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Brainstem Chipmunk Sign: A Diagnostic Imaging Clue Across All Subtypes of Alexander Disease Publisher Pubmed



Armangue T1, 2 ; Whitehead MT3, 5 ; Tonduti D6 ; Farina L7 ; Tavasoli AR8, 9 ; Vossough A3, 5 ; Bennett ML4 ; Vaia Y4, 6 ; Bernard G10, 11, 12 ; Salsano E13 ; Mercimekandrews S14, 15 ; Waldman A4, 5 ; Vanderver A4, 5
Authors
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Authors Affiliations
  1. 1. The Neuroimmunology Program, Institut d’Investigacions Biomediques August Pi i Sunyer (IDIBAPS), Hospital Clinic, Neuroimmunology Unit, Sant Joan de Deu Children’s Hospital, University of Barcelona, Barcelona, Spain
  2. 2. Neurology Department, Neuroimmunology Unit, Sant Joan de Deu Children’s Hospital, University of Barcelona, Barcelona, Spain
  3. 3. Department of Radiology, Children’s Hospital of Philadelphia, Philadelphia, PA, United States
  4. 4. Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, United States
  5. 5. Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
  6. 6. Unit of Pediatric Neurology, Center for diagnosis and treatment of Leukodystrophies, V. Buzzi Children’s Hospital, University of Milan, Milan, Italy
  7. 7. Neuroimaging Laboratory, IRCCS Fondazione Santa Lucia, Rome, Italy
  8. 8. Department of Neurology, Children’s Medical Center, Tehran University of Medical Sciences, Tehran, Iran
  9. 9. Department of Neurology, Barrow Neurological Institute, Phoenix Children’s Hospital, Phoenix, AZ, United States
  10. 10. Departments of Neurology and Neurosurgery, Pediatrics, and Human Genetics, Division of Medical Genetics, McGill University Health Centre, Montreal, QC, Canada
  11. 11. Department of Specialized Medicine, Division of Medical Genetics, McGill University Health Centre, Montreal, QC, Canada
  12. 12. Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, QC, Canada
  13. 13. Unit of Rare Neurological Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
  14. 14. Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
  15. 15. The Hospital for Sick Children, Toronto, ON, Canada

Source: American Journal of Neuroradiology Published:2024


Abstract

BACKGROUND AND PURPOSE: While classic brain MR imaging features of Alexander disease have been well-documented, lesional patterns can overlap with other leukodystrophies, especially in the early stages of the disease or in milder phenotypes. We aimed to assess the utility of a new neuroimaging sign to help increase the diagnostic specificity of Alexander disease. MATERIALS AND METHODS: A peculiar bilateral symmetric hyperintense signal on T2-weighted images affecting the medulla oblongata was identified in an index patient with type I Alexander disease. Subsequently, 5 observers performed a systematic MR imaging review for this pattern by examining 55 subjects with Alexander disease and 74 subjects with other leukodystrophies. Interobserver agreement was assessed by the k index. Sensitivity, specificity, and receiver operating characteristic curves were determined. RESULTS: The identified pattern was present in 87% of subjects with Alexander disease and 14% of those without Alexander disease leukodystrophy (P, .001), 3 with vanishing white matter, 4 with adult polyglucosan body disease, and 3 others. It was found equally in both type I and type II Alexander disease (28/32, 88% versus 18/21, 86%; P = .851) and in subjects with unusual disease features (2/2). Sensitivity (87.3%; 95% CI, 76.0%–93.7%), specificity (86.5%; 95% CI, 76.9%–92.5%), and interobserver agreement (k index = 0.82) were high. CONCLUSIONS: The identified pattern in the medulla oblongata, called the chipmunk sign due to its resemblance to the face of this rodent, is extremely common in subjects with Alexander disease and represents a diagnostic tool that can aid in early diagnosis, especially in subjects with otherwise atypical MR imaging findings and/or clinical features. © 2024 American Society of Neuroradiology. All rights reserved.
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