Anterior Encephaloceles: A Study of 92 Cases

Anterior encephaloceles are a group of rare congenital malformation of the brain encountered in 1:40,000 live births [1, 2]. Surprisingly, a higher incidence is reported from the Southeast Asian countries [3, 4, 5]. In India, the condition is more frequent in the northern parts as compared to western and southern India. In this paper, we analyze a series of 92 cases of anterior encephaloceles. We considered anterior encephaloceles to be those where the swelling was in front of the coronal suture or located in the orbit or nasal cavity.

Ninety-two patients with anterior encephaloceles treated at our Institute over a 30-year period (1971–2000) were retrospectively analyzed. Their clinical features, computed tomography (CT) scan findings and postoperative complications were carefully studied. After 1978, all patients had CT scans with bone windows. CT scans were carefully evaluated for the site of the skull base defect, in order to accurately classify the encephaloceles. Surgery was planned meticulously in consultation with plastic surgeons. Prior to 1988, classical Tessier’s operations [6]were carried out. However, since 1988, hemiorbital advancements were performed, as described by us elsewhere [7, 8]. Postoperative complications were carefully observed and promptly treated. Patients were regularly followed up in outpatient clinics for a period ranging from 6 months to 21 years (mean 8.3 years).

The ages of the patients ranged from 1 day to 15 years. However, there were only 3 patients above the age of 10 years. Surprisingly, only less than 40% were under 1 year of age (fig. 1). Children with nasal obstruction presented earlier than the frontoethmoidal group, even if the encephalocele was apparent at the time of birth. Frontoethmoidal encephaloceles were by far the commonest type (n = 76), followed by orbital encephaloceles, which occurred in 7 patients (6 of them had neurofibromatosis). Rare cases of transsellar transsphenoidal encephaloceles were noticed in 2 patients (table 1).

Clinically, there were two groups, the first being the overt type in which the encephalocele was visible from outside, and the second being the occult type, such as the nasopharyngeal type. Swelling over the nose was recorded in 76 patients and proptosis in 10 patients. Twelve patients had a history of CSF leak, of which 4 had a history of meningitis. Varying degrees of hypertelorism were observed in 66 patients. Two patients had associated cleft palate (table 2). Detailed mental and psychological evaluation was not possible preoperatively since most of the children were small. However, there was no significant derangement of higher mental function or focal neurological deficit.

CT scan was performed in 85 patients and showed a bone defect in 82 patients. Orbital encephalocele and a nasopharyngeal mass were noticed in 7 and 8 cases, respectively. Congenital anomalies like hydrocephalus were noticed in 12 patients and corpus callosum agenesis in 5 patients. Dandy-Walker malformation was recorded in 1 patient only (table 3).

Since our study extended from 1970 to 2000, a large proportion of the cases did not have magnetic resonance imaging (MRI) studies performed. However, in the latter years of the study, MRI scans (12 patients) and three-dimensional CT scans (6 patients) were performed. Three-dimensional CT scans are useful for the proper assessment of the bone defect and evaluation of and surgical planning for hypertelorism (fig. 2a–c). MRI is a useful modality for the diagnosis and management of nasoorbital encephaloceles (fig. 3a, b). We encountered 1 case of polygyria and heterotropia in our series. However, we feel that regular MRI should be done in all cases to check for associated neural dysgenesis.

Surgery was planned according to the type of encephalocele and associated hydrocephalus. Eight patients required a ventriculoperitoneal shunt as the first procedure, several days prior to the corrective surgery. A one-stage operation was carried out in all patients. In all cases of frontoethmoidal encephaloceles, the herniated brain lying in the nose or nasopharynx was excised and did not contain any significant vital structures. Classical Tessier’s operation [6]was undertaken in 30 patients (fig. 4a, b). In 46 patients, medial advancement of the medial half of both orbits was carried out to correct hypertelorism [7, 8](fig. 5a, b). A bone graft repaired the gap created over the supraciliary region in the midline (table 4).

In orbital encephaloceles, the encephaloceles were delivered into the cranial cavity and bone grafting was carried out at the region of the sphenoid wing. Transpalatal repair was carried out for both the patients with transsellar transphenoidal encephaloceles; the brain was pushed into the cranial cavity followed by basal dura and bone repair. In one such case, the hypothalamus and third ventricle were lying in the sac; it was delivered into the intracranial cavity, duraplasty was performed with a pericranial graft and the skull base was repaired with rib graft. However, both these patients developed postoperative CSF leak and meningitis (table 4).

CSF leak was the most frequent postoperative complication, noticed in 20 patients. In 15 of these 20 patients, the CSF leak stopped after a few days, and the remaining 5 patients with persistent CSF leak required a thecoperitoneal shunt. Three children developed postoperative pneumonitis; among them, 1 infant succumbed to fulminant pneumonia. Two other deaths were due to meningitis. Wound infection and osteomyelitis was recorded in 2 and 1 patient, respectively. All the patients received anticonvulsants for a variable duration. Postoperative follow-up ranged from 1 to 21 years (mean 8.3 years). Three children had recurrent convulsions for which they required long-term antiepileptic drugs and 2 developed hydrocephalus in the first 6 months and required a ventriculoperitoneal shunt. The overall long-term cosmetic result was good. No patient had any focal neurological deficit (table 5).

Anterior encephaloceles are uncommon lesions, and except for the series of Suwanwela and Suwanwela [9]in 1972, not many large series have been reported in the literature [7]. Even from India, earlier series reported only a small number of cases [1, 10, 11]. However, in an earlier publication, we had reported a series of 65 cases [7].

It is surprising that only 40% of the children in the present series reached us before 1 year of age. A 1-day-old neonate was the only newborn who came to us, as he was leaking CSF. It was interesting to observe 3 children with a frontoethmoidal encephalocele who were above 10 years of age when they came to us.

Frontoethmoidal encephalocele is the most frequent type [3, 7, 9]. Even in our earlier publications, we found frontoethmoidal encephaloceles to be the commonest, and among them, the nasoethmoidal type was the most frequent [1, 7, 10]. Similar observations have been reported by other authors [2, 9]. In our present study, 76 out of 92 patients had anterior encephaloceles of the frontoethmoidal type; among them, 63 belonged to the nasoethmoidal subgroup.

The type of presentation depends upon the type of encephalocele. Patients with frontoethmoidal encephalocele have an elongated nose and hypertelorism. Patients with the nasopharyngeal type have nasal obstruction or CSF rhinorrhea. Sometimes these patients may present with meningitis. Proptosis is a prominent feature of orbital encephalocele. However, proper diagnosis is necessary for planning surgery. Currently, CT scan is very helpful in evaluating bony defects and the brain for associated anomalies. In our study, hydrocephalus was observed in 12 patients and corpus callosum agenesis was recorded in 5 patients. Associated anomalies have also been reported by other authors [4, 7, 9, 10, 12]. Suwanwela [3]had reported mental retardation in a higher percentage of patients.

Surgery for these lesions is aimed at the repair of the encephalocele and correction of bony anomalies [2, 6, 7, 8, 10, 12]. Hence, accurate assessment of anomalies and planning of surgery is important [2, 4, 6, 8]. A large number of factors influence the type and the extent of the surgery, which include the type of encephalocele, size of external swelling, degree of hypertelorism and associated anomalies like hydrocephalus and cysts.

The presence of hydrocephalus requires ventricular diversion [1, 7, 8], while a leaking encephalocele may need emergency surgery to prevent meningitis. The presence of meningitis would suggest postponement of major surgery for several weeks. The degree of hypertelorism determines the extent of the osteotomies [2, 3, 6, 7, 13, 14, 15]. In the present study, a classical Tessier’s operation [6]was carried out in 30 patients. However, we realized that mobilization of the entire orbit is not necessary for correction of encephalocele. Hence, since 1988, medial advancement of the medial halves of the orbits was carried out [7, 8, 16, 17]. This procedure reduces the blood loss in these patients, who by and large are infants with a body weight under 6–8 kg. Forty-six of these patients had hemiorbital advancement. In 2 patients with transellar transsphenoidal encephaloceles, a transpalatal approach was carried out. Postoperatively, thecoperitoneal shunt was carried out in 5 patients with persistent CSF leak.

Our overall results were good. However, we have previously reported low mortality [1, 7, 16]. Among the 3 deaths in our study, 1 was an 8-month-old baby who developed aspiration pneumonia on the 8th postoperative day and expired within 24 h. Two other deaths were due to meningitis; 1 of them had undergone transpalatal repair of a transsphenoidal encephalocele. The most important complication was CSF leak, which largely stops within a few days. In only 15–20% of patients, the CSF leak may be persistent. Our study is one of the few large studies on the subject and highlights the low mortality and the need for hemiorbital advancement for the correction of hypertelorism.

Anterior encephalocele is a rare condition. We have collected 92 cases over a 30-year period. Hypertelorism is a common bony anomaly associated with these children. A significant number of patients may have hydrocephalus or other anomalies. One-stage correction at the age of 8–10 months is ideal. Lately, we have been undertaking medial advancement of both hemi-orbits, which provides adequate correction of the hypertelorism. Overall, the cosmetic outcome was good in our study.