Session Five (Amnesic Disorders) Flashcards
How can we divide memory disorders?
By permanence (temporary or permanent) or by cause (neurological or psychogenic).
However there is some overlap, as with Alzheimer’s
What are some examples of neurological memory disorders?
- Toxic confusional state
- Mild memory disorder following head injury
- Amnesic syndrome
- Epilepsy
- Dementia
- Cerebral hypoxia
- TGA
- Transient Epileptic Amnesia (TEA)
- HIV neurocognitive disorder
What are some examples of psychogenic memory disorders?
- PTSD
- Fugue states
- Focal retrograde amnesia
Briefly outline the different forms of memory? Which are affected in Amnesia?
- Primary (working memory; Memories of the last few seconds
- Autobiographical memory; Recollection of past incidents and events
- Semantic memory; Knowledge of language, concepts, facts.
- Implicit memory; Skills
Autobiographical memory is severely affected in amnesia, semantic memory may be, other two are usually preserved.
Distinguish Antegrade and Retrograde Amnesia?
AA = Impairment in new learning i.e in recall and recognition for episodes and facts arising after the onset of illness or injury.
RA = Loss of memory for episodes or facts which occurred before the onset of illness or injury
What are some causes of Transient Neurological Amnesia (loss of memory, neuro cause, temporary)?
- Delirium or Acute Confusional state
- Head Injury
- Epilepsy
- Alcoholic blackout
- Cerebral hypoglycaemia
- Transient Global Amnesia
- Transient Epileptic Amnesia
What is Transient Global Amnesia? What are some suggested causes for it?
- Neuro disorder, characterised by a disruption to almost all memory lasting 2-8 hours
- Patient only aware of very short term memory and perhaps some very old memories form childhood
- No other cognitive deficits
- Cause unclear, dominant theories include cerebral ischaemia, migraines or small epileptic attacks (although most EEGs come back normal)
- NO link between TGA and vascular diseases like stroke and CVD.
- Many patient shave history of migraine
- Some patients will go on to develop de novo epilepsy after TGA episodes.
- 1/3 cases have a precipitating event, including regroups exercise, sex, cold water swimming, stress, or medical procedures.
What is Transient Epileptic Amnesia?
- Rare neuro disorder
- Recurring episodes of amnesia caused by underlying temporal lobe epilepsy
- Both RA and AA, although self recognition is preserved.
- Other cognitive functions normally preserved, may be a small episode of unresponsiveness
- 3/4 cases occur during then night with the patient walking up confused
- Cases that hit when awake are normally preceded by smell/taste hallucinations
- Diagnosis is often complicated, most patients have negative EEG findings on initial presentation
- Most are diagnosed at a later date due to the recurring nature of the condition (12+ a year)
- Most patients are men above the age of 50
- Over 50% display repeated questioning behaviour
What is “The Amnesic Syndrome” and what can cause it?
An abnormal mental state in which memory and learning are affected out of all proportion to other cognitive functions in an otherwise alert and responsive patient.
Form of Persistent Neurological Amnesia
Causes:
- Post-encephalitis (e.g. herpes)
- Hypoxia (e.g. from anaesthesia)
- Thiamine deficiency (e.g. in Korsakoff)
- TB Meningitis
- Temporal lobectomy
- Lesions in specific parts of the brain, namely the medial temporal lobes.
Lesions in which parts of the brain can lead to Antegrade Amnesia?
- MEDIAL TEMPORAL LOBES (most common by far)
- Thalamus
- Mammillary bodies
- Retrosplenium
- Basal forebrain
- Frontal lobes
How can Herpes lead to Amnesia?
- 50% first infection
- 50% reactivation brought on by stress/trauma/sunlight…
- Travels along olfactory nerve or via dura to the base of the brain
- From there into the temporal lobes
Outline the neuropsychological features of Amnesic Syndrome
- IQ intact
- Primary short term working memory intact
- Severe impairment of explicit memory
- Extensive autobiographical retrograde amnesia
- BUT older semantic memories remain spared
- Procedural skills intact but lack the explicit memories around them e.g. won’t remember they’ve ever played piano but will be able to play is masterfully
What are some common causes of cerebral hypoxia?
- Heroin overdoses
- Suicide attempts
- Cardiac arrests
- Surgical anaesthetic accidents
How strong is the link between cerebral hypoxia and amnesia, and why?
20% of cases of CH show memory problems, in absence of other cognitive issues.
Hypoxia causes cell loss across the brain, but about 19% of patients show damage in the hippocampi alone, which is an area associated with memory. Suggestion is that hypoxia can in some people specifically affect this region and cause amnesia.
What are Wernicke’s and Korsakoff’s?
Neurological syndromes resulting from profound thiamine depletion, usually caused by alcohol withdrawal.
Technically two different syndromes (K = memory, W = CANON, not memory) but often co-occur in Alcoholic Wernicke-Korsakoff syndrome.
