Background: The natural course of syringomyelia is unpredictable. Only a few cases of adults with spontaneous resolution of syringomyelia associated with Chiari malformation type I (CM-I) have been reported. The timing of surgical intervention for syringomyelia remains controversial. The present report has documented a case with the longest medical history of syringomyelia reported, the associated imaging findings over 16 years, the mild symptom progression after the spontaneous resolution of syringomyelia, and a review of the relevant reported data. The natural history of our patient provides a unique view regarding the factors that might lead to the development and spontaneous resolution of syringomyelia. Case Description: We present the case of a 36-year-old woman who had been monitored for 16 years for mild symptomatic CM-I and syringomyelia. After regular follow-up examinations for the initial 10 years, magnetic resonance imaging revealed partial spontaneous resolution of the syringomyelia and unchanged symptoms. However, after 6 additional years of follow-up examinations, her symptoms had mildly progressed, and the size of the syringomyelia had obviously decreased. Conclusions: The findings from our patient suggest that the natural course of mild symptomatic CM-I in adult patients will be benign and nonprogressive. Patients will commonly present with very few or mild symptoms, despite the presence of a large syrinx. It would be reasonable to observe patients with similar mild symptoms and syringomyelia. Surgery will be indicated by the type, severity, and duration of symptoms at the first clinical visit. Periodic follow-up examinations are also essential after spontaneous resolution because the pathophysiology of syringomyelia is incompletely understood and recurrence possible. © 2019 Elsevier Inc.