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| Year : 2006 | Volume
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| Issue : 3 | Page : 309-311 |
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| IMAGES: Rare type of frontal encephalocele (paramedian) |
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SV Phatak, D Rajderkar
Radio-Diagnosis IGMC and Mayo Hospital, Nagpur, India
Click here for correspondence address and email
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Keywords: Cephaloceles, Frontal, MRI
How to cite this article:
Phatak S V, Rajderkar D. IMAGES: Rare type of frontal encephalocele (paramedian). Indian J Radiol Imaging 2006;16:309-11 |
 Case report | |  |
A six-year male child presented with a painless swelling on right side of frontal region since birth. This swelling showed slow growth in size. Radiograph of skull showed a bony defect on right side in frontal region. MRI was done to further characterize the lesion[Figure - 1][Figure - 2][Figure - 3][Figure - 4]. Routine hematological investigations were normal.
| Introduction | | |
Cephaloceles are congenital malformations consisting of a defect in the cranium and the duramater with extracranial herniation of intracranial structures. The term cranial meningocele is used for the forms in which the herniated sac contains only leptomeninges filled with CSF.The term encephalocele designates the form in which the herniated sac also contains brain tissue [1],[2] A simple skull defect without prolapse of brain or meninges is referred to as cranium bifidum occultum [1] An encephalocele is the result of failure of the surface ectoderm to separate from the neuroectoderm. This results in a bony defect in skull table, which allows herniation of the meninges or brain tissue. Approximately 90% cases involve the midline. Other malformations and / or chromosomal anomalies are noted in at least 60% of patients of encephalocele. Currently most cases are diagnosed antenatally. Maternal surum alpha feto proteins are raised only in 3 % cases as these defects are covered by skin. [3]
| Discussion | | |
The cephalocele represents a prototype of disorders of dorsal induction. (Neurulation) During the third and fourth week of gestation closure of neural tube begins in cervicomedullary region and proceeds rostrally and caudally. The cephalic end of neural tube (anterior neuropore) closes at approximately 25 days of gestation followed by caudal end (posterior neuropore) at approximately 28 days gestation. Limited failure of anterior neural tube closure results in formation of cephalocele with protrusion of intracranial structures from a skull defect. The lesions occur most often in occipital region (70%) followed by frontal, parietal, nasal and nasopharyngeal locations. [2] Cephaloceles occur about once in 4000-5000 live births. Geographic differences in the distribution of cephalocele indicates additional racial and perhaps environmental factors in the formation of encephalocele. Cephaloceles are most common in occipital location in Europe and America and more frequently frontal in location in Russia and South East Asia [1] The absence of brain tissue within the herniated sac is the single most favorable prognostic feature for survival. [3] Fifty- percent cephaloceles are complicated by hydrocephalus. Dandy Walker and Chiari malformation More Details (Type 3) are commonly associated with occipital cephalocele and dysgenesis of corpus callosum is associated with frontoethmoidal and sphenoidal encephalocele. [2] Cephaloceles maybe associated with other anomalies of the kidney, skeleton or face [4]or Neurofibromatosis1, interhemispheric lipoma and subependymal heterotopic gray matter [5] Other known associations are genetic syndromes such as Meckel-Gruber, Von Voss, Chemke, Roberts, and Knobloch syndromes, Amniotic band syndrome, maternal rubella and Diabetes.The most common associated chromosomal anomaly is Trisomy 18. [3]
On the basis of location of the osseous defect one may distinguish four groups of frontal cephaloceles as Naso-frontal, Naso-ethmoidal, Naso-orbital and interfrontal. [1] Most of the frontal encephaloces are in the midline; rare subtypes are paramedian in location. [5] Histopathologically herniated brain tissue is abnormal [6] distorted [4] but may have functional tissue. The protruded brain has the unmyelinated white matter [5]
Neuroradiological investigation centres on providing information regarding the content of the sac (presence or absence of brain or major blood vessels) and delineation of associated anomalies [1] On radiography cranial defects associated with encephaloceles usually occur in the midline of skull and appear any where from the base of the nose to the base of the occipital bone. The skull defect is smooth and well circumscribed without marginal sclerosis. This appearance is quite nonspecific more over plain radiographs rarely provide diagnostic information about contents of encephalocele. Post natal CT gives excellent depiction of bony defect particularly with coronal, Sagittal and 3D reconstruction. But it is less capable in showing soft tissue components within an encephalocele. Water soluble contrast material that is placed within the theca and that flows into encephalocele may allow better evaluation of contents. CT cisternography often demonstrates a communication of herniated sac with the intracranial subarachnoid space. CT is also useful in demonstration of associated anomalies. Fetal MRI requires both fetal and maternal sedation [3]. Postnatal MRI is most sensitive and accurate imaging modality [3],[5] Exqisite detail of cranial defect and herniated contents is seen. Contents of herniated sac may include CSF, disorganized brain tissue and even ventricles. They are visualized clearly on MRI.MRI is also useful in demonstrating associated anomalies. [3] Typical findings are tissue is seen protruding towards the bony defect is distorted, there is general tendency of the ventricles to be elongated and point towards the defect [5] Antenatal sonography shows demonstration of cranial defect with varying degree of brain herniation. Classic sonographic appearance is that of a mass in midline of skull with most case occuring in the occipital and less commonly the frontal region. Size is variable. Consistency may be purely cystic or may contain internal echoes. Because skull ossification begins at 10 weeks diagnosis is not usually possible before this time. Frontal encephalocele always contain brain tissue and involve bridge of nose (60%) and nasal cavity (30%) Radionuclide ventriculography and / or cisternography has been used to demonstrate intracranial extension of an encephalocele. Currently MRI can demonstrate this effectively. Radionuclide cisternography can be performed via lumbar puncture or ventricular injection using TC99MDPA followed by planar or single photon emission computed tomography. Angiography may be needed to evaluate intracranial and extracranial vasculature before surgical repair is performed. Angiography is helpful if concern exists regarding the displacement of the dural venous sinus in the sac. [3]
| References | | |
| 1. | CT and MRI Imaging of the whole Body,vol1 ,4th Edition,Mosby 2003, John R. Hagga, MD, Charles F Lanzieri, MD.  |
| 2. | Radiographic manifestations of the Anomalies of the brain,Yutaka Sato,MD, Simon S Kao,and Wilbrin L Smith, RCNA, VOL 29,NO2, March 1991. |
| 3. | Cephaloceles :Clinical and Neuroradiological appearance.Associated cerebral malformations, C.Diebler and O Dulac.Neuroradiology (1983),25:199-216. |
| 4. | MRI OF Brain And Spine ,3rd edition,vol1,Scott W Atlas, Lippincott Williams and Wilkins, 279-369 Disorders of Brain Development, Richard Robertson, Paul A Caruso. |
| 5. | AJNR 9:315-326,March/April 1988. Classification of the congenital abnormalities of the CNS,M.S Vander Knaap,J Valk. |
| 6. | Diagnostic Ultrasound,vol2 Mosby, 1991,Carol Rummack,MD,J William Charboneau,MD. |
Correspondence Address:
S V Phatak
M.D (Radiology) Honorary Asst Prof. Radio-Diagnosis IGMC and Mayo Hospital, Nagpur
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0971-3026.29003
Figures
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4] |
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