Citation, DOI & article data
Rhombencephalosynapsis is a congenital abnormality of the cerebellum characterized by absence of the vermis and continuity of the cerebellar hemispheres, dentate nuclei, and superior cerebellar peduncles. It either occurs as an isolated anomaly (rare) or as part of wider cerebral malformation and it has variable degrees of neurological impairment.
The condition is very rare and thought to be sporadic. No familial cases have been identified 9.
Clinical presentation includes truncal and/or limb ataxia, abnormal eye movements, head stereotypies, delayed motor development, and other features determined by supratentorial abnormalities (see below) 10. Overall patients tend to die in childhood or early adult life 9.
Rhombencephalosynapsis has been seen to be associated with:
- Gomez-Lopez-Hernandez syndrome: comprises rhombencephalosynapsis, developmental delay, scalp alopecia and trigeminal anesthesia 5
- vertebral fusion anomalies
Embryologically rhombencephalosynapsis is now considered as a failure of vermian differentiation with the fused development of the cerebellar hemispheres, thought to result from an insult between the 28th and 44th day of gestation 6,8. There is classically a transversely oriented single lobed cerebellum.
Rhombencephalosynapsis was traditionally thought to be a complete fusion of cerebellar hemispheres; however, off late cases of partial fusion have also been reported 6,8.
Rhombencephalosynapsis is best seen on MRI brain, and is characterized by 1-4,7,8:
- vermian abnormalities
- absent anterior (rostral) vermis
- deficient posterior (caudal) vermis
- nodulus tends to be formed
- fusion of the cerebellar hemispheres, with transversely oriented inferior cerebellar folia
- fusion of dentate nuclei
- fusion of the superior cerebellar peduncles
Additional frequently associated abnormalities include:
- fusion of the thalami
- fusion of inferior colliculi
- absent septum pellucidum
- ventriculomegaly: often from aqueductal stenosis
- sutural synostosis
- other supratentorial abnormalities 8
Treatment and prognosis
Variable clinical progression ranging from early death to varying degrees of cerebellar dysfunction and neurodevelopmental delay. Some patients may reach adulthood 3.
History and etymology
It was first reported by Heinrich Obersteiner (1847-1922), an Austrian neurologist, in 1914 3.
Imaging differential considerations include:
- 1. Barkovich AJ. Pediatric neuroimaging. Lippincott Williams & Wilkins. (2005) ISBN:0781757665. Read it at Google Books - Find it at Amazon
- 2. Sandalcioglu IE, Gasser T, Van de nes JA et-al. Fusion of the cerebellar hemispheres ventral to the brainstem: a rare hindbrain-related malformation. Childs Nerv Syst. 2006;22 (1): 73-7. doi:10.1007/s00381-004-1065-5 - Pubmed citation
- 3. Truwit CL, Barkovich AJ, Shanahan R et-al. MR imaging of rhombencephalosynapsis: report of three cases and review of the literature. AJNR Am J Neuroradiol. 12 (5): 957-65. AJNR Am J Neuroradiol (abstract) - Pubmed citation
- 4. Patel S, Barkovich AJ. Analysis and classification of cerebellar malformations. AJNR Am J Neuroradiol. 2002;23 (7): 1074-87. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 5. Whetsell W, Saigal G, Godinho S. Gomez-Lopez-Hernandez syndrome. (2006) Pediatric radiology. 36 (6): 552-4. doi:10.1007/s00247-006-0150-1 - Pubmed
- 6. Demaerel P, Morel C, Lagae L et-al. Partial rhombencephalosynapsis. AJNR Am J Neuroradiol. 2004;25 (1): 29-31. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 7. Utsunomiya H, Takano K, Ogasawara T et-al. Rhombencephalosynapsis: cerebellar embryogenesis. AJNR Am J Neuroradiol. 1998;19 (3): 547-9. AJNR Am J Neuroradiol (abstract) - Pubmed citation
- 8. Demaerel P, Morel C, Lagae L et-al. Partial rhombencephalosynapsis. AJNR Am J Neuroradiol. 2004;25 (1): 29-31. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 9. Levene MI, Chervenak FA. Fetal and Neonatal Neurology and Neurosurgery. Churchill Livingstone. (2009) ISBN:0443104077. Read it at Google Books - Find it at Amazon
- 10. Bosemani T, Orman G, Boltshauser E et-al. Congenital abnormalities of the posterior fossa. Radiographics. 2015;35 (1): 200-20. doi:10.1148/rg.351140038 - Pubmed citation