Modified Computed Tomography Classification for Chronic Subdural Hematoma Features Good Inter-Rater Agreement: A Single-Center Retrospective Cohort Study.

OBJECTIVE: The present study aimed to establish whether our modified Nakaguchi computed tomography (CT) classification improves the inter-rater agreement of chronic subdural hematoma (CSDH) classification and prediction of CSDH recurrence relative to two other CT classifications.
METHODS: This retrospective study considered 277 consecutive patients with CSDH and 307 hematomas treated with burr hole surgery between January 2009 and December 2018. Two neurosurgeons blinded to patients' clinical data classified the CT scans of patients with CSDH into four to five types according to the Nomura classification (high, iso, low, mixed, and layering), Nakaguchi classification (homogenous, laminar, separated, and trabecular), and our modified Nakaguchi classification (homogenous, gradation, laminar, separated, and trabecular). The kappa statistic was used to evaluate the inter-rater agreement of the three CT classifications. Univariable and multivariable logistic regression analyses were used to calculate odds ratios for CSDH recurrence.
RESULTS: Kappa values of the modified, Nakaguchi, and Nomura classification were 0.78, 0.63, and 0.70, respectively. During the 3-month follow-up, the recurrence rate for CSDH was 11.4% (35/307 hematomas). Of the types defined by the modified classification, the gradation type was associated with the highest recurrence (mean recurrence rate, 15.9% ± 0.3%). Multivariable logistic regression analyses revealed that a gradation-type hematoma, as defined with the modified classification, was an independent risk factor associated with recurrence (odds ratio: 2.36, 95% confidence interval: 1.11 to 4.98; P = 0.025).
CONCLUSION: The modified classification was useful for preoperative CT classification of CSDH and the prediction of recurrence with high agreement between raters.