Smear technique for the intraoperative examination of nervous system lesions.

To evaluate the accuracy of the smear technique in the rapid diagnosis of lesions of the central and peripheral nervous system, intraoperative diagnoses made on cytologic preparations in 307 consecutive cases were compared with the final paraffin section diagnoses. In 92.2% of cases the final diagnosis obtained on paraffin preparations was similar to that made on smears. In this group there were neuroglial tumors, meningiomas and medulloblastomas, among others. In the cases in which the cytologic diagnoses were not confirmed by paraffin sections, the majority of the cases were unlikely to affect immediate neurosurgical management, while in only 0.7% of all cases (n = 2) an incorrect smear diagnosis might have affected the neurosurgical procedure. The cytologic diagnostic criteria are discussed together with the main difficulties in interpretation with this valuable approach to a rapid neurosurgical diagnosis.