Qualitative Comparison of Cryostat- versus Snap-Frozen Neurosurgical Intraoperative Consultations

Background. Frozen sections (FS) are common in neurosurgery to address varied clinical concerns. Artifacts in central nervous system (CNS) FS can be severe and affect or hinder interpretation. We performed a case-control study using a semiquantitative scale: the Histologic Preservation Score (HPS), and a quantitative scale: the Ice Crystal Vacuolization Score (ICVS), to compare the histologic quality yielded by snap- versus cryostat freezing techniques. Material and Methods. All specimens were sectioned in 2 halves, one half was used for FS and the other for permanent evaluation. HPS assigns a distortion score to the FS sample using the non-frozen half as the comparator: 1 = minimal, 2 = slight, 3 = moderate, 4 & 5 = severe. The ICVS is the average size in µm of the 5 largest vacuoles/0.05 mm², evaluated on digitized slides. Results. 86 CNS-FS were collected: 22 snap- and 64 cryostat-FS. Significant differences in HPS: 2.28 versus 2.84 (p <0.05) and ICVS 7.47 versus 14.56 (p < 0.001) were obtained for snap- versus cryostat-FS, respectively. HPS and ICVS showed a strong correlation: R² = 0.63, p < 0.0001. Histologic distortion was worse for neuroglial than mesenchymal tissue by both methods; however, a significant difference was only observed in cryostat-FS: HPS: 3.23 versus 2.33, p < 0.001; ICVS: 16.86 μm versus 10.26 μm, p < 0.001. Conclusion. Snap-FS yields better histologic quality than cryostat-FS for CNS-FS, and the difference is more pronounced in neuroglial samples. HPS and ICVS correlate strongly, indicating that the histologic quality is inversely proportional to water-crystallization. These results may apply to other areas of surgical pathology.