Chiari-related hydrocephalus: assessment of clinical risk factors in a cohort of 297 consecutive patients.

OBJECTIVE Patients treated for Chiari I malformation (CM-I) with posterior fossa decompression (PFD) may occasionally and unpredictably develop postoperative hydrocephalus. The clinical risk factors predictive of this type of Chiari-related hydrocephalus (CRH) are unknown. The authors' objective was to evaluate their experience to identify risk factors that may predict which of these patients undergoing PFD will develop CRH after surgery. METHODS The authors performed a retrospective clinical chart review of all patients who underwent PFD surgery and duraplasty for CM-I at the Primary Children's Hospital in Utah from June 1, 2005, through May 31, 2015. Patients were dichotomized based on the need for long-term CSF diversion after PFD. Analysis included both univariate and multivariable logistic regression analyses. RESULTS The authors identified 297 decompressive surgeries over the period of the study, 22 of which required long-term postoperative CSF diversion. On multivariable analysis, age < 6 years old (OR 3.342, 95% CI 1.282-8.713), higher intraoperative blood loss (OR 1.003, 95% CI 1.001-1.006), and the presence of a fourth ventricular web (OR 3.752, 95% CI 1.306-10.783) were significantly associated with the need for long-term CSF diversion after decompressive surgery. CONCLUSIONS Younger patients, those with extensive intraoperative blood loss, and those found during surgery to have a fourth ventricular web were at higher risk for the development of CRH. Clinicians should be alert to evidence of CRH in this patient population after PFD surgery.

Assessment of the posterior brain at 11-14 weeks for the prediction of open neural tube defects.

OBJECTIVE: To evaluate the routine midsagittal view of the posterior brain at the 11-13 weeks' ultrasound examination, for predicting open neural tube defects. METHODS: Posterior brain was examined midsagittally for normality of the four-line view (upper and lower border of the brain stem, the choroid plexus of the fourth ventricle and the occipital bone). Intracranial translucency and cisterna magna (CM) were measured. RESULTS: The posterior brain was assessed in 1330 cases. The four-line view was normal in all but one case. In the two cases of open spina bifida contained in the study population, intracranial translucency was within normal range. The CM and the four-line view were normal in the first case, whereas in the second case, the four-line view was abnormal, and CM was obliterated and impossible to measure. No other cases of abnormal four-line view were observed in the study population. CONCLUSION: Obliteration of the CM appears to be the most consistent early sign of open neural tube defects. Attention should focus on either measuring the cisterna magna or simply observing the presence of four lines in the midsagittal view of the posterior brain. However, these early signs of brain herniation are not present in all abnormal cases.

Assessment of intracranial translucency (IT) in the detection of spina bifida at the 11-13-week scan.

OBJECTIVE: Prenatal diagnosis of open spina bifida is carried out by ultrasound examination in the second trimester of pregnancy. The diagnosis is suspected by the presence of a 'lemon-shaped' head and a 'banana-shaped' cerebellum, thought to be consequences of caudal displacement of the hindbrain. The aim of the study was to determine whether in fetuses with spina bifida this displacement of the brain is evident from the first trimester of pregnancy. METHODS: In women undergoing routine ultrasound examination at 11-13 weeks' gestation as part of screening for chromosomal abnormalities, a mid-sagittal view of the fetal face was obtained to measure nuchal translucency thickness and assess the nasal bone. In this view the fourth ventricle, which presents as an intracranial translucency (IT) between the brain stem and choroid plexus, is easily visible. We measured the anteroposterior diameter of the fourth ventricle in 200 normal fetuses and in four fetuses with spina bifida. RESULTS: In the normal fetuses the fourth ventricle was always visible and the median anteroposterior diameter increased from 1.5 mm at a crown-rump length (CRL) of 45 mm to 2.5 mm at a CRL of 84 mm. In the four fetuses with spina bifida the ventricle was compressed by the caudally displaced hindbrain and no IT could be seen. CONCLUSION: The mid-sagittal view of the face as routinely used in screening for chromosomal defects can also be used for early detection of open spina bifida.

The fetal cerebellar vermis: assessment for abnormal development by ultrasonography and magnetic resonance imaging.

Fetal magnetic resonance provides a new tool in the imaging of the posterior fossa and is proving useful in cases that are difficult to assess sonographically by allowing further assessment of the fourth ventricle, cisterna magna, and vermian growth and development. We describe various criteria with which to evaluate vermian growth, including vermian biometry and the relationship between the superior and inferior lobes. We demonstrate 2 markers of normal vermian development: the primary fissure and fastigial point. We illustrate the tegmento-vermian angle, "closure" of the fourth ventricle, and communication of the fourth ventricle with the basal cisterns during development and in several disorders. We correlate those features with the expected embryological course of development and illustrate identification of these features and associated abnormalities of the posterior fossa, brain stem, and central nervous system in mid-trimester scans of fetuses with abnormal development. Correlation with contemporaneous ultrasound examinations is demonstrated.