What are subdural hemorrhages, subarachnoid and epidural hemorrhages and the differences between them?
Epidural, subdural, and subarachnoid hemorrhages are best understood by reviewing the anatomy of the meninges (membrane coverings of the brain): The meninges are divided into three layers: the dura mater, arachnoid, and pia mater. The outer layer, the dura mater, lines the inner surfaces of the skull and forms several reflections that partially separate the cerebral hemispheres along the midline (interhemispheric fissure) and the cerebrum from the cerebellum. The dura mater is rather firmly adherent to the skull, particularly at the junctions (cranial sutures) of the various bones which comprise the skull. The potential space between the skull and the dura mater is referred to as the epidural space. A hemorrhage into this space is referred to as an epidural hemorrhage. These hemorrhages are usually the result of a tear in a meningeal artery. The middle layer of the meninges is the arachnoid. It is a thin membrane likened in appearance to a spider’s web. Under normal conditions, the ara
