The majority of experts believe that PCS results from a mix of factors, including preexisting psychological factors and those directly relating to the physical injury.It is not known what causes PCS to occur and persist, or why some people who have a mild traumatic brain injury later develop PCS while others do not. The nature of the syndrome and the diagnosis itself have been the subject of intense debate since the 19th century. However, certain risk factors have been identified; for example, preexisting medical or psychological conditions, expectations of disability, being female, and older age all increase the chances that someone will have PCS. Physiological and psychological factors present before, during, and after the injury are all thought to be involved in the development of PCS.Some experts believe post-concussion symptoms are caused by structural damage to the brain or disruption of neurotransmitter systems, resulting from the impact that caused the concussion. Others believe that post-concussion symptoms are related to common psychological factors. Most common symptoms like headache, dizziness, and sleep problems are similar to those often experienced by individuals diagnosed with depression, anxiety, or post traumatic stress disorder. In many cases, both physiological effects of brain trauma and emotional reactions to these events play a role in the development of symptoms. Physiological
Conventional neuroimaging studies of the brain following a concussion are typically normal. However, studies have found some subtle physiological changes associated with PCS using more novel imaging modalities. Studies using positron emission tomography have linked PCS to a reduction in glucose use by the brain.
Classically, new widening of the mediastinum on radiograph is of moderate sensitivity for detecting an ascending aortic dissection; however, this finding is of low specificity, as many other conditions can cause apparent widening of the mediastinum.There are several other associated radiographic findings:
The "calcium sign" describes an apparent separation of the intimal calcification from the outer aortic margin by greater than 10 mm. Pleural effusions, more commonly in descending aortic dissections, and typically left-sided. Other: the obliteration of the aortic knob, depression of the left mainstem bronchus, loss of the paratracheal stripe, and tracheal deviation.Importantly, about 12 to 20% of aortic dissections are not detectable by chest radiograph; therefore, a "normal" chest radiograph does not rule out aortic dissection. If there is high clinical suspicion, a more sensitive imaging test (CT angiogram, MR angiography, or transesophageal echo) may be warranted. Computed tomography
Computed tomography angiography is a fast, non-invasive test that gives an accurate three-dimensional view of the aorta. These images are produced by taking rapid, thin-cut slices of the chest and abdomen, and combining them in the computer to create cross-sectional slices. To delineate the aorta to the accuracy necessary to make the proper diagnosis, an iodinated contrast material is injected into a peripheral vein. Contrast is injected and the scan performed using a bolus tracking method. This type of scan is timed to injection to capture the contrast as it enters the aorta. The scan then follows the contrast as it flows through the vessel.