Introduction:
Extracranial brain tissue (outside the skull) is commonly seen in the sides or the posterior part of the scalp. This tissue may have no relation with the brain. This tissue is termed a cutaneous ectopic brain. It is an embryonic defect seen at birth or sometime after the baby is born. They resemble tumors and can be removed easily with surgery. This extracranial brain tissue is like a cystic nodule present under the skin. It may be two to four centimeters in diameter. The cutaneous ectopic brain is a rare phenomenon seen more often in infants and children.
What Is a Cutaneous Ectopic Brain?
Heterotopic brain tissue may be present anywhere in the skull but is more commonly seen in the occipital (posterior part of the brain) and the parietal lobe (present between the frontal and occipital lobes). Due to the histological features of this lesion, it is also known as cutaneous neuroglial choristoma.
Neuroglial choristomas typically appear as well-defined, firm, and sometimes pigmented nodules or masses in the skin, most commonly in the head and neck region. They can occur at birth or develop later in childhood. Histologically, these lesions contain various components of normal brain tissue, including neurons, glial cells, and sometimes other neural elements. However, they lack the characteristic layered structure and organization found in the brain.
What Is the Pathogenesis of a Cutaneous Ectopic Brain?
There are two possible ways in which heterotopic brain tissue may arise -
-
A small fragment of the embryonic tissue may have been retained even after the development of the embryo into the fetus. This is called embryonic cell rests. This cell rests may give rise to such tissues outside the brain.
-
There may be congenital herniation of the tissues (the tissues of the brain are pushed outside, causing a shift from their normal position) of the brain outside the skull with no connection with the brain tissue.
What Are the Signs and Symptoms of This Disorder?
-
Cutaneous ectopic brain or heterotopic brain tissue is usually painless nodules on the scalp. They are compressible. When pressed, the lesion appears blanched (the skin becomes paler than the surrounding area).
-
They are present either on the occipital or parietal parts of the skull. Scalp lesions are predominantly present in the midline.
-
They appear as round, cystic nodules on the scalp that may not have hair. Alopecia (absence of hair) is associated with these lesions, large coarse hair surrounding the borders of the lesion, known as the hair-collar sign.
-
There may be a presence of capillary stains surrounding the lesion. Capillary stains are capillary vascular malformations (irregular patches of pink or purple skin that can occur anywhere on the body) that are present at birth, also known as port-wine stains. These stains are due to dilated blood capillaries in the dermis layer (middle layer of the skin) of the skin. These patches get darker with age.
-
Cutaneous ectopic brain lesions are also seen in the nasal region and sometimes in the face and neck region. It is rarely seen in the orbital area (eye region).
How to Diagnose a Cutaneous Ectopic Brain?
1. The physician requires a thorough clinical examination, followed by an ultrasound of the lesion.
2. A biopsy of the lesion is advised to confirm if there is any connection between the brain tissue and heterotopic tissue. Fine needle aspiration cytology (FNAC) can be carried out to isolate the contents of the lesion for further investigations. Care needs to be taken to avoid damage to the underlying tissues.
3. Brain imaging scans such as MRI (magnetic resonance imaging) and CT (computed tomography) scans are useful for viewing the location and extent of the lesion. CT scans may show a large heterogeneous mass extruding out of the skull. The brain scans help identify any connection with the brain tissue. No skull defects are seen on the scan.
How to Treat a Cutaneous Ectopic Brain?
The cutaneous ectopic brain can be treated by complete surgical excision. The lesion is properly evaluated by following all the diagnostic procedures. Post-operative healing is also good and uneventful. The physician prescribes analgesics to manage pain. Antibiotics are also given to prevent infections at the site of surgery. All surgical procedures are planned meticulously after a proper diagnosis is confirmed that the heterotopic tissue is not connected to the brain tissue. The excised tissue is further sent for histopathological studies.
What Are the Complications of Surgically Removing the Heterotopic Lesion?
1. If the cutaneous ectopic brain lesion is resting on a blood vessel, there may be a risk of potential hemorrhage (loss of blood due to damage to a blood vessel).
2. Delayed wound healing may be a possible complication.
3. There is a risk of infection at the site of surgery. Following proper methods of asepsis are necessary to prevent these complications.
What Is the Prognosis of This Condition?
The prognosis of cutaneous ectopic brain (CEB) is generally good. This is because the tissue is not connected to the underlying brain and there are usually no other serious associated anomalies. In most cases, the only symptom is a small, painless lump on the skin.
CEB is a rare condition that occurs when brain tissue develops outside of the brain. The exact cause of CEB is unknown, but it is thought to be due to a developmental abnormality. CEB can occur anywhere on the body, but it is most commonly found on the scalp. After surgery, patients usually make a full recovery and have no further problems. In rare cases, CEB can be associated with other congenital anomalies, such as seizures or mental retardation. However, these complications are uncommon. Overall, the prognosis for patients with CEB is good. With early diagnosis and treatment, most patients can expect a full recovery.
Conclusion:
The cutaneous ectopic brain is a rare benign condition that may be congenital. There is no definite cause for this condition. Patients usually live a normal life-span provided they get proper treatment. Communication between the surgeon and pathologist is very critical in confirming the diagnosis of this condition, as it can be easily mistaken for other tumors. Histopathological examination after surgery is essential to rule out any possibility of cancer. This disease is treatable and does not cause further complications to the patient.
