Association between a black band on the inner membrane of a chronic subdural hematoma on T2*-weighted magnetic resonance images and enlargement of the hematoma.

Abstract

The cause and indication for enlargement of chronic subdural hematomas (CSDHs) have remained unresolved. The authors observed a black band on the inner membrane of a CSDH on T2*-weighted magnetic resonance (MR) images obtained in patients with symptoms. After surgical treatment, the band disappeared. The T2*-weighted sequence of MR imaging is an excellent diagnostic tool for detecting ferromagnetic substances, but it is rarely performed in cases of a CSDH. The authors speculate that the black band may be associated with the development of CSDH. To investigate how the black band observed on T2*-weighted MR images contributes to the development of a CSDH, 59 lesions in 50 patients with CSDH (41 men and nine women, mean age 70 +/- 11 years [range 48-93 years]) were investigated prospectively. The incidence of black bands on the first T2*-weighted MR image obtained in patients with symptomatic CSDH was 97% (31 of 32 CSDHs), which was significantly higher than that associated with asymptomatic CSDH (11% [three of 27 CSDHs], p < 0.001). The black bands associated with symptomatic CSDH disappeared soon after surgical treatment in 31 CSDHs and became fainter in another. In two instances the CSDH recurred with reappearance of the band. Twenty-four of 27 asymptomatic CSDHs had no accompanying black band. Follow-up MR images demonstrated a later formation of bands in two of 24 asymptomatic CSDHs that enlarged to symptomatic size. Logistic regression analysis revealed that the heterogeneity and thickness of the CSDH on computerized tomography scans were independently and significantly associated with the black band. The dynamics of the black band may depend on the enlargement or shrinkage of the CSDH.