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Amnesia, dissociative disorders and delirium: Pathology review



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Psychological disorders review

Amnesia, dissociative disorders and delirium: Pathology review


0 / 7 complete

USMLE® Step 1 style questions USMLE

7 questions

A 72-year-old woman is brought to the emergency department by their son for evaluation of confusion. The patient's son reports that he went to the patient’s apartment to check on the patient and found her lying on the ground. The son explains that “She couldn’t tell me what happened, so I called 911.” The patient’s past medical history includes hypertension, hyperlipidemia, diabetes, and a recent left femoral neck fracture. The patient’s current medications include lisinopril, metformin, atorvastatin, ibuprofen, and acetaminophen. The patient is currently employed as a lawyer and has been working at home since the fracture. Temperature is 38.3°C (100.9°F), pulse is 104/min, respirations are 22/min, blood pressure is 107/70 mmHg, and O2 saturation is 93% on room air. Initial assessment demonstrates an elderly female who appears confused. The patient states, “What you are trying to do to me here is illegal. You are trying to lock me up and throw away the key!” Physical examination reveals a left lower extremity in a cast with adequate capillary refill and without other signs of injury or trauma. The patient is not physically abusive and follows directions given by the physician and nurses. A chest X-ray is demonstrated below.  Which of the following best describes the etiology of this patient’s confusion?

Reproduced from: wikipedia


Content Reviewers:

Antonella Melani, MD

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.

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.

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!

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.

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.

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.

And that is why it used to be called multiple personality disorder.


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.

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  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "Dissociative disorders in DSM-5" Depression and Anxiety (2011)
  5. "Prevalence of dissociative disorders among women in the general population" Psychiatry Research (2007)