The many faces of Alzheimer’s
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.
Language variant (Logopenic variant) of Alzheimer's disease
With this atypical form, language becomes the first presentation of cognitive impairment. Instead of traditional forgetfulness or memory, the primary difficulties are choosing the right word, completing a sentence, retrieval or expressive language difficulties.
This form of Alzheimer's disease, a logopenic primary progressive aphasia, is very similar to the language variant of frontotemporal dementia (primary progressive aphasia). A comprehensive language evaluation can be helpful for further diagnostic clarification between these two syndromes. Approaches can include the Mississippi Aphasia Screening Test, Boston Naming Test, a speech therapy consultation with a more comprehensive language evaluation, neuropsychological testing and comprehensive neurocognitive, neurological and neuropsychiatric evaluations.
After a complete clinical assessment, a reversible dementia workup with laboratory examinations should be employed to rule out treatable etiologies including mood disorder and other causes of language disorders. Again, the FDG PET scan can be useful for differentiating between the language variant of frontotemporal dementia (primary PPA) and logopenic variant of Alzheimer's disease. The clinical course is also very different, as well as treatment modalities including treatment with cholinesterase inhibitor Aricept and glutamatergic agent Namenda for the logopenic Alzheimer's disease as it still belongs to the same family of Alzheimer's disease.
Posterior cortical atrophy (PCA) variant of Alzheimer's disease
Posterior cortical atrophy (PCA) is a syndrome where the brain atrophy is more prevalent in the posterior aspect of the parieto-occipital cortex. The syndrome of this type begins with neurocognitive and neurobehavioral symptoms affected by parieto-occipital cortex, including an early presentation of visual processing and visual symptoms, as well as visuospatial impairment.
Patients with this type may have spent years in consultation with eye doctors or ophthalmologists because they felt their problem was the eyes rather than the memory. They also have early problems with the visuospatial functioning including driving, navigation and geographic disorientation. Falling can be an early presentation due to spatial inattention and difficulty with navigation, difficulty with visual processing when driving or when navigation, which causes significant safety concerns.
This group of patients also suffers from significant neuropsychiatric symptoms including anxiety, mood changes and preceptory distortion. This type of Alzheimer’s also often includes two classic syndromes—Balint syndrome and Gerstmann syndrome.
Posterior cortical atrophy can be very different than the traditional amnestic variant of Alzheimer's disease. After a comprehensive neurocognitive and neuropsychiatric evaluation, a brain MRI can be useful because it will show the predominant posterior cortical atrophy in the parieto-occipital region. FDG PET scan also can be useful for the differential diagnosis of this syndrome from other types of atypical dementias and could show a reduced glucose perfusion or metabolic activities in the posterior parieto-occipital cortex in general.
Dementia is only a syndrome; it is not a disease. Alzheimer's disease is one cause of dementia, but it also can present in many atypical ways. Misdiagnosis is the barrier for early intervention, quality of life and the advancement of understanding the facts of the disease. We must support the proper referral for neurocognitive evaluations and gain a comprehensive diagnosis of the specific form of the disease at hand in order to provide early intervention, treatment, caregiver support and education.
Nicole Absar, MD, is Medical Director of The Senator William and Ellen Proxmire Memory Clinic at Integrace Copper Ridge, Sykesville, Maryland. She is trained in behavioral neurology and neuropsychiatry. She can be reached at firstname.lastname@example.org.
Topics: Alzheimer's/Dementia , Clinical