Elsevier

World Neurosurgery

Volume 108, December 2017, Pages 62-68
World Neurosurgery

Original Article
Complete Reversibility of the Chiari Type II Malformation After Postnatal Repair of Myelomeningocele

https://doi.org/10.1016/j.wneu.2017.08.152Get rights and content

Objective

It was believed that Chiari type II malformation (CM-II) was always present in a myelomeningocele (MMC). In fact, it is associated in about 80% of cases. Improvement of the hindbrain herniation after prenatal closure of MMC has challenged the idea that this condition was irreversible. Only 2 studies report ascent of the cerebellar tonsil after postnatal closure. This work aimed to study a large group of patients with MMC who benefited from a postnatal repair to evaluate the rate of long-term total reversibility of CM-II.

Methods

Sixty-one patients were included. Mean time of follow-up was 8.1 years. The presence of CM-II after closure of the MMC was assessed on the most recent brain scan available for each patient.

Results

Forty-seven patients (77%) had a CM-II at birth (confirmed before the MMC repair). There was a significant correlation between the level of the malformation and the presence of a CM-II at birth (P = 0.003). After MMC closure, only 28 (45.9%) patients had a remaining CM-II. The reversibility rate was 40.4%. The reversibility was higher in lower level malformations (P = 0.004). The number of patients treated for hydrocephalus was significantly higher in the group of patients with remaining CM-II (P = 0.004). Only 11.5% of the children needed surgery for a symptomatic CM-II.

Conclusions

MMC is not always associated with CM-II. The outcome of CM-II has improved. Postnatal closure can reverse the CM-II. This must be kept in mind when analyzing the result of prenatal series.

Introduction

Chiari type-II malformation (CM-II) has long been associated with spina bifida and especially myelomeningocele (MMC).1 The first description of CM-II was made by Jean Cruveilhier (1791–1874)2 in a patient with MMC, long before Arnold and Chiari provided its definitive anatomic description. His description was “…the upper part of the cervical region, considerably enlarged, contained both the medulla oblongata and the corresponding parts of the cerebellum which was elongated and covered the fourth ventricle which itself became longer and wider”.2 It has been reported that >80% of patients with MMC at birth have tonsillar herniation.3, 4 This finding seems to be stable as data remain comparable among studies.5, 6, 7, 8, 9 Improvement of the hindbrain herniation after prenatal closure of MMC5 has challenged the idea that this condition was irreversible.10 To our knowledge, only 2 studies8, 11 reported the possibility of the ascent of the tonsil in a group of patients with MMC who were operated on after birth. However, these studies had several limits, such as the small number of patients and a short follow-up.

The knowledge of the reversibility of CM-II after postnatal repair is of tremendous importance as one of the main arguments for prenatal repair is the prevention of the CM-II. However, it is knows, prenatal repair is associated with fetal and maternal complications that cannot be underestimated.5, 12 In addition, CM-II may lead to later symptoms that could require surgery.3, 6, 8, 13 Therefore, we studied a large group of patients with MMC who benefited from a postnatal repair to evaluate the rate of long-term complete ascent (total reversibility) of CM-II.

Section snippets

Subjects

Inclusion criteria were all patients with MMC who were operated on postnatally in our center, a radiologic examination that confirmed the diagnosis of MMC, a preoperative brain radiologic evaluation (magnetic resonance imaging [MRI] or computed tomography scan) to assess the presence or absence of CM-II, a postoperative brain radiologic evaluation (MRI or computed tomography scan) to assess the reversibility of CM-II, data regarding the management of hydrocephalus (need for surgery to control

Results

Ninety-five patients were extracted from the service database. Sixty-one patients met the inclusion criteria and were included in this study. They were operated on between October 1997 and September 2016 by the same senior neurosurgeon (C.M.). The mean time of follow-up was 8.1 years (minimum, 6 months; maximum, 18 years; standard deviation, 4.6 years).

Prenatal diagnosis of MMC was done in 36 of 61 cases (59%). Mean gestational age at delivery was 38 weeks. Among the 61 patients included in the

Discussion

CM-II is frequently associated with MMC, as reported in historic6 and recent5, 7, 8, 9 cohorts. The belief of a systematic association MMC and CM-II is, however, not accurate. Radiologic examination with a systematic MRI performed after birth and before the closure of the MMC have showed that only 80% of the patients with MMC have a CM-II as reported in the literature. From a clinical point of view, the improvement of surgical techniques with the use of microscope and the decrease of infectious

Conclusions

CM-II remains a main feature of the MMC, but it is not always associated with it. One could argue whether a MMC without a CM-II can be considered an authentic one, but at present, it is not possible to say otherwise as the radiologic examination performed at birth confirmed it with typical MMC on MRI, the absence of CM-II is not uncommon. Therefore, the absence of CM-II on prenatal examination cannot rule out the diagnosis of MMC. The overall outcome of CM-II has improved with less morbidity

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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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