The Ishikawa classification of cavernous sinus lesions by clinico-anatomical findings.

PURPOSE The Jefferson classification has been used to localize cavernous sinus lesions. However, this classification occasionally showed dissociation between identified localization and clinical findings. We investigated the clinical applicability of the newly proposed Ishikawa classification based on serial topographic sections of human cavernous sinus and the clinical findings. METHODS In the Ishikawa classification, the cavernous sinus is divided into three portions, that is, anterior, middle, and posterior, demarcated by the location of the intracranial orifice of the optic canal and the entry of the maxillary nerve into the cavernous sinus. A total of 162 patients with cavernous sinus lesions were classified using both the Jefferson and the Ishikawa classifications and the clinical applicability of these two classifications was studied. Characteristics of the localization of lesions were also examined in each etiological type. RESULTS By the Jefferson classification, 11% of the 162 patients had the anterior type of lesion, 12% the middle, 8% the posterior type, and 69% the unclassifiable type. However, by the Ishikawa classification, 35% had the anterior type, 10% the middle type, 22% the posterior type, 5% the whole type, and 28% the unclassifiable type of lesion. Furthermore, the Ishikawa classification revealed that the etiology of the anterior type was mainly inflammation, and that the etiology of the posterior and whole types was tumors. CONCLUSION The Ishikawa classification is clinically useful to identify and classify the localization of cavernous sinus lesions.