Indian Journal of Radiology and Imaging Indian Journal of Radiology and Imaging

: 2005  |  Volume : 15  |  Issue : 1  |  Page : 27--28

Rhomboencephalosynapsis with associated supratentorial anomalies - a case report.

S Kundu, SK Sharma, S Roy, B Kundu, S Chatterjee 
 EKO-MRI Centre, Kolkata, India

Correspondence Address:
S Kundu
EKO-MRI Centre, Kolkata-700 071

How to cite this article:
Kundu S, Sharma S K, Roy S, Kundu B, Chatterjee S. Rhomboencephalosynapsis with associated supratentorial anomalies - a case report. Indian J Radiol Imaging 2005;15:27-28

How to cite this URL:
Kundu S, Sharma S K, Roy S, Kundu B, Chatterjee S. Rhomboencephalosynapsis with associated supratentorial anomalies - a case report. Indian J Radiol Imaging [serial online] 2005 [cited 2019 Sep 18 ];15:27-28
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Full Text


Rhomboencephalosynapsis is a rare malformation of the cerebellum where fusion of both cerebellar hemispheres is present with vermian agenesis or hypogenesis. It can be associated with supratentorial anomalies. Here we report a case of Rhomboencephalosynapsis associated with supratentorial anomalies.

 Case report

A 15 years male presented with history of intractable seizures & mental retardation with poor scholastic aptitude. His birth history was unremarkable and he had no other physical complaints. On examination the patient was of average build but had below normal intelligence for his age. He had no cognitive dysfunction or neurologic deficit. He had no disequilibrium or visual complaints. His routine investigation of blood was within normal limits. EEG was normal. A CT scan done was reported as normal except for absence of septum pellucidum. However, the posterior fossa was partially obscured by artifacts.

Non-contrast M R I of brain was performed with conventional spin echo T2 & T1 weighted images in transverse, coronal & sagittal planes along with oblique coronal images perpendicular to axis of hippocampus.

Posterior fossa revealed fusion of both cerebellar hemispheres & middle cerebellar peduncles with absence of cerebellar vermis [Figure 1][Figure 2]. IV ventricle was small. Cerebellar tonsils were in normal position. Brainstem was normal. Both hippocampi showed hypoplasia without any obvious signal abnormality. There was also absence of septum pellucidum [Figure 3]. There was widening of temporal horn of both lateral ventricles. Optic chiasma & optic nerves were normal. Parenchymal signals of both cerebral hemispheres were normal. Corpus callosum was normal.


Rhomboencephalosynapsis is a rare posterior fossa malformation arising possibly from embryological defects that are caused by mutation or mutations of genes because of which developmental defects arise in the pontomesencephalic junction.[7] Rhomboencephalosynapsis patients may present with seizures, mental retardation, abnormal behaviour & disequilibrium, convergent strabismus, optic nerve atrophy, dysarthria, apraxia & spasticity.

Very often the symptoms are related to supratentorial anomalies. Majority of patients die in infancy though the oldest living case has been reported at the age of 39 years.[4] Posterior fossa anomalies include fusion of cerebellar hemispheres, dentate nuclei & cerebellar peduncles with the cerebellar folia appearing continuous across the midline due to absence of vermis. IV ventricle is small with key hole appearance. Brainstem may be small and quadrigeminal plate may be dysplastic. There may be an incomplete tentorial incisura.

Associated supratentorial defects can be absence of septum pellucidum, hydrocephalus & thalamic fusion. Dysgenesis of corpus callosum and hypoplasia of hippocampi may be found. Cases have been reported with hypoplasia of anterior commissure, schizencephaly & cortical malformations. Cephalocele and multiple suture synostosis are also found. Vermian agenesis is also found in Joubert's syndrome but absence of cerebellar fusion separates it from rhomboencephalosynapsis. Obesteiner first described this posterior fossa abnormality in 1914.[1] MRI, because of the excellent demonstration of brain morphology in vivo, is the modality of choice for the detection of these anomalies. The exact incidence of Rhomboencephalosynapsis is not known.[2] There were few reported cases prior to the routine use of M R I for evaluation of patients with suspected intra-cranial abnormalities. There has been one reported case of diagnosis of rhomboencephalosynapsis by computed tomography[3] and one case by antenatal ultrasonograpy.6 However, several cases have been reported in the recent past on MRI and we add one more example of rhomboencephalosynapsis with supra-tentorial anomalies.


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