We reviewed serial computed tomographic (CT) scans of 58 patients with traumatic subdural hygroma (SDG) to investigate its natural history. All were re-evaluated with a special reference to the size and density of SDG. Thirty-four patients (58.6%) were managed conservatively and 24 patients (41.4%) underwent surgery. The lesion was described as remained, reduced, resolved, enlarged and changed. Means of interval from injury to diagnosis and any changes in CT were calculated. SDGs were resolved in 12 (20.7%), reduced in 15 (25.9%), remained in 10 (17.2%), enlarged in 2 (3.4%), and changed into chronic subdural hematoma (CSDH) in 19 patients (32.8%). SDG was diagnosed at 11.6 days after the injury. It was enlarged at 25.5 days, remained at 46.0 days, reduced at 59.3 days, resolved at 107.5 days, and changed into CSDH at 101.5 days in average. SDGs were developed as delayed lesions, and changed sequentially. They enlarged for a while, then reduced in size. The final path of a SDG was either resolution or CSDH formation. Nearly half of SDGs was resolved or reduced within three months, however, 61.3% of unresolved or unreduced SDG became iso- or hyperdense CSDH. These results suggest that the unresolved SDG is the precursor of CSDH.

For a working criteria of the recurrence of CSDH, we propose the early recurrence as return of symptoms or reaccumulation of the hematoma after a surgery within 3 months regardless of the location, amount or repeated operations. The late recurrence can be defined as reappearance or enlargement of a liquefied hematoma within the cranial cavity surrounded by the membranes or persistent CSDH beyond 3 months after surgery.

To characterize the recurrence of bleeding in patients who had hypertensive intracerebral hemorrhage (HICH), the authors reviewed 989 patients who underwent treatment for HICH between 1989 and 1995. Fifty-three patients (5.4%) had two episodes of HICH within a median interval of 22.9 ± 16.3 months (range 1.5–72 months), and of these 3 (5.7%) had three episodes of HICH. The recurrence of bleeding most commonly occurred within 2 years of the first hemorrhage: in 66% of the 53 patients the second hemorrhage occurred soon after the first (within 1 year in 34%, within 1–2 years in 32.1%). The site of the second hemorrhage was different from the initial site in all patients. Only 1 patient had a third hemorrhage in the same site as the second hemorrhage. The common patterns of recurrence were ‘ganglionic (putamen/caudate nucleus)-thalamic’ in 26.8% and ‘ganglionic-ganglionic’ in 21.4%. The ‘lobar-lobar’ pattern was noted in only 2 patients. The volume of the hematoma was increased at the second hemorrhage. The overall mortality was 28.3%. The risk of recurrent hemorrhage significantly increased in the patients who had antihypertensive therapy of less than 3 months after the initial attack compared to those with further long-term therapy (p < 0.005). Long-term regular control for hypertension is needed to prevent recurrent hemorrhage.

ObjectiveDensity of the chronic subdural hematoma (cSDH) is variable. It often appears to be mixed density. Multiple densities of cSDH may result from multiple episodes of trauma. We investigated the frequency of mixed density and the causes of head injuries representing each density.MethodsWe could collect 242 cases of chronic SDH. The cSDHs were classified into four groups; hypodensity, homogeneous isodensity, layered type, and mixed type on the basis of CT scans.ResultsThe density of cSDH was isodense in 115 patients, hypodense in 31 patients, mixed in 79 cases, and layered in 17 cases. The cSDH was on the left side in 115 patients, on the right side in 70 patients, and bilateral in 40 patients. The history of trauma was identifiable in 122 patients. The etiology could be identified in 67.7% of the hypodense hematomas, while it was obscure in 59.5% of the mixed hematomas.ConclusionMixed density of cSDH results from multiple episodes of trauma, usually in the aged. It is hard to remember all the trivial traumas for the patients with the mixed density cSDHs. Although there were membranes within the mixed density hematomas, burr-holes were usually enough to drain the hematomas.

Acute subdural hematoma (ASDH), chronic subdural hematoma (CSDH) and subdural hygroma (SDG) occur in the subdural space, usually after trauma. We tried to find a certain relationship among these three traumatic subdural lesions in 436 consecutive patients. We included all subdural lesions regardless of whether they were main or not. We evaluated the distribution, age incidence and interval from injury to diagnosis of these lesions, and the frequency of new subdural lesions in each lesion. ASDH constituted 68.6%, SDG 15.8%, and CSDH 15.6%, Age incidence of CSDH was similar to that of SDG, but differed from that of ASDH. Mean interval from injury to diagnosis was 0.4 days in ASDH, 13.4 days in SDG, and 51.6 days in CSDH. Focal brain injuries accompanied in 37.5% of ASDH, 5.8% of SDG, and no CSDH. In ASDH, 2 recurrent ASDHs, 17 SDGs and 9 CSDHs occurred. In SDG, 3 postoperative ASDHs and 8 CSDHs occurred. In CSDH, 2 postoperative ASDHs, 2 SDGs and 1 CSDH occurred. These results suggest that the origin of CSDH is not only ASDH, but also SDG in upto a half of cases. SDG is produced as an epiphenomenon by separation of the dural border cell layer when the potential subdural space is sufficient. A half of CSDHs may originate from ASDHs. ASDH may occur in CSDH by either a repeated trauma or surgery. Such transformation or development of new lesions is a function of a premorbid condition and the dynamics between the absorption capacity and expansile force of the lesion.