Neurology India
menu-bar5 Open access journal indexed with Index Medicus
  Users online: 1483  
 Home | Login 
About Editorial board Articlesmenu-bullet NSI Publicationsmenu-bullet Search Instructions Online Submission Subscribe Videos Etcetera Contact
  Navigate Here 
 Resource Links
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
    Article in PDF (849 KB)
    Citation Manager
    Access Statistics
    Reader Comments
    Email Alert *
    Add to My List *
* Registration required (free)  

  In this Article
   Article Figures

 Article Access Statistics
    PDF Downloaded36    
    Comments [Add]    

Recommend this journal


Table of Contents    
Year : 2016  |  Volume : 64  |  Issue : 6  |  Page : 1381-1383

Rhombencephalosynapsis: A rare cerebellar malformation associated with aqueductal stenosis and obstructive hydrocephalus

1 Department of Pediatric Neurology, Deenanath Mangeshkar Hospital and Research Center, Pune, Maharashtra, India
2 Department of Radiology, Star Imaging and Research Center, Pune, Maharashtra, India

Date of Web Publication11-Nov-2016

Correspondence Address:
Dr. Umesh Kalane
Flat no. 202, G Building, Wonder City Society, Katraz Serve No. 75, Pune, Maharashtra
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0028-3886.193837

Rights and Permissions

How to cite this article:
Kalane U, Atre A. Rhombencephalosynapsis: A rare cerebellar malformation associated with aqueductal stenosis and obstructive hydrocephalus. Neurol India 2016;64:1381-3

How to cite this URL:
Kalane U, Atre A. Rhombencephalosynapsis: A rare cerebellar malformation associated with aqueductal stenosis and obstructive hydrocephalus. Neurol India [serial online] 2016 [cited 2021 Jan 26];64:1381-3. Available from:

A 2-year-old boy was presented for evaluation of developmental delay. He had both motor and cognition delay. He developed neck holding by 9 months of age and started sitting at 1 year of age. He was able to stand with support by the age of 2 years; however, he could not walk independently at presentation. There was significant speech delay and he could not express words with meaning; he was, however, able to follow simple commands. He was first in birth order, born of non- consanguineous marriage, and without significant family history of neurological disorders. His birth history was also unremarkable.

On examination, he had a head size of 50 cm, which was on the 90th percentile for his age standard. The anterior fontanel was closed. No obvious dysmorphic features were noted. On neurological examination, there were no deficits; however, mild limb hypotonia was noted with brisk deep tendon reflexes, suggesting pyramidal tract involvement. His electroencephalography and brainstem auditory evoked response (BERA) tests were normal. His magnetic resonance imaging (MRI) of the brain showed complete absence of cerebellar vermis, and across the midline continuity of the cerebellar hemispheres and deep cerebellar nuclei with posteriorly pointing fourth ventricle, consistent with rhomboencephalosynapsis [Figure 1]. In addition, there was gross ventriculomegaly affecting both lateral and third ventricles. The septum pellucidum was absent with severe narrowing of the aqueduct [Figure 2]. Based on the MRI brain findings, he was diagnosed as a case of rhomboencephalosynapsis with aqueductal stenosis causing obstructive hydrocephalus, which is a rare cerebellar malformation disorder.
Figure 1: Axial T2 image showing cerebellar hemispheric fusion across the midline with continuity of white matter tracts, absence of vermis, and posteriorly pointing 4th ventricles

Click here to view
Figure 2: Axial T2 image showing aqueductal stenosis with hydrocephalus and rhombencephalosynapsiscerebellar

Click here to view

Rhombencephalosynapsis is a cerebellar anomaly characterized by lack of separation of the cerebellar hemispheres with vermian hypogenesis or agenesis and fusion of the cerebellar hemispheres, the middle cerebellar peduncles, and the dentate nuclei. Obersteiner, in 1914, described rhombencephalosynapsis for the first time.[1] The vermian maldevelopment is characterized by an absence of the anterior vermis and a deficiency of the posterior vermis; the nodulus tends to be formed.[1],[2],[3],[4],[5] It is not associated with disconnected cerebellar hemispheres, such as seen in Dandy–Walker malformation, Joubert syndrome, or tectocerebellar dysgraphia.[3],[5],[6],[7] Until now, there have been approximately 50 case reports worldwide. Their number is increasing with the use of MRI. All published cases are mostly sporadic, as in our case, with a single familial occurence.[4] MR features of rhombencephalosynapsis are characteristic. A diamond-shaped fourth ventricle, instead of the normal crescentic shape, is seen on axial sections, and this abnormal configuration of the fourth ventricle indicates vermian hypogenesis or agenesis.[7],[8] Fusion or apposition of the dentate nuclei and middle cerebellar peduncles can be observed behind a pointed fourth ventricle, as seen in our case [Figure 1].

Rhombencephalosynapsis has been described in conjunction with Gomez–Lopez–Hernandez syndrome and VACTERAL association.[4],[5] Deficiency or absence of the septum pellucidum is described in literature, as was seen in our case.[7] Rhombencephalosynapsis is also associated with multiple forebrain abnormalities including absent olfactory bulbs, dysgenesis of the corpus callosum, absent septum pellucidum, and, in rare patients, atypical forms of holoprosencephaly.[3],[4],[6],[7]

Aqueductal stenosis, which may cause congenital hydrocephalus, is commonly associated with this anomaly, as was also seen in our case.[8] Therefore, rhombencephalosynapsis should be suspected in infants in whom both congenital hydrocephalus and a flat-based cerebellum without formation of the cerebellar vallecula is observed.[8]

A spectrum of severity, ranging from mild (the partial absence of nodulus, anterior, and posterior vermis), to moderate (the absence of posterior vermis with some anterior vermis and nodulus present), to severe (the absence of posterior and anterior vermis with some nodulus present), to complete (the absence of the entire vermis including nodulus) has been proposed.[7]

The clinical presentation of rhombencephalosynapsis is variable and ranges from severe congenital hydrocephalus, severe cerebral palsy and mental retardation, to mild truncal ataxia and normal cognition. In our case, the presentation was delayed development with a large head due to the presence of hydrocephalus.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Obersteiner H. Ein Kleinhirn ohne Wurm. Arb Neurol Inst 1914;21:124-36.  Back to cited text no. 1
Romanengo M, Tortori-Donati P, Di Rocco M. Rhombencephalosynapsis with facial anomalies and probable autosomal recessive inheritance: A case report. Clin Genet 1997;52:184-6.  Back to cited text no. 2
Kepes JJ, Clough C, Villanueva A. Congenital fusion of the thalami (atresia of the third ventricle) and associated anomalies in a 6 months old infant. Acta Neuropathol 1969;13:97-104.  Back to cited text no. 3
Ishak GE, Dempsey JC, Shaw DW, Tully H, Adam MP, Sanchez-Lara PA, et al. Rhombencephalosynapsis: A hindbrain malformation associated with incomplete separation of midbrain and forebrain, hydrocephalus and a broad spectrum of severity. Brain 2012;135:1370-86.  Back to cited text no. 4
Pasquier L, Marcorelles P, Loget P, Pelluard F, Carles D, Perez MJ, et al. Rhombencephalosynapsis and related anomalies: A neuropathological study of 40 fetal cases. Acta Neuropathologica 2009;117:185-200.  Back to cited text no. 5
Truwit CL, Barkovich AJ, Shanahan R, Maroldo TV. MR imaging of rhombencephalosynapsis: Report of three cases and review of the literature. AJNR Am J Neuroradiol 1991;12:957-65.  Back to cited text no. 6
Passi GR, Bhatnagar S. Rhombencephalosynapsis. Pediatr Neurol 2015;52:651-2.  Back to cited text no. 7
Whitehead MT, Choudhri AF, Grimm J, Nelson MD. Rhombencephalosynapsis as a cause of aqueductal stenosis: An under-recognized association in hydrocephalic children. Pediatr Radiol 2014;44:849-56.  Back to cited text no. 8


  [Figure 1], [Figure 2]


Print this article  Email this article
Online since 20th March '04
Published by Wolters Kluwer - Medknow