Cognitive and behavioral characteristics of patients with a clinical diagnosis of Alzheimer's disease (AD) and a past history of traumatic brain damage

<p>Background: Epidemiological studies have demonstrated that head injury is a risk factor for Alzheimer's disease (AD). Based on our clinical experience at a memory clinic, the clinical characteristics of elderly patients with progressive dementia who have a history of head trauma are often atypical when compared to those of AD. Objective: To investigate the cognitive and behavioral characteristics of patients with slowly-progressive cognitive impairment and a past history of traumatic brain damage. Subjects: From a series of 787 patients who completed full examination and were registered to the database of our memory clinic, we retrospectively extracted the patients who met all of the following criteria: 1) a history of major head trauma was identified, 2) at the time of the head injury, the patient had a finding (such as disturbed consciousness and skull fracture) or medical record indicating head trauma, 3) people who well know the patient were not aware of any changes in the patient's cognitive, behavioral or personality status after the head trauma, 4) the patient retained his/her function at work and at home after head trauma, 5) slowly-progressive cognitive impairment occurred definitely after the head trauma, and 6) a brain imaging showed an old traumatic lesion. As a result, 6 patients met the criteria. Methods: We retrospectively evaluate the cognitive impairment and behavioral and psychological symptoms of the 6 patients at examination at our memory clinic based on their medical records. Results: Three patients had many of the core diagnostic criteria and supportive diagnostic features in the clinical diagnostic criteria for frontotemporal dementia (FTD), such as disinhibition, affective and emotional changes, and stereotypic behavior. However, the clinical diagnoses of the three patients were AD because their initial symptom was recent memory impairment and they also showed constructive disturbance and defective root findings. The other three patients had typical clinical characteristics of late-onset AD. Discussion: Traumatic brain damage often involves the orbitofrontal, anterior temporal and basal temporal areas. Thus, the decrease in brain reserve due to traumatic brain damage is considered to be more profound in these areas. We assume that FTD-like symptoms in the three patients occurred at the earliest stage of AD because the brain reserve in the lesions responsible for frontal lobe symptoms had already been decreased by head trauma.</p>