Other advantages of CT over MRI scan are ability to detect bony fractures, vascular injury, and cerebrospinal fluid (CSF) leak. It also does not need to screen for MRI safety of implants/foreign body especially for penetrating or blast injuries.However, MRI has higher sensitivity than CT scan for the detection of epidural hemorrhage, subdural hemorrhage, subarachnoid hemorrhage, nonhemorrhagic cortical contusions, hemorrhagic parenchymal contusions, brainstem injuries, and white matter axonal injuries. If CT scan shows normal findings, but the subject has persistent neurological symptoms, MRI is also indicated. However, MRI safety concerns on metallic foreign bodies, limited availability, longer imaging time, high sensitivity to motion, and higher cost limits the usefulness of MRI.Swirl sign on CT scan (areas of low densities with surrounding areas of high densities) is indicative of active intracranial bleeding, high chance of death within one month, and poor subjects function in three months if the subject is still alive.When ICP is increased the heart rate may be decreased. Traumatic
Types of intracranial hemorrhage are roughly grouped into intra-axial and extra-axial. Intra-axial hemorrhage is bleeding within the brain itself, or cerebral hemorrhage. This category includes intraparenchymal hemorrhage, or bleeding within the brain tissue, and intraventricular hemorrhage, bleeding within the brains ventricles (particularly of premature infants). Intra-axial hemorrhages are more dangerous and harder to treat than extra-axial bleeds. Hemorrhagic parenchymal contusions and cerebral microhemorrhages are examples of traumatic intra-axial bleeds.Extra-axial hemorrhage, bleeding that occurs within the skull but outside of the brain tissue, falls into three subtypes: epidural hematoma, subdural hematoma, and subarachnoid hemorrhage.
Complications include focal neurologic deficits depending on the site of hematoma and brain injury, increased intracranial pressure leading to herniation of brain and ischemia due to reduced blood supply and seizures. Subarachnoid hemorrhage
A subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain. Trauma can also cause SAH when the arteries and veins coursing through the subarachnoid space are ruptured. It is usually located at the cerebral sulci near the vertex of the head and spare the basal cisterns on CT scan. Severe trauma can cause SAH in all parts of the brain. When the SAH volume is large, rarely it can cause cerebral infarction a few days after trauma due to arterial vasospasm. Although CT scan is performed more often than MRI to detect SAH, MRI is more sensitive than CT in this aspect. SAH shows hyperintense signal of Fluid-attenuated inversion recovery (FLAIR) sequence and blooming artifact on susceptibility weighted imaging (SWI).Computed tomography angiography (CT angiography) or Magnetic resonance angiography (MR angiography) should be done if fracture involves the carotid canal, because in such cases, posttraumatic vasospasm can occur, thus cutting blood supply to the brain. Besides, intracranial hemorrhage that are atypical for trauma should also be investigated further with CT or MR angiography to look for other causes of intracranial bleeds apart from trauma causes. Such atypical patterns includes: isolated SAH in the basal cisterns, isolated large-volume SAH in the Sylvian fissure, and isolated SAH in the anterior interhemispheric fissure.