Hippocampal atrophy is a form of brain damage that impacts both memory and spacial navigation. It is often associated with memory-loss conditions, such as dementia and Alzheimer's disease. Causes include severe trauma, oxygen deprivation and encephalitis and may also include both long-term stress and neurological disorders, such as multiple sclerosis, epilepsy and schizophrenia. While prescription medications can slow atrophy and therapy can help manage the effects, there is no known cure for hippocampal atrophy.
The hippocampus is an extension of the cerebral cortex and is located in the medial temporal lobe. Most experts agree that it plays a significant role in both memory and in spacial awareness, though the details of its involvement are widely disputed. It also appears to play a significant role in olfactory memory. Atrophy is a shrinking or lessening; hippocampal atrophy, then, is a shrinking of the hippocampus.
Lack of oxygen is a main cause of brain damage, including this type of atrophy. When the oxygen supply to the brain is cut off, brain cells begin dying and portions of the brain begin to atrophy. Head trauma, often caused by a severe blow or impact or to conditions that cause the brain to "slosh" around within the skull, is another cause. Certain diseases, such as encephalitis, are also known to damage the hippocampus. People who experience bilateral hippocampal damage, which is damage to both sides of the hippocampus, may be unable to form new memories.
While epileptic seizures are often known to focus in the hippocampus, there is some debate as to whether the seizures cause hippocampal atrophy or whether the atrophy causes the seizures. There is also a known link between shrinkage of the hippocampus and Cushing's syndrome and both are thought to be tied to excess cortisol levels. Schizophrenia sufferers frequently experience atrophy in this portion of the brain, though the causal relationship, if any, is unclear.
The hippocampus can also be impacted by long-term stress and, more specifically, by the steroids often used to control long-term stress. Long-term use of such medications can limit the activity of existing neurons in the hippocampus and can also prevent the formation of new ones. This type of damage is often associated with post-traumatic stress disorder and severe depression.
Early symptoms of hippocampal atrophy in humans can include difficulty recalling the recent past and disorientation. It may also be marked by a difficulty in performing spatial navigation, which generally equates to a tendency to get lost, even in familiar environments. In animals, the atrophy is often marked by increased, almost harried, activity. Function of the hippocampus is demonstrated by the presence and frequency of electrical activity, which can be measured by an electroencephalogram and evaluated by a professional.
