Frontotemporal Lobe Dementia

Article Author:
Israr Khan
Article Editor:
Orlando De Jesus
Updated:
6/30/2020 12:20:58 PM
PubMed Link:
Frontotemporal Lobe Dementia

Introduction

Frontotemporal dementia (FTD) is a spectrum of clinical syndromes characterized by neuronal degeneration involving the frontal and anterior temporal lobes of the brain.[1][2] In patients age ≥ 65, it is the third most common cause of dementia and is the second most common cause of early-onset dementia (age <65) and usually involves patients with age ranges from 45 to 65. Arnold Pick was the first to report frontotemporal associated clinical syndromes in 1892. Onari and Hugo Spatz coined the term “Picks disease” in 1926 for frontotemporal lobe atrophy with the presence of cytoplasmic inclusion bodies known as Pick bodies. It was later replaced by the term FTD based on distinct clinical and histopathological criteria, assigned by a research group from the United Kingdom and Sweden in 1994.[3]

FTD targets brain areas that are responsible for personality, behavior, language learning, motivation, abstract thinking, and executive function. Behavior changes and or language difficulty are the presenting clinical features followed by loss of executive function and cognitive abilities.[4] It is classified into two distinct clinical types; behavior variant (bvFTD) and language type. The language type of FTD is further classified into non-fluent variant primary progressive aphasia (nfvPPA), and semantic variant primary progressive aphasia (svPPA) depending on the areas of neuronal loss in frontal and temporal lobes.[5][6]

Etiology

Frontotemporal dementia is mainly a sporadic disease. Genetics also plays a key role where approximately 40% of cases are familial in origin.[7] Among them, 13.4% of cases have an autosomal dominant inheritance. Mutations in over 20 genes have been identified in the possible development of FTD. Commonly involved genes are microtubules associated protein tau located on chromosome 17q21.32, granulin on chromosome 17q21.32, and hexanucleotide repeat expansion of the chromosome 9 open-reading-frame 72 (C9orf72) on chromosomal location 9p21.2 (responsible for cytoskeleton organization).[8][9][10] It is also postulated that C9orf72 gene mutation is a continuum between FTD and amyotrophic lateral sclerosis and is responsible for the occurrence of both entities. Head trauma and thyroid disease have been linked with the development of FTD with a 3.3-fold higher risk and 2.5-fold higher risk, respectively.

Epidemiology

The incidence is 2.2/100,000 between age 40-49, 3.3/100,000 between 50-59, and peaks to 8.9/100,000 between age 60-69.[6][8] Although the age at onset varies, the mean age at presentation is 58. Overall prevalence is 15-22 persons /100,000 population. Behavior variant (bvFTD) and semantic variant (svPPA) are more prevalent in men, while nfvPPA predominantly occurs in women. The average survival time is 7.5 years.

Pathophysiology

Frontotemporal dementia has three distinct clinical syndromes based on the underlying pathologic mechanism characterized by intracellular deposition of abnormal proteins aggregates in the frontal and temporal lobes resulting in the degeneration of neurons, microvacuoles formation, and astrocytosis; hence the term frontotemporal lobar degeneration. Abnormal aggregates of transactive DNA-binding protein TDP-43 account for 50% of cases, Microtubules-associated tau protein for 45%, and in 5 to 10% cases, tumor-associated protein fused in sarcoma has been found.[5] The abnormal tau protein aggregates have been identified as the main culprit in patients with both sporadic and familial types of FTD except in the svPPA, in which TDP-43 aggregates predominate.[6][7]

History and Physical

The diagnosis of frontotemporal dementia is challenging. The initial clinical presentation may be mistaken for psychiatric disorders or a stroke.[11] Therefore, a thorough history and physical examination, especially from the caregivers, are pertinent. FTD has a wide range of presentations in relation to the areas involved. In all forms of FTD, functional ability and activities of daily living are compromised.[2][4][12]

Behavior variant type FTD (bvFTD): It is the most common phenotype. Patients suffering from bvFTD may present with a cluster of altered behavior and personality changes earlier in the disease process, which include disinhibition, loss of emotional reactivity and disease insight, apathy, impaired abstract thinking and executive function that gradually worsens over time. Additionally, it may demonstrate a change in dietary behavior and loss of fundamental emotions and empathy but with intact memory until late in the disease.[5][10]

Semantic variant FTD: In this form of FTD, patients manifest language difficulties characterized by paraphasia (impaired word-finding ability or loss of vocabulary), difficulty in understanding the meaning of words, impaired comprehension, and difficulty in recognizing unfamiliar objects or faces.[5] Their speech is fluent but not making any sense. Memory is affected late in the disease.

Non-fluent variant Primary Progressive Aphasia (nfvPPA): Patients with this type of FTD presents clinically with effortful halted speech and paraphasia (jumbled words), difficulty in understanding complex sentences and naming objects.[5] Their memory, abstract thinking, and calculating abilities are spared earlier in the disease course.

 Various bedside tests can be performed if clinical suspicion for FTD is high.

  • Go-no-go test: In this test, the patient is asked to perform an action in response to a particular stimulus and inhibit that action in response to different stimuli.
  • Letter fluency test: In this test, the patient is asked to say as many words (except proper nouns), starting with a single letter in one minute.
  • Attention test: It is used to evaluate the attention span. It is done either by serial seven subtractions from 100 or spells the word “world” backward.
  • Similarities and differences: It is done to evaluate abstract thinking. The patient is instructed to compare items (table and chair, apple, and orange).

Evaluation

Patients with frontotemporal dementia should be evaluated as follows:

Laboratory: Neural and axonal cytoskeletons are mainly composed of neurofilaments, which are further made up of small subunits called neurofilament light chain. Neurofilament light chain, among other biomarkers, can be increasingly seen in blood and cerebrospinal fluid of FTD patients.

Radiographic tests: Magnetic resonance imaging, computed tomography scan, or single-photon emission tomography can be used to demonstrate atrophy and hypoperfusion in the frontal and temporal lobes. However, the findings are not specific. Imaging may aid in the diagnosis or to rule out other etiologies.[4][9]

Electroencephalography (EEG): It is not very helpful for FTD as it is for Alzheimer’s disease; however, in comparison to the healthy group, a typical EEG pattern was observed in several FTD patients and was marked by the reduction of fast activities (alpha, beta1- beta3), but no difference in slow activities (delta & theta waves).[5]

Neurocognitive exams: Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment, and Functional Cognitive Assessment. For primary care, the Cochrane dementia and cognitive improvement group support the utilization of two tests; MMSE (the most commonly used test in primary care) and the Informant Questionnaire for Cognitive Disorders in the Elderly. MMSE assesses different domains of dementia, including but not limited to memory, cognition, language, attention/orientation, and executive functions.[13][14]

Treatment / Management

A multidimensional approach is required to manage patients suffering from FTD. Genetic counseling, in terms of genetic testing and recommendations, should be provided to patients and their families.

Non-Pharmacologic Treatment

It includes a multidisciplinary approach, such as social support services, physical therapy & occupational therapy, speech therapy, cognitive behavior therapy, rehabilitation services, and caregivers' education. Regular monitoring of the behavior of both the patient and caregiver for assessing activities of daily living, such as financial account managing, driving, environmental modification, and eating, is mandatory.[5]

Pharmacological Treatment

Acetylcholinesterase inhibitors and N-methyl-D-Aspartate inhibitors have no proven benefit. Similarly, selective serotonin reuptake inhibitors (SSRI) have a limited role. It can improve certain behaviors, but not cognition. Antipsychotics have mixed results but comes with a price of severe extrapyramidal side effects to which the FTD patients are susceptible; therefore, they are not approved by the US food and drug administration as a treatment for FTD. Selective dopaminergic antagonists can improve motivation and apathy. Several disease-modifying drugs like Salsalate (tau acetylation inhibitor) and Gosuraneb (anti-tau monoclonal antibodies) targeting different biomarkers are being studied, but no recommendations yet have been made. Several other promising disease-modifying drugs are currently under clinical trials.[15][16]

Differential Diagnosis

Frontotemporal dementia syndrome overlap can occur and may be confused with other psychiatric disorders. Therefore, a comprehensive history and a thorough physical examination are required to distinguish each clinical entity. The neurological exam plays an essential role in assessing the condition. Ruling out of other causes of the decline in cognitive functioning such as endocrine and metabolic disorders should also be considered.[4][5][6]

  • Alzheimer disease
  • Vascular dementia
  • Lewy body dementia
  • Parkinsonism
  • Supranuclear palsy
  • Alcoholism
  • Bipolar disorders
  • Schizophrenia
  • Borderline personality disorder
  • Obsessive-compulsive disorder

Prognosis

The presentation at a younger age may cause a delay in the diagnosis of FTD, resulting in significant detrimental emotional, financial, and social impact on patients, family, and their caregivers. The mortality risk associated with FTD is six-fold as compared to Alzheimer's disease, which has a fourfold.[6][10] The average survival time is 7.5 years.

Complications

According to survey-based studies, sleep, or nighttime behavior disturbance is demonstrated by 33-76% of FTD patients. More likely reported in patients with PPA than bvFTD. Similar is the case in the caregivers of PPA patients. All sleep disorders require sleep hygiene and routine maintenance. Also, there is a risk of an overlapping syndrome with FTD, such as FTD- motor neuron disease, FTD-progressive supranuclear palsy, FTD-amyotrophic lateral sclerosis. All require both pharmacologic and non-pharmacologic approaches as well as treatment of underlying disease.

  • Insomnia: reported in 48% of cases
  • Sleep-disordered breathing: reported in 68% of cases[17]
  • Excessive day time sleepiness: reported in 64% of cases
  • Restless leg syndrome: reported in 8% cases
  • Risk of falls[18]
  • Hypersexuality
  • Eating disorders, (such as hyperphagia/binge eating, lack of appetite, a particular food preference)[19]

Deterrence and Patient Education

Frontotemporal dementia is a clinical syndrome that encompasses three different entities. All FTD subtypes can significantly impair a patient’s social, occupational, and functional status. They required proper education about the disease process, family support, assistance with activities of daily living, and access to integrated rehabilitation services. Education and regular support should be provided to caregivers because of care burden and demanding management.

As heredity plays a key role with approximately 40% of cases with the familial origin, and 13.4% with an autosomal dominant inheritance, individuals who have a family member presenting the disease should be carefully monitored for early signs and symptoms.

Enhancing Healthcare Team Outcomes

FTD is a progressive neurodegenerative disorder that involves three different spectra of clinical syndromes characterized by loss of intellectual functions. To improve patient outcomes and quality of life, an interprofessional approach has to be adopted. It includes collaboration and coordination of healthcare professionals, including neurologists, psychiatrists, audiologists, nurses, social workers, physical therapy, occupational therapy, and speech therapists. Family, friends, and caregiver must meet with the primary care provider and/or local community mental health team regularly. The role of caregiver is crucial in the management of FTD; therefore, a therapeutic partnership between the healthcare team and caregivers is warranted.

For the end of life care, living arrangements, and decision making about financial and medical services, a proper future planning regarding assessing decision capacity, surrogate’s decision-makers, living will, power of attorney, and medical arrangements are to be implemented.[2][12]

Here is a checklist of problem-oriented management that can optimize the quality of life if implicated.

  • Employment: Assessing occupational health, rehabilitation, and medical retirement plan.
  • Safeguarding: Identify any potential social, psychological, and physical risks to patients or their caregivers.
  • Financial support: Assessing for eligibility to work, providing disability support, financial experts for banking account management.
  • Driving: Assessing for visual, auditory, motor, and impulse control while driving.
  • Home environment: Keep the home environment and surroundings safe to prevent and or reduced fall risk.
  • Insomnia: Avoid evening caffeine, excess fluid intake, and alcohol in addition to maintaining sleep hygiene and routine.
  • Depression/Anxiety: Psychosocial support
  • Hypersexuality and hyperphagia: Avoid triggers, limiting access to food, distracting, and consider SSRIs.

References

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