Term Paper: Ectopic/Heterotopic Brain Tissue

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[. . .] There objective was to call to attention to a cutaneous marker for neural tube defects of the scalp. The "hair collar" sign consists of "a ring of long, dark, coarse hair surrounding a midline scalp nodule" (Drolet and Lawrence 309). There are several different types of ectopic brain tissues or heterotopic brain tissue. Most of these fall under the CEB, but some of them point to serious problems in the infant. It is important that the pediatrician have these checked by a neurologist.

The skin and the nervous system are both derived from ectoderm. Separation of neural ectoderm from epithelial ectoderm occurs during the third to fifth week of gestation concurrent with the formation of the neural tube. This chronological association during embryogenesis may explain the association of neural closure defects and cutaneous abnormalities" (Drolet and Clowry 309).

As early as 1989, a team of researchers introduced the term "hair collar" to describe cutaneous heterotopic brain tissue that is encircled by a peculiar ring of long, coarse hair. The hair collar sign may be found in other scalp malformations. In the study written by Droplet and Lawrence, they used clinical photographs, scans, and skin biopsies from four children. They used the S-100 stain, vimentin, and epithehal membrane antigen monoclonal antibodies to identify brain and meningeal tissue in paraffin-embedded specimens (Drolet and Lawrence 309).

The study was to call attention to a cutaneous marker for neural tube closure defects of the scalp or the "hair collar" sign. "Four children with small congenital scalp nodules and the hair collar sign were studied from the standpoint of clinical findings, radiological scans, and histology of the excised nodules" (Drolet et al. 309). The four children had an overlying vascular stain. The first two patients had encephaloceles, one of the children had heterotopic brain tissue, and the fourth child's parents refused to have the surgery. This team of researchers pointed out that the "hair collar" sign should tell pediatricians that there is a possibility of ectopic neural tissue in the scalp and the possibility of underlying central nervous system malformations (Drolet et al. 309).

The team of researchers discusses the problem with ectopic or heterotopic brain tissue is that the language used by many researchers and physicians are different, but they often mean the same thing.

As in the case with many rare conditions, the terminology used in the classification of congenital cranial neural tube defects is inconsistent and confusing. Cephalocele is the appropriate general term for congenital herniation of intracrania structures through a scalp defect" (Drolet and Lawrence 309).

When brain tissue is found in the scalp and has no underlying defect on the cranium, the proper terms are ectopic or heterotopic brain tissues. "Meningeal or arachnoid tissue may also be found in the scalp unassociated with brain tissue and in the absence of a cranial bone defect" (Drolet and Lawrence 309). The common name for this is heterotopic meningeal tissue is used. The term "hair collar" has only been recently termed, but it is one will be appreciated. Two of the children had small parietal encephaloceles. The third child had heterotopic brain tissue. Another cutaneous lesion that has been written about is aplasia cutis.

Why the "Hair Collar"

Perhaps the question can be asked why the researchers termed the phrase, "hair collar." Why is there a hypertropic ring of long hair that surrounds these lesions? If these were examined, the hair follicles would be found to increase in number and many of these will be quite large. In fact, the angle that each hair follicle exits the skin does not fall randomly, but are located at precise directions that the hair follicles take.

The hair pattern is thought to be dictated by differential shearing forces and the point of maximal tension, the vertex, is where the parietal scalp whorl is commonly found. Perhaps at some point early in development, encephaloceles and meningoceles produce aberrant shearing forces during the formation of the follicles forcing them to point outward, away from the defect" (Drolet and Lawrence 309).

The prognosis of infants with hair collars will vary depending on the type of neural tissue present. "True encelphaloceles and rudimentary encephaloceles tend to have worst prognosis, particularly if they are parietal in location" (Drolet and Clowry 309). In a study of 70 children with scalp nodules, only 37% had lesions that extended into the brain. The four children in this study had a persistent, faint pink vascular stain that overlaid the nodule. This vascular stain is a sign that there may be underlying bony and CNS defects.

It is important for a pediatrician to do a thorough evaluation of a child with a hair collar. This should include a complete examination, neurologic evaluation, and a MRI scan of the head. "If an intracranial communication is found, a prompt neurosurgical referral is recommended" (Drolet and Clowry 309). Some cases are not serious, but the ones that are make it necessary to for a neurologist to check out thoroughly.

When an infant is done, the pediatrician thoroughly checks the infant for various problems. This routine assessment includes several areas, such as the examination for size, macrocephaly or microcephaly, changes in color, respiratory distress, posture, tone, and for any malformations. One of the areas that the pediatrician checks is the head and neck. The circumference and fontanelle size of the head may be a signal of a congenital or head trauma. The pediatrician wants to know if there are any scalp nodules, because these may signal that there are serious problems. "Congenital exophytic scalp nodules should always be evaluated further because 20 to 37% of these lesions connect to the underlying central nervous center" (Fuloria and Kreiter 62). Many of these nodules of the scalp can be determined at birth whether they are serious or not. "Large meningoceles or encephaloceles are usually diagnosed prenatally or at birth. Smaller defects may be mistaken for cutaneous lesions such as hemangiomas or dermoid cysts" (Fuloria and Kreiter 63). As mentioned earlier, cutaneous signs of cranial dysraphism include the "hair collar" sign.

Cultaneious signs of cranial dysraphism include the "hair collar sign" (darker, coarser hair encircling the scalp nodule), vascular malformations, and cutaneous dimples and sinuses.

Cephaloceles and exophytic scalp nodules should be assessed by magnetic resonance imaging (MRI), and a neurosurgical consultation should be obtained" (Fuloria and Kreiter 63).

The earlier these problems are discovered and evaluated the better for the infant. That is why all pediatricians should get these evaluated. Another type of ectopic brain tissue is aplasia cutis congenital. "Aplasia cutis congenital is a developmental inherited defect and may occur at any time from the embryonic stage to very early childhood. It is a total absence of the skin epidermis in small patches" (Keratin 1). These can occur anywhere, but they usually appear on the scalp. Most of these occur on the "vertex at the center point of the hair growth whorl (scalp hair grows in a whorl pattern if you look closely at the back of the head)" (Keratin 1). Usually aplasia cutis congenital appears with other types of deformities.

Ectopic Brain As Orbital and Conjunctival Mass

Ectopic brain tissue is seldom found in the orbit, but there have been isolated cases of brain tissue in the orbit A.J. Scheiner and team reported a case of a 9-month-old male infant with heterotopic brain tissue in the orbit. The biopsy of the growth was performed with an anterior orbitotomy. This infant had a history of "congenital left 'anophthalmia' and a slowly growing mass in the left orbit" (13). When an MRI was done, it showed that the orbital mass was solid and had cystic components. After a histological study was completed, it showed that the mass was a rare example of heterotopic brain tissue in the orbit. This is one of the only instances in literature in which a "formed eye was absent but in which a scattered primitive ocular structure could be identified" (Scheiner et al. 13).

In a case study by Geeta Kashyap Vemuganti and Chandra G. Shekar, they found that the present of brain tissue in the orbit as a "rare finding, whether it occurs isolated, in continuity with intracranial contents, or within a tumor" (305). They discovered a rare case of ectopic brain in the orbit of a young 15-day-old female infant. There are other cases of ectopic brain tissues. Liarth and researchers discovered that the "specimens of ectopico brain generally consist of gliais cells and fabric conjunctive fibroso.... To the birth, the children generally present proptose, with expansion of the orbit unilaterally, being able to present other malformations associates. Other times, present primitive anoftalmia or ocular structures or cysts" (641). This is a congenital malformation. The diagnosis is made through "prenatal biopsia of orbiaria mass" (Liarth et al. 641). By doing a tomographic study of the orbit, "it can demonstrate, among other findings, the presence or… [END OF PREVIEW]

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