They also occur in the posterior cranial fossa, and near the falx cerebri and tentorium cerebelli. Unlike epidural hematomas, which cannot expand past the sutures of the skull, subdural hematomas can expand along the inside of the skull, creating a concave shape that follows the curve of the brain, stopping only at dural reflections like the tentorium cerebelli and falx cerebri.On a CT scan, subdural hematomas are classically crescent-shaped, with a concave surface away from the skull. However, they can have a convex appearance, especially in the early stages of bleeding. This may cause difficulty in distinguishing between subdural and epidural hemorrhages. A more reliable indicator of subdural hemorrhage is its involvement of a larger portion of the cerebral hemisphere. Subdural blood can also be seen as a layering density along the tentorium cerebelli. This can be a chronic, stable process, since the feeding system is low-pressure. In such cases, subtle signs of bleeding—such as effacement of sulci or medial displacement of the junction between gray matter and white matter—may be apparent. Fresh subdural bleeding is hyperdense, but becomes more hypodense over time due to dissolution of cellular elements. After 3–14 days, the bleeding becomes isodense with brain tissue and may therefore be missed. Subsequently, it will become more hypodense than brain tissue. Classification
Subdural hematomas are classified as acute, subacute, or chronic, depending on the speed of their onset.Acute bleeds often develop after high-speed acceleration or deceleration injuries. They are most severe if associated with cerebral contusions.
Reinstatement of the AVIP (2006-2016)
On October 16, 2006, the DoD announced the reinstatement of mandatory anthrax vaccinations for more than 200,000 troops and defense contractors. (Another lawsuit was filed by the same attorneys as before, challenging the basis of the vaccines license on scientific grounds.) The reinstated policy required vaccinations for most military units and civilian contractors assigned to homeland bioterrorism defense or deployed in Iraq, Afghanistan or South Korea. A modification of previous policy allowed military personnel no longer deployed to higher threat areas to receive follow up doses and booster shots on a voluntary basis. As of June 2008, over 8 million doses of AVA had been administered to over 2 million US military personnel as part of the AVIP. In December 2008, the FDA approved the new BioThrax IM formulation for intramuscular injections thus reducing the immunization schedule from a total of 6 shots to 5 shots (see below). On February 12, 2009, Emergent BioSolutions announced that the Drugs Controller General of India (DGCI) had approved licensing of BioThrax for distribution by Biological E. of Hyderabad.In 2011, BioThrax was approved for sale in Singapore by the Singapore Health Sciences Authority. Building 55 approval (2016)
The FDA approved the companys license (officially called a supplemental Biologics License Application, or sBLA) to manufacture BioThrax in a large building in Lansing, Michigan known as "Building 55." According to Homeland Preparedness News, "The use of Building 55 to manufacture BioThrax could expand manufacturing capacity to an estimated 20 to 25 million doses annually.