Assessment of memory deficit

Memory is the tie that binds together thoughts, impressions, and experiences. Memory function is dependent on several mental or cognitive abilities using several brain systems. Many disease processes can lead to compromise of these systems.

When evaluating a patient with a concern of memory loss, the following questions should be considered:

• Does the patient truly have memory loss or is there another cognitive problem causing the memory disorder?

• What is the localisation within the brain of the memory problem?

• What is the temporal profile for the memory loss: acute (seconds/minutes/hours), subacute (days/weeks), or chronic (many months to years)?

• What aetiologies could be responsible for the memory disorder?

The first consideration is to determine whether the patient truly has memory loss or another cognitive problem. Depression may present with similar symptoms to dementia, particularly in older people.[1]Dillon DG, Pizzagalli DA. Mechanisms of memory disruption in depression. Trends Neurosci. 2018 Mar;41(3):137-49. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5835184 http://www.ncbi.nlm.nih.gov/pubmed/29331265?tool=bestpractice.com Patients with delirium often have symptoms of memory loss, but have symptoms of inattention and altered consciousness as well.[2]Inouye SK, Westendorp RG, Saczynski JS. Delirium in elderly people. Lancet. 2014 Mar 8;383(9920):911-22. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4120864 http://www.ncbi.nlm.nih.gov/pubmed/23992774?tool=bestpractice.com Patients with vision or hearing problems may appear to have dementia. 

Memory dysfunction can affect episodic, working, semantic, or procedural memory. It may result from lesions in the hippocampus, limbic circuits, prefrontal cortex, angular gyrus, temporal lobes, cerebellum, basal ganglia, or supplementary motor area. In many cases, memory is encoded properly in the hippocampus, but patients have trouble retrieving the stored memory. This retrieval deficit is typically due to problems with frontal lobe function, often caused by white matter disease.

The temporal profile of memory loss is an essential part of the history that can rapidly refine the differential diagnosis. For example, neurodegenerative disease typically causes chronic symptoms, inflammatory disease usually causes subacute symptoms, and neurological conditions such as seizure or migraine cause acute symptoms.

Neurodegenerative, neurological, inflammatory, infectious, traumatic, endocrine, vascular, neoplastic, and metabolic conditions may all cause memory loss.