case_images: PMC11225525_01
case_images: Brain magnetic resonance imaging at diagnosis. (a) Axial T1 and (b) sagittal T1 show a spontaneously hyperintense mass anterior to the pontomedullary junction.
case_images: SNI-15-195-g001.jpg
case_images: PMC11225525_01_SNI-15-195-g001.jpg
case_images: F1
case_images: T1 and T2/T2 fluid-attenuated inversion recovery, with facilitated diffusion, no chemical-shift artifact (not a fatty lesion), and no gadolinium enhancement, with a small nodule within of low signal on T1, T2, and T2*, suggestive of calcification. The lesion measured about 10 x 9 x 8 mm in size (anterior-posterior x transversal x craniocaudal) and 280 mm3 of volume and had no surrounding edema, with a slight mass effect on the BS [Figure 1].
case_images: Brain magnetic resonance imaging on a 2-year follow-up, showing an increase in lesion volume and mass effect on the brainstem. A small nodule within of low signal on T1, T2, and T2* is apparent. An anteriorly displaced but not encased basilar artery is also visible (a) sagittal T1, (b) sagittal T1 with contrast, (c) axial T2, and (d) axial T2.
case_images: SNI-15-195-g002.jpg
case_images: PMC11225525_01_SNI-15-195-g002.jpg
case_images: F2
case_images: This led to the decision of neurosurgical treatment [Figure 2].
case_images: (a) Exposure of the lesion's capsule through the cerebellopontine angle between the 5th and the 7th nerve and its inferior part of the cyst viewed between the 7th and the 9th nerves, (b) the capsule was opened, and a dense yellow fluid was aspirated, and (c and d) final view after fluid drainage and partial removal of the capsule, part of the capsule (*) left adherent overlying the brainstem (bs). The basilar artery (ba) is also viewed.
case_images: SNI-15-195-g003.jpg
case_images: PMC11225525_01_SNI-15-195-g003.jpg
case_images: F3
case_images: The part of the cyst wall adherent to the BS and basilar artery was not removed [Figure 3].
case_images: Postoperative brain magnetic resonance imaging T1 sequence with gadolinium (a) axial view and (b) sagittal view showing no evident residual cyst and resolution of the mass effect on the brainstem.
case_images: SNI-15-195-g004.jpg
case_images: PMC11225525_01_SNI-15-195-g004.jpg
case_images: F4
case_images: At 1 year follow-up, the patient was well, active, and with no symptoms, and imaging showed no evidence of recurrence of the lesion [Figure 4].