Memory
Memory Enhancing Agents
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Impairments in attention and memory have been well documented following traumatic brain injury. Cognitive problems, including difficulties with memory, often present the greatest barrier to successful community reintegration and return to work after a brain injury. In fact, existing studies reveal that “memory problems” or “forgetfulness” is the most frequently reported symptom following TBI. Acetylcholinesterase Inhibitors are within a class of drugs that may be helpful in alleviating memory problems for some patients after a brain injury.
The hippocampus is a structure in the brain that is important in the regulation of emotion, attention, and memory. Due to its location near bony protuberances of the bottom of the skull, the hippocampus is particularly susceptible to damage during head trauma. Animal research has shown that nerve cells in the hippocampus are frequently injured more than other nerve cells in the brain following head trauma. Damage to the hippocampus is likely responsible for memory deficits in many individuals with traumatic brain injury.
The primary chemical messenger, or neurotransmitter, in the hippocampus is a substance called acetylcholine. Studies have shown that abnormalities in function of acetylcholine may lead to alterations in memory and executive functioning. Research into improving memory by using medications that improve the function of nerve cells that use acetylcholine began many years ago, starting with a drug called physostigmine, and later with a drug called tacrine. Although many patients demonstrated improvement in memory with these medicines, both were associated with some serious side effects as well as the need to take many, frequent doses of the medicine throughout the day for them to be clinically effective. These problems limited their usefulness.
Recently, several new medications that act on the neurotransmitter acetylcholine have become available. They were all devised to treat the memory problems associated with Alzheimer’s disease, which also affects the hippocampus. These newer medications, donepezil (brand name ARICEPT), rivastigmine (brand name EXELON) and galantamine (brand name REMINYL) work by making more acetylcholine available in the areas of the brain that are responsible for memory, by inhibiting an enzyme called acetylcholinesterase, which breaks down acetylcholine. They are longer-acting than the older medications, so that once-or twice-daily dosing is possible, making compliance easier. Additionally, they are not associated with many of the problematic side effects associated with the older medications.
Doctors who treat brain injury may recommend one of these medications for the treatment of memory problems. Additionally, there is some new information that suggests that in certain cases, these medicines may be helpful in individuals who have behavioral problems associated with loss of inhibition, as is seen frequently in persons with damage to the frontal lobes of the brain. Research with rodents has demonstrated other benefits, such as improvement in motor function, and improved performance on physical tasks. However, this effect has not been observed in humans. Lastly, these medications have been used to successfully treat a number of psychiatric symptoms, although the way that they do this is unknown. Although these medicines were specifically designed to treat Alzheimer’s disease, they have been used in a number of other conditions, such as Down’s Syndrome, Multiple Sclerosis, and of course, Traumatic Brain Injury.
Although these new acetylcholinesterase inhibitors have much fewer side effects than the older versions, they are not completely without problems. The most common side effects reported are gastrointestinal, and include, nausea, vomiting, diarrhea, and abdominal cramping. Some clinicians believe that these medicines may lower the seizure threshold in individuals who have seizures, although whether this is true is still unclear. To decrease the chances of the gastrointestinal side effects, it is generally recommended to start the medicine at a low dose and gradually increase the dose monthly until the desired affect is observed. In many cases, if gastrointestinal side effects occur, they generally will subside after a few days even if the medicine is continued. Most patients tolerate these medicines very well and have no problems.
Mental Health lists numerous medications with pharmacology, indications, warnings, dosages, research, etc.
Dr. Ripley joined the staff of The Shepherd Center in August of 2001, and assumed responsibility as Medical Director of Brain Injury Research and Medical Director of Post-Acute Services. He serves as Co-Medical Director of the Georgia Model Brain Injury System (GAMBIS). Prior to this, he held a position on faculty of Emory University School of Medicine with a primary appointment in the Department of Rehabilitation Medicine, where he served as Medical Director of Brain Injury Services.