Images in Fetal Medicine Received: May 22, 2011 Accepted after revision: July 14, 2011 Published online: September 2, 2011
Fetal Diagn Ther DOI: 10.1159/000330859
Pre- and Postnatal Ultrasound and Magnetic Resonance Imaging of Intracranial Extra-Axial Glioneuronal Heterotopia Avner Meoded a Sifa Turan c Chris Harman c Andrea Poretti a James Zinreich b Thierry A.G.M. Huisman a
Divisions of a Pediatric Radiology, b Neuroradiology, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Hospital, and c Obstetrics, Gynecology and Reproductive Sciences, University of Maryland, Baltimore, Md., USA
Key Words Intracranial extra-axial glioneuronal heterotopia ⴢ Craniofacial malformation ⴢ Fetal MRI ⴢ Diffusion tensor imaging
Abstract Glioneuronal heterotopias are rare malformations composed of differentiated derivates of neuroectodermal tissue that include disorganized neuronal and glial cells. They are typically located extracranially. The nasal cavity represents the most common location. Glioneuronal heterotopias have also been reported in the orbit, pharynx, middle ear, neck and thorax. Rarely, glioneuronal heterotopias may be located intracranially. We are aware of only 15 patients reported with intracranial extra-axial glioneuronal heterotopia (IEGH). We present the prenatal ultrasound and MRI as well as the matching postnatal CT, conventional MRI and diffusion tensor imaging findings of a newborn with an infratentorial IEGH accompanied with craniofacial anomalies. Copyright © 2011 S. Karger AG, Basel
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Case Report A 36-year-old female, gravida 1 para 0, received a routine first trimester ultrasound (US) screening scan at 12 weeks of gestation. US showed only a slight asymmetry of the cerebral hemispheres (R! L). Follow-up US at 18 weeks of gestation showed an absent right eye globe, a small and deformed nostril, and hypoplasia of the right orbit, mandible and ear (fig. 1a–c). The asymmetry of the cerebral hemispheres had increased and an irregular skull base was noted. In addition, at 31 weeks of gestation a 5.5 ! 2.6 cm mass lesion was detected in the right posterior fossa (fig. 1d, e) and mild polyhydramnios had developed. Subsequent fetal MRI at 32 weeks of gestation confirmed all US findings and characterized the mass lesion as a ‘brain-like’ disorganized heterogenic mass compressing and displacing the cerebellum and brainstem (fig. 2). At 355/7 weeks a baby girl was born by spontaneous vaginal delivery. The Apgar scores were 2/7/8 at 1/5/10 min, respectively. Resuscitation with suction of meconium was needed. The birth weight was 2,430 g (low for gestational age) and the head circumference was 33 cm (appropriate for gestational age). The baby developed severe respiratory distress requiring intubation. After an extubation trial, persistent severe obstructive apneas required tracheostomy. In addition, swallowing difficulties and mild global muscular hypotonia were noted. Postnatal MRI on the third day of life confirmed a large wellcircumscribed extra-axial mass in the posterior fossa, anterior to the compressed and posteriorly displaced brainstem and cerebel-
Thierry A.G.M. Huisman, MD, EQNR, FICIS Division of Pediatric Radiology, Johns Hopkins Hospital 600 North Wolfe Street Nelson Basement, B-173, Baltimore, MD 21287-0842 (USA) Tel. +1 410 955 6140, E-Mail thuisma1 @ jhmi.edu
Color version available online
Fig. 1. a–c 3D tomographic US at 18 weeks
of gestation. Axial image (thickness 2.2 mm; a, b) and 3D surface rendering of the fetal face (c) demonstrate an absent eye globe (long arrows in b, c), a hypoplastic orbit, small deformed nostril (short arrow), markedly hypoplastic mandible (arrow in a) and hypoplastic ear on the right side. d 3D tomographic US at 31 weeks of gestation. Axial image (slice thickness 3.3 mm) shows a 5.5 ! 2.6 cm mass lesion in the right posterior fossa (white arrows), which compresses the cerebellum and brainstem. e 3D surface rendering of the facial structures at 34 weeks of gestation confirms the craniofacial abnormalities, with absence of the right eye globe (black arrow).
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imaging (fig. 3d, e) demonstrated signal characteristics similar to gray matter and white matter without any higher end fiber structures within the lesion. No fibers were identified that connected the extra-axial lesion with the adjacent brainstem. The major fibers within the brainstem and the cerebellum appeared intact but displaced. Based upon the MRI findings, the mass was interpreted as an intracranial extra-axial glioneuronal heterotopia (IEGH). An additional CT study showed the osseous malformation in better detail and identified a complex right hemifacial dysgenesis with absence of the right zygomatic arch; severe dysplasia of the right maxilla, mandible and sphenoid wing; atresia of the right nasal cavity; and hypoplasia of the right orbit and external auditory canal (fig. 3f). Partial resection of the mass was performed on day 5 of life, in order to reduce the mass effect on the brainstem. Histological study confirmed diagnosis. Fig. 2. Prenatal coronal ultrafast T2-weighted MR image at 32 weeks of gestation confirms the infratentorial mass lesion (arrows).
Discussion lum (fig.3a–c). The mass appeared predominantly T1/T2-isointense to gray matter with several small inclusion cysts. The right eye globe was absent, the orbit significantly hypoplastic, and the ipsilateral ear malformed and anteriorly displaced. The inner and middle ear structures appeared unremarkable, without a definite external auditory canal. On post-contrast images a few small foci of faint intralesional enhancement were seen. Diffusion tensor
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Fetal Diagn Ther
IEGH are rare congenital disorders that may be seen in the head, face, spine and thoracic region. They are composed of disorganized but mature neuronal and glial elements. IEGH are considered to be a rare subtype of glioneuronal heterotopia. To our knowledge, only 15 cases have previously been reported [1–3]. Meoded /Turan /Harman /Poretti / Zinreich /Huisman
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Fig. 3. a–d Postnatal axial T1-weighted (a), T2-weighted (b), and post-contrast T1-weighted (c) MR images show a well
circumscribed mass lesion (arrows) anteriorly to the compressed and posteriorly displaced brainstem and cerebellum. The lesion exhibits intermingled T1 and T2 gray matter/white matter signal characteristics with small enclosed cysts (arrowheads). Absence of the right eye globe and optic nerve is also appreciated. A few small foci of faint enhancement are noted within the lesion. d Axial ADC and e color FA maps show an internal architecture that partially resembles cerebral cortex/GM. f CT with 3D reconstruction demonstrates the osseous craniofacial abnormalities in better detail.
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Different theories have been proposed to explain the pathogenesis of IEGH. The detachment theory refers to glioneuronal heterotopia as ‘accessory brains’ [4]. According to this theory, IEGH appear between the 5th and 6th week of gestation while the forebrain vesicle is divided into the telencephalon and diencephalon. Because most IEGH are large at presentation, it is likely that the etiological event indeed occurs early in gestation. Additionally, IEGH are frequently associated with congenital craniofacial anomalies. Our findings support the detachment theory and an early development of IEGH.
References
Intracranial Extra-Axial Glioneuronal Heterotopia
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IEGH are clinically and pathologically benign, and must be differentiated from true neoplasms. The rarity of lesions and the small number of cases reported in the literature necessitate biopsy for the definite diagnosis and to rule out malignant neoplasm. However, high-resolution anatomical and functional neuroimaging facilitates diagnosis. In addition, radiologists should be familiar with this rare entity. The intracranial extra-axial location, lack of infiltration of adjacent brain structures, signal characteristics of intermingled gray matter/white matter, faint or absent contrast enhancement, lack of growth on serial imaging, and diffusion tensor imaging characteristics support diagnosis.
1 Oya S, Kawahara N, Aoki S, Hayashi N, Shibahara J, Izumi M, Kirino T: Intracranial extracerebral glioneuronal heterotopia. Case report and review of the literature. J Neurosurg 2005;102:105–112. 2 Gyure KA, Morrison AL, Jones RV: Intracranial extracerebral neuroglial heterotopia: a case report and review of the literature. Ann Diagn Pathol 1999; 3:182–186.
Fetal Diagn Ther
3 Huisman TA, Brehmer U, Zeilinger G, Stallmach T, Gysin C: Parapharyngeal neuroglial heterotopia extending through the skull base in a neonate with airway obstruction. J Pediatr Surg 2007;42:1764–1767. 4 Harris CP, Townsend JJ, Klatt EC: Accessory brains (extracerebral heterotopias): unusual prenatal intracranial mass lesions. J Child Neurol 1994;9:386–389.
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