MRI study of the natural history and risk factors for pseudomeningocoele formation following postfossa surgery in children.

Surgical approaches to the posterior fossa may be complicated by pseudomeningocoele formation. We report on its natural history and risk factors for its formation, as seen on serial MRI postoperatively in children with posterior fossa tumours. In a retrospective study of 84 children undergoing surgery for posterior fossa tumours, 13 (16%) developed clinically apparent pseudomeningocoeles. On postoperative MRI, pseudomeningocoeles were apparent in 34 (41%) patients at 1-5 days, but in only four patients at 10-15 months postsurgery. There was a progressive decrease in the mean depth of pseudomeningocoele measured from the MRI scans postoperatively. Patients with pseudomeningocoeles were more likely to have a postoperative CSF leak from the wound (39 v. 13%), lumbar punctures or lumbar drains (54 v. 25%), wound re-closures (23 v. 1%) and prolonged hospital stay (19.9 v. 14.5 days). On multivariate analysis, patients with pseudomeningocoeles were also more likely to have undergone a suboccipital craniectomy than those without pseudomeningocoeles (69 v. 38%). Postoperative pseudomeningocoele formation following posterior fossa surgery is more apparent radiologically than clinically, but there is clinical and radiological evidence that pseudomeningocoeles gradually resolve over the postoperative period. The risk of pseudomeningocoele formation is increased by performing a suboccipital craniectomy and there is an association with increased CSF leaks, needing re-closure of the wounds.