Both in clinical practice and in research settings, neuropsychological assessment typically has two aims; the first is to contribute to the differential diagnosis of diseases or syndromes, the second is to provide information about cognitive strengths or weaknesses that can be used for decision-making with respect to treatment or care or educate the patient or his caregivers or significant others about neurocognitive changes that may be present. For making a reliable medical diagnosis, however, neuropsycholog-ical testing rarely contributes uniquely. While a low score on the MMSE is indicative for cognitive decline typically seen in Alzheimer dementia, a low performance may also be due to vascular cognitive impairments, Parkinson's disease, or even to problems in hearing. If cognitive tests or screening instruments are used for establishing medical diagnoses, information about the test's sensitivity and specificity should be available. To prevent the occurrence of missed diagnoses or false-positive test results, a good instrument should have a good sensitivity and an adequate sensitivity. Neuropsy-chological tests generally lack this combination, simply because cognitive impairments can be the results of a wide range of medical conditions and low test scores may also occur in healthy people. Related to this, many older neuropsychological tests had been originally developed as tests for organic-ity (as opposed to functional complaints or psychiatric disease), but more recent studies combining neuropsychological test results and measures of cerebral dysfunction, such as MRI, PET, or EEG, indicate that when these tests are used in isolation they are invalid for this purpose. Also, function localization on the basis of test outcome has been found to lack validity, not only because of inadequate test characteristics but also because original theories on lateralization (e.g., the left hemisphere mediates verbal cognitive functions and the right hemisphere is specialized in spatial function) have been found to be inaccurate or even completely incorrect. Nowadays, advanced neuroimaging techniques, such as SPECT and MRI, outperform behavioral tests with respect to lesion localization. Still, combining imaging data and neuropsychological test results provide valuable insight into the working of the brain and impairments in patients with cerebral dysfunction.
Was this article helpful?