Functional imaging: A necessary prerequisite to neuropsychological assessment

After traumatic brain injury, neuropsychological testing may be insensitive in documenting functional brain injury. Imaging with single-photon emission computed tomography (SPECT) and F-fluorodeoxyglucose positron emission tomography (FDG-PET) scanning may identify brain injury that is missed on neuropsychological testing. A 27-year-old man had loss of consciousness after hydrogen sulfide exposure and a fall; he had markedly impaired function (short-term memory, sequential thinking, attention, and initiative), but neuropsychological testing showed only mild to moderate impairments. A 37-year-old woman had a whiplash injury and head trauma after an automobile accident; she had apprehension, dysphoria, word finding problems, impaired memory and concentration, and slowed thinking; neuropsychological testing was normal. In the man, SPECT scan showed decreased activity in the striatum, amygdala, and hippocampus bilaterally (decreased more in the right than left hemisphere); an FDG-PET scan showed markedly decreased metabolism in the left thalamus, heterogeneous abnormal uptake in the basal ganglia, and abnormally decreased metabolism in both temporal and inferior parietal lobes. In the woman, FDG-PET scan showed several regions of abnormal metabolic activity not restricted to single vascular territories and decreased activity in the left frontal lobe, left thalamus, and left caudate nucleus. Repeat neuropsychiatric testing in both patients showed cognitive and motor impairments that seriously limited routine activities of daily living. In summary, after traumatic brain injury associated with neuropsychological symptoms, SPECT and FDG-PET scanning may be more sensitive than neuropsychological testing in detecting objective signs of brain injury.