Surgical management of Chiari malformation type II

Abstract

Background: Chiari malformation type II is present in almost all patients with myelomeningocele but usually remains asymptomatic. Symptoms are generally more severe in neonates, who have the worst prognosis. The association symptoms/hydrocephalus is well known, and first treatment usually consists of ensuring adequate ventricular drainage. Craniovertebral decompression may be required in patients who do not improve after drainage. However, mechanisms of symptom development are not yet completely understood, timing and techniques of surgery are not codified, long-term evolution is poorly reported, and there are few paper reporting clinical onset and treatment in older patients.

Methods: We reviewed our personal series of 42 consecutive symptomatic patients that required surgical treatment. Age at surgery ranged from 1 week to 44 years (mean 6.6 years). Surgical timing strictly depended on clinical conditions: urgent management in the more compromised patients (usually infants) and elective treatment before severe deterioration in patients with less severe conditions. All patients first underwent external ventricular drainage, which resolved the symptomatology in 17 cases (40%). Craniocervical decompression was required by 25 patients (60%) who received no benefit from the ventricular drainage.

Results: Early mortality (2 cases = 4.7%) occurred only in neonates. Clinical improvement was achieved in 37 of 40 survivors (92%). During a follow-up ranging from 2 to 20 years (mean 10.3 years), late mortality consisted of 4 cases (10%), mainly due to cardio-respiratory arrest. Twenty-two patients (55%) required surgery for shunt malfunction and 4 for cord detethering. Six patients (15%) required reoperation owing to symptom recurrence.

Conclusion: Early treatment of symptomatic Chiari II malformations may warrant satisfactory results in a significant number of patients, even in neonates. Nevertheless, overall mortality remains relatively high, throughout the patient life. Formal transition programs and adult spina bifida care processes have become crucial.

Keywords: Chiari II malformation; Craniocervical decompression; Myelomeningocele; Spina bifida; Ventriculoperitoneal shunt.