Unilateral Facial Paralysis in an Infant Post-vaccination: Insights Into Bell's Palsy.

Facial nerve palsy is already a rare adverse effect in infants, and its association with routine vaccinations is even less common. Our case report shares the story of a unique instance of Bell's palsy in a two-month-old infant with unilateral facial paralysis one day following standard immunizations. Neuroimaging revealed enhancement of the left seventh cranial nerve, consistent with Bell's palsy with lower motor neuron involvement. An extensive infectious workup, including polymerase chain reaction (PCR) and serologies for a wide range of pathogens, was negative, and cerebrospinal fluid analysis indicated no signs of infection or inflammation. Given the temporal association with vaccination, our clinical case raises important questions about the potential neurological side effects of immunizations in very young infants. While this condition typically has an encouraging prognosis, there exists a significant gap in research regarding the pathogenesis and etiology of Bell's palsy as it relates to pediatric vaccination. Our report highlights the need for further investigation into the risk of post-vaccination neurological complications, particularly in the pediatric population.