Keywords
Chiari malformation - Lückenschädel - craniosynostosis - hydrocephalus - ventriculostomy
Palavras-chave
malformação de Chiari - Lückenschädel - craniossinostose - hidrocefalia - ventriculostomia
Introduction
Lückenschädel and craniosynostosis are an unusual and little-known association with
possible genetic origin, representing one of many possible phenotypes for a mutation
in the FGFR2 gene.[1]
[2]
[3]
[4] The Chiari malformations are a complex group of anatomic anomalies that usually
is associated either to the Lückenschädel or to craniosynostosis. To the best of our
knowledge, the association between these three anomalies has not been reported before.[1]
[2]
[4]
[5]
[6]
[7]
[8] In this study, the authors aim to describe this extremely rare association and to
provide a review of the literature.
Discussion
The complex of Chiari malformations was first described in 1883 by Cleland, and graded
in 1891 by the Austrian pathologist Hans Chiari. It denotes a heterogeneous group
of anatomical anomalies involving the posterior cranial fossa, the cerebellum, brain
stem, and cranial-cervical junction, with or without changes in the lower cord. Classically,
there are four accepted subtypes of malformations. Types 1 and 2 are the most prevalent,
with an incidence ranging from 1 to 5 thousand births. Recently, authors have proposed
subtypes 1.5 and zero, although this has not yet become widespread.[5]
[6]
[7]
[8]
[9]
[10]
Subtype 4, presented by the authors, is uncommon, and rarely is associated with tonsillar
herniation. It is characterized by a small posterior fossa, with cerebellar hypoplasia,
hypoplasia of the tentorium, and low-setting torcular herophili.[5]
[6]
[7]
[8]
The Lückenschädel is one bone abnormality that can be found in association with Arnold-Chiari
(assimilation of Atlas, atlantoaxial dislocation, Klippel-Feil anomaly, platibasia,
basilar invagination), being the most unusual and generally associated with subtype
2, the most serious of the complex. This condition reaches 82% incidence in some series;
however, the frequency of association with other subtypes of Chiari malformations
is not known.[1]
[2]
[11]
[12]
Also called craniolacunia, lacunar skull, or fenestrated skull, the Lückenschädel
consists of a defect in the bones of membranous origin that form the cranial vault.
This anomaly is due to periosteal dysplasia, and is characterized by rounded and irregular
gaps in the skull, bounded by bony ridges. Pathologically such failures are completely
devoid of bony structure formed by only a membranous diaphragm of periosteum and dura
mater. The same defect is not found in the skull base bones, which have cartilaginous
origin.[1]
[2]
[3]
[4]
[11]
[12]
[13]
[14]
[15]
[16]
The association between Lückenschädel and craniosynostosis is already known, but uncommon,
occurring in 10% of cases of craniosynostosis. It is likely caused by mutations in
the FGFR2 gene (fibroblast growth factor receptor 2) involved in the genesis of craniosynostosis,
which have been found in cases of craniolacunia, raising suspicion that mutations
in different exons would be responsible for different phenotypes.[4]
[17]
[18]
[19]
[20]
[21]
[22] This would explain the association in the present case.
The Lückenschädel and craniosynostosis diagnoses are done through imaging studies,
both X-ray and computed tomography, in which is possible to see the bone defects and
fusion of the cranial sutures. When examining X-rays or CT with 3D reconstruction,
the skull assumes the aspect of a hive, which is a typical characteristic of Lückenschädel.[1]
[2]
[3]
[4]
[11]
[12]
[13]
[15]
[16]
[21]
[23]
[24]
This anomaly usually does not require treatment because the ossification tends to
normalize between the fourth and sixth month of life, and does not directly reflect
in brain development.[1]
[3]
[4] Given its spontaneous and early resolution, it is not seen in adults, which contributes
to the low rate of diagnosis of this condition.[1]
[3]
[4] The Chiari malformation type IV also tends to be asymptomatic, except for the few
cases where there may be tonsillar herniation, determining syringomyelia and/or hydrocephalus.
In this case, neurosurgical intervention is required, as in the present case.[5]
[6]
[7]
Craniosynostosis implies surgery for aesthetic and functional purposes and should
be performed as early as possible after diagnosis.[23]
[24]
The association between Chiari 4 malformation, Lückenschädel and craniosynostosis
is extremely unusual, being so little known and diagnosed; however, newborn imaging
studies may increase the diagnostic rate of these diseases and better guide the medical
care of such cases.
