Ectopic/Heterotopic Brain Tissue. Extracranial Brain Tissue Without

¶ … ectopic/heterotopic brain tissue. Extracranial brain tissue without direct connection to the brain itself may be an isolated cutaneous embryonic defect that is usually located on the occipital or parietal area of the scalp. Most of the time these are harmless and can be removed. These often are called heterotopic brain tissue or cutaneous ectopic brain tissue or (CEB).

ECTOPIC OR HETEROTOPIC BRAIN TISSUE

Extracranial brain tissue that is directly connected to the brain itself may be an isolated cutaneious embryonic defect. These are usually located on the occipital or parietal areas of the scalp. They are often called heteropic brain tissue or cutaneous ectopic brain (CEB) (Janniger 1). Most of the time these are simple defective tissue that can easily be removed from the scalp. However, there are several different types of ectopic brain tissues and some of these can be signs of underlying central nervous system problems. Each of these cases shows the importance of getting a thorough evaluation of the tissue. Several different cases have been documented in the past and show the difference between benign cutaneous ectopic brain tissue and those that point to severe nervous system problems. The pediatrician should give a thorough evaluation of the brain tissue to determine if it is a serious problem.

Definition of Cutaneous Ectopic or Heterotopic Brain Tissue

Extracranial brain tissue without direct connection to brain itself may be an isolated cutaneous embryonic defect, usually on occipital or parietal areas of the scalp. It also is know as heterotopic brain tissue or cutaneous ectopic brain (CEB) (Janniger 1). There have been few actual studies concerning ectopic or heterotopic brain tissue, because these are rare. The cases that have been studied are similar. Lee and McLaurin described the first case in 1955 concerning a 1-year-old girl with an almost perfect circular, bluish-red plague that was almost 3 cm in diameter located on the posterior midline of the scalp. "Microscopically, heterotopic glial tissue in a pattern suggestive of abortive gyri and sulci was evident within the dermis" (Janniger 2). Since this case there have been several others described. It is frightening to the parent to find that her infant has an ectopic brain tissue on the head. It is important to reassure the parents so proper care can be given to the infant. The majorities of heterotopic brain tissue have no effect on the neurological development and are a rare development abnormality. However, there are cases that are similar and do present a serious problem for the infant. It is these cases that must be thoroughly evaluated to make sure there are no serious risks to the infant.

The heterotopic brain tissue may be an isolated embryonic rest or they can be a congenital herniation through the skull that eventually will lose connection. "Perhaps the neural tube initially outgrows, preventing closure of cranial or spinal coverings. Thus, its pathogenesis is uncertain" (Janniger 2). Any of these brain tissues should be thoroughly checked by neurologists. There have been some serious cases that lead to various serious problems in the child and can be fatal. Most of these are not "true" heterotopic brain tissue. There are many congenital cutaneous disorders of the scalps; most of these are quite uncommon. Heterotopic brain tissue or CEB are less common than encephalocele. "Encephaloceles usually are in the midline scalp, either hairless or with a collarette of hair. The nasal glioma, like CEB, may have no connection to underlying central nervous system structures. It appears on the nose as a smooth, often polypoid, tumor" Janniger 309). Most CEB cases do not tend to lead to serious deformities or anomalies. The prognosis for the infant is usually good without any serious underlying structures or any serious associated anomalies. The definition and explanation should be thoroughly to the parent so she does not get frightened and refuse treatment. This is a scary observation for the parent who needs assurance to give her infant the best medical care that can be provided. CEB usually does not lead to death and the prognosis is good in the majority of cases. It is important that these bald scalp plague or nodule by thoroughly evaluated by a neurosurgeon.

Summary of Four Patients with Scalp Nodules Surrounded by Hair Collars In the Study by Drolet and Clowry

The first patient observed had a 2.5 x 2.0 cm, fleshy, lobulated nodule with a central dimple. The MRI showed that posterior parietal encephalocele with bony defect and a Dandy Walker malformation. This was determined to be an encephalocele with an overlying port wine stain of 2 cm.

The second patient observed had a tense, translucent nodule 1.3 cm in diameter that was partially bisected by a fibrous band. This was determined to be a small parietal encephalocele with a dermal aggregation of neural tissue.

The third patient had a 2 x 1.8 cm translucent, blue cystic nodule. The infant was determined to have a heterotopic brain tissue with an overlying port wine stain.

The fourth infant had a 1.5 x 2.0 cm spongy, dermal nodule. The MRI showed subcutaneous mass with small intracranial communication. The fourth parent refused the surgery.

It could be that the parents of the fourth infant might have been frightened to allow their infant to go through surgery. This is not definitely true, but it is important to explain the situation to the parents and ensure them that most CEB's are not fatal and are often quite simple. Only in some cases are the CEBs fatal or are actually more than ectopic brain tissue that needs to be removed. The thorough evaluation of the pediatrician should reassure the parents about their infant.

History of CEB

Either the parents or physician will notice a cystic nodule at birth or shortly afterwards. "CEB usually is seen at birth as a 2-4 cm diameter, solitary, circular, bald scalp plague or cyst, which may be compressible" (Janniger 2). This plague or cyst may be skin colored or bluish and often tends to be located on the midline occipital or parietal scalp. There may be a collar of hypertrophic hair that surrounds the plague or cyst. There may be a cutaneous marker for neural tube closure defects on the scalp or sometimes this is called "hair collar" and consists of a ring of long, dark course hair that surrounds a midline scalp nodule. This should be a signal to the physician of an ectopic neural tissue that may be located in the scalp and that there may be serious underlying central nervous system malformations. A neurologist should always check these CEB. The cause for CEB is unknown. These ectopic brain tissues may begin during pregnancy or happen during the birthing. The heterotopic brain tissues may be an isolated ectopic neural tissue in the scalp or they can be underlying central nervous system malformations. These brain tissues need to be thoroughly evaluated and determine the best choice of treatment.

The neurologist may need to consider other problems, such as encephalocele, meningocele, cutaneous ectopic meningioma, neurofibroma, aplasia cutis congenital, hemangioma, lymphangioma, or melanotic progonoma. "The prominent collarette of hair that may have been seen in CEB also may be evident in a number of other neurocutaneous disorders (eg. Encephalocele, cutaneious meningioma)" (Janniger 3). There could be the possibility of dermal sinus or a direct connection to the central nervous system. The parents should seek a neurologist to evaluate any bald scalp nodule with diagnosis medical equipment, such as ultrasound or cranial tomograms. The neurosurgeon will decide on the best choice of treatment and explain this is to the parents before deciding what to do.

These procedures should be carefully and skillfully done because they can lead to retrograde infection should the lesion communicate with the brain. Sometimes these areas can become infected and need further treatment. Another serious problem of removing the CEB might happen if it overlaid "a large blood vessel such as the sagittal sinus, removal of what appears to be a crust of dried serum may produce a fatal hemorrhage" (Janniger 4). Most of the time CEB prognosis is good and leads to few complications. However, there are different cases that will be discussed that are serious complications. The medical team must not fail to be "alerted by the 'hair color' sign to the possibility of ectopic neural tissue in the scalp and/or underlying central nervous system malformations or fail to "perform complete evaluation, including possible ultrasound, cranial tomograms, and neurosurgical consultation, before cutaneous ectopic brain is excised" (Janniger 5).

There needs to be caution practiced in removing these ectopic brain tissues, because some of these may actually be attached to the brain and cause death. "Histological examination may show neural tissue staining with S-100 protein and glial fibrillary acid protein, but not with a neurofilament stain that suggests a glial cell origin" (Jannigar 309). Caution cannot be over stated due to the risks of some types of heterotopic brain tissues that are more serious.

The Hair Collar Sign: Marker for Cranial Dysraphism

Beth Ann Droplet and Lawrence investigated the cutaneous marker for neural tube closure of the scalp that is called, "hair collar" sign. 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 absence of an osseo defect, characterizing the continuity of ectopia, respectively, of the orbital mass with the brain" (Liarth et al. 641).

Heterotopic Brain and Meningeal Tissue

Both extracranial and extraspinal meningiomas are rare J.P. Alappat Marthandapillai from the Department of Neurosurgery writes about a case of a young woman who was admitted with complaints of bulge in the left temporal region. She was a twenty-year-old woman that had a bulge in the left temporal region for two years. Both a neurological and ENT examination was normal. A CT scan of the head showed "a mass in the pterygopalatine fossa extending into the left subtemporal region." (Marthandapillai 695). They did a craniofacial excision of the tumor and a 3 cms x 2 cms encapsulated firm mass was removed.

Most heterotopic brain and meningeal tissue occur in the midline of the head, neck, and trunk due to displacement of such tissue during the fusion of skull and spine in the embryonic state.

The largest group of ectopic meningiomas had occurred within the orbit, the origin probably being the arachnoid cells in the sheath f the optic nerve followed by primary meningiomas of the nasal cavity and paranasal sinuses. The other ectopic sites, include parotid gland, bifurcation of carotid artery, little finger of right hand, brachial plexus, scalp, face and parvertebral region" (Marthandapillai 695).