Functional Neurological Disorder After SARS-CoV-2 Vaccines: Two Case Reports and Discussion of Potential Public Health Implications

Design

Case series

Case 1

A 38-year old female, with no past medical history, developed weakness on the left side of her face and body about 20 minutes after receiving the Pfizer-BioNTech SARS-CoV-2 vaccine (in her left arm). The “weakness” sensation, as reported by the patient, began in her left ear, traveled down to the left side of her mouth and face, and then to her left arm and leg. No other symptoms were noted.

The next day, the patient’s general practitioner called an ambulance. The emergency department documented mild left side arm weakness, downward deviation of the left side of the mouth, and tongue deviation to the right. The patient had score of 4 on the Medical Research Council (MRC) Scale for Muscle Strength, indicating movement against gravity and resistance.

The patient’s blood pressure, glucose level, heart rate, electrocardiogram, and computerized tomography brain scan were all normal. She was discharged from the emergency department with a working diagnosis of either a transient ischemic attack or Bell’s palsy and was started on 75 mg of aspirin once daily.

The patient had ongoing left-sided weakness when presenting at the stroke clinic one week later, along with new complaints of intermittent word-finding difficulty and stammering. An MRI brain scan was done during the appointment and came back normal.

Two months post-vaccination, the patient presented to the general neurology clinic, with ongoing left-sided weakness, albeit improved from last time, and a new complaint of difficulties with short-term memory. A neurological exam indicated Hoover’s sign and a positive hip abduction test, and the patient was diagnosed with FND.

A 36-year old female patient experienced severe bilateral leg heaviness, difficulties in fine movements of the right hand, and fatigue after walking short distances two days after receiving the second dose of the Moderna SARS-CoV-2 vaccine in her right arm. The patient sought medical attention after several days of these symptoms.

Upon examination, the patient was noted to have mild weakness (MRC scale score ≥4) in the right upper and lower limbs, but her reflexes and sensory examination were normal. She started physical therapy. About seven weeks postvaccination, she reported fluctuation in her left- and right-sided weakness, as well as tightness and heaviness in her neck extensors, and difficulty with daily living tasks.

On examination, the patient had an MRC scale score of 5 for all limbs, a positive Hoover’s sign on the right leg, and a low-amplitude rapid postural tremor in both hands. She was diagnosed with functional weakness, tremor likely due to anxiety, and fatigue symptoms similar to those of chronic fatigue syndrome.

Author Conclusion

Functional Neurological Disorder is likely to arise in multiple cases within the large-scale SARS-CoV-2 vaccination program and should be considered as a differential diagnosis when assessing postvaccine neurological symptoms.

InpharmD Researcher Critique

Clinicians recognizing FND reactions to COVID-19 vaccines can be beneficial as early recognition can increase the chances of symptom improvement with evidence-based treatment.

It is also important to note that physiological reactions from the vaccine (e.g., vasovagal or flu-like symptoms), as well as pain from the injection site, may trigger or evolve into functional symptoms.