Characteristics of symptomatic chronic subdural haematomas on high-field MRI.

We studied the frequency of various features of the appearances on high-field MRI in symptomatic patients with chronic subdural haematomas (CSDH). The ability to predict recurrence after treatment with one burr-hole procedure using MRI was evaluated. A total of 40 patients with symptomatic CSDH underwent MRI at 1.5 T. All haematomas were evacuated within a few days of the MRI examination. Symptomatic CSDH were divided into five groups according to the MRI findings: group A (11 cases), isointense or low signal on T1- and low signal on T2-weighted images; group B (18 cases), high signal on T1- and low signal on T2-weighted images; group C (5 cases), high signal on both T1- and T2-weighting; group D (1 case), low signal on T1- and high signal on T2-weighted images; group E (5 cases), heterogeneous intensity on T1- and T2-weighting throughout the haematoma cavity. The mean interval between onset of symptoms and MRI for group A was 5.0 +/- 4.1 days, which was significantly shorter than that for group B (9.4 +/- 4.4 days, P < 0.02), group C (27.8 +/- 20 days, P < 0.005) or group E (17.8 +/- 12.2 days, P < 0.01). Recurrence was seen in three haematomas of group A and one of group B. Reoperation was most closely correlated with diffuse low signal on T2-weighted images but not with a multiloculated appearance. Low signal on T2 weighting was surprisingly high (72.5%) and the age of the haematomas as estimated on the MRI correlated well with the interval between the onset of symptoms and MRI. Our findings support the causative role of recurrent bleeding in the enlargement of CSDH.