Long-term outcome of surgical management of adult Chiari I malformation.

Chiari I malformation continues to inspire controversy. Debate still exists about surgical options. The aim of this study is to evaluate the long-term outcome of posterior fossa decompression procedure (PFD) in the treatment of adult Chiari I malformation, focusing on some factors or technical aspects which might influence the outcome. Forty-six adult patients with Chiari I malformation operated by PFD are the subject of this study. The group included 21 males and 25 females, with mean age of 37.4 years. Patients were divided into two groups: group I (32 cases) with syringomyelia and group II (14 cases) without syringomyelia. Group I was further subdivided into three subgroups according to the surgical procedure adopted: group Ia (12 cases) operated by PFD only, group Ib (14 cases) operated by PFD with fourth ventricular shunt, and group Ic (six cases) operated by PFD and syringosubarachnoid shunt. All cases included in group II were operated by PFD only. In group I, symptoms improved in 14 cases (43.8 %) and stabilized in 18 cases (56.3 %), whereas in group II, symptoms resolved in ten cases (71.4 %) and improved in four cases (28.6 %). Postoperative magnetic resonance imaging showed that the syrinx was resolved in 21 cases (65.6 %), improved in seven cases (21.9 %), and unchanged in four cases (12.5 %). Among the mean follow-up period (5.8 years), recurrence of symptoms occurred in five cases (10.9 %), all of them are included in group I, and were reoperated again. Posterior fossa decompression is recommended as the treatment of choice in adult Chiari I malformation with or without syringomyelia. The presence of syringomyelia predicts a less favorable response to surgical intervention. Syringosubarachnoid shunting did not improve the long-term outcome either clinically or radiologically. Implanting a fourth ventricular shunt in cases of syringomyelia associated with adhesions at the foramen of Magendie decreases the long-term incidence of recurrence significantly. For recurrent cases, re-exploration of the initial posterior fossa decompression is recommended before any consideration is given for direct management of the syrinx.