Understanding Neurology

Disorders of cognition 93CASE 3 (continued)His cognitive deficit is restricted to memory.Absent delayed recall confirms anterogradeamnesia. This is acute onset anterograde amnesia.There is also a significant retrograde amnesia,extending back 40 years. MRI showed alteredsignal in the periaqueductal grey matter of themidbrain (85). It transpired that when presentingto the Accident and Emergency Department, hehad been given IV dextrose but no thiamine cover,and this had precipitated acute Wernicke’sencephalopathy with subsequent Korsakoff’ssyndrome. Ataxia and peripheral neuropathy alsooccur in this condition.85REVISION QUESTIONS1 All memories reach conscious awareness.2 Remembering last month’s holiday is short-termmemory.3 Premorbid intelligence does not affect bedsidecognitive performance.4 It is easy to determine the time of onset ofneurodegenerative disease.5 A normal Mini-Mental State Examination scoreexcludes Alzheimer’s disease.6 Digit span is a useful bedside test of short-termmemory.7 Korsakoff’s syndrome results in a significantretrograde amnesia.8 With memory impairment, loss of personalidentity usually indicates a nonorganic cause.9 Herpes encephalitis may selectively impair eitherepisodic or semantic memory.10 Insight may be retained early in Alzheimer’sdisease.85 Magnetic resonance image showing increasedsignal in periaqueductal grey matter of themidbrain, consistent with Korsakoff's syndrome.11 Depression can superficially resemble earlydementia.12 Hippocampal pathology primarily results in ananterograde rather than retrograde amnesia.13 Short-term memory relies on the frontal lobes.14 Retrograde memory can be tested by askingabout autobiographical memories, and also byasking about famous public events.15 Semantic memory can become impaired only ifthere is also episodic memory impairment.Answers1 False.2 False.3 False.4 False.5 False.6 True.7 True.8 True.9 True.10 True.11 True.12 True.13 True.14 True.15 False.