PMC5858048_01
Initial sagittal (a) and axial (b) T2 magnetic resonance images of the male patient at 58 days of age. The image demonstrates a cystic lesion with the septum (arrow) in the posterior fossa
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F1
Based on the detection of an ultrasonographic abnormality, magnetic resonance imaging (MRI) was performed at 58 days after birth and a cystic lesion (1.2 cm x 2.9 cm at its largest diameter) was identified in the left retrocerebellar region of the posterior fossa [Figure 1].
PMC5858048_02
Preoperative sagittal (a) and axial (b) T2 magnetic resonance images of the patient at 4 months of age. An enlarged cystic lesion can be observed descending into the foramen magnum with the septum expanding beyond the midline (arrow). Blocked communication with the fourth ventricle, compression of the brainstem and fourth ventricle (arrowheads), and marked ventriculomegaly (stars) were evident
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F2
At 4 months of age, the patient's head circumference increased to 48.0 cm (>2 standard deviations above the mean for his age), and MRI showed significant enlargement of the cyst (4.0 cm x 3.5 cm at its largest diameter) with compression of the cerebellum and hydrocephalus caused by obstruction of the fourth ventricle outlets [Figure 2].
PMC5858048_03
Intraoperative photographs. (a and b) The cyst wall was exposed and resected. (c) Opening of the cerebral aqueduct was confirmed. (d) Opening of the foramen magnum was confirmed
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F3
Because the inner membrane of the cyst adhered to the rostral medullary velum and compressed the fourth ventricle, we carefully detached and resected both the outer and inner membranes of the cyst to open the fourth ventricle and cisterna magna [Figure 3].
PMC5858048_04
Computed tomography performed 4 years after the surgery. The image demonstrates absence of the septum as well as reduced compression of the brainstem and fourth ventricle. Furthermore, the image clearly depicts the sulci of the cerebellum, the cerebellopontine angle, and amelioration of the patient's obstructive hydrocephalus
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F4
At the last follow-up (performed 4 years postoperatively), the cyst wall was unidentifiable and the cerebellum had grown to near-normal size [Figure 4].