Reversible cognitive and gait impairment by a giant quadrigeminal cistern arachnoid cyst: A case report of marked reversal following neuroendoscopic fenestration.

BACKGROUND

Quadrigeminal cistern arachnoid cysts are rare in adults, but can cause reversible gait and cognitive impairment secondary to obstructive hydrocephalus. Differentiating these structural lesions from idiopathic normal-pressure hydrocephalus (iNPH) or neurodegenerative diseases is essential because they are surgically treatable.

CASE DESCRIPTION: A 71-year-old woman presented with progressive gait disturbance and mild cognitive impairment. Neuropsychological tests showed a Montreal Cognitive Assessment-Japanese version (MoCA-J) score of 21/30 and a frontal assessment battery (FAB) score of 13/18, indicating executive dysfunction. Standard cognitive screening such as mini-mental state examination did not detect the subtle deficits identified by MoCA. Magnetic resonance imaging revealed a giant arachnoid cyst in the quadrigeminal cistern compressing the midbrain and cerebral aqueduct, resulting in obstructive hydrocephalus. Endoscopic cyst fenestration was performed through a right frontal burr hole. The cyst was opened and communication with the third ventricle was achieved. Gait and cognitive functions markedly improved postoperatively (MoCA-J 26/30, FAB 17/18) and radiographic findings showed that the hydrocephalus had resolved. Ocular symptoms, including difficulty gazing upward, also resolved after surgery.

CONCLUSION

Quadrigeminal cistern arachnoid cysts can mimic iNPH or neurodegenerative disorders, but represent a reversible cause of cognitive and gait impairments. Detailed neuroimaging and sensitive cognitive assessments are essential for diagnosis. Neuroendoscopic fenestration provides a treatment, i.e., minimally invasive and effective, even in elderly patients.