Figure 2From: Short lasting activity-related headaches with sudden onset in children: a case-based reasoning on classification and diagnosis Sagittal contrast-enhanced T1-weighted (a) showing a caudal protrusion (12Â mm) of the elongated triangular-shaped tonsils below the foramen magnum (white arrows). Axial T1-weighted image (b) confirms cerebellar tonsils filling the foramen magnum and effacing the cysterna magna (white arrows). Back to article page