Spontaneous cerebrospinal fluid hypotension as a cause of progressive tonsillar descent and syrinx formation 12 years after uncomplicated Chiari decompression

Recurrence of tonsillar descent after successful surgical decompression for Chiari malformation type I (CMI) is very rare. Spontaneous intracranial hypotension (SIH) can mimic CMI by causing cerebellar tonsillar descent secondary to low cerebrospinal fluid (CSF) pressure in the thecal sac from a dural defect and CSF leak. We report a case of SIH secondary to spinal CSF leak in a pediatric patient with prior successful and uncomplicated Chiari decompression. The patient’s symptoms and radiographic findings initially mimicked CMI recurrence after 12 years of asymptomatic status; however, further clinical investigation suggested CSF leak and SIH as the cause. The patient was treated with an empirical epidural blood patch, which led to the resolution of symptoms, stabilization of tonsillar position, and syrinx regression. To the best of our knowledge, this is the first case of its kind describing cerebellar tonsillar descent due to spontaneous CSF hypotension in a patient more than a decade after successful surgical treatment for CMI.