Dynamic Cerebellar Tonsils in Chiari Malformation

Abstract

A 5-year-old asymptomatic boy had apparent optic nerve head elevation on routine ophthalmology examination. Magnetic resonance (MR) imaging of the brain revealed a previously undiagnosed Chiari I malformation with crowding of the foramen magnum and low-lying cerebellar tonsils (Figure, A). Cine phase sagittal MR imaging (Video; available at www.jpeds.com) showed altered cerebrospinal fluid egress through the foramen magnum. It also demonstrated dynamic motion of the cerebellar tonsils that correlated with the cardiac cycle. Shortly after the carotid systolic pulsation, the tonsils appear to elongate, with several millimeters of additional caudal descent (Figure, B and C). This represents direct MR visualization of abnormal fluid dynamics at and force transmission through the crowded foramen magnum. Despite this, the patient remains asymptomatic and will continue routine clinical surveillance. In 1891, pathologist Hans Chiari reported autopsy findings of hindbrain malformation.1Chiari H. Concerning alterations in the cerebellum resulting from cerebral hydrocephalus. 1891.Pediatr Neurosci. 1987; 13: 3-8Crossref PubMed Google Scholar Chiari I is the most common of a group of disorders characterized by abnormal morphology and positioning of posterior fossa structures. The condition is primarily diagnosed on MR imaging, often incidentally, by noting inferiorly displaced, pointed cerebellar tonsils.2Elster A.D. Chen M.Y. Chiari I malformations: clinical and radiologic reappraisal.Radiology. 1992; 183: 347-353Crossref PubMed Scopus (360) Google Scholar, 3Chiapparini L. Saletti V. Solero C.L. Bruzzone M.G. Valentini L.G. Neuroradiological diagnosis of Chiari malformations.Neurol Sci. 2011; 32: S283-S286Crossref PubMed Scopus (27) Google Scholar Although some affected patients are asymptomatic, others can present with a range of symptoms potentially necessitating surgical intervention. The latter scenario is more common with severe cerebrospinal fluid flow obstruction and can be associated with spinal cord syrinx or hydrocephalus.2Elster A.D. Chen M.Y. Chiari I malformations: clinical and radiologic reappraisal.Radiology. 1992; 183: 347-353Crossref PubMed Scopus (360) Google Scholar However, this case reveals that even asymptomatic patients can have visible manifestations of altered flow and pressure dynamics at the foramen magnum. Cerebellar tonsil motion has been reported in a few studies4Pujol J. Roig C. Capdevila A. Pou A. Martí-Vilalta J.L. Kulisevsky J. et al.Motion of the cerebellar tonsils in Chiari type I malformation studied by cine phase-contrast MRI.Neurology. 1995; 45: 1746-1753Crossref PubMed Scopus (97) Google Scholar, 5Cousins J. Haughton V. Motion of the cerebellar tonsils in the foramen magnum during the cardiac cycle.AJNR Am J Neuroradiol. 2009; 30: 1587-1588Crossref PubMed Scopus (39) Google Scholar, 6Radmanesh A. Greenberg J. Chatterjee A. Smyth M.D. Limbrick D.D. Sharma A. Tonsillar pulsatility before and after surgical decompression for children with Chiari malformation type 1: an application for true fast imaging with steady state precession.Neuroradiology. 2015; 57: 387-393Crossref PubMed Scopus (18) Google Scholar and can decrease after decompressive surgery.6Radmanesh A. Greenberg J. Chatterjee A. Smyth M.D. Limbrick D.D. Sharma A. Tonsillar pulsatility before and after surgical decompression for children with Chiari malformation type 1: an application for true fast imaging with steady state precession.Neuroradiology. 2015; 57: 387-393Crossref PubMed Scopus (18) Google Scholar The MR imaging herein illustrates a particularly clear example of this dynamic pathology, emphasizing that Chiari malformation is more than a static anatomical abnormality. eyJraWQiOiI4ZjUxYWNhY2IzYjhiNjNlNzFlYmIzYWFmYTU5NmZmYyIsImFsZyI6IlJTMjU2In0.eyJzdWIiOiJjY2NkMTc2OWUzNzQxN2U5Nzc3NWJlNTViNjQ1MzNiZSIsImtpZCI6IjhmNTFhY2FjYjNiOGI2M2U3MWViYjNhYWZhNTk2ZmZjIiwiZXhwIjoxNjc4OTQ5OTU0fQ.iEJruWjYCXGyMYx6mLdX6zUjkyUf4A6owLtOmiid7kz71Qco8UeiZgXOJow40XxG9l6fhptHepvypuID2ryWAkNCRL4_8Q-as1M1aYLC9YwIqYCV8DMs3cWrnQ2aEvRGvS4zOYQ5Y-o94qF42aQyajJ3ToAkL7gQ_urKDnNmbF3bIW-tNFha7SwbPwO9EbMGQzgk-JHCfrb9EIyuNnrB2xXGH0AWLe0FMd0HmOEk_PlEZXpmqrpLcLR5WJvA0ed37APpAjEPgMbslTWrqiyWL9iJhw1i3q3B0FxxO6xFRb8PkiD8c4XP9tAyLuzUvRolZUWMw2MOJWJA4Z6XKxXo9w Download .mp4 (1.3 MB) Help with .mp4 files VideoCine cerebrospinal fluid dynamic flow magnetic resonance imaging demonstrates low-lying cerebellar tonsils which descend further into the upper cervical canal (arrow) shortly after the cavernous carotid systolic pulsation (demarcated by an * at the 2-second time stamp).