Background and Purpose-We have previously shown that nicotinamide (NAm) acutely reduces brain infarction induced by permanent middle cerebral artery occlusion (MCAo) in rats. In this study, we investigate whether NAm may protect against ischemia/reperfusion injury by improving sensory and motor behavior as well as brain infarction volumes in a model of transient focal cerebral ischemia. Methods-Forty-eight male Wistar rats were used, and transient focal cerebral ischemia was induced by MCAo for 2 hours, followed by reperfusion for either 3 or 7 days. Animals were treated with either intraperitoneal saline or NAm (500 mg/kg) 2 hours after the onset of MCAo (ie, on reperfusion). Sensory and motor behavior scores and body weight were obtained daily, and brain infarction volumes were measured on euthanasia. Results-Relative to treatment with saline, treatment with NAm (500 mg/kg IP) 2 hours after the onset of transient focal cerebral ischemia in Wistar rats significantly improved sensory (38%, PϽ0.005) and motor (42%, PϽ0.05) neurological behavior and weight gain (7%, PϽ0.05) up to 7 days after MCAo. The cerebral infarct volumes were also reduced 46% (PϽ0.05) at 3 days and 35% (Pϭ0.09) at 7 days after MCAo. Conclusions-NAm is a robust neuroprotective agent against ischemia/reperfusion-induced brain injury in rats, even when administered up to 2 hours after the onset of stroke. Delayed NAm treatment improved both anatomic and functional indices of brain damage. Further studies are needed to clarify whether multiple doses of NAm will improve the extent and duration of this neuroprotective effect and to determine the mechanism(s) of action underlying the neuroprotection observed. Because NAm is already used clinically in large doses and has few side effects, these results are encouraging for the further examination of the possible use of NAm as a therapeutic neuroprotective agent in the clinical treatment of acute ischemic stroke. (Stroke. 2000;31:1679-1685.)

The diffusion-weighted magnetic resonance (MR) imaging characteristics of chronic subdural hematoma and the correlation between hematoma liquidity and apparent diffusion coefficient (ADC) were investigated in 26 consecutive patients, 16 males and 10 females aged 42 to 92 years (mean ± SD 73.3 ± 13.1 years), with 31 chronic subdural hematomas. The chronic subdural hematomas were divided into homogeneous, separate, and trabecular types based on diffusion-weighted MR imaging findings. Almost all hematomas were low intensity on diffusion-weighted imaging, and the mean ADC value was 1.81 ± 0.79 × 10 -3 mm 2 /sec. The high intensity areas in the subdural hematomas consisted of several types: high intensity line along the dura mater (subdural hyperintense band), high intensity along the intrahematoma septum, and laminar shape along the inner membrane. The subdural hyperintense bands accounted for almost all high intensity areas in the subdural hematomas. The mean ADC value of the high intensity areas was 0.76 ± 0.24 × 10 -3 mm 2 /sec, close to that of the normal brain. The subdural hyperintense bands were considered to be intracellular and/or extracellular methemoglobin based on the T 1 -and T 2 -weighted imaging and intraoperative findings. The subdural hyperintense band is an important finding indicating relatively fresh bleeding from the outer membrane. Diffusionweighted imaging shows liquid subdural hematoma as low intensity, and measurement of the ADC values can differentiate between liquid and solid components of the chronic subdural hematoma.

A 59-year-old male presented with a left organized subdural hematoma. The hematoma appeared as a homogeneous low density area on brain computed tomography and as hyperintense and isointense area on both fluid-attenuated inversion recovery and T 2 -weighted magnetic resonance (MR) imaging. Echoplanar diffusion-weighted MR imaging showed a crescent hyperintense area under the dura mater and an irregular hypointense area over the brain surface in the left subdural space. The apparent diffusion coefficient (ADC) values of the solid and liquid hematoma were 0.86 ± 0.32 × 10 -3 and 2.56 ± 0.39 × 10 -3 mm 2 /sec, respectively. The ADC value of the solid hematoma was similar to acute subdural or intraparenchymal hematoma, and that of the liquid was similar to cerebrospinal fluid. Burr-hole surgery failed to remove all the hematoma, and he complained of persistent headache. The hematoma was removed through a craniotomy without further neurological deficits. Organized subdural hematoma often requires craniotomy for evacuation because of its solid content. Diffusion-weighted MR imaging and measurement of ADC values can differentiate solid from liquid hematoma, so are useful for selection of the surgical procedure.

Five cases of traumatic subdural hematomas in the subacute stage (from 7 to 20 days after head injury) were treated in one male and four females, aged from 63 to 82 years, with evacuation via craniotomy in three and aspiration via burr hole surgery in two. All hematomas were evaluated by T 1 -, T 2 -, and diffusion-weighted magnetic resonance imaging, and measurement of the apparent diffusion coefficient (ADC). Diffusion-weighted imaging showed the hematoma as a crescent high intensity area with a low intensity rim close to the brain surface (two-layered structure) in four cases and as high intensity with low intensity components in one case. The high intensity areas under the dura mater on diffusion-weighted imaging appeared as homogeneous high intensity on T 1 -and T 2 -weighted imaging in four cases, and inhomogeneous high intensity on T 1 -and isointensity on T 2 -weighted imaging in one case. The mean ADC value of the high intensity areas was 0.58 ± 0.23 (mean ± standard deviation) × 10 -3 mm 2 /sec. The operative findings revealed the high intensity areas as solid clots. The low intensity areas on diffusion-weighted imaging appeared as homogeneous high intensity in four cases and inhomogeneous isointensity with high intensity components in one case on T 1 -and T 2 -weighted imaging. The mean ADC value of the low intensity areas was 2.03 ± 0.27 × 10 -3 mm 2 /sec. The operative findings revealed the low intensity areas as mixtures of resolved clot and cerebrospinal fluid. Diffusion-weighted imaging showed the characteristic two-layered structure in traumatic subdural hematomas in the subacute stage, and analysis of the ADC values was useful for differentiating solid from liquid hematoma and for selection of the surgical procedure.