Observation of the progression of tension in intracranial arachnoid cyst: a case report and review of literature.

The intracranial arachnoid cyst (IAC) are common benign intracranial space-occupying lesions in children, which can be categorized into tension and non-tension IAC based on imaging features. As observed cases of tension progression in IAC are extremely rare, the relationship between the two is currently unclear. Here, we present a rare case that demonstrates the transition from a non-tension IAC to a tension cyst by complete imaging evidence. Magnetic Resonance Imaging (MRI) of the brain performed 6 days after birth revealed the presence of a small non-tension IAC at the left cerebellopontine angle, with no significant compression of adjacent brain tissue and clear boundaries of the cerebral gyrus and sulcus. At 15 months, MRI revealed a significant enlargement of IAC, displacement of the brainstem, loss of the cerebral gyrus in the neighboring brain tissue, and tension-arc changes at the cyst-brain tissue interfaced with obstructive hydrocephalus. Through fenestration, the IAC were reduced, exhibiting non-tension changes, significantly alleviating pressure on adjacent brain tissue, and hydrocephalus significantly improved. Subsequent follow-up showed no obvious abnormalities. In conclusion, the degree of tension seen in IAC imaging was the result of IAC enlargement, which provides a basis for surgical intervention and postoperative efficacy evaluation.