Neurocognitive disorders often present themselves vaguely and can be easy to misdiagnose. In the early stages of the disease, memory loss may not be the only key feature of dementia. In addition, several types of dementia may not present with memory loss, but instead involve other cognitive domains, including executive functioning, visual/spatial functioning, praxis, language or behavioral domains. If we try to diagnose these types of dementia with a traditional memory screening, we will fail because memory is not the primary problem. Providing an accurate diagnosis requires updated clinical and neurological education to focus on each of the neurocognitive domains.
Clinical presentation of Alzheimer's disease and the syndrome of dementia can be confusing. Although the majority of dementia secondary to Alzheimer's disease usually presents as memory loss and forgetfulness, Alzheimer's disease can also present in an atypical way, with non-amnestic presentations at the onset of the disease. These cases tend to occur at a younger age and often have a different clinical course than the traditional amnestic variant of Alzheimer's disease. Here are three examples of atypical presentations of Alzheimer's disease:
Frontal variant of Alzheimer's disease
Unlike traditional Alzheimer's disease, the frontal variant manifests with the early onset of frontal executive system impairment as well as mood, behavioral and personality changes. This form also tends to occur at an earlier age than the traditional amnestic variant of Alzheimer's disease. Diagnostically, it initially looks similar to frontotemporal dementia and often even gets misdiagnosed as a primary psychiatric condition because of their earlier presentation of mood and behavior.
In addition to traditional neurocognitive memory screening it is essential to screen patients with frontal executive function screening tests, which could be a combination of Frontal Assessment Battery (FAB), Montgomery Depression Rating Scales, and modified Folstein's Micro-Mental State Examination rather than the traditional Mini-Mental Examination test. A reversible dementia workup should also be employed since various secondary neuropsychiatric syndromes could also cause Reversible Dementia similar to Alzheimer's disease or frontotemporal dementia.
Therefore, full metabolic, neuroinfectious, neurobiochemical, nutritional, autoimmune panels need to be ordered as well as a neuroendocrine panel to rule out any thyroid condition and underlying endocrine condition which also can manifest with mood and behavioral changes as well as executive function known as reversible subcortical dementia syndrome. Neuroimaging can then be employed. An FDG PET scan can be useful in differentiating between early frontotemporal dementia and atypical Alzheimer's disease.
For intervention, a treatment with a cholinesterase inhibitor as well as a glutamatergic agent (NMDA receptor antagonist), including Aricept and Namenda, can be used for this form of Alzheimer's disease. The frontal variant may progress rapidly compared to traditional Alzheimer's disease, so life planning and caregiver planning also are crucial to families.