en Editorial The entity of Chiari formation was&nbsp;described by Hans Chiari in 1891 [1,2].&nbsp;Since then the subject has been evaluated&nbsp;elaborately by a number of authors. However,&nbsp;it may only be correct to state that confusion&nbsp;in the understanding of pathogenesis and the&nbsp;nature of anomaly, significance of associated&nbsp; abnormal soft tissue and bone anomalies&nbsp;and more importantly the treatment of the&nbsp;entity has not been resolved. The number of&nbsp;described treatment patterns are a testimony&nbsp;to the inadequacy of the understanding. The&nbsp;general consensus is that uncal herniation&nbsp;and tonsillar herniation are both similar in&nbsp;their pathogenesis wherein the part of the&nbsp;temporal brain or the cerebellum are pushed&nbsp;out of their compartment through a hiatus&nbsp;or hole into the other body compartment.&nbsp;In the process of herniation, there is&nbsp;congestion of space and compromise of&nbsp;the neural structures in the vicinity that<br> leads to neurological symptoms or deficits.&nbsp;The factor that causes the push in case of&nbsp;Chiari malformation is unclear. However,&nbsp;the presence of an increased volume of&nbsp;cerebellar mass, a smaller volume of the&nbsp;posterior cranial fossa bone compartment or&nbsp;a combination of both these factors could be<br> the possible cause.&nbsp;The general understanding is that the&nbsp;addition of the tonsillar volume in the&nbsp;foramen magnum limits the space for the<br> neural structures that are compressed and&nbsp;results in related symptoms. Foramen&nbsp;magnum decompression is an established&nbsp;and a gold standard form of treatment.<br> &nbsp; Chiari, Atlantoaxial Instability, Anomaly, 36 38 http://irjns.org/browse.php?a_code=A-10-196-1&slc_lang=en&sid=1 Atul Goel dratul@gmail.com 10031947532846001525 10031947532846001525 Yes Department of Neurosurgery, Seth G.S. Medical College and KEM Hospital, Parel, Mumbai – 400012, India