The cine-phase contrast magnetic resonance imaging (MRI) evaluation has played an important role in visualizing cerebrospinal fluid (CSF) flow through the aqueduct. It is highly sensitive, even to slow flow, and has been used to evaluate flow changes in various pathologies, such as normal pressure hydrocephalus, obstructive hydrocephalus, and Chiari malformation⁸⁾. Additionally, it is an efficient modality for pediatric patients due to its noninvasive and highly sensitive characteristics.

Suprasellar arachnoid cysts (SAC) are rare heterogeneous entities, accounting for 9% to 21% of all pediatric arachnoid cysts¹⁾. They can grow through a slit-valve mechanism, with CSF flowing upward from the fourth ventricle and the foramina of Luschka⁹⁾.

There is no clear consensus regarding the management of SAC; however, the presence of hydrocephalus and visual symptoms is an important factor in determining surgical treatment⁷⁾. In this report, we present a case of preoperative aqueductal peak flow changes without hydrocephalus in an 8-year-old male with a SAC.

An 8-year-old patient presented with complaints of mild headaches, rated at visual analogue scale (VAS) score of 5, typically lasting less than 1 hr, for the past 3 weeks. The pain was most pronounced in the morning and was not associated with visual disturbances or tinnitus. Cine MRI was performed with a velocity encoding of 20 cm/sec, synchronized with peripheral gating. The slice was positioned perpendicular to the cerebral aqueduct. While the normal peak velocity in the pediatric population typically ranges from 5 to 8 cm/sec. Revealing the presence of an arachnoid cyst located in the interpeduncular and prepontine cisterns, with the cerebral aqueduct CSF flow remaining intact. The peak aqueduct flow was measured at 2.43 cm/sec. Due to the mild symptoms and normal CSF flow, we periodically observed him in the outpatient department without surgery.

Eight months later, the patient returned with worsened headaches, rated at VAS 8-9, which had intensified over the past month. He also presented with bitemporal hemianopsia. Follow-up cine MRI indicated no significant changes in arachnoid cyst volume or ventricle size, with the CSF flow through the cerebral aqueduct remaining intact. Notably, the peak aqueductal flow increased significantly to 11.56 cm/sec (Fig. 1).

An endoscopic third ventriculostomy (ETV) was performed, involving the fenestration of the caudal and rostral membranes (Fig. 2). Postoperative cine MRI showed a reduction in aqueduct peak flow to 4.26 cm/sec. His headache disappeared after the operation, and this improvement has been preserved.

Arachnoid cysts are benign but challenging lesions in the pediatric population, and they sometimes require surgical management. There are still controversies surrounding their nomenclature and treatment^1,2,5,6). Cysts in infants and younger children can grow to a substantial size^4,10). However, there is controversy surrounding early surgical treatment of incidentally discovered SAC in pediatric patients. This is the reason we initially observed this case, which presented with mild headaches but had a relatively low peak velocity of aqueductal flow and no hydrocephalus.

Eight months later, the patient experienced sudden and severe headaches despite no significant volume change in the SAC and the absence of hydrocephalus. However, a cine MRI revealed a remarkable increase in the peak velocity of aqueductal flow, exceeding 11 cm/sec, which is higher than normal in childhood⁸⁾. In the treatment of functional aqueductal stenosis in normal pressure hydrocephalus, a peak velocity value over 5 cm/sec represents a favorable factor for considering ETV³⁾. ETV functions by creating an alternative pathway for CSF to reach the prepontine cistern, thereby compensating for the dysfunctional aqueductal flow and restoring intracranial pressure dynamics.

Insufficient aqueductal flow and severe headaches are considered important factors in determining surgical treatment, even in childhood. It appears that even a small increase in cystic volume can lead to significant changes in the CSF dynamics within the aqueduct. Through endoscopic fenestration, we achieved both volume decompression and direct CSF flow between the prepontine cistern and the third ventricle.

Compared to standard ETV, SAC fenestration requires more advanced techniques to penetrate both the rostral and caudal membranes. Specifically, approaching and penetrating the caudal membrane from Kocher's point while preventing injury to the fornix and basilar artery presents significant challenges.

Fortunately, with the development of endoscopic instruments, ventriculocisternostomy has become an increasingly preferred first-line treatment for SACs. An endoscope with a diameter of less than 4 mm has proven effective in perforating the caudal membrane of the SAC through a small ventricle and the foramen of Monro in pediatric patients.

After surgical treatment, the aqueductal peak flow significantly decreased to within the normal range, and the severe headaches disappeared. Additionally, the patient was satisfied with the small incision line (<2 cm) on the right vertex. At the outpatient follow-up 2.5 years after surgery, the patient remained asymptomatic.

A sudden increase in aqueduct peak flow may be associated with severe headaches in childhood SAC, even in the absence of significant cyst enlargement or hydrocephalus. Endoscopic cyst fenestration can be considered an effective treatment option for SAC presenting with increased aqueductal peak flow. Our findings suggest that this procedure may address functional aqueduct obstruction by creating an alternative CSF pathway. Furthermore, we recommend cine MRI as a valuable tool for the longitudinal observation of SAC to detect potential hemodynamic changes.