Amnesia, dissociative disorders and delirium: Pathology review

Definitions & Key takeaways

Pathologically, amnesia is defined as a loss of memory despite otherwise normal cognitive function. It can be due to damage to the brain like in stroke, or degenerative diseases that affect the brain. Dissociative disorders are a group of conditions that involve disruptions in consciousness, identity, and/or memory. Delirium is a mental state characterized by alteration of attention, consciousness, and cognition.

Amnesia can be divided into three subtypes: anterograde amnesia, retrograde amnesia, and transient global amnesia. Anterograde amnesia is the inability to form new memories following the onset of amnesia. Retrograde amnesia is the inability to recall memories that were formed before the onset of amnesia. Transient global amnesia is a brief episode of complete or nearly complete memory loss.

Chapters:

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Case studies0:00–1:12

78 year old Joanne is brought in by her son, who is worried because Joanne seems to forget things all the time. You start by introducing yourself, and then explain to Joanne the reason she’s in the hospital.
You then ask her a few things about herself. She looks confused and tells you that she used to be a Broadway singer before retiring and she has travelled all around Europe.
Her son tells you she used to work as a sales woman and she’s never been to Europe in her entire life. A few minutes later, Joanne asks her son where they are and who you are.
On physical examination, you notice a strong alcoholic odor, so her son reluctantly tells you that Joanne has a history of chronic alcohol abuse.
Next to her, a 66 year old man is also brought to the hospital, after being found by the police wandering in the streets, with a battered suitcase.
He doesn’t seem to know his name, location, or where he was going, and stares blankly when you ask him anything.The only thing he is able to tell you is that he is going on a business trip.
When you contact his relatives, they tell you that his name is Matthew, and that he was recently fired from his job. Physical examination is unremarkable.Based on the initial presentation, both Joanne and Matthew seem to have some form of amnesia, dissociative disorder, or delirium.Okay, starting with amnesia, this can be categorized into two types.

Pathology1:12–1:22

Amnesia1:22–2:16

The first type is anterograde amnesia, which refers to an inability to form new memories, often forgetting what happened hour to hour.
The second and probably most high yield type of amnesia is retrograde amnesia, and it refers to an inability to recall old memories.
As a result, they may completely forget important people or moments in their life, which can cause anxiety for the individual experiencing retrograde amnesia, as well as their friends and family.
Both anterograde and retrograde amnesia can be caused by acute and chronic conditions. Acute causes include traumatic brain injury or infections that may cause brain inflammation, such as herpes simplex.
On the other hand, chronic causes include brain tumors and neurodegenerative diseases, including Alzheimer disease or other forms of dementia.
For your exams, what’s extremely high yield to remember is that amnesia can also result from vitamin B1 or thiamine deficiency.

Wernicke encephalopathy 2:16–3:36

Now, thiamine deficiency is typically caused by chronic alcohol abuse, and it can first lead to Wernicke encephalopathy.
This is an acute and reversible neurologic condition that occurs when there’s damage to the brainstem, cerebellum, and limbic system.
What’s high yield is that Wernicke encephalopathy is characterized by a classic triad of symptoms, including ophthalmoplegia, or paralysis of the eye muscles, ataxia, or unsteady gait, and altered mental status.
If not promptly treated, Wernicke encephalopathy can progress to Korsakoff syndrome. Korsakoff syndrome occurs due to damage in the thalamus, more specifically, in the anterior and dorsomedial nucleus, and is chronic and irreversible.
Now, the hallmark of Korsakoff syndrome is severe and permanent memory impairment, which includes both anterograde and retrograde amnesia.
Another characteristic finding is confabulation, which is when the person fills in the gaps in their memory by making up stories that they believe to be true.
Finally, individuals with Korsakoff syndrome may also experience personality changes like apathy or indifference.Okay, let’s switch gears and talk about dissociative disorders!

Dissociative disorders3:36–4:50

Now, maybe you’ve had the experience of driving on “autopilot.” One minute you got in your car, and the next minute you’ve arrived at your destination, but you can’t actually remember the details of the drive.
This is an example of dissociation or disconnection from what is going on around you. Normally this day-dreamy state doesn’t last very long, and most people can snap out of it if something or someone requires their attention.
But for some people, dissociation may become so intense and happen so often that it stops a person from functioning in their daily life.
When this is the case, we say the person has a dissociative disorder. This is a group of disorders that impair awareness of your own actions, thoughts, physical sensations, and even your identity, or sense of who you are.
These disorders usually stem from trauma, such as childhood abuse or neglect, and are thought to be a way of adapting to negative experiences.
For your exams, remember that there are three main dissociative disorders: depersonalization/derealization disorder, dissociative amnesia, and dissociative identity disorder.
Starting with depersonalization/derealization disorder, depersonalization refers to a feeling of detachment from oneself, or one’s own body, thoughts, and actions, while derealization refers to a feeling of detachment from one’s surroundings, like the world around you is unreal.

Depersonalization4:50–6:11

Individuals with depersonalization/derealization disorder often feel as if they’re watching themselves from the outside.
A classic description is feeling like they’re watching a movie about their life. Other symptoms include an altered sense of time, where things seem to move too fast or slow, brain fog or light-headedness, and being prone to anxiety and rumination or deep thoughts on life and reality.
However, what’s important to keep in mind is that during the depersonalization or derealization experiences, there’s intact reality testing, which is an individual’s ability to distinguish their thoughts and feelings from the real world, unlike psychosis, where reality testing is disturbed.
Another thing to remember for your exams is that individuals with depersonalization/derealization disorder might feel emotionally or physically numb, and thus express little or no emotion.
In addition, they might have trouble forming relationships. In severe cases, a person might have trouble recognizing familiar places, people, or objects.
Next is dissociative amnesia, which is when a person blocks out or forgets important personal information like where they lived as a child, or what their mother was like.

Dissociative amnesia6:11–7:08

For your exams, the most important thing to know about dissociative amnesia is that the onset is usually sudden and it is typically related to a traumatic experience or severe stress.
Now, dissociative amnesia is most often localized and selective, meaning that individuals have trouble specifically recalling a traumatic event and sometimes the months or years surrounding it.
However, some individuals may experience generalized amnesia, which is when they can’t remember any of their past, even the non-traumatic parts.
A high yield fact is that generalized amnesia is often accompanied by a dissociative fugue. That’s a temporary period of disorientation and wandering or travelling far away from home.
In a fugue state, a person might be confused about who they are, or they may believe they are someone else. The third type of dissociative disorder is dissociative identity disorder, which is when individuals have two or more distinct identities, sometimes called personalities, or alter egos.

Dissociative identity 7:08–8:30

And that is why it used to be called multiple personality disorder. What’s interesting is that these multiple identities tend to talk and act differently than the original person.
For example, they may have opposing tastes or political views, and be different ages, gender identities, or even nationalities.
Now, these alternate identities completely take over a person’s body and mind, temporarily suppressing all other identities.
Keep in mind that the original identity is usually unaware that this is happening, and may have memory gaps, sometimes forgetting entire portions of their day when an alternate identity took over.
Because of that, having a dissociative identity disorder can potentially endanger the affected individual, especially if one identity engages in self-mutilation or risky behavior.
What’s important to keep in mind here is that dissociative identity disorder is more common in females, and it’s often associated with history of physical or sexual abuse, as well as psychiatric conditions like major depressive disorder, post traumatic stress disorder or PTSD, borderline personality disorder, somatic symptom disorder, as well as substance misuse like LSD or PCP.
The last high yield disorder is delirium, which is an acute and sudden disturbance in consciousness characterized by mental confusion.

Delirium8:30–12:38

For your exams, an incredibly high yield fact to know is that delirium most often affects elderly individuals. So in a test question, look for an ill elderly individual in an emergency department, intensive care unit, hospital floor, or a nursing home.In fact, delirium often occurs in the setting of an acute medical illness, including central nervous system disorders, such as a stroke, brain tumor, or trauma, but also sleep deprivation, infections like pneumonia or urinary tract infections.
Another important cause of delirium includes substance misuse or withdrawal, as well as various medications, such as benzodiazepines and anticholinergicsFinally, delirium may result from metabolic diseases like kidney disease, or electrolyte disturbances, as well as urinary retention or constipation.
Now, symptoms of delirium typically represent a shift from the individual’s baseline mental status. That could mean hyperactivity and agitation, or it could involve hypoactivity and drowsiness in a person that didn’t experience these before.
For your test, remember that family members typically say that the person “isn’t acting like themselves”. Oftentimes, individuals have a decreased attention span, meaning that they’re distractible and cannot maintain a coherent flow of ideas.
They can also get disoriented to time, meaning they don’t know what day, month or year it is; to place, meaning they don’t know where they are; or to self, meaning they don’t know who they are, often forgetting their own name.
Other high yield symptoms of delirium include illusions or misperception of sensory stimuli, as well as hallucinations or perceiving something that’s not real, most commonly visual, but can also be auditory, or involve bodily sensations like pain or tickles.
Other features of delirium include sleep-wake cycle disturbances, which means that their internal clock isn’t synchronized with the surrounding environment.
For your exams, be sure to remember that, in general, the symptoms of delirium develop abruptly and tend to fluctuate and shift back and forth, which is called “waxing and waning”.
For diagnosis of delirium, the main thing you need to know is that an electroencephalogram or EEG for short might reveal a diffuse slowing of background activity.
Now, all of this can seem very similar to what happens with dementia. So, for your test, it’s important not to confuse them.
Now, remember that unlike in delirium, where the onset can be pretty sudden, people with dementia typically experience a slow mental decline that can take months or even years.
Early on, people with dementia are generally alert and oriented, and they don’t have hallucinations. The good news is that unlike dementia, delirium is usually temporary, resolving when the underlying cause is addressed.
The treatment of delirium is two-fold: first is treatment of the underlying cause, and second is treatment of the delirium itself.
Treating the underlying cause is the most effective way of reversing delirium, and examples include discontinuing an offensive medication or starting antibiotics in case of an infection.
As for treating the symptoms of delirium, the initial approach involves supportive care. This includes maintaining adequate hydration, encouraging the individual to walk, reducing excess noise and bright overhead lights, having windows in the room, providing the individual with a clock and a calendar, managing pain, as well as providing frequent reassurance, and helping them re-orientate themselves with family members at the bedside.
If this isn’t enough, antipsychotic medications can be given. Keep in mind that certain medications must absolutely be avoided, as they may worsen delirium.
These include anticholinergics, opioids, and benzodiazepines. And that’s very high yield!
Finally, it’s important to remember that physical restraints should only be used as a last resort. All right, as a quick recap… There are two main types of amnesia.

Recap12:38–14:05

Anterograde amnesia causes a person to be unable to form new memories, while in retrograde amnesia, a person is unable to recall old memories.
Some important causes of amnesia include trauma, infections, or tumors involving the brain, as well as neurodegenerative diseases, and Korsakoff syndrome from vitamin B1 or thiamine deficiency.
Next, dissociative disorders. In depersonalization/derealization disorder, there is a feeling of detachment from oneself and the surrounding environment, associated with a disruption in the normal perception of events, while reality testing remains intact.
Dissociative amnesia can be localized to a specific traumatic period of time, or generalized, which is when a person can’t remember any of their past, and can be accompanied by dissociative fugue, which is a sudden and unexplained travel away from home.
Finally, in dissociative identity disorder, individuals have two or more distinct identities or personality states along with memory gaps and noticeable changes in their emotions and behavior.
Last but not least, delirium is an acute, reversible condition, characterized by sudden confusion, disorientation, and decreased attention span, which is most common in the elderly and often occurs in the setting of an acute medical illness.Okay, back to our cases.

Summary14:05–15:11

Joanne is the 78 year old woman who was brought in by her son because of memory loss. She is unable to recall her old memories like her past job.
She also can’t remember where she is and who you are, although you had just introduced yourself, meaning that she’s unable to form new memories.
So this indicates that she has both retrograde and anterograde amnesia. She also made up a false job and a story about trips to Europe, probably as a way to conceal her memory loss.
So that’s a sign of confabulations. All this, along with her history of chronic alcohol abuse, points to Korsakoff syndrome.
After Joanne, you see a 66 year old man named Matthew, who was found wandering in the streets by the police. He can’t recall his own name, location, or where he was going and stares blankly when you ask him anything.
The most important clues here though are that he was recently fired from his job, meaning that he was under major stress, and he thinks that he is going on a business trip.
So that’s a classic case of dissociative fugue, which often accompanies generalized dissociative amnesia.