Figure 2 Brain CT and MRI scans of affected patients: (A–D) VI and (E, F) IV6. (A, B) Axial CT scan: global severe thickening of the calvarium related to osteopetrosis, global caudate nucleus and patchy thalamus hyperdensity. (C) T2 gradient‐echo MRI: low heterogeneous signal in putamen and a signal in pallidum (black arrow). (D) Axial T2 scan in optic‐nerve plane: decreased calibre of optic nerve due to compression of the optic nerve within the optic canal (white arrow). (E) Axial CT scan: mild thickening of calvarium and hypredensity of the caudate nuclei. (F) Sagittal T2‐weighted MRI: mild ventricular dilatation without stenosis of acqueduc of Silvius (black arrow), and mild vermian hypoplasia (dotted line).