Encephaloceles most probably occur as a result of mesodermal abnormality that causes a defect in the calvarium and dura through which protrudes the brain tissue. This usually occurs at 8–12 weeks of gestation [13]. The associated risk factors remain obscure. Risk factors include hyperthermia, genetic background, maternal nutritional deficiency, aflatoxin, or other environmental factors [14]. Children with occipital encephaloceles had a higher rate of progressive hydrocephalus and developmental delay than those with anterior lesions [3].
Females were affected predominantly (10/17, 58.8%) in this study which correlates with previous reports [14]. The mean age of the children was 1.6 (range, 0–15) months. The size of the encephalocele sac ranged from 1.5 to 15 cm, with a mean of 4.5 cm in maximal diameter. Ten encephaloceles (58.8%) contained neural tissue. Kiymaz et al. reported 30 children with occipital encephaloceles (22 girls and 8 boys), whose ages varied between newborn and 14 months. The encephalocele sac was located in the occipital region in 27 patients (90%) and in the occipitocervical region in 3 patients (3%). The range of size measurements of 21 sacs was from 1 × 1 cm to 20 × 20 cm. Neural tissue was present in 16 of the patients, while it was absent in 14 patients [9].
The contents of the sac varied from dysplastic diverticulum to brain tissue with some amount of CSF always present. The skull defects are frequently small. Larger occipital encephaloceles herniating through smaller bony defects require urgent surgical intervention to avoid damage to the functioning brain tissues and intracranial vessels that go in and out of the sac to supply the brain tissue. Excision of the protruded neural tissue should be performed without affecting the vessels, especially veins and sinuses; otherwise, massive brain infarction may occur [15]. Microscopic surgery can achieve these goals more efficiently. In this series of patients, there was no infarction postoperatively after the repair.
Prenatal ultrasonography can be used to detect an encephalocele and the presence or absence of brain tissue within the sac [5]. Hydrocephalus is often not present prenatally. Hydrocephalus may develop due to torsion of the aqueduct of the Sylvius, sinus, or aqueduct stenosis. Hydrocephalus may also occur after elimination of the encephalocele because of changes in the CSF circulation dynamics or obstruction of the sagittal sinus which may occur during closure of the encephalocele. Various patient series show that hydrocephalus is associated with large posterior encephaloceles [10, 11], although it is more likely to develop following repair of the lesion than be present at birth. In our study, hydrocephalus was observed preoperatively in four patients (36.4%) who were treated by placing VP shunt before the repair of the sac. Meanwhile, seven children (63.6%) developed hydrocephalus after surgery; six of them were again successfully managed by VP shunt as second surgery.
There is always a chance of infection in large encephalocele usually because there is a leakage of CSF [16]. In this study, one neonate presented with infected CSF leaking from the encephalocele and he was managed with proper antibiotics and regular sterile dressings and a temporary CSF drainage. VP shunt was required later on after clearance of infection. All surgeries were elective except two patients that were admitted with rupture of the sac and CSF leakage which were repaired on emergency basis. Infections could increase the rates of morbidity and mortality in these patients.
In this study, eleven children (64.7%) had hydrocephalus where ten of them (90.9%) were managed by VP shunt. We did not apply endoscopic third ventriculostomy (ETV) in any child in this study due to the known poor results of ETV in this age group due to underdeveloped subarachnoid space. However, in one study, it was concluded that ETV can be an effective treatment option for encephalocele-associated hydrocephalus, even in children under the age of 1 year and it may obviate the need for placement of CSF shunts that have a risk of infection and malfunction. However, they reported that delayed failure of ETV may occur as seen in their first patient, indicating the need for careful and long-term follow-up [17].
In our study, 35.3% of children had severe developmental delay and 47.1% had mild or moderate delay while 17.6% had a normal neurological outcome. This result is higher than other reports which found that 16–31% of the children were physically and/or mentally disabled such as those reported by Tsuchida et al. [18], Docherty et al. [19], Date et al. [20], Macfarlane et al. [21], and Martínez-Lage et al. [22]. This is maybe due to many of encephaloceles in our study contained neural tissue (10, 58.8%), most of the children had hydrocephalus (11, 64.7%), and many infants had associated intracranial and extracranial anomalies (10, 58.8%). Among the hydrocephalic patients in this study, none had a normal neurological outcome. This is in agreement with previous reports that found that hydrocephalus is significantly associated with cognitive deficit in children with encephaloceles [3, 20, 23]. Da Silva et al. reported seventy children with encephalocele (14 anterior and 56 posterior encephaloceles). Their outcome showed that 14 patients (20%) had severe developmental delay, 28 (40%) had mild/moderate delay, and 28 (40%) were neurologically normal. In their series, none of the patients with hydrocephalus had a normal neurological outcome; all 17 children had some degree of developmental delay, including 11 (65%) with mild/moderate delay and 6 (35%) with severe delay [24].
Microcephaly is a poor prognostic factor which is associated with developmental delays. It sometimes makes the relocation of herniated neural tissue more difficult, with a subsequent increase in intracranial pressure [9]. Gallo described a technique where an extracranial compartment is prepared utilizing fine tantalum mesh to enclose the neural contents. This mesh is attached to the periphery of the skull defect providing a rigid extracranial compartment for the encephalocele. As intracranial pressure increases, the calvarium is forced to expand [25]. We did not face this problem in our series as all the gliotic brain tissue which was protruding out of the skull was excised when needed with the aid of preoperative imaging that was carried out to identify this type of tissue and to detect any involved blood vessels. This is similar to the findings of other series [9]. Three of our patients had associated Dandy–Walker cysts along with hydrocephalus. Hydrocephalus should not be treated before treatment of Dandy–Walker cyst due to the risk of upward herniation of posterior fossa contents. Hydrocephalus and Dandy–Walker cyst are usually treated in the same setting by a single shunt system connected through Y connector. Other options include posterior fossa cyst drainage alone or ventricular drainage alone [26].
A seizure is an important factor to affect the quality of life in children with occipital encephalocele [3]. Bui et al. reported an incidence of seizures in occipital encephalocele of 17% [27]. In our study, the seizure was noted in two children (11.8%) who developed it following the repair which is slightly less than other reported studies [3, 19]. Seizures in these patients were well-controlled with antiepileptics after surgery. Mortality was 5.9% in this study which correlates to recent reports [24].
The limitations of this study include that it is a retrospective one with no limitation during patient selection by the volume of viable neural tissue. Prospective studies with more concern about the volume of viable neural tissue and the quality of the life of the patients following surgery for occipital encephaloceles with hydrocephalus are recommended to authenticate the results.
