However, regardless of whether transudative or exudative, large, refractory pleural effusions causing severe respiratory symptoms can be drained to provide symptomatic relief. The management of exudative effusions depends on the underlying etiology of the effusion. Pneumonia, malignancy, and TB cause most exudative pleural effusions, with the remainder typically deemed idiopathic. Complicated parapneumonic effusions and empyemas should be drained to prevent development of fibrosing pleuritis.
Retrograde amnesia is inability to recall memories before onset of amnesia. One may be able to encode new memories after the incident. Retrograde is usually caused by head trauma or brain damage to parts of the brain besides the hippocampus. The hippocampus is responsible for encoding new memory.
Retrograde amnesia after a trauma such as a car accident is often a form of retrieval failure. We know this because memories lost in retrograde amnesia (e.g. memories for the time right before the crash) often come back. By contrast, lost memories in anterograde amnesia never come back, probably because they were never properly formed in the first place. The following essay from a student illustrates both retrograde and anterograde amnesias triggered by a powerful hit on the football field.