Clinical and brain imaging features of affected patients with EXOC2-related neurological disorder. (A–F) Patient 1 (1:IV-2): In the axial sections, the pons and fourth ventricle have an abnormal shape, which is only in part reminiscent of the molar tooth appearance; there is ponto-cerebellar and brainstem hypoplasia (asterisks in C), with more severe involvement of the inferior vermis with respect to the other cerebellar structures; narrow isthmus (not shown here); severely hypoplastic under-rotated hippocampi (downward pointing arrows in E); thin corpus callosum with cavum septi and large ventricles; and midline thalamic fusion and hypoplastic caudate nuclei. Microcephaly was also noted, with dilated subarachnoid spaces in correspondence with the temporal poles (asterisk in D). (G–L) Patient 2 (1:IV-8): The same observations apply as in Patient 1, but all observations are more severe. In particular, the brainstem and cerebellum are severely hypoplastic (asterisk in I and L), and the hippocampi are barely visible on both sides (see asterisks in H and upward-pointing arrows in K). The septum pellucidum is absent. Mild generalized atrophy is noted. (M–R) Patient 3 (2:II-1): Molar tooth–shaped pons and fourth ventricle in the axial sections (encircled in M and N); narrow isthmus; cerebellar vermis hypoplasia; cleft separating the two dysplastic areas of the vermis; rhombencephalosynapsis and vertical orientation of the folial pattern; and under-rotated hippocampi.