Spontaneous lateral sphenoid cephaloceles: anatomic factors contributing to pathogenesis and proposed classification

SUMMARY

Spontaneous lateral sphenoid cephaloceles arise from bony defects in the lateral sphenoid, in the absence of predisposing factors such as trauma, surgery, mass, or congenital skull base malformation. We reviewed CT and MR imaging findings and clinical data of 26 patients with spontaneous lateral sphenoid cephaloceles to better understand anatomic contributions to pathogenesis, varying clinical and imaging manifestations, and descriptive terminology. Two types of spontaneous lateral sphenoid cephaloceles were identified. In 15 of 26 patients, a type 1 spontaneous lateral sphenoid cephalocele was noted, herniating into a pneumatized lateral recess of the sphenoid sinus, and typically presenting with CSF leak and/or headache. In 11 of 26 patients, a type 2 spontaneous lateral sphenoid cephalocele was noted, isolated to the greater sphenoid wing without extension into the sphenoid sinus, presenting with seizures, headaches, meningitis, cranial neuropathy, or detected incidentally. All patients had sphenoid arachnoid pits, and 61% of patients had an empty or partially empty sella, suggesting that altered CSF dynamics may play a role in their genesis.

Are encephaloceles neural tube defects?

OBJECTIVE

Encephalocele is classified as a neural tube defect, but questions have been raised regarding whether its epidemiological characteristics are similar to those of other neural tube defects.

DESIGN

We compared characteristics of temporal trends in, and the impact of folic acid grain fortification on, the prevalence of encephalocele, spina bifida, and anencephaly using data from the Metropolitan Atlanta Congenital Defects Program, a population-based birth defects surveillance system. Prevalences of encephalocele, spina bifida, and anencephaly were compared by maternal age, gender, race, birth weight, ascertainment period (1968-1981, 1982-1993, or 1994-2002), and fortification period (1994-1996 [prefortification] and 1998-2002 [postfortification]) using prevalence ratios with 95% confidence intervals. Temporal trends were assessed using Poisson and negative binomial regression models.

RESULTS

Prevalence rates of encephalocele (n = 167), spina bifida (n = 650), and anencephaly (n = 431) were 1.4, 5.5, and 3.7 per 10 000 live births, respectively. Encephalocele was similar to anencephaly in showing an increased prevalence among girls and multiple gestation pregnancies and to spina bifida and anencephaly in an annual prevalence decrease between 1968 and 2002 (-1.2% for encephalocele, -4.2% for spina bifida, and -3.6% for anencephaly). With fortification, prevalence decreased for spina bifida but not significantly for encephalocele or anencephaly.

CONCLUSIONS

Encephalocele shows more similarities to spina bifida or anencephaly than it shows differences with respect to characteristics, temporal trend, and impact of fortification. Additional studies should be done to explore the etiologic heterogeneity of encephalocele using better markers of folate status and a wider range of risk factors.

Frontoethmoidal encephalomeningocele: new morphological findings and a new classification

Given a lack of a comprehensive classification for the frontoethmoidal encephalomeningocele (FEEM), clinical, photographic, and computed tomography (CT) data of 23 nonoperated patients were reviewed. Extracranial pathological findings of interest included herniation masses, facial deformities, and frontonasal bone morphology. Intracranial pathological findings of interest included morphology of the anterior cranial floor and brain malformations. Stereographic software processed data from a new-generation CT scanner into three-dimensional pictures that revealed some interesting morphological findings not often appreciated (eg, herniation mass without underlying external bone defect; mass at location far from external bone defect ["sequestrated cephalocele"]; new type of external bone defect characterized by a combination of nasoethmoidal and naso-orbital defects; correlation between mass, external bone defect, and exit pathway of herniation). Given these observations plus current knowledge available in the medical literature, a new classification system was developed that covers phenotypes and severity of the disease. The "FEEM classification" is an alphanumeric system based on facial deformities, external bone defect, exit pathway of herniation, and malformation of brain. It was tested in 42 patients for usability and validity. When combined with a newly designed "FEEM diagram," relevant pathological findings can be recorded in an objective manner so that diagnosis becomes more precise and uniform and comparison of outcome is possible. It also emphasizes the fact that FEEM has a range of manifestations governed by dynamic interaction between structural defects and herniation. Each clinical entity is a final result of its own disease course (stable, progressive, or regressive FEEM), with a varying degree of communication between the external mass and the central nervous system.

Common craniofacial anomalies: facial clefts and encephaloceles

The wide variety of craniofacial malformations makes classification difficult. A simple classification system allows an overview of the current understanding of the causes, assessments, and treatments of the most frequently encountered craniofacial anomalies. Facial clefts and encephaloceles are reviewed with respect to their diverse causes, pathogenesis, anatomical features, and treatments. Approaches to the surgical treatment of these conditions are reviewed.

Encephalomeningocele cases over 10 years in Thailand: a case series

BACKGROUND

Encephalomeningocele, especially in the frontoethmoidal region, is a form of neural tube defect which affects patients in Southeast Asia more commonly than in Western countries. Its underlying cause is not known but teratogenic environmental agents are suspected. However, nutritional deficiency, as in spina bifida, cannot be excluded.

METHODS

This study reports 21 cases of meningocele (without brain tissue in the lesion) and encephalomeningocele (with brain tissue) that were admitted to our hospital for surgical corrections in the period of ten years, from 1990 to 1999. Clinicopathological findings, as well as occupations of family members and prenatal exposures to infectious agents or chemicals were reviewed and analyzed.

RESULTS

The most commonly involved area was the frontoethmoidal region, found in 20 cases. The combined pattern between nasoethmoidal and nasoorbital defects was found most frequently (11 from 21 cases) and had more associated abnormalities. Encephalomeningocele had more related abnormalities than meningocele with proportions of 0.6 and 0.3, respectively.

CONCLUSIONS

Here, we confirmed that genetic defects are not likely to be the single primary cause of this malformation. However, we could not draw any conclusions on etiologic agents. We suggest that case control studies and further investigation on the role of nutritional deficiencies, especially folic acid, in the pathogenesis of encephalomeningocele are necessary to clarify the underlying mechanisms.

Dermoid cysts, gliomas, and encephaloceles: evaluation and treatment

The fronto-orbitonasal malformations of encephaloceles, dermoid sinus cysts, and gliomas represent a continuum of neuroectodermal anomalies. The differentiation between them and other similar-appearing lesions is essential for effective management to proceed. Obtaining a reliable history, completing a careful physical examination, and obtaining accurate radiographic documentation represent the first steps. Establishing the timing, staging, and specific surgical techniques for management of a fronto-orbitonasal encephalocele remains as much an art as a science.

Can prognostic indicators be identified in a fetus with an encephalocele?

Encephaloceles, like other congenital malformations of the brain diagnosable in utero, can be either complicated (there being an associated chromosomal abnormality, abnormalities in the remainder of the central nervous system (CNS) and/or other organs), or isolated (no abnormalities in the chromosomes, the remainder of the CNS or other organs). Complicated cases invariably have a poor prognosis but amongst those with isolated lesions the outcome is variable with some affected children having poor mental and physical development but others who are only mildly or moderately disabled. To be able to make an informed decision about how to manage their pregnancy parents need to know what the prognosis is likely to be for their fetus with an encephalocele. To see if the necessary information could be reliably gathered by prenatal assessment of affected fetuses, a review was carried out of the medical records and ultrasound scans of 31 fetuses with encephaloceles referred to the Fetal Management Unit at St. Mary's Hospital in Manchester between January 1991 and December 1997. Eighteen of the cohort were classified as having a complicated encephalocele. Thirteen of the pregnancies were terminated; there were three intrauterine deaths, and one neonatal death. There is only one surviving child who is severely disabled. Thirteen fetuses were classified as having isolated encephaloceles, six had a mass of neural tissue in the encephalocele sac and were terminated, one died in utero and six had a cystic lesion or only a nubbin and have survived with few or no abnormalities. This study has shown that it is possible to identify fetuses with an encephalocele with a favourable outcome.

Morphologic study of 120 skull base defects in frontoethmoidal encephalomeningoceles

Frontoethmoidal encephalomeningocele is a herniation of brain and meninges through a congenital bone defect in the skull at the junction of the frontal and ethmoidal bones. From 1992 to 1996, 120 cases of frontoethmoidal encephalomeningocele were seen in our institutes, and the morphology of the skull defects was studied. The patients underwent thorough physical examinations and radiographic investigations including spiral three-dimensional computed tomography scan. Together with intraoperative findings, we found more types of the defects than previously reported. Our findings were categorized into the following types: type I, a single external opening between frontal, nasal, ethmoidal, and orbital bones; type IA, opening is limited between two bones of the area; type IB, opening is extended transversely or cephalad to involve adjacent structures; type II, multiple external openings in the region; type IIA, all of the openings are limited types; type IIB, one or more of the openings is/are extended type(s) that involve adjacent structures. There are 14 subtypes in these two types: 3 in type IA, 6 in type IB, 3 in type IIA, and 2 in type IIB. This classification is helpful in understanding the herniation pathway and in keeping informative records.

Spinal and cranial neural tube defects

Developmental lesions of the central nervous system with failure of normal midline fusion are often referred to as being dysraphic and vary from inapparent and insignificant to a massive deformity incompatible with survival. Several different schemata are used to classify this wide variety and often complex set of malformations; however, the nomenclature is confusing and even contradictory. As most of these congenital lesions of clinical significance involve an aberration in the formation of the neural tube, it is suggested that the term neural tube defects (NTD) be used to characterize this entire group of anomalies. From a practical clinical standpoint, NTD can be subdivided into three main groupings: open spinal NTD, closed spinal NTD, and cranial NTD. This article briefly covers the epidemiology, embryology, classification, clinical presentation, and management of this group of congenital lesions.

Chiari complex in children--neuroradiological diagnosis, neurosurgical treatment and proposal of a new classification (312 cases)

Chiari malformations are a group of anomalies particularly involving the hindbrain and cervical spinal cord. Since these malformations present many common features, we called them "Chiari Complex". After reviewing our 312 patients affected by different types of Chiari malformations we propose the following classification: Chiari I (30 cases): 1) This malformation may be divided in two sub-types: a) classic and b) myelencephalic forms. 2) Only three children were admitted with specific clinical symptoms and they had an occipito-cervical surgical decompression. Chiari II (276 cases): 1) Most of our patients (70%) presented with progressive hydrocephalus and they needed a CSF shunt to be inserted. 2) Seven sub-types of 4th ventricle morphology and size were identified. 3) Only 11 patients underwent a cervical decompression; in 182 children CSF shunting resulted in a good clinical outcome. Chiari III (2 cases): Chiari II signs must be associated with an occipito-cervical cephalocele. In both cases there were other severe associated CNS malformations. Chiari IV (4 cases): We propose this name for patients with myelomeningocele (MMC) and severe cerebellar hypoplasia.

Cephaloceles: classification, pathology, and management--a review

The spectrum of diseases that give rise to cephaloceles is reviewed with particular reference to conditions encountered by craniofacial teams. The broad term cephalocele contains the more focused term meningoencephalocele, which is most commonly used by craniofacial surgeons. The interesting pathology of frontoethmoidal meningoencephaloceles is described with reference to the experience of the Australian Craniofacial Unit from 1975 to 1993. Further observations supporting the uniqueness of this entity are made. Although the meningoencephalocele associated with craniofacial clefts does not in itself affect treatment, the management of frontoethmoidal meningoencephaloceles is dependent on a knowledge of their unique natural history. Long-term follow-up has allowed a number of conclusions to be reached in the light of treatment. Basal and posttraumatic encephaloceles are described with respect to their place in the classification system as well as the principles of treatment.

[Anatomical classification of anterior encephaloceles]

The authors present an anatomical classification of the anterior encephaloceles. The importance of a topographic knowledge of such anomalies in their diagnosis and treatment is emphasized in order to avoid complications during the investigation of a cranio-facial protrusion.

Spontaneous temporal encephalocele. Case report

The authors report a 36-year-old woman with a 23-year history of simple and complex partial seizures who was treated surgically for an anteroinferior temporal encephalocele, with resolution of the seizure disorder. This patient's presentation, findings, and response to treatment are typical of those associated with anteroinferior temporal encephalocele, and different from the clinical patterns of four other types of spontaneous temporal encephalocele.

Intraoperative management of an infant with a nasofrontal encephalocele

1. An encephalocele is a congenital malformation in which the structures of the central nervous system, in communication with cerebrospinal fluid pathways, herniate through a cranial defect. 2. Classification of encephaloceles depends on their anatomical location within the cranium, and the prognosis and treatment largely depend on the site of such defects. 3. Although the operation is delayed until the infant gains strength, early correction (within the first month) minimizes facial deformity, prevents further damage to brain tissue herniating through the defect, and increases the chance of normal binocular vision.

Cephaloceles: classification, pathology, and management

A cephalocele is defined as a herniation of cranial contents through a defect in the skull. Cephaloceles are classified according to their contents and location. We have reviewed a total of 112 patients with cephaloceles, 51 of whom had sincipital meningoencephaloceles (fronto-ethmoidal meningoencephaloceles). This group is distinctive in its demographic distribution, in the effect on growth of other facial structures, and in the combined craniofacial approach needed to treat them. This review is based on the sincipital encephaloceles with the other cephaloceles included for completeness. Despite many theories, the cause of congenital cephalocele is not known. Preoperative work-up includes 3-dimensional computed tomography scan of the facial skeleton, and surgical management is multidisciplinary in nature. The aim is to remove the lesion before the deformity has time to greatly distort facial growth, which appears to realign itself after surgery. The 50 patients who underwent surgery for fronto-ethmoidal encephalocele all survived with minimal complications.

Parietal cephalocele: clinical importance of its atretic form and associated malformations

In this study of atretic cephaloceles, the authors have considered the pedunculated or sessile type of cephalocele and also small nonpedunculated scalp defects developing in the vertex midline. Parietal cephaloceles were found in 15 infants (10 boys and five girls), and accounted for 37.5% of all cephaloceles. They consisted of four encephaloceles, six meningoceles, and five atretic cephaloceles. The clinical and morphological characteristics of parietal cephaloceles were investigated and compared with those arising at other locations. Parietal cephaloceles carried a much less favorable prognosis than those in the occipital region, regardless of the type of cephalocele; they were associated with cerebral malformations more frequently and were more severe than occipital cephaloceles. Grave congenital anomalies were found in 87% of patients with parietal cephalocele, and only two patients (neither of whom had any other malformation) attained normal development. Brain malformations were closely related to the site from which the cephalocele issued, and dorsal cyst malformation was found in eight patients with parietal cephalocele. Two types of atretic cephaloceles were found, each in a different location. The first type was an alopecic lesion occurring in the parietal midline; all five patients with this type had dorsal cyst malformations and none developed normally. The second type was a nodular lesion developing at the occipital midline, not associated with cerebral anomalies; all five patients with this type showed normal development. The pathogenesis of atretic cephaloceles and their associated intracranial malformations are discussed.

[Basal encephalocele--a report of two cases and consideration of its pathogenetic classification]

The authors have experienced two cases of basal encephalocele without intra and extra cranial anomalies. We have reviewed previous reported cases and studied, from the view point of developmental pathology, reasons why these cases did not have associated anomalies. In this paper we will report our two cases of basal encephalocele and propose a new classification for it, based upon the developmental pathology of the basal part of the skull and associated anomalies. Case 1. A 32 year old male complained of continuous rhinorrhea for 8 months. Coronal CT scan demonstrated a defect of the right sphenoid and ethmoid bone, and a protrusion of isodensity mass, which was enhanced by administration of metrizamide in the subarachnoid space. During the operation, the protruded mass was removed, and the defects of bone and dura mater were repaired. Postoperative course was uneventful. Case 2. A 33 year old male was referred from the department of otology to the department of neurosurgery, because of rhinorrhea and the presence of brain tissue at the time of nasal operation 3 months before. Coronal CT scan revealed a defect of the left ethmoid bone and a protrusion of isodensity mass in it. RI cisternography clearly demonstrated the leakage of CSF through the left nasal cavity. During the operation, the protruded mass was removed and the bone and dura mater defects were repaired. Postoperative course was uneventful. The common findings of both cases are that they were diagnosed by accident in adulthood cases of rhinorrhea, and midsagittal basal bone structure was preserved without extra and intra cranial anomalies.(ABSTRACT TRUNCATED AT 250 WORDS)

Intrasphenoidal encephaloceles--a clinical entity

In the current classification basal encephaloceles are grouped together with real transsphenoidal encephaloceles. But those encephaloceles extending only into but not through the sphenoid sinus seem to represent a specific clinical entity and therefore should be regarded as a rare subgroup of sphenoidal encephaloceles. One personal case and six cases from the literature are reviewed, the own case being associated with an empty sella turcica. The initial sign is rhinorrhea, almost invariably. The association with other intracranial anomalies is uncommon. The extradural transsphenoidal or transethmoidal midline approach accompanied by a shunting procedure today is the most suitable method of surgical treatment.

Cephaloceles

The meningoceles and encephaloceles of the calvaria and base of the skull are reviewed with regard to origin and local behavior. An additional variant is added to the subgroup of nasopharyngeal cephaloceles, the basioccipital nasopharyngeal cephalocele, which only recently has become recognized. The clinical importance, techniques for its identification, and surgical management are discussed with the aid of a case report.

[Basal encephalomeningocele in an adult--a case report and clinico-anatomical classification]

A 53-year-old male was admitted with complaints, of the recurrent cerebrospinal fluid rhinorrhea and meningitis. Basal encephalomeningocele was revealed by radionuclide cisternography, skull x-ray studies, and CT scan. Then, it was confirmed by operation. In reviewing the literature, we proposed a new classification of fronto-basal encephalomeningocele from clinical standpoints. 1) Anterior type; detectable facial anomalies, hypertelorism, building frontal mass or masses. Reparative operation is easy. 2) Intermediate type; no facial anomalies, cerebrospinal fluid rhinorrhea, meningitis, nasal polyp. Good results can be expected through intracranial approach. 3) Posterior type; associated many congenital anomalies such as coloboma, agenesis of the corpus callosum, and cleft palate and lip. In this type, intracranial operation has potential hazards. In our case, elevated CSF pressure due to hemodialysis for chronic renal failure may result in the late onset of CSF rhinorrhea. Etiology of 10 reported cases of the basal encephalomeningocele in Japan was also discussed.

[A case of nasofrontal encephalomeningocele with review of literatures and experiences of 14 cases of cephaloceles (author's transl)]

A case of 2-month-old boy with nasofrontal encephalomeningocele was presented, which was excellently treated via intradural approach, followed by removal of herniated sac. Under the knowledge of reviewed literatures and our experiences of 14 cases of cephaloceles, its symptomatology, diagnosis and policy of treatments were discussed. As rare case was an intracranial meningoencephalocele in our series described, which showed a supracollicular cyst with brain tissue wall, communicating with aqueduct. Other emphases were placed on the differential diagnosis from holoprosencephaly with extracranial dorsal sac, the usefulness of CT-scan as a diagnostic tool and our method of closing dural defects in anterior cranial fossa by reflecting dura on frontal lobe.

Computed tomography in the evaluation of encephaloceles in infants and children

Computed tomography (CT) is an accurate diagnostic modality in the evaluation of encephaloceles. The axial and coronal planes, contrast enhancement attenuation measurement of the contents of the encephalocele, and the use of the standard and reverse modes for viewing the CT images are all valuable in this evaluation.

Chronic tonsillar herniation: an attempt at classifying chronic hernitations at the foramen magnum

A system is presented for the classification of chronic herniations of the cerebellar tonsils in the absence of space-occupying intracranial lesions, based on a survey of the literature and 13 own cases. The Arnold-Chiari malformation in adults typically involves herniation of the cerebellar tonsils instead of herniation of the vermis as is typical when it occurs in infancy. Identification of chronic tonsillar herniation with the Arnold-Chiari malformation in adults was thought to require at least one other sign of the Arnold-Chiari complex, e.g. a medullary deformity. Cases for which chronic herniation and sclerosis of the cerebellar tonsils present as the only nervous lesion are classified as "chronic tonsillar herniation". Such cases may manifest with neurological symptoms during adult life, or they may be found incidentally at autopsy. Attention is drawn to the occurrence of chronic tonsillar herniation in 7 infants and children where it apparently represents a cause of sudden unexpected death. The overlap between chronic tonsillar herniation and the Arnold-Chiari malformation of adults is discussed in regard to the frequence of associated osseous anomalies, hydrocephalus and syringomyelia.

A morphological classification of sincipital encephalomeningoceles

✓ Cranial defects and cerebral abnormalities as revealed by postmortem dissection in 12 patients with sincipital encephalomeningocele are reported. The various methods of classifying this lesion are discussed. A classification based on the location of the defect in the cranium is outlined. The clinical application of such a classification and its usefulness in the surgical management are emphasized.