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|Year : 2022 | Volume
| Issue : 4 | Page : 1652-1654
Fetal Pontine Tegmental Cap Dysplasia- A Case Report
C Priyanka1, Rajeswaran Rangasami1, Indrani Suresh2
1 Department of Radiology, Sri Ramachandra Institute of Higher Education and Research, Chennai, Tamil Nadu, India
2 Department of Fetal Medicine, Mediscan Systems, Chennai, Tamil Nadu, India
|Date of Submission||16-Aug-2020|
|Date of Decision||02-Sep-2020|
|Date of Acceptance||30-Oct-2020|
|Date of Web Publication||30-Aug-2022|
(Ph.D Scholar), Department of Radiology, Sri Ramachandra Institute of Higher Education and Research, Porur, Chennai - 600 116, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Pontine tegmental cap dysplasia (PTCD) is a very rare hindbrain malformation recently described and the affected children show a bad prognosis. We present this case to increase the awareness of this rare condition and to highlight the importance of early prenatal diagnosis. A 25 years old female with 22 weeks gestation was referred after sonography for fetal magnetic resonance imaging (MRI) in the evaluation of cerebellar hypoplasia. Prenatal MRI confirmed cerebellar hypoplasia. Follow up postnatal MRI showed flattening of the ventral pons, beak-like tissue in the posterosuperior pons suggesting the diagnosis of PTCD. In retrospect the fetal MR images revealed features consistent with PTCD. To the best of our knowledge, this is the fifth prenatal case and with the earliest gestational age of 22 weeks.
Keywords: Cerebellar hypoplasia, fetal MRI, pontocerebellar hypoplasia
Key Message: PTCD is a rare malformation, mimics cerebellar hypoplasia on imaging and shows poor prognosis. We recommend that every case of cerebellar hypoplasia be carefully evaluated for ponto cerebellar hypoplasia and PTCD by fetal MRI at around 24 weeks.
|How to cite this article:|
Priyanka C, Rangasami R, Suresh I. Fetal Pontine Tegmental Cap Dysplasia- A Case Report. Neurol India 2022;70:1652-4
Pontine tegmental cap dysplasia (PTCD) is a very rare hindbrain malformation and shows features that include ventral hypoplasia of the pons, dorsal vaulted tegmentum cap, absence of the middle cerebellar peduncles, vermian hypoplasia and absent inferior olivary nucleus. Clinically the affected patients present with severe motor, cognitive disorders and cranial nerve impairment. Here we are present the prenatal and postnatal magnetic resonance imaging (MRI) findings of PTCD.
| » Case Report|| |
A 25-year-old female with 22 weeks of gestation was referred for fetal magnetic resonance imaging (MRI) in the evaluation of her fetus who showed cerebellar diameter less than 3rd centileand single umbilical artery on antenatal sonography. The parents were unrelated and there was no family history for congenital anomalies. Her provisional sonographic diagnosis was cerebellar hypoplasia. Fetal MRI performed using Half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence subsequently revealed, smaller dimensions of the cerebellar hemisphere and vermis [Figure 1]a, [Figure 1]b, [Figure 1]c with transverse cerebellar diameter measuring 19mm and vermian height measuring 10.5mm.A radiological diagnosis of cerebellar hypoplasia was made and the couple decided to continue the pregnancy. Clinical examination at 4months after birth, revealed that the infant had developmental delay and left facial nerve palsy. The postnatal MRI showed flattening of the ventral pons, beak-like tissue in the postero superior pons [Figure 1]f, hypoplastic middle cerebellar peduncles, molar tooth appearance at the level of superior pons [Figure 1]d and [Figure 1]e suggesting the diagnosis of PTCD. In retrospect, the fetal MR images showed flattening of the ventral pons and beaking in the dorsal pons [Figure 1]c. The patient was lost for further follow-up.
|Figure 1: Antenatal T2 Weighted HASTE axial (a), coronal (b), MR images show hypoplastic cerebellar hemispheres (white arrows).T2Weighted HASTE Sagittal (c) image shows flattening of the ventral pons (arrow head) and beak like tissue in the dorsal pons (open arrow). Postnatal MR T2 weighted FSE axial images (d and e) show hypoplastic inferior cerebellar peduncles (broken arrow) and molar tooth appearance (black arrow). T2 weighted FSE Sagittal image (f) shows flat ventral pons (arrow head) and a dorsal vault (open arrow) projectinginto the fourth ventricle. (HASTE- Half-Fourier-Acquisition Single-shot Turbo spin Echo; FSE-Fast spin echo)|
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| » Discussion|| |
Embryologically, the structures of the posterior fossa are derived from hindbrain. Pons cerebellum and superior part of the fourth ventricle are derived from the metencephalon. Bulb and inferior part of the fourth ventricle are derived from the myelencephalon. During sixth week of gestation pontine flexure divides the fourth ventricle into anterior and posterior membranous areas. Cerebellar vermis appears in anterior membranous area. PTCD is a sporadic malformation with unknown genotype and no familial recurrence.The pathogenesis of PTCD is unknown. It has been postulated that it occurs due to a defective migration or navigation of axons of the rhombencephalicneurons.
PTCD is characterized by a flattened ventral pons with dorsal vaulted tegmentum cap, absence/hypoplasia of the middle cerebellar peduncles, vermian hypoplasia, a molar tooth-like aspect of the pontomesencephalic junction and absent inferior olivary prominence. Blondiaux et al. have also erroneously reported three cases of Fetal PTCD as pontocerebellar hypoplasis in their 4 cases where fetal MR imaging was done between 28 to 33 weeks. They have highlighted the importance of looking for the dorsal beak-like tissue in the antenatal scans. During early II trimester, when pontine flattening may be subtle the authors believe that every case of cerebellar hypoplasia should be carefully evaluated for ponto cerebellar hypoplasia and PTCD as the prognosis is not favorable in the latter two conditions. Another challenge is presence of PTCD with normal cerebellar diameter and to avoid missing this diagnosis, the anterior pontine bulge should always be sought for in antenatal scans. When there is ambiguity in the imaging diagnosis, a follow-up scan may be advised by 24 weeks. MR diffusion tensor imaging shows ectopic bundle of transverse fibers and the absence of normal transverse pontine fibers. Clinical presentation of PTCD include sensory neural hearing deafness, ataxia, speech disturbances, facial palsy, spine anomalies, swallowing problems and failure to thrive. Vertebral anomalies, rib malformation and congenital heart defects have also been reported.
PTCD needs to be differentitated from other conditions like global cerebellar hypoplasia, pontocerebellar hypoplasia (PCH) and moebius syndrome. Global cerebellar hypolplasia (GCA) is characterized by reduced cerebellar volume even though cerebellar shape (near) normal. Important causes of GCA are chromosomal abnormalities, infections, metabolic disorders and syndromes associated with multiple anomalies.It is diagnosed on imaging when the cerebellar dimensions are below the normal range.The affected patients can present with developmental delay, ataxia, hypotonia and movement disorders. Pontocerebellar hypoplasia represents a group of autosomal recessive neurodegenerative disorders characterized by prenatal abnormal development of the cerebellum and pons. Initially pontocerebellar hypolpasia was categorized into two subtypes depending on the presences or absence of motor neuron degeneration in the anterior horn of the spinal cords. Present PCH is classified into ten subtypes based on clinical and genetic features, all subtypes share similar characteristics including hypoplasia/atrophy of cerebellum and pons, progressive, microcephaly and variable cerebral involvement. Pontocerebellar hypolpasia does not show the ectopic dorsal pontine tissue on imaging, though there is flattening of the ventral pons and reduced cerebellar dimensions.
Moebius syndrome is characterized by the presence of bilateral 6th and 7th nerve palsies, which is not seen PTCD. Moebius syndrome also shows other features like absent hypoglossal prominence and hypoplasia of the dorsal pons with absence of medial colliculus at the pontine level leading to depression in fourth ventricle. The prognosis of PTCD appears highly variable, ranging from mild delay in cognitive development to severe disability.
| » Conclusion|| |
PTCD is a rare hindbrain malformation, carries a poor prognosis and may present as cerebellar hypoplasia when imaged in second trimester ultrasound.We recommend that every case of cerebellar hypoplasia be carefully evaluated for ponto cerebellar hypoplasia and PTCD by fetal MRI at around 24 wks.
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Conflicts of interest
There are no conflicts of interest.
| » References|| |
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