The chipmunk sign refers to the MRI appearance of the medulla in some patients with leukodystrophies, particularly Alexander disease. The same appearance has been described in adult polyglucosan body disease, vanishing white matter disease, Pelizaeus-Merzbacher disease, 4H syndrome, and adult-onset dominant leukodystrophy 1.
Radiographic appearance
MRI
On axial T2 weighted imaging through the medulla oblongata, increased signal involving central parts of the inferior olivary nucleus, the cuneate fasciculus and gracile fasciculus and the medullary pyramids 1. The medial longitudinal fasciculus and inferior cerebellar peduncles are generally spared.
The likeness is due to the overall shape of the medulla, already reminiscent of the silhouette of a chipmunk head, with the spared peripheral parts of the inferior olivary nucleus forming the eyes and the spared inferior cerebellar peduncles the adorable cheeks 1.
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