Glial heterotopia of maxilla: A clinical surprise.

Glial heterotopia is a rare congenital mass lesion which often presents as a clinical surprise. We report a case of extranasal glial heterotopia in a neonate with unusual features. The presentation, management strategy, etiopathogenesis and histopathology of the mass lesion has been reviewed.

INTRODUCTION

Glial heterotopia is a rare non-hereditary, benign congenital malformation, which is composed of normal glial tissue isolated from the central nervous system.[1] Nose and nasopharynx are the most common sites involved, hence usually called as “nasal glioma” which is erroneous, as it is a developmental anomaly rather than a true neoplasm. The incidence of nasal glioma is one in 20,000–40,000 live births with female preponderance.[23] Extra nasal glial heterotopias are still rarer.[1] We report a case of extra nasal glial heterotopia in a neonate with unusual features, which was managed successfully.

CASE REPORT

A 12-day-old female neonate was admitted for a mass lesion since birth arising from the premaxilla above the upper lip. There was no history of birth asphyxia, respiratory distress, bleeding or alteration in the size of the swelling. The child was feeding well. On physical examination, the mass was extra-oral and pedunculated, the base of which was bony and the stalk and body were fleshy with erythematous skin. A few hair strands were seen arising from the cranial aspect of the lesion with a broad and flat nose [Figure 1]. A cleft upper lip was noted with palate being normal. There was no visible pulsation or increase in size when the child cried. The rest of the physical examination was unremarkable. Cranial computed tomographic (CT) scan showed left-sided soft tissue mass over the alveolar process of the maxilla with a small defect in the underlying bone and a bony bar projecting anteriorly from the defect. No associated calcification or fat densities were seen. The brain parenchyma appeared normal and there was no direct communication with the intracranial cavity. Fine needle aspiration cytology revealed only blood aspirate. The mass was completely excised along with the premaxilla with a good cosmetic result and the postoperative course was uneventful.

Figure 1

Preoperative photograph showing the pedunculated mass and hair arising from it

The mass was 3×3 cm in size, covered with skin and hair with attached tooth. The cut surface was fleshy. No areas of hemorrhage, necrosis or cystic spaces were identified. The microscopic examination revealed the presence of lobules of glial tissue below the epidermis. Intervening stroma showed many foci of acute inflammatory infiltrate and congested blood vessels. Foci of fibrinoid necrosis were also noted [Figure 2]. Immunohistochemistry showed positivity for glial fibrillary acidic protein [Figure 3].

Figure 2

Microphotograph showing the presence of lobules of glial tissue (H and E, ×200)

Figure 3

Immunohistochemistry showing positivity for glial fibrillary acidic protein (GFAP, ×400)

DISCUSSION

Extra nasal sites of glial heterotopia, though rare are described in scalp, orbit, lip, tongue, palate, pharynx, submandibular region, middle ear, neck and overlying spine as well as in the lungs, skin, uterine cervix and endometrium and other soft tissues.[4-7]

These lesions usually present at birth or within the first few years of life but may occur at any age. Intranasal lesions produce a nasal mass causing stuffiness and nasal obstruction resulting in respiratory distress in neonates and infants. Extra nasal lesions usually present as a mass lesion causing disfigurement as in our case. Occasional associated intracranial communications are seen.[1] A fibrous stalk is found in 15–20% of cases as a relict of this connection, which was also seen in our case.[2] The differential diagnosis includes encephalocele, teratoma, dermoid cyst, rhabdomyosarcoma and cystic lymphangioma.[4] Prenatal diagnosis of nasal glioma is possible with antenatal ultrasonography and fetal MRI, which can be confirmed postnatally.[7] Preoperative evaluation by computed tomography and magnetic resonance imaging helps in determining the exact extent and location of the mass and to rule out any contiguity with the central nervous system, thereby avoiding any complication like cerebrospinal fluid leakage and meningitis.[1] Biopsy or fine needle aspiration is traditionally contraindicated fearing meningitis and removal of any functional brain material.[1]

The exact pathogenesis of this lesion is unknown, although various hypotheses have been postulated.[47] These include: (a) A sequestrated encephalocele; (b) Separation of primitive embryonic neural tissue from the main portion of the developing brain due to change in timing of fusion of chondrocranium; (c) Displacement of isolated pleuripotential cells during early embryogenesis with potential for differentiation to mature neural tissue; and (d) Entrapment of abnormal glial cells from the olfactory bulbs.

Glial tissue involving the uterine cervix and endometrium have been hypothesized to arise from implanted fetal tissue during evacuation of the conception (abortion) which has been proven with DNA genotyping by Siddon et al.[6] Our index case is unique and rare as though there was growth of hair and bony element which would otherwise indicate a teratoma preoperatively, the histopathology came out to be a glial heterotopia as a clinical surprise. The location was also extra nasal, over the premaxilla which is never been reported earlier. As evident by the CT scan, there was a defect in the underlying bone and this bony structure was in the base of the lesion. Apparently this bone may be a part of the underlying bone and had projected outside due to the growth of the mass in-utero. This is classically explaining the first hypothesis of embryogenesis of glial heterotopias.

The treatment of choice is a complete surgical excision with aesthetic reconstruction, without sacrificing any vital structures or compromising function. Early surgical intervention is advocated as there is chance of distortion and erosion of facial bone due to growth of the glial heterotopia and also delay in resection might preclude normal development of swallow function and pharyngeal coordination.[7]

Histologically, glial heterotopia is characterized by varying proportions of neurons and glial cells without mitoses, interlaced with fibrous and vascular connective tissue with occasional gemistocytic astrocytes.[17] Mason's trichrome stain combined with S-100 protein and glial fibrillary acidic protein (GFAP) on immunohistochemistry is most helpful for diagnosis. Neuron-specific enolase and positive synaptophysin also aids in confirmation of diagnosis.[12]

Glial heterotopia can be differentiated from encephalocele clinically and radiologically. Encephaloceles occur as a nonprogressive mass which may be pulsatile, change size during crying and may enlarge during jugular vein compression (Furstenberg sign).[2] These show an obvious intracranial connection on CT or MRI. Teratoma has cells from three germ cell layers, so they have variety of content from ectodermal, mesodermal and endodermal component. So, usually they have variegated appearance on CT and MRI. Teratoma with glial element and glial heterotopia can be differentiated by the fact that in association with glial element, teratomas have other components like fat, calcification and glands etc., which is unusual in glial heterotopias.

In conclusion, any mass lesion of the face in and around nasal area in neonates should evoke high index of suspicion for glial heterotopia.