Keywords
encephalocele - transpalatine - transsphenoidal - meningoceles
Palavras-chave
encefalocele - transpalatal - transesfenoidal - meningocele
Introduction
Encephalocele consists of the herniation of parts of the intracranial contents through
a bony defect in the skull. Cranial meningoceles involve cases in which the content
of the herniated sac is composed of meninges, delimiting a sac containing cerebrospinal
fluid (CSF).[1]
The incidence of encephalocele is approximately one case per 3,000–5,000 live births.[2]
[3]
[4] Basal encephaloceles are less common, with an incidence of one case per 35,000 live
births.[5]
[6]
[7] Basal encephaloceles are classified into transethmoidal, spheno-orbital, sphenomaxillary,
and transsphenoidal.
The transsphenoidal type represents less than 5% of all cases of basal encephalocele,
with an incidence of one in 700,000 live births.[8]
The treatment is controversial because of the rarity of the condition. Herein we present
the case of an 8-month-old child operated via the transsphenoidal–transpalatine route.
Case Report
An 8-month-old female child presented with difficulty in breathing (respiration via
tracheostomy) and difficulty in feeding (fed via a nasogastric tube). Oroscopy indicated
bulging of the palate without evidence of cleft palate. The endocrinological and ophthalmological
examinations were unremarkable. Cranial computed tomography (CT) and magnetic resonance
imaging (MRI) revealed sphenoid bone defect ([Fig. 1]) with the presence of transsphenoidal meningoencephalocele ([Fig. 2]).
Fig. 1 Axial computed tomography (CT) scan with sphenoid bone defect (arrow).
Fig. 2 Sagittal T2-weighted magnetic resonance imaging (MRI) showing (arrows) transsphenoidal
meningoencephalocele.
The patient underwent surgical correction of the malformation via the transsphenoidal–transpalatine
route ([Fig. 3]). Under general anesthesia, a midline incision was made in the soft palate until
the limit of the hard palate. This procedure was followed by the dissection of the
mucosa and the herniated sac, and the reduction of the herniated sac to a minimum
by bipolar coagulation without opening the dura mater. After marking the edges of
the bone defect, an incision was made in the herniated sac, a segment of the sac was
resected, and the sac was closed with a reinforcement suture. Then, Surgicel (Ethicon,
Somerville, NJ, USA), a hemostatic sponge, and a dural sealant were used. Postoperatively,
the clinical course of the patient was uneventful (without bleeding, fistulae, or
endocrinological changes). On the fifth postoperative day, the patient was decannulated,
and she could spontaneously breathe again ([Fig. 4]). On the 15th postoperative day, the nasogastric tube was removed, and the patient
began to eat via the oral route without gagging.
Fig. 3 Transsphenoidal–transpalatine approach.
Fig. 4 Sagittal T1-weighted magnetic resonance imaging (MRI) showing the status after treatment
with permeabilization of the upper airways (arrow).
Discussion
Several theories have been proposed to explain the formation of transsphenoidal encephalocele.
The classical theory postulates that the lack of separation of the neuroectoderm from
the ectodermal surface during the formation of the neural tube prevents the insertion
of the mesodermal tissue between the two germ layers and causes changes in the skull
ossification, as well as a secondary herniation.[9]
[10] Another theory states that the incomplete closure of the neural tube, together with
the herniation of the meninges and neural tissue, may be due to a persistent craniopharyngeal
canal.[8]
[11]
[12]
Transsphenoidal encephalocele is associated with abnormalities in the development
of the face, the optical system, and the encephalon.[10]
[13]
[14]
[15] Facial malformations are usually present and involve hypertelorism, median nasal
fissure, enlarged nasal base, cleft lip or palate, median cleft face syndrome, or
occult frontal cranium bifidum.[7]
[16]
[17] Optical abnormalities include anophthalmia or microphthalmia, coloboma, retinal
abnormalities, and hypoplasia of the optical nerve or chiasm.[16]
[18] Brain changes include agenesis of the corpus callosum (in more than 50% of cases),
hydrocephalus, and pituitary dystopia or hypoplasia.[19]
[20]
[21]
Transsphenoidal encephalocele is usually asymptomatic or is occasionally diagnosed,
and the most common presentation is the presence of a mass in the cranial midline.[10] Clinical manifestations, when present, depend on the age of the patient.[16] In the absence of facial changes, the diagnosis can be made in adolescence or adulthood
in cases in which rhinorrhea, meningitis, or unexplained progressive visual defect
require examination and diagnosis.[5]
[7]
[22] Other complications may occur, including hypothyroidism, growth retardation, hypogonadism,
or diabetes insipidus.[16]
[22]
[23] The sphenoid bone defect may cause herniation of intracranial structures, including
the third ventricle, segments of the hypothalamus and pituitary gland, anterior cerebral
arteries, or optical chiasm.[5]
[7]
[16]
[23] Considering that the tissue is a nasal mass, the differential diagnosis for glioma,
dermoid cysts, and polyps should be considered.[24]
Imaging studies are essential for the confirmation of diagnosis and the evaluation
of the contents of the herniated sac.[25] Non-contrast CT scans with three-dimensional reconstruction should be conducted
to evaluate the defect at the skull base. Magnetic resonance imaging should also be
conducted to determine the constituents of the herniated sac.[26] Digital angiography or magnetic resonance angiography are not routinely used, but
may be considered in cases in which the MRI suggests the involvement of the anterior
cerebral arteries.[27]
In the past, many cases of basal encephalocele were wrongly treated as tumors or nasal
polyps, resulting in high mortality because of CSF rhinorrhea and meningitis.[1] At present, because of the rarity of transsphenoidal encephalocele and the small
number of cases reported in the literature, standardization of treatment is controversial.[4]
[7]
[16] Surgical intervention is indicated in cases of airway obstruction and CSF rhinorrhea
or meningitis attributed to the lesion.[28] In asymptomatic individuals and in those with hormonal changes or stable visual
deficit, the indications for repair are less clear.[5]
[7]
[16] Some authors argue that early repair reduces the risk of infection, the growth of
the encephalocele, and the risk of trauma to the herniated sac.[16]
[29]
The use of the transcranial access in the treatment of transsphenoidal encephalocele
remains controversial, especially in neonates and children.[28] Some studies have shown that the transcranial access, with retraction of the frontal
lobe and elevation of the herniated elements via sella turcica, with or without resection
of the cephalocele and its contents, is associated with high rates of hypothalamic
dysfunction, morbidity, and mortality.[7]
[29] Moreover, the use of this route increases the complexity of the surgery because
of the involvement of important blood vessels and nerves located in the area of transcranial
access.[27]
In a few select cases, transnasal endoscopic surgery may be an optional treatment,
particularly for transsphenoidal encephaloceles with a small neck.[1] Its use is well described in adult patients, but less common in pediatric patients,
for which there are fewer descriptions in the literature.[30]
The transsphenoidal–transpalatine approach is an acceptable strategy, without reports
of fatality, despite the higher risk of infection due to the incomplete repair of
the dura mater.[16]
[31]
The choice of correction for the described case was via the transsphenoidal–transpalatine
route. This was possible because, although the child did not have a cleft palate,
we believed that this access route was appropriate for her age and could result in
excellent dural closure. Our patient did not present hypothalamic–pituitary dysfunction,
and we believe that this was either due to the small size of the sphenoid bone defect
or due to us carefully cauterizing the herniated sac to reduce its size to the maximum
before opening it for correction. This strategy prevented greater CSF leakage and
consequently herniation of the pituitary gland.
Conclusion
Although transsphenoidal encephalocele is a rare congenital anomaly, with no consensus
on treatment, the transsphenoidal–transpalatine route is a safe option for the described
age. Moreover, a favorable outcome can be achieved with follow-up by a multidisciplinary
team.
