Posterior fossa decompression for Chiari malformation type I: clinical and radiological presentation, outcome and complications in a retrospective series of 105 procedures.

OBJECTIVE: Determining clinical and radiological characteristics, complication rates and outcome for patients undergoing posterior fossa decompression (PFD) and duraplasty for Chiari malformation type I (CM-I).

METHODS AND MATERIALS: Retrospective, single-university hospital study of all PFDs for CM-I between January 1995 and December 2016.

RESULTS: PFD was performed in 105 patients with CM-I (n = 105), of whom 62 suffered from associated syringomyelia and 37 were pediatric cases. There was a female preponderance in the syringomyelia, non-syringomyelia, pediatric and adult groups (62.9%, 65.1%, 54.1% and 69.1%, respectively). Mean age at diagnosis was higher in the syringomyelia group (32.3 versus 26.9 years, p = 0.06) and in both groups delay for diagnosis was long (33.4 and 47.1 months, p = 0.50). Headache during Valsalva maneuver and on exertion was significantly more present in the non-syringomyelia group (27.9% versus 16.1%, p < 0.0001 and 39.5% versus 11.3%, p = 0.0009); cranial nerve dysfunction and cerebellar signs did not differ significantly (p = 0.07 and p = 0.53). Spinal cord syndrome was significantly more present in the syringomyelia group (72.6% versus 25.6%, p < 0.0001). Scoliosis was present in five patients, of whom four had syringomyelia. Duraplasty was performed in 101 surgeries. For 100 patients, PFD was the primary treatment of CM-I; 2 patients had previously undergone syrinx drainage and 3 ventriculoperitoneal shunting for hydrocephalus. Only one patient presented with hydrocephalus. Duraplasty (n = 101) was complicated by CSF leak in 4.0% (n = 4), symptomatic pseudomeningocele in 4.0% (n = 4), aseptic meningitis in 2.0% (n = 2) and hydrocephalus in 1.0% (n = 1). Osseous decompression without duraplasty was performed in only four highly selected patients, not allowing a comparative analysis with duraplasty. Post-operative symptom improvement is reported for 67.3% of all patients and stabilization of symptoms in 23.9%. Symptom improvement was significantly more frequent in the non-syringomyelia group (p = 0.03). Outcome seemed similarly good in the pediatric and the adult groups.

CONCLUSION: PFD performed with duraplasty is a safe procedure. The majority of patients do report symptom stabilization or improvement. Non-syringomyelia patients reported significantly more frequent improvement of clinical symptoms.