A Case of Atretic Parietal Cephalocele
Saliha ?ENEL 1, Ümit Murat ?AH?NER 1, Nilgün ERKEK 1, Aysel YÖNEY 1, Can Demir KARACAN 1
1 Dr. Sami Ulus Children's Hospital, Department of Pediatrics, ANKARA
An encephalocele is a rare congenital malformation of the central nervous system. It is defined as a congenital herniation of the intracranial compartments through a bony defect and contains various rudimentary cerebral tissue components, or sometimes only cerebrospinal fluid. They are located at the midline of the parietal or occipital region. Herein we present a case of atretic parietal encephalocele and would like to emphasize that when a scalp mass is noted at the midline or near the vertex the possibility of an atretic cephalocele should be ruled out.
Key Words: Atretic encephalocele, rudimentary encephalocele, rudimentary meningoencephalocele.
Encephalocele is a congenital malformation of the central nervous system. It is the result of failure of the surface ectoderm to separate from the neuroectoderm. This results in a bony defect which allows herniation of the meninges or herniation of the brain tissue1-3. Since the report of McLaurin4 a number of investigators have reported small, skin covered midline subscalp masses or cysts described as atretic cephaloceles, atypical meningoceles, rudimentary meningoceles and meningeal heterotopias4-6. The incidence of atretic cephaloceles is 4-17% of all cephaloceles1 and the parietal location compromises 40 to 50 % of cases.
We report a nine-month-old boy presented with a scalp mass present since birth and diagnosed as atretic parietal encephalocele.
A nine-month-old boy was admitted to our clinic for a small scalp mass present since birth. On physical examination a soft, flattened and fluctuating mass over the posterior part of the right parietal region and near the midline was found. It was about 2x1.5 cm in diameter with hairy skin overlying the lesion. The weight, height and head circumferences were all within normal percentiles. Except the lesion on the scalp, physical examination was totally normal and psychomotor development was parallel with the age of the child. Pre-natal, natal and post-natal history was unremarkable. A superficial tissue ultrasonography showed a subcutaneous hypo-echoic lesion with a diameter of 1.5 cm and there were no vascularization within the lesion. Magnetic Resonance Imaging (MRI) revealed a sub-capsular lesion at the posterior parietal region and midline with a cranial defect underlying the lesion. There was not a prominent communication with the sagittal sinus and no vascular lesion was demonstrated (Figure 1). The lesion was diagnosed as atretic parietal encephalocele. The patient was consulted with the neurosurgery department and an operation was planned for the child.
Figure 1. MRI of the patient. Sagittal T1-weighted image showing a flattened cystic lesion and high signal fat and low signal bone beneath the lesion in the parietal region representing an atretic encephalocele
Failure of the separation of cutaneous ectoderm from the neuroectoderm results in herniation of the intracranial structures. This pathology is always with a cranial bone defect. If the cranial defect is large enough, herniation of cerebral tissue results in encephalocele formation in the embryo. If the defect is small, only meninges herniate and sometimes these meningoceles may resolve before birth and so called atretic cephaloceles may be formed. Atretic cephaloceles mostly occur in parietal and occipital regions1,7.
Atretic cephaloceles may be related with a number of anomalies including corpus callosum agenesis, dermal sinus, hydrocephalus, Chiari II malformation, Dandy-Walker malformation and macrocephaly1,3. Yokota et al1 stressed the importance of location of the atretic cephalocele as related to the prevalence of additional cranial anomalies. He stated that atretic parietal cephaloceles were much more related with extracranial anomalies and showed worse prognosis. In contrast, in our patient there was not any malformation. However in another study by Martinez-Lage3 occipital cephaloceles were more related with cranial malformations and showed a worse prognosis. In both of the series the total number of the patients was quite small so we need larger series to have more definite comments.
The development of atretic cephaloceles is not clear yet and a variety of pathogenetic explanations have been described including persistence of neural crest remnants and nearly complete resolution of a larger meningoencep-halocele in early fetal life3,6. There are some genetic factors implicated8 and hypervitaminosis A, X-ray exposure during pregnancy, teratogens like trypan blue may also lead to development of cephaloceles3. In our patient neither of these predisposing factors was present.
In the differential diagnosis of the cephaloceles hemangiomas, cystic hygroma, lipoma, teratoma, dermoid cysts and other scalp lesions should be evaluated.
Atretic encephalocele itself is usually an unimportant clinical entity and because there may be a fibrous tract through the dura, simple surgical excision at the level of the dura, is the treatment of choice9. The prognosis of the atretic parietal encephaloceles depend on whether there is an accompanying central nervous system or other systemic malformation1,3,8 .
With this case we would like to emphasize that when a scalp mass is noted at the midline or near the vertex the possibility of an atretic cephalocele should be ruled out as a rare cause of cranial masses.
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2. Lopez DA, Silvers DN, Helwig EB. Cutaneous meningiomas-a clinicopathologic study. Cancer 1974;34: 728-44.
3. Martinez-Lage JF, Sola J, Casas C, Poza M, Almagro MJ, Girona DG. Atretic cephalocele: tip of the iceberg. J Neurosurg 1992;77: 230-5.
4. McLaurin RL. Parietal cephaloceles. Neurology 1964;14: 764-72.
5. Bale PM, Hughes L, De Silva M. Sequestrated meningoceles of the scalp: extracranial meningeal heterotopia. Hum Pathol 1990;21: 1156-63.
6. Drapkin AJ. Rudimentary cephalocele or neural crest remnant ? Neurosurgery 1990; 26: 667-673.
7. Barkovich AJ. Pediatric Neuroimaging 2nd edn. New York, Raven Pres; 1995, pp177-275.
8. Martinez-Lage JF, Piqueras C, Poza M. Atretic cephalocele in the adult. Acta Neurochir 1997;139: 585-6.
9. Patterson RJ, Egelhoff JC, Crone KR and Ball Jr WS. Atretic parietal cephaloceles revisited: an enlarging clinical and imaging spectrum ? Am J Neuroradiol 1998;19: 791-5.
Ümit Murat ?AH?NER M.D.
Dr.Sami Ulus Hospital, Telsizler ? Ankara
Acceptance date: 01.10.2007