Limitations of MRI in differentiating solid and cystic components of craniopharyngiomas

Craniopharyngiomas (CP) present with both solid and cystic structures in magnetic resonance imaging (MRI) studies. Contrary to MRI appearance, components described as cysts are not infrequently found as non-fluent structures during surgery. This study aims to address the discrepancy between radiology and surgery regarding the nature of these lesions and to evaluate them for their preoperative predictability.

Preoperative MRI images of 24 CP patients were analyzed. The cystic components of the tumors were assessed in terms of quantitative and qualitative signal properties and contrast enhancement on conventional pulse sequences, and analyzed based on their macroscopic appearances.

Thirteen of 31 lesions (42%) that suggested cyst on MRI were solid during surgery, with none showing contrast uptake. MRI demonstrated 100% sensitivity and negative predictive value (NPV), 71.7% specificity, and 58% positive predictive value (PPV) in identifying true cysts. Most lesions resembling cysts were hyperintense on FLAIR and T1WI and isointense on ADC maps, suggesting high protein content. However, surgically confirmed fluid-filled cysts exhibited similar signal characteristics in a comparable proportion. The only significant imaging indicator was a hypointense appearance on T2WI, with a mean intensity ratio close to that of the basal ganglia.

Accurate identification of solid and cystic components in craniopharyngiomas is critical for effective treatment planning. Although MRI is traditionally considered reliable for this purpose, 42% of lesions that appeared cystic without contrast enhancement were ultimately confirmed as non-fluid or solid during surgery. This study was unable to establish definitive MRI characteristics to reliably differentiate between cystic and solid components. Further research with larger cohorts is warranted to validate potential imaging markers and improve diagnostic accuracy.