Chiari I malformation after cranial radiation therapy in childhood: a dynamic process associated with changes in clival growth

Chiari I-a 'not so' congenital malformation?

The term Chiari I malformation (CIM) is imbedded in the paediatric neurosurgical lexicon; however, the diagnostic criteria for this entity are imprecise, its pathophysiology variable, and the treatment options diverse. Until recently, CIM has been considered to be a discrete congenital malformation requiring a uniform approach to treatment. Increasingly, it is recognised that this is an oversimplification and that a more critical, etiologically based approach to the evaluation of children with this diagnosis is essential, not only to select those children who might be suitable for surgical treatment (and, of course those who might be better served by conservative management) but also to determine the most appropriate surgical strategy. Whilst good outcomes can be anticipated in the majority of children with CIM following foramen magnum decompression, treatment failures and complication rates are not insignificant. Arguably, poor or suboptimal outcomes following treatment for CIM reflect, not only a failure of surgical technique, but incorrect patient selection and failure to acknowledge the diverse pathophysiology underlying the phenomenon of CIM. The investigation of the child with 'hindbrain herniation' should be aimed at better understanding the mechanisms underlying the herniation so that these may be addressed by an appropriate choice of treatment.

Acute Foramen Magnum Syndrome Following Single Diagnostic Lumbar Puncture: Consequence of a Small Posterior Fossa?

BACKGROUND

Type I Chiari malformation (CMI) is a rare complication of lumbar cerebrospinal fluid (CSF) drainage that is usually reported after lumbar drain or lumboperitoneal shunt placement. It usually remains asymptomatic; however, even if it becomes symptomatic, symptoms are usually mild. There are only a few reports of acute foramen magnum syndrome following continuous lumbar CSF drainage, and acute foramen magnum syndrome after a single diagnostic lumbar puncture (LP) has not been previously reported. We encountered this catastrophic complication in one of our patient.

CASE DESCRIPTION

A 30-year-old woman with a large supratentorial meningioma and associated asymptomatic CMI presented with holocranial headache. She underwent successful and uneventful excision of the tumor. However, she developed quadriplegia and respiratory arrest 48 hours following a diagnostic LP performed on postoperative day 9. She underwent urgent posterior fossa decompression after magnetic resonance imaging showed increased tonsillar impaction and swelling along with cervicomedullary compression. Postoperatively, she steadily improved and regained normal power after 3 months. Retrospective quantitative analysis of magnetic resonance imaging (MRI) revealed a small posterior fossa.

CONCLUSIONS

The association of intracranial tumors and lumbar CSF drainage with CMI is uncommon. The documentation of a small posterior fossa signifies the importance of both developmental (small posterior fossa) and acquired (intracranial tumor/lumbar CSF drainage) factors in pathogenesis of CMI. Although the extreme rarity of acute deterioration following a single LP does not warrant LP to be contraindicated in such patients, documentation of resolution of CMI with postoperative MRI before performing lumbar CSF drainage (whether therapeutic or diagnostic), might be helpful in avoiding this rare complication.

Rate of Chiari I malformation in children of mothers with depression with and without prenatal SSRI exposure

Selective serotonin reuptake inhibitors (SSRIs) are frequently prescribed to pregnant women. Therefore, research on in utero exposure to SSRIs can be helpful in informing patients and clinicians. The aim of this retrospective two-cohort study was to determine whether there is a statistically significant increase in Chiari I malformations (CIM) in children exposed to SSRIs during pregnancy. A total of 33 children whose mothers received a diagnosis of depression and took SSRIs during pregnancy (SSRI-exposed cohort) were matched to 66 children with no history of maternal depression and no SSRI exposure. In addition, 30 children whose mothers received a diagnosis of depression, but did not receive antidepressants during pregnancy (history of maternal depression cohort), were matched to 60 children with no history of maternal depression and no SSRI exposure. Main outcome was presence/absence of CIM on MRI scans at 1 and/or 2 years of age. Scans were reviewed by two independent neuroradiologists who were blind to exposure status. The SSRI-exposed children were significantly more likely to be classified as CIM than comparison children with no history of maternal depression and no SSRI exposure (18% vs 2%, p=0.003, OR estimate 10.32, 95% Wald confidence limits 2.04-102.46). Duration of SSRI exposure, SSRI exposure at conception, and family history of depression increased the risk. The history of maternal depression cohort did not differ from comparison children with no history of maternal depression and no SSRI exposure in occurrence of CIM (7% vs 5%, p=0.75, OR estimate 1.44, 95% Wald confidence limits 0.23-7.85). Replication is needed, as is additional research to clarify whether SSRIs directly impact risk for CIM or whether this relationship is mediated by severity of depressive symptoms during pregnancy. We would discourage clinicians from altering their prescribing practices until such research is available.