# Unilateral and Reversible Hypoglossal Nerve Palsy in Infectious Mononucleosis Syndromes: Two Rare Cases from Our Clinic

## TL;DR

Two children with infectious mononucleosis developed temporary one-sided tongue weakness, which improved with treatment.

## Contribution

Reports two rare pediatric cases of transient hypoglossal nerve palsy linked to EBV and CMV mononucleosis.

## Key findings

- Unilateral hypoglossal nerve palsy resolved within 2–4 weeks in both patients.
- Symptoms included tongue deviation, sialorrhea, dysarthria, and dysphagia.
- Systemic corticosteroids and antibiotics were effective in treatment.

## Abstract

Background and Clinical Significance: Hypoglossal nerve palsy is an uncommon neurological complication of infectious mononucleosis and is only rarely reported. Putative mechanisms include virus-triggered neuritis (Epstein–Barr virus (EBV) or Cytomegalovirus (CMV)) and/or mechanical compression related to cervical lymphadenopathy. Case Presentation: We report two children with infectious mononucleosis and transient unilateral hypoglossal nerve palsy. Case 1 was a 15-year-old boy with 7 days of fever and typical mononucleosis features who developed leftward tongue deviation accompanied by sialorrhea, dysarthria, and dysphagia. Laboratory testing showed marked hepatocellular injury and EBV-specific IgM positivity. Case 2 was a 9-year-old girl with a 24 h history of bilateral lateral cervical lymphadenopathy with overlying inflammatory signs; examination revealed rightward tongue deviation with similar associated symptoms. CMV-specific IgM antibodies were detected on serological testing. Both patients received systemic corticosteroids and empiric intravenous antibiotics, with supportive care. Hypoglossal nerve function fully recovered within 2–4 weeks of treatment initiation. Conclusions: These cases underscore that isolated hypoglossal nerve palsy may complicate EBV- or CMV-associated mononucleosis in children. Although the prognosis is generally favorable, the presentation warrants careful evaluation to exclude alternative causes of lower cranial neuropathies and close follow-up until complete neurological resolution.