might be explained by the retrograde spillover of inflammatory mediators from the parotid gland into the facial nerve, despite no direct evidence.

This study had several limitations. First, we could not perform a biopsy to determine the pathological etiology of abnormal findings in the parotid gland. Malignancy could be a differential diagnosis; however, considering the course of recovery of the patient, we did not firmly insist on the necessity of the investigation. Second, we did not follow the international clinical practice guidelines for BP [8] while treating the patient. In the guidelines, monotherapy with corticosteroids or antivirals is not recommended. Combined therapy with corticosteroids and antivirals could be an option; however, it is recommended to be initiated within 72 h of symptom onset in the guideline. A review article by Cochrane suggested a significant benefit from the combination of antivirals with corticosteroids compared with corticosteroids alone for people with BP [9]. Furthermore, people with severe BP (House-Brackmann scores of V and VI or the equivalent in other scales) found a reduction in the rate of incomplete recovery at month six, when antivirals plus corticosteroids were used compared to corticosteroids alone [9]. However, a recent randomized, double-blind, placebo-controlled, multicenter trial on the efficacy of prednisolone for BP in children did not demonstrate that early prednisolone administration improves the complete recovery of the palsy [10]. Vitamin B₁₂ administration has not been described in the guideline, and there has been no evidence of it having a better outcome for BP [8]. Hence, our patient might have fully recovered spontaneously without requiring any treatment. However, we report this case to accumulate similar cases, so that the association between facial nerve palsy and parotid lesions can be further evaluated in the future.

We encountered a pediatric case of BP, in which an ipsilateral parotid gland anomaly was simultaneously observed. The accumulation and evaluation of similar cases will be necessary in the future to elucidate the association between BP and ipsilateral parotitis.

Informed consent

Written informed consent was obtained from the parent of the patient for the publication. No identifiable information was included in the report.

Disclosure statement

No potential conflict of interest was reported by the author(s).