Shunt-related craniocerebral disproportion: treatment with cranial vault expanding procedures.

Two patients with intracranial arachnoid cysts, one with myelomeningocele-hydrocephalus and the other with a subdural fluid collection, were given a cerebrospinal (CSF) extracranial shunt. All four patients developed features of CSF overdrainage following shunting and were treated by cranial vault expanding procedures. Before undergoing decompressive craniotomy, the patients were treated by a variety of procedures, including changing of obstructed ventricular catheters (n=4), insertion or upgrading of programmable valves (n=3), and foramen magnum decompression (n=1). Clinical manifestations of these four patients were attributed to craniocerebral disproportion caused by chronic and progressive skull changes due to dampening of the CSF pulse pressure, which is necessary for maintaining normal cranial growth. On the basis of our previous experience with expanding craniotomies in cases of minimal forms of craniosynostosis, we treated these patients with bilateral parietal craniotomies, with satisfactory results. In conclusion, biparietal decompressive craniotomy constitutes a useful and safe procedure for relieving the clinical manifestations of some CSF overdrainage syndromes, especially in cases with slit-ventricle syndrome and craniocerebral disproportion that prove to be refractory to simpler management procedures.