Central Nervous System Lesions: Correlation of Intraoperative and Final Diagnoses, Six Year Experience at a Referral Centre in a Developing Country, Pakistan

Background and Aims: Intraoperative consultation of CNS lesions provides accurate diagnosis to neurosurgeons. Some lesions, however, may cause diagnostic difficulty. In this study accuracy of intraoperative consultations of CNS lesions and discrepancies in diagnosis and deferrals were analysed.
Methods: All CNS cases from May 1, 2004 to September 20, 2010 in which intraoperative frozen section had been performed, and which were reported in the Section of Histopathology, Aga Khan University Hospital, Karachi Pakistan were retrieved. The diagnoses given on FS were compared with the final diagnosis given on permanent sections (and additional material if received), as indicated in the frozen section and final pathology report.
Results: During the study period, 171 CNS cases were received for intraoperative consultation. In all cases, cryostat sections (FS) plus cytology smears were prepared. The ages of the patients ranged from 03 to 77 years. 106 were males and65 were females. Out of these 171 cases, 160 cases (94.1 %) were concordant, 10 cases (5.8 %) were discrepant, and one case was deferred until permanent sections. The diagnostic accuracy of frozen section was 88.9%. The sensitivity and specificity were 94.8% and 87.5% respectively. The positive predictive value was 98.6% andnegative predictive value was 63.6%. All our cases in which intraoperative consultation was requested were sent for primary diagnosis. Adequacy per se was not a criterion for sending cases for intraoperative consultation.
Conclusions: Our results show a reasonably high percentage of accuracy in the intraoperative diagnosis of CNS lesions. However, there are limitations and some lesions pose a diagnostic challenge. There is a need to improve our own diagnostic skills and establish better communication with neurosurgeons.