Key-words:
Intradiploic - leptomeningeal cyst - posterior fossa growing skull fracture - syringomyelia
Introduction
Growing skull fracture (GSF) is a progressively enlarging diastatic fracture associated
with an underlying dural laceration. It is a rare complication of head injury. The
incidence of GSF is reportedly in 0.05%–1.6% of pediatric skull fractures.[[1]] They mostly occur in the first decade of life although occurrence in later decades
has been reported.[[2]],[[3]],[[4]] The posterior fossa is an uncommon location for the development of GSF, as it is
intradiploic in nature. Only a few cases of pediatric GSF of the posterior fossa and
intradiploic location have been reported in the literature.[[2]],[[3]],[[5]],[[6]],[[7]],[[8]]
We report a 15-year-old boy with a large posterior fossa intradiploic GSF associated
with syringomyelia that developed progressively over 5 years after a documented linear
occipital fracture.
Discussion
GSF most commonly occurs in the parietal bone. It rarely occurs in the temporal or
occipital bones probably because of the overlying muscles in these areas that prevent
its development.[[2]] Only a few previously reported pediatric cases of posterior fossa GSF were intradiploic
in the location.[[2]],[[3]],[[5]],[[6]],[[7]],[[8]] Palaoglu et al.[[3]] reported that leptomeningeal cysts involving the occipital bone represent a different
radiological entity showing an intraosseous location. Posttraumatic intradiploic leptomeningeal
cysts are extremely rare complications of calvarial fractures occurring in pediatric
patients. These cysts are characterized by fracture of the inner table and laceration/tear
of the dura mater with accumulation of CSF in a sac with a covering lined by arachnoid
membrane and situated within the diploic space. Almost all patients have a history
of trauma with the time interval between trauma and diagnosis of posttraumatic intradiploic
leptomeningeal cyst being extremely variable. Clinical presentation may include a
slow-growing swelling associated with headache, giddiness, and occasionally ataxia.[[9]]
The most widely agreed-upon hypothesis proposes the herniation of leptomeninges into
the intradiploic space through the traumatic rent in the dura mater and inner table.
The ball and valve effect due to the child's growing brain and the continuous CSF
pulsations act as driving expansile forces facilitating the growth of the intradiploic
cyst over the years with resultant thinning of the outer table. The thickness of the
occipital bone and the thick muscle cover buttressing its outer table explain the
predilection of this entity to normally prevent occurring in the occipital region.
Other contributory factors in this regard may include the more capacious diploic space
as well as cartilaginous origin of the occipital bone compared to the membranous origin
of the rest of the calvaria. Communicating type of hydrocephalus is often seen to
occur along with posterior fossa GSF and may be attributed to the intraventricular
hemorrhage at the time of initial trauma.
The common features of intradiploic GSFs are an intact outer table, a CSF-filled cyst,
and a defect in the inner table and dura. The cysts are generally lined with arachnoid
membrane.[[6]] It has been argued that because of the actual thickness of the occipital bone,
a fracture confined to the inner table and the associated dural laceration might result
in leptomeningeal cyst formation.[[2]],[[3]],[[6]] In our patient, however, the occipital linear fracture involved both inner and
outer tables and was associated with syringomyelia, and thus the presented case differs
from other cases reported in the literature.[[2]],[[3]],[[5]],[[6]],[[7]],[[8]]
Surgical repair of the dural and bony defect is the mainstay of treatment. It involves
watertight duraplasty followed by cranioplasty using autologous split calvarial graft
or Osteomesh. The technique of cranioplasty using Osteomesh is our original adaptation
for this type of bone defect.[[10]]
To our knowledge, this is only the seventh reported case of a large GSF of the posterior
fossa which was intradiploic in the location.[[2]],[[3]],[[5]],[[6]],[[7]],[[8]] It demonstrates that a GSF may reach a considerable size, and although uncommon,
intradiploic development and occipital localization of GSF are also possible.
Our case is unique from previously reported cases in regard to the fact that he had
cervical syringomyelia, which is highly unusual. We postulate that syrinx might be
secondary to altered CSF dynamics at CVJ due to posttraumatic adhesions.
Informed consent
Written informed consent was taken from the parent for the publication of data in
this journal.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form, the patient has given her consent for her images and other clinical information
to be reported in the journal. The patient understands that name and initial will
not be published and due efforts will be made to conceal identity, but anonymity cannot
be guaranteed.
