• Concezio Di Rocco and Francesco Velardi.
• Institute of Neurosurgery, Section of Pediatric Neurosurgery, Catholic University Medical School, Policlinico "A. Gemelli", Largo Gemelli 8, 00168, Rome, Italy. cdirocco@rm.unicatt.it
• Childs Nerv Syst. 2003 Dec 1;19(12):800-7.

IntroductionAcquired Chiari type-I malformation in hydrocephalic patients who have undergone surgical treatment was initially thought to depend on a craniocephalic disproportion induced by the cerebrospinal (CSF) shunt. However, most of the reports in the literature deal with children with lumbo-peritoneal shunts and emphasize the pathogenic role of the cranio-spinal pressure differential across the foramen magnum brought about by this type of shunt.MethodIn the present report, the authors describe two further cases of symptomatic acquired Chiari type-I malformation observed in two adolescents operated on for correction of pseudotumor cerebri in one (lumbo-peritoneal shunt) and of a suprasellar arachnoid cyst (cysto-ventriculo-peritoneal shunt) in the other.ResultsIn both subjects, both the clinical manifestations and the cerebellar tonsillar herniation regressed after supratentorial cranial expansion, without the need for any manipulation of the shunt devices implanted earlier.DiscussionThese results, together with the observation of the concomitant upward and downward herniation of the cerebellum in both patients, indicate that secondary craniocephalic disproportion plays a relevant role in the genesis of acquired Chiari type-I malformation in children bearing extrathecal CSF shunts.

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