Unusual presentation of idiopathic Bell’s palsy with involvement of the oculomotor nerve

Abstract

Our patient presented with symptoms consistent with Bell’s palsy. The involved cranial nerves were the facial and oculomotor nerves. She had preceding upper respiratory tract infection symptoms. She had no risk factors or significant illnesses, and no other causes were found. Although there are reported cases of multiple cranial nerves affected in Bell’s palsy, our review of literature revealed no prior cases of involvement of the parasympathetic oculomotor fibres in Bell’s palsy.

Background

We believe that this case is important as it presents a clinical finding that has not previously been reported in the literature: Bell’s palsy with involvement of the parasympathetic fibres of the oculomotor nerve. Additionally, the inner fibres of the oculomotor nerve responsible for extraocular movement were spared.

We present a woman in her 40s who came to our institution’s emergency department with left-sided facial symptoms. We diagnosed her with Bell’s palsy. Alongside her facial nerve involvement, her parasympathetic oculomotor nerve fibres were also affected, which is atypical. She had a complete recovery. Presentation and complete resolution of symptoms were documented prior to the COVID-19 pandemic.

Case presentation

A woman in her 40s with no diagnosed medical history presented to the emergency department with a 4-day history of left-sided facial weakness, left ear hyperacusis, left-sided tongue lack of taste, left eye pupillary dilation and blurred vision. She had upper respiratory tract infection symptoms 1–2 weeks prior to her presentation, which resolved spontaneously without treatment. Prior to presenting to our emergency department, the patient did not seek any treatment for her current symptoms. There was no history of surgery and she did not take over-the-counter or prescribed medications at home. She was a former smoker of less than a pack a week for a few years in her youth, drank alcohol rarely and did not use any illicit drugs. She had an administrative job and no known allergies. Her family history was positive for diabetes and hypertension in her father and thyroid disease in her mother. She denied polydipsia, polyuria or polyphagia, and blood pressure readings during hospital stay and on outpatient follow-up were within normal limits. On physical examination, she had blurred vision in the left eye, as well as a dilated left pupil which was not reactive to light and had no significant response to accommodation. She had a negative consensual reflex in the left eye. She also had a left-sided facial droop with poor blink and lack of taste on the left side of her tongue. She had intact extraocular movements, intact facial sensation bilaterally, no visual field deficits, normal fundi and deep tendon reflexes of +2 throughout.

Investigations

MRI of the brain showed abnormal enhancement along the labyrinthine segment of the left facial nerve compatible with Bell’s palsy, and no abnormal enhancement demonstrated elsewhere (figure 1). CT angiogram of the head and neck revealed no aneurysms.

Figure 1.

Axial MRI of the brain. Abnormal enhancement along the labyrinthine segment of the left facial nerve (dashed arrow within white circle), which can be seen in Bell’s palsy.

Laboratory workup included erythrocyte sedimentation rate (ESR) elevated at 30 mm/hour (normal 0–28) and C reactive protein (CRP) at 1.1 mg/dL (normal <0.3); asparate transaminase (AST) and alanine transaminase (ALT) were also elevated at 138 U/L and 137 U/L, respectively (normal AST 6–58 U/L, normal ALT 14–67 U/L). Extensive diagnostic workup for potential aetiologies of her presentation was negative and included serological testing of hepatitis B, hepatitis C, HIV, Treponema pallidum, Lyme antibody, QuantiFERON-TB Gold, West Nile IgG/IgM, neuromyelitis optica IgG, ACE, methylmalonic acid, homocysteine, cryoglobulin, rheumatological panel and serum urine drug screen. Serum protein electrophoresis showed a polyclonal increase in gamma fraction. Serum immunofixation electrophoresis was negative for M-component or free light chains. Serum autoimmune panel was positive for glutamic acid decarboxylase (GAD) antibody. Haemoglobin was low at 11. Vitamins B₁, B₆, E and B₁₂ were within normal range. Thyroid-stimulating hormone and free T4 were normal. Lumbar puncture was not performed. hemoglobin A1c (HbA1c) at time of presentation was 6.8%.

Treatment

We diagnosed the patient with Bell’s palsy, and she was treated with prednisone 80 mg daily and valacyclovir 1000 mg three times a day for 7 days.

Outcome and follow-up

Follow-up was done one time, 7 months after her emergency department visit. Physical examination, particularly that of the cranial nerves, was normal. The patient reported gradual improvement of her symptoms with complete resolution in 3 weeks. Repeated laboratory tests including ESR and CRP were consistently elevated at 34 mm/hour and 1.1 mg/dL, respectively, along with consistently elevated AST and ALT at 148 U/L and 142 U/L, respectively. Further diagnostic workup was done during the clinic follow-up visit which included positive herpes simplex virus I (HSV I) IgG and negative HSV II IgG but with positive HSV I/II IgM at 1.3 IV (normal ≤0.89). HSV I/II serum PCR was not detected. Varicella zoster virus (VZV) IgG was positive with negative IgM. VZV serum PCR was not detected. Chest X-ray was performed and showed no radiographic evidence of sarcoidosis.

Discussion

The anatomy and function of the seventh cranial nerve and its involvement with unilateral facial paralysis were first described by Sir Charles Bell (1774–1842).^{1 2} Briefly, the anatomy of the facial nerve is complex but contains numerous branches responsible for sympathetic, parasympathetic and sensory functions. Arising in the pons, the facial nerve begins as a large motor root and a small sensory root which then travel through the internal acoustic meatus near the inner ear and exit into the facial canal, fusing together to form the geniculate ganglion and lastly branching into its smaller branches. It is estimated that the annual incidence of Bell’s palsy per 100 000 per year ranges from 17 to 19,³ 20,⁴ 22⁵ and 25.⁶ The aetiology of the disease is hypothesised to be secondary to viral infection, particularly HSV,^7–9 whereas other studies have suggested that herpes zoster virus (VZV) can also be a cause.¹⁰ Although the facial nerve is classically affected in Bell’s palsy, other cranial nerves can be involved, such as our patient who demonstrated an involvement of the parasympathetic fibres of the oculomotor nerve. In one case series of 1048 patients diagnosed with Bell’s palsy, there was involvement of the trigeminal, glossopharyngeal and vagus nerves.⁵ In another prospective study of 51 patients with Bell’s palsy, there were multiple cranial neuropathies in approximately 8% of patients including trigeminal, glossopharyngeal and hypoglossal.¹¹ The mainstay of treatment of Bell’s palsy is steroids, and antiviral therapy can also be considered.¹²

In our patient, we hypothesise that a viral phenomenon triggered an inflammation of both the facial nerve and the parasympathetic fibres of the oculomotor nerve, which are responsible for pupillary constriction and accommodation. This may have been caused by HSV, particularly type I (HSV I) in the setting of positive IgG and slightly elevated IgM in a follow-up visit 7 months later, though definitive aetiology is undetermined. The sparing of the oculomotor inner fibres responsible for extraocular movement and other parts of the central and peripheral nervous systems further supports our hypothesis in that this was not a systemic or extensive disease. We searched PubMed database and there has not been any previously reported cases of involvement of the parasympathetic fibres of the oculomotor nerve. After treatment with prednisone 80 mg daily and valacyclovir 1000 mg three times a day for 7 days, the patient reported improved left eye dilation after 2 days, as well as improved taste on the left side of the tongue and improved left-sided facial droop at 10 days. Although this regimen was effective for our patient, there is no clear optimal dose of treatment as studies vary in their choice of steroids and duration, as well as that of antivirals.¹²

There are some limitations to our case study. This includes not performing a lumbar puncture at the time of initial presentation and not testing for HSV and VZV initially. Although there is no follow-up MRI of the brain, we did not think it was necessary since the patient had complete recovery. There was also no follow-up testing for serum protein electrophoresis. GAD antibody was not repeated since it is non-specific¹³ and the patient did not seem to exhibit clinical autoimmune syndromes.

Patient’s perspective.

I still have an issue with saying my ‘S’s’ in words. My husband also notices that I don't do math calculations as quick like I did before. For example counting money I have to do it twice or three times to make sure I counted it correctly. I have to reassure myself on what I counted. Sometimes I wonder if this will ever happen again or is this a one-time thing. I have read that people have experienced it two or more times. I have not worn eye contacts since before that is all I wore. I wear glasses since this happened.

Learning points.

• Bell’s palsy classically affects the facial nerve and may involve other cranial nerves (CNs) such as V, IX, and/or XII.

• As reported in our case, Bell’s palsy may involve the oculomotor nerve, though rare.

• Involvement of CNs other than those classically seen clinically or reported in literature (ie, CNs V, VII, IX and XII) may be seen in Bell’s palsy as demonstrated here.

Ethics statements

Patient consent for publication

Obtained.