Pediatric Arnold-Chiari I Malformation With Syrinx Presenting With Unilateral Hand Weakness: A Case Report

Diagnostic suspicion of Chiari I malformations (CM-I) can be challenging in the pediatric population due to highly variable neurologic symptoms and cognitive immaturity impairing symptom identification. Especially in an atypical presentation without obvious central neurological abnormalities, the diagnosis can often be missed. We present a case of a left-hand-dominant 14-year-old boy presenting to an orthopedic hand clinic with right-hand weakness, tingling, and impaired grip strength. The medical history was notable for mild scoliosis and acute lymphoblastic leukemia in remission treated with chemotherapy. The patient denied headaches, neck pain, or balance dysfunction on initial presentation. Neurodiagnostic studies were consistent with C7 and C8 radiculopathies, and magnetic resonance imaging of the brain and entire spine revealed herniation of the cerebellar tonsils with expansive syrinx extending into the lower thoracic spine. After successful posterior fossa decompression, upper extremity strength and hand clawing improved, which was corroborated with postoperative imaging. The patient met his physical therapy goals 6 months after surgery. A thorough history and neurologic examination are essential for earlier detection of pediatric CM-I and a favorable prognosis, particularly in patients with an unclear neurologic cause.