In mammals, many classes of noncoding RNAs (ncRNAs) are expressed at a much 
higher level in the brain than in other organs. Recent studies have identified a 
new class of ncRNAs called circular RNAs (circRNAs), which are produced by 
back-splicing and fusion of either exons, introns, or both exon-intron into 
covalently closed loops. The circRNAs are also highly enriched in the brain and 
increase continuously from the embryonic to the adult stage. Although the 
functional significance and mechanism of action of circRNAs are still being 
actively explored, they are thought to regulate the transcription of their host 
genes and sequestration of miRNAs and RNA binding proteins. Some circRNAs are 
also shown to have translation potential to form peptides. The expression and 
abundance of circRNAs seem to be spatiotemporally maintained in a normal brain. 
Altered expression of circRNAs is also thought to mediate several disorders, 
including brain-tumor growth, and acute and chronic neurodegenerative disorders 
by affecting mechanisms such as angiogenesis, neuronal plasticity, autophagy, 
apoptosis, and inflammation. This review discusses the involvement of various 
circRNAs in brain development and CNS diseases. A better understanding of the 
circRNA function will help to develop novel therapeutic strategies to treat CNS 
complications.