Retrograde amnesia (RA) refers to the loss of recent memories due to a traumatic injury or illness. Patients that are newly diagnosed with this condition are characterized as having limited or no recollection of events that happened prior to the onset of retrograde amnesia.
While certain memory functions are adversely affected, retrograde amnesia does not hinder a person’s ability to learn new things – as is the case with anterograde amnesia.
Retrograde amnesia ranges in severity and can also be temporary or permanent. The loss of memory is usually isolated to specific events or subject matters (episodic and declarative memory). In extreme cases, the person may not be able to process their identity; however, this is more commonly referred to as generalized amnesia.
Medical providers reference Ribot’s Law, where it describes patients forgetting endeavors leading up to the traumatic event or illness rather than distant memories.
Psychoanalysts believe that long-term memory is strengthened over time and the information collected in our short-term memory is transferred to the other regions of the brain that may go unaffected by a sharp blow or blunt force trauma, for instance.
There is no clear definitive answer for how long an episode of retrograde amnesia will last. Per Science Direct, however, neurobiologists often classify the severity of retrograde amnesia by its duration.
Temporally graded retrograde amnesia – As the name suggests, the memory loss is temporary and patients are usually able to recall past events. Focal Retrograde Amnesia – Memory loss in this type of diagnosis is usually minute and the result of drug use, in most cases.
Isolated Retrograde Amnesia – Brain scans sometimes link RA to lesions. In these cases, the patient is significantly unable to recollect past events and medical intervention is required.
Pure retrograde amnesia – In this finding, the patient is unable to draw on distant memory and past learned behaviors. The patient, however, is not usually significantly impaired in terms of carrying out normal daily activities or acquiring new skill sets.
The brain’s structure is vast and complex. Medical researchers have dissected and identified different regions of the brain that are responsible for specific functions. The hippocampus, for example, transfers short-term memory into long-term storage while the temporal lobes’ key function is to process factual memory.
If one of the numerous brain regions were to be damaged due to illness or an accident, it could impair the patient’s ability to complete what would be considered normal activities, such as speaking or naming things, just to give a few examples.
However, the prognosis isn’t always dire, due to a safety net that doctors refer to as “brain plasticity”.
According to Sage Journals, our brain compensates for damage by using detours in neuropathways to complete specific functions. Our brains are therefore believed to be flexible vs. static.
Most people that are diagnosed with retrograde amnesia can describe long-term memories easily. It is the recent episodic and/or declarative events that are challenging to remember.
To explain the main causes of retrograde amnesia, neurologists often focus their attention on the hippocampus and prefrontal cortex. This is due, in part, to the fact that these brain regions are studied extensively to be the most impacted in cases of retrograde amnesia.
Extreme retrograde amnesia is believed to be caused by brain damage starting out at the hippocampus and spreading to other brain structures over time.
Traumatic brain injury (TBI) – From shaken baby syndrome in infants to adult head injuries caused by extreme contact sports, TBI can be the result of numerous blunt forces or sudden blows to the brain.
PTSD – Retrograde amnesia can be caused by traumatic events that incite patients to find a coping mechanism, namely memory loss. In these cases, which are referred to as psychogenic amnesia, the patient has no physical injuries to the brain. In essence, therefore, the patient uses memory loss as a coping mechanism. The patient may take on a new identity or be found wandering in faraway places.
Malnutrition – Alcoholic patients are sometimes observed to have retrograde amnesia, particularly those who have been diagnosed with Korsakoff’s syndrome. Neuroscientists pinpoint the link to a lack of Vitamin B1 or thiamine.
Bloodborne infections – Neuroscientists also cite brain and spinal cord infections as primary causes of retrograde amnesia.
Surgery – Despite advances in medicine and technology, neuroscientists still don’t have all the answers on the vast complexity and plasticity of the brain. Based on past surgical procedures and the results that followed, however, neuroscientists now know that the temporal lobes directly correlate to memory.
In the 1950s, one patient who went by the name Henry Molaison underwent brain surgery in an effort to treat his progressively worsening epilepsy. After portions of his temporal lobe were removed, the said patient exhibited retrograde amnesia as well as other forms of amnesia. He became an infamous poster child for neuroscientists to study memory function in relation to the temporal lobe.
Other medically induced causes of retrograde amnesia are reported to be electroconvulsive shock and therapy.
Before devising a custom treatment plan for retrograde amnesia, neurologists must first examine the cause and make a diagnosis. There are multiple methods for diagnosing retrograde amnesia including an Autobiographical Memory Interview, which tests if the subject is able to recollect factual knowledge, such as the names of loved ones, places of work, and so forth.
Most scientists believe that these standardized tests have many drawbacks and are instead turning to more advanced imaging technologies to determine anomalies in the brain.
Standard Treatment Plans for RA Due to TBIs
In the typical emergency response setting, doctors aim to keep the supply of oxygenated blood consistent to reduce and stop brain cells from dying. There are a number of ways to do this, including via endotracheal intubation (EI).
When a patient has been diagnosed with a life-threatening infection, such as meningitis, the standard protocol is to stop the spread of the virus using a combination of antibiotics, anticonvulsants, and steroids.
As discussed earlier, the heavy use of alcohol can lead to thiamine deficiency. To expedite recovery in RA patients, medical providers will typically administer thiamine supplements via an IV.
Resolving dehydration due to alcohol use has also been proven to speed up the recovery process. In addition to medical interventions, patients are usually counseled by psychologists and nutritionists to avoid future RA diagnoses.
In cases where RA is triggered by psychological stress and a way for the individual to escape reality, hypnotherapy is thought to be an effective treatment plan.
Some experts believe in using the reminder effect where past knowledge is recited in hopes of stirring up lost memories. Another treatment plan for retrograde amnesia is spontaneous recovery. In this treatment, patients are exposed to familiar places and things in hopes of eliciting a response in stored memory. In other words, psychoanalysts and neurologists will jog someone’s memory to hasten the recovery process.
There is no magic cure for RA. However, healthcare workers can use a variety of standardized treatments like those discussed above to aid in the recovery process.
Neurologists believe that if recovery is indeed plausible, it is the result of the brain’s ability to heal itself.
Moreover, when patients are newly diagnosed with retrograde amnesia, doctors typically ask loved ones to take a wait-and-see approach in order to get a more accurate prognosis.
Since a large majority of retrograde amnesia cases are the result of a traumatic brain injury (TBI), the best preventative method is to take precautions while engaging in physically demanding activities.
As an example, contact sports players should always wear a helmet on the field as well as construction workers who operate heavy equipment and work at high altitudes daily. Seatbelts should be also worn while driving. In addition, parents should educate themselves and caregivers about the dangers of shaking a baby.
In the event of an injury, urgency is of utmost importance. Lack of oxygen to the brain is proven to cause brain damage. By administering CPR on the spot and calling EMTs, the damage can be significantly reduced based on the speed of treatments given.
Retrograde amnesia is often characterized by losing one’s most recent memories after a traumatic brain injury or illness for example. The memory affected is usually isolated to events that transpire before the retrograde amnesia started.
Even with the memory loss of certain life events, people, and places, in patients with retrograde amnesia, it is said that their personality remains relatively the same.
In forensic settings, defendants sometimes cite retrograde amnesia as a defense. Due to its overuse as a defense strategy in the courtroom, law experts are pushing for more standardized exams to be developed.
Different versions of amnesia can coexist with each other simultaneously, including retrograde and anterograde amnesia. They are, however, dissimilar as the latter is the inability to store or learn new behaviors.