Neurosurgical management of anterior meningo-encephaloceles about 60 cases

Anterior meningo-encephaloceles (AME) are congenital malformations characterized by herniation of brain tissue and meninges through a defect in the cranium, in frontal, orbital, nasal and ethmoidal regions. The management of this complex congenital malformation is controversial according to whether use, an intracranial, extra-cranial or combined approach. This is the first largest series published in Africa, in which we present our experience in the operative management of AME; we share our recommendation in technical consideration for surgical approach with review of the literature. All patients beneficed of neuro-radiological investigations including Plan X rays, Spiral Three dimensional CT scan and MRI. Ophthalmologic and maxillo-facial evaluations were done in all the cases. MEA are surgically approached in various ways, mainly on the basis of its location and type, by cranio-facial approach in one-step, or in two stages by intracranial approach followed by facial approach, only by cranial approach or facial approach. The surgical results were evaluated in the follow up on the basis of disappearance of cranio-facial tumefaction with correction of hypertelorism. 60 children with AME were treated in our department between January 1992 and December 2012. The mean age at time of surgery was 14 months (20 days to 18 years) with slight men predominance (28 females/32 males). Cranio-facial team operated 21 patients, 16 were operated in two stages by intracranial approach followed by facial approach, 20 cases beneficed the neurosurgical approach and three only the facial approach Some post operative complications were observed: 2 cases of post operative hydrocephalus underwent shunt; CSF fistulas in three cases cured by spinal drainage, one death due to per operative hypothermia, 3 cases of recurrence how needed second surgery. After mean follow up for 80 months (1 year to 19 years) theses techniques permitted a good cosmetics results in 42 cases, average cosmetics results in 8 cases, poor results in 5 cases and worse cosmetics results in 4 cases, The AME are rare conditions we used the multiples approach first intracranial approach followed by facial approach, but after 1998 we used one-step correction by combined approach, only cranial approach when needed or facial correction.


Introduction
In 1855, Finnish physician Karl Benedikt Mesterton described a congenital malformation characterized by the herniation of the mining's and cerebral tissue through a defect in the anterior cranium. He classified this pathological entity, now known as frontoethmoidal meningo-encephaloceles (MEC) into three types according to its location: nasofrontal, nasoethmoidal and naso-orbital. In the same time spring in 1854 wrote an excellent monograph on the subject, which was probably the first major work about this condition. He made a distinction between a meningocele and cerebral hernia. It is an endemic deformity found more commonly in the eastern hemisphere. In Southeast Asia (Thailand, Burma and Cambodia) and parts of India, Russia and Africa, the Highest incidence reported in 13500 live births, this lesions often affect poor rural children in developing countries [1] in contrast North America, Japan, Hong Kong and the western state of Europe the incidence is as low as 1/35000 live births [2]. Its aetiologies are still debated and poorly understood. Many papers have been published on AME treatment with modern medical infrastructures and endoscopy for the transethmoidal encephaloceles. In our department we have operated them in different techniques with cranial or facial approaches depending on the type of the meningo-encephalocele. This is the first largest series published in Africa, in which we present our experience in the operative management of MEA; we share our recommendation in technical consideration for surgical approach with review of the literature.

Methods
All of our patients underwent a clinical evaluation including family history, the follow of pregnancy and delivery, cranio-facial examination and ophthalmologic study. Plain X rays, CT scan and tridimensional computed tomography and MRI study were done for all the patients. We have classified our cases according the classification of Swanwela et al [2] Rosenfeld et al [3] into frontoethmoidal and basal meningo-encephaloceles. Four cases of transethmoidal MEC were referred by ORL after trans-nasal biopsy and CSF leakage, the diagnosis was confirmed by MRI study in this cases. All patients had ophthalmological, ORL examination, to explore others systemic malformations we complete by echocardiography and abdominal echography. Before each operation for the fronto-ethmoidal meningo-encephaloceles, the photographs of the face in different incidences were obtained. The postoperative photographs were tacked and also three months after surgery and yearly schedule.
Surgical technique: All operations were performed with the patient under general anaesthesia. A standard neurosurgical procedure was used to treat AME. After shaving the patient's head, the skull and face were prepared with Betadine and draped. The adrenaline solution was infiltrated along the bicoronal incision line. A frontal galeal flap was elevated, and the dissection continued to the supra-orbital rim. Both supraorbital nerves were dissected from their osseous notch and preserved but when we found the osseous canal we have some difficulties to preserve these nerves. Tissues on the glabellas were then elevated until the rim of the defect made by the herniation was reached. A frontal bone flap was then outlined, with two frontal bur holes and two bur holes at the super medial part of the orbit. The electric drills or giggly saw were used to connect the holes and the rim of the defect to raise the flap. Once the bone flap was elevated and removed, the cerebral hernia was exposed at its base and could then be manipulated to allow ligature of the base (Figure 1). The hernia dissection is the most difficult part of the procedure because the Dura mater in this area in children is thin and adherent to the bone; dissection must be careful to avoid dural tears. The dura was sutured after total resection of the hernia content, the sutures of the dura was usually reinforced with a patch of pericranium and fibrin glue. A piece of cortical bone was used for reconstitution of the glabella region and for the closure of the bony defect in the ethmoidal region; we had never use the osteosynthesis. Medial canthopexy was achieved in all patients. We have used several techniques according the type of the meningoencephaloceles.
The first surgical technique: In the patient with large herniation covered by a large expansion of the facial skin, a combined transcranial and facial procedure was used. The amount of facial surgery varied with the size of the mass and associated abnormalities.
Redundant Para nasal soft tissue was removed in an inverted Yshape, and the nasal tip was hitched up to the nasal bones with no absorbable sutures Outlining incision and resecting the skin, to obtain a minimal residual scar designed to fall into the medial canthal area extending down to the naso-labial fold or up to the midline of the forehead. The meningo-encephalocele was then totally or partially resected so that facial contours would be normalized (Figure 1).

Results
It's the retrospective study about 60 cases of AME treated between 1992 and 2012 in our department. The number of cases has remained similar over the last twenty years ranging from two to three cases on the average per years. This number is higher than the posterior meningo-encephaloceles how is 27cases received in the same period. showed the hypertelorism and the growth of the head circumference was present in 5 cases. The long nose deformity showed in 5 cases, the cornea dystrophy noted in two cases, one case of exophthalmia, 12 patients had dacryocystis. 4 cases were received with Rhinorrhoea after ORL biopsy and one 18 years old girl with orbital encephaloceles was received with ocular leakage of CSF after ophthalmologic surgery. Psychological retardation was found in 3 patients ( Table 1).

Radiological examination
Based on clinical examination and radiological finding, Plain X rays, CT scan and MRI examinations the 53 frontoethmoidal encephaloceles could be classified into: 25 nasofrontal, 7 nasoethmoidal unilateral, 8 nasoethmoidal bilateral, 9 naso-orbital, 4 naso-ethmoido-orbital and 4 trans-ethmoidal ( Table 2). All patients showed an internal median skull defect. In 25 patients this skull defect was situated at the site of the foramen caecum. In the 10 with naso-frontal encephaloceles the skull defect was located just superior to the foramen caecum. In 7 patients the defect was located just lateral of the foramen caecum and in 5 patients with Page number not for citation purposes 4 trans-ethmoidal encephaloceles the defect was located in the cribriform plates. The size of the skull defect ranged between 0.5 x 0.5 to 4.0 x 3.5 cm. the herniated mass was related to one frontal lobe in 35 cases and to both frontal lobes in 22 cases. In three cases it was only meningocels treated by facial approach. Additional intracranial anomalies were seen in 34 patients with 26 patients with normal brain in CT scan and MRI. These additional anomalies were well interpreted with MRI. A list of these findings is presented in ( Table 3).  Table 4).

The illustrative cases
First case: 50 days girl who presented a fronto -nasal meningocele has been operated by neurosurgeons and the maxillofacial procedure simultaneously (Figure 4) shows the preoperative Page number not for citation purposes 5 appearance and Figure 5 shows the appearance of the child 3 years later with a good result Second case: the 9 months old boy with fronto-nasal meningo-encephalocele (Figure 6). Operated first with cranial approach, and facial approach 6 years later. The same boy after facial surgery (Figure 7) with average cosmetics results.

Geographical distribution, incidence and aetiology
Meningo-encephaloceles are not a homogeneous disease entity, occipital MECs predominate in Europe and north America whereas sincipital or AME are common in southeast Asia such Cambodia, Thailand, Burma, Malaysia and Indonesia [1,11,12]. Monteith et al [13] reported ethnic distinctions in New Zealand, with patients of Pacific Island descent having a much higher incidence of sincipital lesions (44%) than those of European origin. Suwanwela et al [2] reviewed the world's literature up to 1970, and also found a very high incidence of sincipital lesions reported from Russia (86%). In the same review, he reported relatively high incidences from South Africa (47%), and Morocco in northern Africa (39%). This condition is also found in India [14], remains obscures and it's same to be sporadic in most cases [12].
The several aetiologies were suggested, genetic predisposition, parental consanguinity. In our series the consanguinity was reported in only 5 cases. The Vitamin B deficiency due to maternal malnutrition and drugs proposed by Suphapeetiporn K et al [15], but refuted by others. Furthermore it's evident for the majority of authors [1,15] this disease has preferential occurrence in poor and rural people. In our series 70% of our patients had rural origin, which could also explain the very low prevalence of AME in developed western countries. Familial cases are very rare we haven't found any familial cases in our series. Oucheng et al. [1] demonstrated that the conception in the wet season might play a role by founding fungal and teratogen agent such Alfa-toxin or Ochratoxin. Wangikar et al [16] reported that the toxins may be present in the diet in higher concentration during the hot, humid months and when foodstuffs are stored for long periods in poorly ventilated rooms. Furthermore, they had demonstrated that the children from Thailand, where AME frequently occur, have high Alfa-Page number not for citation purposes 6 toxin concentration in their secretion and tissues. Warf BC et al [17] in his study for encephaloceles in Uganda in which he compared the date of birth for all the patients and selected those born in rainy season months or dry season months. He concluded: there was not relationship between season of birth and number of sincipital meningo-encephaloceles versus others lesions. In our series we haven't found any correlation between the date of birth and the meningo-encephaloceles, but the majority of the children with this malformation are coming from the rural and poor regions of Morocco. Another factor also maybe involved in the development of encephaloceles is the deficiency of folic acid. Rowland CA et al [18] demonstrated that the prevalence for the encephaloceles hasn't change after fortification with folic acid, but the prevalence rate for Spina bifida had decreased significantly. Although the cause of encephaloceles remains unclear, it appears to involve a variety of genetic and environmental factors.

Pathogenesis and natural history
There has been much speculation about the pathogenesis of AME.
There are several hypotheses: The first hypothesis involves neural tissues herniating through a point of weakness in the facial skeleton. Oucheng et al., [1] demonstrated that the hydrocephalus wasn't an important issue in the treatment of AME, only 4 out of 200 children treated required shunt in the post operative course. David DJ et al [19] concluded: that the presence of hydrocephalus or ventricular enlargement does not necessarily cause problems or require treatment. In our series 4 patients with symptomatic hydrocephalus underwent shunt before craniofacial surgery, and 2 children who developed hydrocephalus after craniofacial repair required shunt 8 days and 15 days post operatively.

Surgical issues
Surgical therapy for this malformation is a complex task, its primary aim being to close reliably the connection between the intra-dural and extra-dural space. The choice of the best surgical treatment for AME is still debated. Meticulous planning is necessary for this choice depending in the type and size of the encephaloceles and associated hydrocephalus. Most authors recommend the combined procedure [1,12,20], the intracranial approach seems essential to us because only this technique guarantees a secure closure of the dura, to remove the encephaloceles and to repair the skull defect. We have used several techniques: neurosurgeon and maxillo-facial team operated 20 patients, 17 cases were operated by craniotomy first followed by facial approach and 19 patients were operated only by craniotomy. 5 were cured by the facial approach. In the interventions using only facial approach by only latero-nasal incision the relapse are common, we used this technique in 5 meningocels with very little cranial defect under 1,5 cm and we haven't had any relapse. But for two cases with a large skull defect, operated in others departments had relapsed and they were transferred in our department, the cranial approach was performed without relapse.
The HULA procedure [14,20] separates the supraorbital region from the medial canthal bone segment to allow for independent movement. The supraorbital bar is lowered and the medial canthal bone segment is positioned postero-medially. It is also important to stress that although the medial canthal segment must be moved medially, hypertelorism isn't treating by this technique. Finally, the procedure stressed a low radix position for the nasal cranial bone graft. We haven't used this method because of the difficulties of dissecting dura matter and meningo-encephalocele and to have a good closure of dura. Each method had its own value in certain situations. We had used several techniques: Facial technique when the skull defect is small and when we have only a meningocele or small meningo-encephalocele. It's easier by paralateronasal approach the meningocels or meningo-encephalocele was dissected and closed in this neck by sutures; we reinforced closure by human glue and a little bone graft, tacked away in iliac crest when needed.
The cranial approach was used for 38 cases with total removal for the meningo-encephalocele and its closure by pericranial graft, the bone defect was closed by bone graft, tacked from the outer table of the skull. This technique permitted a good results and ovoid the scar in the face for 19 patients. But for the 17 patients operated before 1998 the facial repair was performed 5 years after cranial approach. We prefer a combined procedure, which has 3 major advantages: It's allows a better fronto-ethmoidal meningoencephalocele closure, the better telecanthus correction and also reduce a facial scar. All the authors emphasized the advantage of one stage correction.

Post operatives issues
The postoperative complications like any skull base procedure; the CSF leak is the most frequent and dread complication [1,14]. Two patients in our series had postoperative CSF leak treated by spinal drainage. Three factors explain CSF leak: The no watertight closure of dura, an inadequate reconstruction of the skull base and also trans-facial approach. The recommendations of all the authors: The cranial base reconstruction is fundamental with bone graft pericranial patch and surgical glue. The dura mater around the meningo-encephalocele is very thin and must be dissected meticulously in this procedure we recommend to found the thick dura and to do sutures between pericranial patch with dura and reinforced by surgical glue. The trans-facial approach can be avoided when the MEC is small and facial skin of good quality. We hadn't used Trans facial approach for 19 cases. The scars could be avoided by daily treatment. We had only one case that developed the scars healing with trans-facial approach, which was treated by local care. The recurrence can be manage by second surgery, three cases in our series, recurred: one trans-ethmoidal-meningoencephaloceles, operated at the age of 50 days, presented meningitis at the age of three years and the CT scan and MRI showed the local recurrence with total resorption of the bone graft, he underwent second surgery by cranial approach. The two others fronto-ethmoidal-meningo-encephalocele had swelling in the facial scar, two months and six months post operatively, and despite the lumbar puncture followed by spinal drainage, the swelling had persisted, so we decided to do the second surgery by trans-cranial approach. The three cases had good outcome. We have good cosmetics results in 42 cases, medium in 8 cases, poor in 5 cases Page number not for citation purposes 8 and worse in 4 cases ( Table 4). All the patients had a long follow up over 5 years, only 7 cases hadn't schooling; one of them with schizencephaly had delayed psycho motor development. All others children had normal schooling. However the patients with medium or poor cosmetic results have needed some cosmetics surgery they were transferred in the maxillofacial department.

Conclusion
We present our experience on 60 cases of anterior encephaloceles who is one of the largest series in Africa. This malformation can be detectable by antenatal ultra-sonography screening (16-18 weeks).
Imaging workup by CT scan tomography and 3 dimensional CT scan and also MRI allows precise study of meningo-encephaloceles, and associated malformations. Pathogenesis, classification and terminology remain a matter of debate. Surgical repair should be performed as early as possible to ovoid progressive enlargement of this conditions but the caution is required for the anaesthetics difficulties for the new born. The collaboration between neurosurgeon and maxillo-facial surgeon and neuro-paediatric anaesthesiologist is fundamental in this disease.

Competing interests
The authors declare no competing interests.

Authors' contributions
All authors have read and agreed to the final version of this manuscript and have equally contributed to its content and to the management of the case.        Naso-orbital 9