Abstract
Background and Study Aims Chiari malformation type 1 (CM1) is one of the most discussed neurosurgical disorders.
No consensus exists how to manage adult CM1 patients. We aimed to evaluate all adult
CM1 patients consecutively managed at our institutions and discuss our approach based
on the phase-contrast (PC) magnetic resonance imaging (MRI).
Patients and Methods The medical charts of adult patients diagnosed with CM1 at two referral neurosurgical
centers between 2010 and 2017 were reviewed. The patients were either managed conservatively
or surgically. We evaluated the patients clinically with the Chicago Chiari Outcome
Scale (CCOS). The radiologic diagnosis was based on both craniocervical and PC-MRI.
Results Ninety adult CM1 patients were managed conservatively. Conservative treatment failed
in 5 of these 90 patients. Seventy-two patients (including those 5 patients who did
not benefit from conservative treatment) underwent posterior fossa decompression with
duraplasty. Eighty-five patients (94.4%) from the conservative group and 61 patients
(84.7%) from the surgical group were treated successfully. An aqueductal stroke volume
(ASV) value of 12 µL was found as the cutoff value for surgical candidates. A strong
positive correlation between the increase in ASV values and clinical improvement was
observed.
Conclusions PC-MRI can help in the management and follow-up of adult CM1 patients. Conservative
management is possible in selected symptomatic CM1 patients with a high ASV (ASV > 15
µL). Surgery should be considered in patients with an ASV ≤ 12 µL. CM1 patients with
ASV ≤12 to >15 μL require close follow-up. Long-standing symptoms, severe sleep apnea,
symptoms influencing functionality, and syrinx are factors that affected outcomes
negatively.
Keywords chiari malformation type I - conservative therapy - posterior fossa decompression
with duraplasty - CSF flow MRI - phase-contrast MRI
