Discussion of Subdural hematoma
- Usually occur as a result of trauma.
- Deceleration injuries are often the cause of subdural bleeding from rupturing of veins via a shearing mechanism.
- Other etiologies include:
- Nonaccidental trauma
- Spontaneous hemorrhages may occur in patients receiving anticoagulants or patients with a coagulopathy condition.
 Imaging Findings of Subdural hematoma
- Unlike epidural hematomas, subdural hematomas are not restricted by dural tethering at the cranial sutures.
- They can cross suture lines and continue along the falx and tentorium.
- They do not cross the midline because of the meningeal reflections.
- In the acute phase, subdural hematomas appear as a crescent-shaped extra-axial collection with increased attenuation that, when large enough, causes effacement of the adjacent sulci and midline shift.
- The attenuation changes as the hematoma ages.
- Subacute subdural hematomas may be difficult to detect because they may have isoattenuation compared with adjacent gray matter
- Chronic subdural hematomas have isoattenuation relative to the cerebrospinal fluid.
- Rebleeding into subdural hematomas also may occur and is depicted as a layer of high-attenuation hemorrhage within a lower attenuation hematoma
- MRI is more sensitive than CT scanning in the detection of subdural hematomas because the multiplanar and superior tissue differentiation of MRI makes detection easier.
- The shape of the subdural hematoma on axial images is the same crescent-shaped pattern seen on CT scan images.
- The signal depends on the age of the hemorrhage and follows the signal pattern of intraparenchymal hematomas in acute and subacute cases.
- Chronic subdural hematomas, which appear as isoattenuation relative to CSF on CT scans, often demonstrate increased signal intensity on T1-weighted images because of the presence of free methemoglobin, though the intensity decreases over time.
 See Also
- Epidural hematoma
- Subarachnoid hemorrhage
- Intracerebral parenchymal hemorrhage
- Intraventricular hemorrhage
 External Links
- Andrew L Wagner. E-medicine radiology article.