PMC5894312_01
Axial T2-weighted image (A) shows hypoplastic left side of ventral pons (thick white arrow), with abnormal lateral orientation of superior cerebellar peduncles (thin white arrows).Sagittal T1-weighted image (B) shows flattened ventral pons (dotted white arrow)
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F1
T1/T2-weighted MRI, we observed hypoplastic left side of ventral pons [Figure 1A]. The ventral pons appeared flattened on the corresponding sagittal images [Figure 1B]. Additional MRI features observed were abnormal morphology and slight lateral orientation of the superior cerebellar peduncles [Figure 1A and 4A].
An aberrant exophytic structure (thick white arrows) is seen protruding into the fourth ventricle from the dorsal pontine tegmentum at pontomedullary junction on corresponding sagittal T1-weighted (A and B) and axial T2-weighted images (C)
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F2
On axial and sagittal T1/T2-weighted MRI, an ectopic aberrant structure, isointense to the pons, was noted arising from the left side of dorsal pontine tegmentum, at the pontomedullary junction, protruding into the fourth ventricle posteriorly and inferiorly [Figure 2A-C].
Axial DRIVE sequence shows normal origin of right 7th and 8th cranial nerves (thin white arrow), with impingement at the origin of left 7th and 8th cranial nerve (thick white arrow)
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F3
On heavily T2-weighted axial DRIVE sequence, this aberrant exophytic dorsal pontine tissue was seen to impinge upon and compress the left seventh and eighth cranial nerves at their origin [Figure 3].
Coronal T2-weighted image (A) shows elongated and laterally oriented superior cerebellar peduncles (thin white arrows). Axial T2-weighted image (B) shows hypoplastic right middle cerebellar peduncle (thick white arrow)
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F4
Additional MRI features observed were abnormal morphology and slight lateral orientation of the superior cerebellar peduncles [Figure 1A and 4A]. The middle cerebellar peduncles appeared hypoplastic on the right side [Figure 4B].
Axial FA color images show elongated and laterally oriented superior cerebellar peduncles (A) seen as green (thin white arrows) and hypoplastic right middle cerebellar peduncle (B) (thick white arrow). Sagittal fractional anisotropy color DTI image (C) shows anteroposteriorly directed white matter axons in ectopic dorsal pontine tissue seen as green (dotted white arrow). Axial fractional anisotropy color DTI imageshows near complete absence of transverse pontine fibers (D) and normal transverse pontine fibers in a healthy control as red (E) (white stars)
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F5
DTI, with the cross-sectional FA color maps depicted elongated and laterally oriented superior cerebellar peduncles [Figure 5A]. The middle cerebellar peduncles appeared hypoplastic, with paucity of white matter tracts, markedly on the right side [Figure 5B]. An abnormal bundle of white matter axons, directed anteroposteriorly and depicting green color on color maps, was noted in the dorsal exophytic band of tissue [Figure 5C]. Significantly, the transverse pontine fibers were observed to be virtually absent [Figure 5D]. The normal transverse pontine fibers in a healthy control are shown in Figure 5E.