Intraoperative neuromonitoring (IONM) has been used in neurosurgical procedures to assess patient safety and minimize risk of neurological deficit. However, its use in decompressive surgeries of Chiari malformation type I (CM-I) remains a topic of debate. Here we present the case of a 5-year-old girl who presented with acute right lower extremity monoplegia after accidental self-induced hyperflexion of the neck while playing. Imaging revealed 15 mm of tonsillar ectopia with cervical and upper thoracic spinal cord edema. She was taken to surgery for a suboccipital decompression with expansile duraplasty. IONM demonstrated improvement in motor evoked potentials during the decompression. Postoperatively, she had full recovery of strength and mobility. This is a case of acute weakness after mild trauma in the setting of previously asymptomatic CM-I that showed close correlation with IONM, clinical findings, and imaging. IONM during decompressive surgery for CM-I may be useful in patients who present acutely with cervical cord edema.