Several conditions can closely resemble Alzheimer’s disease (AD) in their cognitive and functional decline, leading to potential misdiagnosis and inappropriate treatment. Recognizing these Alzheimer mimickers is critical for clinicians to ensure accurate diagnosis and avoid ineffective treatments.
Among the most notable mimickers of AD are normal pressure hydrocephalus (NPH), Lewy body dementia (LBD), frontotemporal dementia (FTD) and vascular dementia (VaD). While they share overlapping features with AD, each has distinct clinical presentations, diagnostic workup and treatment strategies.
Normal Pressure Hydrocephalus
Normal pressure hydrocephalus (NPH) is classically described by the triad of gait disturbance, urinary incontinence and cognitive dysfunction.1 Gait disturbance is typically the earliest and most prominent feature, presenting as a broad-based, shuffling, apraxic pattern. Cognitive changes tend to be milder at first and may include slowed processing and reduced attention, which is how it can mimic early AD. However, the early emergence of urinary incontinence often helps to differentiate NPH from AD.
Clinical workup hinges on neuroimaging findings, preferably the use of MRI, to look for ventriculomegaly in greater proportion than cortical atrophy.1-2 Importantly, CSF opening pressures often remain within normal limits. A large-volume lumbar puncture or extended lumbar drainage trial can lead to temporary improvement in gait, further supporting the diagnosis.
Treatment differs significantly from AD management. While AD utilizes newer immunotherapies, cholinesterase inhibitors and supportive therapies, NPH can often be improved surgically via ventriculoperitoneal shunting, which may result in significant symptom relief. Early recognition and intervention can significantly improve functional outcomes and quality of life in these patients.
Lewy Body Dementia
Lewy body dementia (LBD) is the most frequently overlapping misdiagnoses with Alzheimer’s, given its similarities in cognitive decline.5 However, it is uniquely characterized by fluctuations in cognition, visual hallucinations, REM sleep behavior disorder and parkinsonism, such as rigidity or bradykinesia. These cognitive fluctuations can occur rapidly, presenting as abrupt shifts in attention and alertness over hours or even minutes. While memory impairment is seen, it is often less pronounced early on compared to the deficits in executive function and visuospatial skills. Of note, approximately 13%-30% of AD patients have mild non-specific parkinsonism on examination.
Clinical workup involves a thorough neurological examination and cognitive assessment, as the diagnosis is clinical. Imaging with MRI may help exclude other structural causes, while a DaTscan (dopamine transporter imaging) can detect reduced striatal dopaminergic function, supporting an LBD diagnosis. More recently, the use of a highly sensitive skin biopsy to identify alpha-synuclein deposits in subcutaneous tissue has become clinically available. This new tool will hopefully allow for earlier identification of LBD patients and improve recruitment for clinical trials.
Antipsychotic agents, particularly first-generation agents, can precipitate severe motor worsening and confusion. Instead, cholinesterase inhibitors (rivastigmine) may improve cognitive and neuropsychiatric symptoms, while cautious use of atypical antipsychotics may be considered for persistent hallucinations. Accurate differentiation from AD is critical due to LBD’s unique therapeutic vulnerabilities and management nuances.
Frontotemporal Dementia
Frontotemporal dementia (FTD) comprises a collection of disorders predominantly affecting the frontal and temporal lobes. Unlike AD’s hallmark memory impairment, behavioral variant FTD (bvFTD) features personality changes, disinhibition, compulsive behaviors and apathy. Alternatively, language variants include primary progressive aphasia with non-fluent speech or semantic dementia with impaired word comprehension, often with relatively preserved episodic memory in early stages.10 These atypical presentations can be misinterpreted as psychiatric conditions or as AD with unusual features.
Clinical workup includes a detailed cognitive and behavioral assessment, as well as neuroimaging, often revealing focal atrophy in frontal or anterior temporal regions. Genetic testing may be indicated if a family history suggests an autosomal dominant inheritance pattern.
Treatment options are notably different from those for AD, in that the newer anti-amyloid therapies will have no role in this tauopathy. Cholinesterase inhibitors and memantine, mainstays in AD, have limited efficacy in FTD but are still often used early in the disease. A combination of atypical antipsychotics, SSRIs or other behavioral interventions may help manage problematic behaviors, while speech therapy can support language function in primary progressive aphasia. Early differentiation from AD is crucial to ensure appropriate therapies and to provide accurate prognostic information.
Vascular Dementia
Vascular dementia (VaD) arises from cerebrovascular pathologies, such as multiple infarcts or chronic ischemia. VaD often presents with stepwise decline in cognition, where patients experience abrupt deteriorations following vascular events. Executive dysfunction is common, and focal neurological signs, such as hemiparesis or sensory deficits, may be present depending on the location of infarcts. Although memory can be affected, it is often less uniformly impaired than in AD.
Clinical workup involves neuroimaging, CT or MRI, to identify areas of infarction or ischemic white matter changes. A thorough cardiovascular assessment is essential, given the high prevalence of hypertension, atrial fibrillation and other vascular risk factors in this population.
Treatment primarily focuses on vascular risk reduction through strict blood pressure management, antiplatelet therapy and lifestyle modifications to prevent further infarcts. While some studies suggest benefits from cholinesterase inhibitors, the mainstay of therapy differs from AD by focusing on preventing additional cerebrovascular insults. Early recognition of VaD allows clinicians to implement targeted interventions that may slow progression and reduce future stroke risk.
Accurately distinguishing Alzheimer’s disease from its mimickers is essential for prognosis and treatment. Identifying a precise diagnosis is particularly important in the context of anti-amyloid therapies such that early identification of immunotherapy candidates is likely to impact patient outcomes.
As research advances, the ability to distinguish these disorders will continue to improve, allowing for earlier interventions and better patient outcomes. Recognizing these mimickers is fundamental to optimizing dementia care, reinforcing the need for continued clinical vigilance and education in distinguishing Alzheimer’s disease from related conditions
Mr. Busse is a third-year medical student applying for residency in adolescent psychiatry. His interest in neurology stems from his dual degrees in Biology and Psychology with a focus on neuroscience, as well as his mother’s diagnosis of both multiple sclerosis and Parkinson’s disease.
Dr. Salamatova is a board-certified neurologist with expertise in Parkinson’s and Movement Disorders. She obtained her undergraduate degree in Physiology from Novosibirsk State University in Russia before pursuing her Doctor of Osteopathic Medicine at Lake Erie College of Osteopathic Medicine. Dr. Salamatova underwent residency training at the University of Florida Jacksonville, where her passion for movement disorders blossomed. She further honed her skills through a fellowship at Emory University.
References
1. Zhang L, Hussain Z, Ren Z. Recent advances in rational diagnosis and treatment of normal pressure hydrocephalus: A critical appraisal on novel diagnostic, therapy monitoring and treatment modalities. Curr Drug Targets. 2019;20(10):1041-1057. doi:10.2174/1389450120666190214121342
2. Wang Z, Zhang Y, Hu F, Ding J, Wang X. Pathogenesis and pathophysiology of idiopathic normal pressure hydrocephalus. CNS Neurosci Ther. 2020;26(12):1230-1240. doi:10.1111/cns.13526
3. Tullberg M, Wikkelsø C. Normal pressure hydrocephalus: pathophysiology and diagnosis. J Neurol. 2018;265(8):1850-1855. doi:10.1007/s00415-018-8948-8
4. Relkin N, Marmarou A, Klinge P, Bergsneider M, Black PM. Diagnosing idiopathic normal-pressure hydrocephalus. Neurosurgery. 2005;57(3 Suppl):S2-8. doi:10.1227/01.NEU.0000168185.29659.C5
5. Shim YS, Roe CM, Buckles VD, Morris JC. Clinicopathologic study of Alzheimer’s disease: Alzheimer mimics. J Alzheimers Dis. 2013;35(4):799-811. doi:10.3233/JAD-121594
6. McKeith IG, Boeve BF, Dickson DW, et al. Diagnosis and management of dementia with Lewy bodies: fourth consensus report of the DLB Consortium. Neurology. 2017;89(1):88-100. doi:10.1212/WNL.0000000000004058
7. Tangen, G. G., Bergland, A., Engedal, K., & Mengshoel, A. M. (2017). The importance of parkinsonian signs for gait and balance in patients with Alzheimer’s disease of mild degree. Gait & posture, 51, 159–161. https://doi.org/10.1016/j.gaitpost.2016.10.009
8. Galvin JE, Duda JE, Kaufer DI, Lippa CF, Taylor A, Zarit SH. Lewy body dementia: caregiving and management. Alzheimer Dis Assoc Disord. 2020;34(3):221-225. doi:10.1097/WAD.0000000000000391
9. Rascovsky K, Hodges JR, Knopman D, et al. Sensitivity of revised diagnostic criteria for the behavioral variant of frontotemporal dementia. Brain. 2011;134(Pt 9):2456-2477. doi:10.1093/brain/awr179
10. Kurz A, Kurz C, Ellis K, Lautenschlager NT. What is frontotemporal dementia? Maturitas. 2014;79(2):216-219. doi:10.1016/j.maturitas.2014.07.001
11. Gazzina S, Manes MA, Padovani A, Borroni B. Clinical and biological phenotypes of frontotemporal dementia: Perspectives for disease-modifying therapies. Eur J
12. Mackenzie IR, Neumann M. Frontotemporal dementia: molecular and clinical aspects. Nat Rev Neurol. 2016;12(4):318-330. doi:10.1038/nrneurol.2016.35
13. O’Brien JT, Thomas A. Vascular dementia. Lancet. 2015;386(10004):1698-1706. doi:10.1016/S0140-6736(15)00463-8
14. Bir SC, Khan MW, Javalkar V, Toledo EG, Kelley RE. Emerging concepts in vascular dementia: A review. J Stroke Cerebrovasc Dis. 2021;30(8):105864. doi:10.1016/j.jstrokecerebrovasdis.2021.105864
15. Skrobot OA, O’Brien J, Black S, et al. The vascular impairment of cognition classification consensus study. Lancet Neurol. 2016;15(6):606-616. doi:10.1016/S1474-4422(16)00052-5
