Loss of Consciousness from Brain Injury versus Amnesia
Biology 202
2000 First Web Report
On Serendip
Loss of Consciousness from Brain Injury versus Amnesia
Paula Green
Brain injuries have been traditionally classified as mild, moderate and severe based upon the duration of loss of consciousness and memory. More recently these classifications have been reconsidered based upon the length and severity of amnesia (4). How can you measure loss of consciousness and memory? How does the length of amnesia better predict the severity of a brain injury versus the traditional method of classifying brain injury based upon the length of loss consciousness? Head trauma is by far the most common cause of amnesia, but the condition often goes unrecognized as patients more serious medical problems become the foremost concern (3). Traumatic amnesia is brain damage caused by a severe non-penetrative blow to the head, such as in a road accident. It can lead to anything from a loss of consciousness for a few seconds to coma. During post-traumatic amnesia, a patient usually fails to remember not only the accident, but also all information learned for several years before the brain injury. A severe blow to the head is likely to cause loss of consciousness lasting seconds up to months. This state of puzzlement and confusion can pass with time for many cases (1).A brain is exposed to injury as a result of external forces, which are directed to the head. Those forces can include a blow to the head, the head hitting something, and a rapid acceleration/deceleration movement, such as whiplash (2).The extent of brain injury can be classified as either a state resulting in coma or not. This distinction is used not because the ultimate outcomes are necessarily different, but because coma resulting in a head injury can evoke "the vigil between life and death." The patient is typically the primary source who is asked the most significant question: Did you lose consciousness as a result of your injury? In order for a brain injury victim to answer such a question, they would have to undergo extensive examination recollecting past events (3). Any change in mental state can be significant in understanding a patient's condition and if loss of memory (amnesia) occurred immediately before or after the trauma (4).
In response to trauma, changes may occur in the brain, which require extensive monitoring to prevent further damage. The brain's size could increase after a severe head injury. Brain swelling occurs when there is an increase in the amount of blood to the brain caused by leakage from blood vessels. The more damage the brain receives, the more it swells. When the brain swells, because it is housed inside the skull, it has no room to expand (2).This leads to a rise in pressure within the brain, therefore affecting the blood flow to the brain. This excessive swelling and pressure in the brain is called "Intracranial Pressure." Strong medications are used to help draw fluid back out of the brain and back into its respective blood vessels. Many medications can help by decreasing the "metabolic requirements" of the brain, while other medications increase blood flow into the brain which can help diminish the "spiral effect" caused by brain swelling. In some cases, removal of small amounts of fluids from the brain or surgery may be beneficial and in other cases, removal of damaged tissue may prevent further damage (2).
Two common developments that happen in people with brain injuries are retrograde and anterior grade amnesia. Retrograde amnesia is the inability to retrieve information that had been stored prior to the onset of the amnesia. People with this condition do not tend to forget their childhood or who they are, but have trouble remembering day-to day events. Social skills and intellectual capabilities other than memory are usually conserved. Anterior grade amnesia is the inability to acquire new information for long-term storage and retrieval. (5).The learning of word lists helps to distinguish short-term from long term memory. When recalling items from a list of 12 words, for example, patients tend to retrieve a substantially higher number of words that were presented at the beginning and end of the list. The recall of initial items is known as the "primary effect" and reflects processes related to long-term memory, whereas the recall of late items is known as the "recency effect" and is more closely related to short-term memory. Certain forms of neurological damage may spare short-term but impair long-term memory, while other types of damage may impair both types of memory. The existence of such "dissociation" illustrates the independence of short-term versus long-term memory (7).
An intriguing feature of human amnesia is that it can arise from damage to either of two distinct brain regions: the medial temporal lobes or the midline diencephalic nuclei. The medial temporal and diencephalic structures associated with memory function are the hippocampus, mammillary bodies, mammillo-thalamic tract, and dorsomedial thalamic nucleus. They comprise part of the limbic system and may therefore form a memory circuit. Components of the limbic and paralimbic zones of the cerebral cortex, especially the hippocampus and entorhinal cortex, play critical roles in long-term storage and explicit recall. Although the hippocampo-entorhinal complex also participates in the neural regulation of emotion, autonomic activity, endocrine control, and immunoregulation, its principal behavioral affiliation is associated with memory and learning (8).
Some specific disorders also causing amnesia for example are the Wernicker-Korsakoff syndrome. This syndrome is memory loss caused by alcohol abuse. A person's short-term memory may be normal, but they will have severe problems recalling a simple story, faces and complex patterns. This tends to be a progressive disorder and is usually accompany by neurological problems, such as uncoordinated movements and loss of feeling in the fingers and toes. Studies of chronic alcoholics with the Wernicker-Korsakoff syndrome have shown to have damage within limbic diencephalic structures such as the mammillary bodies, the mediodorsal nucleus of the thalamus, and the medieval pulvinar which are all located in the medial temporal lobe (6). Anoxic amnesia: Classic amnesia that may result from anoxia (total deprivation of oxygen) caused by acute cardiopulmonary arrest. With reinstatement of oxygenated blood flow, many patients now survive short periods of total brain anoxia. If the period of anoxia is sufficiently short, recovery may be complete, but if somewhat longer, recovery may be accompanied by persistent amnesia. The most prominent findings are cell loss in the hippocampus. Psychogenic Amnesia: An amnesia that involves inability to remember one's owns name or other highly personal information. One view is that this form of amnesia represents an attempt to escape an overwhelming psychic trauma, leading to selective forgetting. Patients with this condition cannot remember their own name, the names of family members, current home addresses, or recent personal events, but they easily recall the names of Presidents, news events, and sports results. They retain vocabulary usage and all social behaviors (6).
Rehabilitation for victims with brain injuries involves learning new ways to compensate for abilities that may have permanently changed due to brain injury. Some medications taken after traumatic brain injury include anticonvulsant. These are used to prevent seizures, but also to help decrease irritability and headaches, improve frustration tolerance and stabilize mood swings. Antianxiety agents can be used for muscle tension/spasticity, but they can worsen short-term memory if used on a long-term basis. Short-term use is appropriate if closely supervised by the physician (2).
The rehabilitation of memory or loss of consciousness is one of the greatest challenges for clinical neuroscience. While animal research has provided evidence for extensive brain studies, the relevance of this knowledge to human amnesia and its recovery remains unclear. The rehabilitation process is usually catered to each person's needs. The process is different for everyone (1,2).
So, Is loss of consciousness necessary for the brain to be injured?
WWW Sources
1)Anatomy of a Head Injury7)Amnesia
8)Children with amnesia cast new light on memory and learning?
9)About Traumatic Brain Injury
For a long time I did not want to talk about the accident or my condition but a year and a half later I am now talking-writing. One of the things I have learned is that we do not know anything about the brain. The brain is not predictable. Rehabbing the brain has to be very individual. Every brain is different. The brain is delicate, but has the potential to be stronger than the body ... Jennifer, 15 March 2006
Hi, i was writing a story and need to do some research about memory loss because the main character gets into a car accident. If someone suffers memory loss, could they forget who they are and things about their home life and social life, but remember thier recent school education? When memories come back, do they come back in chunks, one at a time, or all at once? Do these people remember the period of time when they had no memories? ... Jessie, 28 November 2007
TBI 16 Feb 1995
Its been some 14 years, since I had a TBI, for the most part if you meet me now, you would not know. But, that is the scary part to me. While I spent the most part of three days in a coma (Level 7) I read the reports years later, as we prepared for the court case. I do not remember anything of the injury, I remember some things earlier in that day, but nothing from that day, til about June of that same year. Sadly, I have tried to remember things, but no luck. I can not remember things prior, from about 1989 to the date of the accident. While I know many of these things happened, because I have seen pictures, or people I trust tell me they did, I have no vivid or accurate memory of any of these things in this time period. To include my wedding, my 2nd sons birth, and my participation in the Gulf War. I sometimes spend several days, trying to remember a word that would describe something, I may be thinking. My short term is still effected, and I must meet someone several times to remember their names. In turn if I dont see them for some time, I will forget their names. When, I was coming out of the coma, I knew what I wanted to say, I could not get the words out. I am easily frustrated, and lash out. Cursing is not an issue, and many times, I do not know I am expressing myself this way. Its all sad.
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