A 35-year-old woman recently separated from her boyfriend of 5 years was brought to the A&E with loss of memory. On examination, her memory loss is specific to events associated with her boy friend. But she remembers other events that took place around the same time.
She is most probably suffering from:
E. The woman described in the question probably suffers from dissociative amnesia, in this case precipitated by the stress of separation. Systematized amnesia is the loss of memory for a certain category of information such as material relating to one’s family or a particular person. In this case, her boy friend. Localized amnesia is the condition where the individual fails to recall events that occurred during a circumscribed period of time. In selective amnesia the person can recall some but not all events during a circumscribed period of time. Generalized amnesia is characterized by a failure to recall all of a person’s past life. There may be dissociation between explicit and implicit memory, for example the person may retain all his learned skills, but completely forget who he is or his past (a la Jason Bourne in the Bourne trilogy). Continuous amnesia is a condition featuring an inability to recall events subsequent to a specific time up to and including the present.
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After an enjoyable evening with friends at a pub, Tom calculates the cost of the number of drinks that he had, subtracts the total from the value of money he gave the bartender, and calculates the change that is due.
The system of memory that enables such calculation is:
D. Working memory describes the ability to temporarily hold information in mind and manipulate it as required by circumstances, for example doing mental arithmetic. It may be phonological, such as keeping a phone number in mind for as long as it takes to dial or visuospatial, such as following a mental map while cycling to work. Baddeley described a central executive system in working memory, which is central to manipulation of the data held in the ‘phonological loop’ or the ‘visuospatial sketchpad’. In short, working memory is what allows us to mentally add up the cost of the number of pints of lager we had at the pub, subtract the total from the value of the money we give the bar tender, and calculate the change that is due to us. Prefrontal cortex is the most important structure for working memory, due to the extensive role played by the central executive; other structures involved include posterior parietal cortices. Disturbances of working memory can result in anterograde disturbances to other systems of memory as well, because intact working memory is generally required for the encoding of information. Episodic memory may be particularly affected.
Which of the following conditions does not show predominant abnormality in procedural memory?
E. Procedural memory describes the ability to learn and perform tasks without conscious thought. This is disturbed in conditions that involve subcortical basal ganglia structures such as Parkinson’s disease, Huntington’s disease, progressive supranuclear palsy, and olivopontocerebellar degeneration. Procedural memory deficits may also be found in depression and OCD. In conditions such as Alzheimer’s disease, mild cognitive impairment, Lewy body dementia, vascular dementia, the frontal variant of frontotemporal dementia, encephalitis, Korsakoff’s syndrome, traumatic brain injury, hypoxic–ischaemic brain injury (including cardiac bypass surgeries), temporal lobe surgery, seizures, vitamin B12 deficiency, hypoglycaemia, transient global amnesia, and multiple sclerosis, episodic memory is more likely to be impaired. Mood, anxiety, and psychotic disorders may also show episodic memory disturbances. Finally, episodic memory impairment may be a side-effect of treatment with anticholinergic drugs and ECT. Semantic memory may be disturbed in conditions such as Alzheimer’s disease, the temporal variant of frontotemporal dementia, traumatic brain injury, and encephalitis. Working memory is disturbed in most of the conditions listed above. Working memory is also impaired in anxiety, depression, schizophrenia, OCD, ADHD, other psychiatric states, and medications. Finally, impairments in working memory occur as part of normal aging.
A patient who had developed a pyloric stenosis following ingestion of sulphuric acid develops a confusional state, ophthalmoplegia, and ataxia.
Which of the following is not true?
E. The condition described is Wernicke–Korsakoff syndrome. Although the common cause for the syndrome is malnutrition secondary to alcohol use, a number of other conditions including hyperemesis during pregnancy, gastrectomy, pyloric stenosis, etc. are associated. In addition to difficulty learning new information, patients with Korsakoff’s syndrome usually have a retrograde amnesia which could extend back up to several years prior to the onset of the syndrome. Patients usually remain amnesic for 1–3 months after onset and then begin to recover gradually over a 10-month period; 25% recover completely and 25% have no demonstrable recovery. CT scan may reveal bilateral hypodense areas in the medial thalamus in patients with acute Wernicke’s encephalopathy, and mamillary body atrophy may be demonstrated by MRI in some patients with chronic Korsakoff’s syndrome. Confabulation is common during the early phases of Korsakoff’s syndrome but is unusual in the chronic phase of the condition. Administration of thiamine during the acute Wernicke’s phase may prevent emergence of Korsakoff’s syndrome. Once the memory defect is established, however, thiamine has little effect except to prevent further deterioration.
Which of the following is the least valuable clinical indicator of severity of head injury?
A. There are several clinical indicators that predict severity of a head injury. They include duration of retrograde amnesia, the depth of unconsciousness as assessed by the worst score on the Glasgow Coma Scale (GCS), the duration of coma, neurological evidence of cerebral injury, using an MRI or EEG, and the duration of post-traumatic amnesia. Of these, the least useful clinical indicator is the duration of retrograde amnesia. Duration of post-traumatic amnesia is the best marker of outcome. Patients with a post-traumatic amnesia of less than 1 week will have minimal disability, while duration of more than 1 month is suggestive of enduring and significant disability. Other predictors of a bad outcome include previous head injury, older age, APOE e4 status, and alcohol dependence. Head injury can be classified as mild wherein a GCS score of 13 to 15 is likely to be associated with only a short duration of loss of consciousness (less than 20 minutes) and a short post-traumatic amnesia (less than 24 hours). In moderate head injury, GCS score 9 to 12 is likely to be associated with loss of consciousness of more than a few minutes but less than 24 hours and a post-traumatic amnesia of more than 1 day but less than 1 week. In severe head injury, a GCS score 3 to 8 is likely to be associated with a loss of consciousness of more than 1 day or a post-traumatic amnesia of more than 1 week.
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