Confronting the Clinical Challenges of Frontotemporal Dementia

Ask a member of the general public what images they pull together when they think of the term “dementia” and they likely will focus on age. A nursing home, a grandparent, the end of life—these are all understandably conceptualized. What is more difficult to imagine is dementia overtaking their middle-aged father, wife, or sister and cutting down their loved one to a fraction of their former self. Because of this, it seems unlikely families would consider a neurologic disorder when they begin seeking help for the patient with new onset of symptoms. This can make early diagnosis of frontotemporal dementia (FTD) especially difficult.

The two chief clinical presentations of FTD are:

1.) Behavioral, characterized by impulsive behaviors and disinhibition, change in personality such as apathy and indifference, and poor judgment and

2.) Language, characterized by either a nonfluent aphasia with anomia (primary progressive aphasia) or fluent aphasia with early loss of word meaning (semantic dementia)¹

New developments in comprehending the pathophysiology of FTD have suggested that the majority of cases have underlying ubiquitin-positive inclusions, whereas some have tau-positive inclusions. ¹ Genetic mutations, especially on chromosome 17 in the tau or progranulin genes, have been identified. But any sort of gene therapy remains far in the future. The current approach to management includes a trial of symptomatic medications and a multifaceted approach, including environmental modification, and long-term care planning.¹

Prognosis
The outlook for patients diagnosed with FTD is bleak. And patients with definite frontotemporal dementia with language deficits have an even poorer prognosis, according to Garcin, et al.² Their study found that the median survival rate of the 91 initial cases they examined was nine years from symptom onset and 5.4 years from diagnosis.² After excluding 24 “phenocopy” cases, the analysis was repeated in a subgroup of 67 patients. “The mean age at symptom onset of the pathologic group was 58.5 years and 16 percent had a positive family history. Their median survival was 7.6 years (95 percent confidence interval [CI] 6.6-8.6) from symptom onset and 4.2 years (95 percent CI 3.4-5.0) from diagnosis.”2 In contrast, those with the phenocopy had an “extremely good” outcome: of their 24 patients, only one had died (of coincident pathology) despite, in some cases, several years of follow-up.

Managing FTD primarily involves the use of psychoactive medications.3 Selective serontonin receptor inhibitors, such as sertraline, paroxetine, or fluoxetine, can reduce several issues, including disinhibition- impulsivity, repetitive behaviors, and eating disorders. ³ And there has not been a shortage of drugs physicians have been willing to try. They include trazodone, galantamine, idazoxan, lithium plus fluoxetine, lithium plus paroxetine, 1-deprenyl, moclobemide, methylphenidate, piracetam, rivastigmine, donepezil, olanzapine, risperidone, amantadine, guanfacine, allopurinol, and bromocriptine.⁴

Low doses of trazodone or an atypical antipsychotic such as aripriprazole can also help manage significantly disturbed or agitated behavior. Acetylcholinesterase inhibitors have not had significant efficacy for patients with FTD, but memantine has had interesting results in recent studies.

In the most recent publication examining memantine and FTD, Boxer, et al. looked at 43 patients who met clinical criteria for FTLD (21 with FTD, 13 with semantic dementia (SD), and nine with progressive nonfluent aphasia (PA)) who received 26 weeks of open-label treatment with memantine at a target dose of 20mg daily.⁵ The study found that “most subjects were able to tolerate the target dose of memantine. A transient improvement was observed on the total (Neuropsychiatric Inventory) score primarily in the FTD group. Variable declines were observed on the (Alzheimer's Disease Assessment Scale- Cognitive), (Frontal Behavior Inventory), (Executive Interview, Frontal Behavior Inventory), NPI, (Texas Functional Living Scale), and UPDRS scores.”

They found that the FTD and SD groups' scores decreased on the majority of cognitive and behavioral outcome measures, but remained steady on the UPDRS, whereas the progressive nonfluent aphasia group remained fairly stable on the ADAS-cog, NPI, and TFLS, but declined on the UPDRS. Memantine was well-tolerated in these subjects. Concurrent treatment with acetylcholinesterase inhibitors was prohibited.

Imaging
“MRI, PET, and SPECT all are useful at differentiating FTD and AD,” says Lawrence S. Honig, MD, PhD, a Professor of Clinical Neurology at Taub Institute for Research on Alzheimer's Disease and the Aging Brain, G. H. Sergievsky Center, and Department of Neurology at Columbia University. “MRI shows a pattern of frontal—and anteiror temporal— atrophy, although this may be difficult to ascertain, particularly early in the course. PET and SPECT show decreased brain function, metabolism and perfusion respectively, in frontal and anterior temporal regions,” he says. This contrasts markedly with the more posterior pattern of parietal, as well as temporal involvement in AD.

Methods measuring cortical thickness using MRI have recently seen some success in differentiating between clinically-defined AD and frontotemporal dementia in addition to showing disease-related patterns of atrophy.⁶ Lehmann et al. found “patients with AD pathology, irrespective of clinical diagnosis, showed reduced cortical thickness bilaterally in the medial temporal lobe, posterior cingulate gyrus, precuneus, posterior parietal lobe, and frontal pole compared with controls.”

For their study, researchers used FreeSurfer, an automated freeware tool, to measure cortical thickness in 28 pathologically-confirmed AD patients, 11 of whom had a typical amnestic presentation and 17 an atypical presentation during life, 23 pathologically- confirmed FTLD subjects, and 25 healthy controls.

For their study, researchers used FreeSurfer, an automated freeware tool, to measure cortical thickness in 28 pathologically-confirmed AD patients, 11 of whom had a typical amnestic presentation and 17 an atypical presentation during life, 23 pathologically- confirmed FTLD subjects, and 25 healthy controls.

The study authors also discovered that lower cortical thickness in the posterior cingulate gyrus, parietal lobe, and frontal pole is indicative of AD pathology in patients who have behavioral or language issues. “In contrast, lower cortical thickness in the anterior temporal lobe and frontal lobe is indicative of the presence of FTLD pathology in patients with a clinical presentation of FTD,” they write. A reduction in cortical thickness in the posterior cingulate gyrus is a trait of AD pathology in patients who have typical and atypical clinical presentations of AD. Researchers feel this may assist a clinical distinction of AD pathology from FTLD pathology.

Differential Diagnosis
Making the right diagnosis between AD and a FTD, such as semantic dementia requires characterizing the different patterns of global and temporal lobe atrophy through MRI. The manual delineation of such regions is time-consuming.⁷ As previously mentioned, FreeSurfer is an automated technique that has the ability to label cortical and subcortical brains automatically and is available for free. In another study, Lehmann et al. compared the automated technique with the existing methods and found that despite differences in protocol and volumes, both FreeSurfer and manual segmentations “showed similar atrophy patterns in the patient groups compared with controls, and similar right-left differences, suggesting that both methods accurately distinguish between the three groups.”

For the study, researchers delineated eight temporal lobe structures in each hemisphere using FreeSurfer, and these were compared with manual segmentations in 10 control, 10 AD, and 10 SD subjects. The reproducibility errors for the manual segmentations ranged from three percent to six percent. The authors write, “differences in protocols between the two methods led to differences in absolute volumes with the greatest differences between methods found bilaterally in the hippocampus, entorhinal cortex and fusiform gyrus (p<0.005).”

However, they go on to say that good correlations between the methods were found for the majority of regions, “with the highest correlations shown for the ventricles, whole brain and left medial-inferior temporal gyrus (r>0.9), followed by the bilateral amygdala and hippocampus, left superior temporal gyrus, right medial-inferior temporal gyrus and left temporal lobe (rgt;0.8). Overlap ratios differed between methods bilaterally in the amygdala, superior temporal gyrus, temporal lobe, left fusiform gyrus and right parahippocampal gyrus (p<0.01).”

Other Frontal Dementias
There are other forms of frontal dementia whose hallmarks are not merely language or behavioral presentations. They can muddy an already difficult situation with manifestations of other disorders and create a mix-and-match game between symptoms and diagnosis, leaving patients and caregivers frustrated with the lack clarity.

ALS dementia. ALS dementia is now recognized as a frontal dementia in which there is motorneuron disease.⁸ Patients typically are first symptomatic with dementia. They may not present to a neurologist until ALS symptoms have worsened, but families usually report that personality changes preceded weakness, fasciculations, and motor findings.⁸

This was a disorder poorly understood, often with less prominent upper motor neuron involvement, according to Dr. Honig. “This disorder was originally viewed as a variant of ALS, but with the understanding that motor neuron involvement is not so infrequent in FTDs and the pathology of ALS—dementia being ‘FTD-U' w/TDP43 inclusions,” he says. “This is clearly an FTD–with involvement of motor neurons.”

"Dementia of ALS" is another area of increased interest. “Many persons with ALS do have subtle cognitive deficits, and some amount to dementia,” Dr. Honig says. However, it is often difficult to be certain of cognitive function as ALS advances because patients become mute and quadriplegic. “Nonetheless, it is now recognized that while originally described as a disease completely sparing cognition, in many cases of ALS there are these cognitive changes, and that these can be correlated with some PET, SPECT, and pathological changes,” he says. Finally, the finding that both ALS and FTD-U, each classically clinically defined, involve inclusions of TDP-43 increases the rationale for claiming "ALS with cognitive change" as an FTD.

Progressive supranuclear palsy (PSP). PSP is defined, pathologically, by the buildup of neurofibrillary tangles. Different rates and patterns of the accrual of phosphorylated tau protein could explain the variation in clinical phenomena seen in patients with PSP.⁹

This is a Parkinsonian disorder that can be considered a frontotemporal dementia, although frontal functions are affected much more than temporal.⁸ Patients typically present with prominent axial rigidity and eye movement abnormalities, but very frequently also have cognitive disturbance, particularly in language and subcortical executive functions.⁸

Cortico-basal degeneration. “CBD seems best categorized as an ‘FTD' because there is marked clinical involvement of frontal/subcortical systems clinically/neuropsychologically,” Dr. Honig says. It is another disorder that isn't strictly frontotemporal dementia, but is more broadly classified as one of the frontal dementias.⁸ Pathologically the involvement includes both precentral and postcentral involvement. But some of the other FTD's also involve anterior parietal cortex. It is distinguished by abnormality of praxis, unlike frontotemporal dementia per se, in which praxis is not affected.⁸ “It is difficult to say exactly where the deficit localizes in this disease, but the motor deficits likely relate mostly to precentral cortical and brainstem nigral (parkinsonian) involvement,” Dr. Honig says. People cannot carry out their organized, sequential, and programmed movements of ordinary life. Difficulty putting on clothes, writing, driving, or doing many simple tasks are characteristics of CBD.⁸

Huntington's Disease. While HD also has substantial frontal/subcortical involvement, it is generally not categorized as an FTD at this time, Dr. Honig says. “This is likely because

a.) pathology is really more subcortical than frontal, and

b.) there is neither Tau nor TDP pathology, and

c.) is has its own genetics and pathology.”

Grouping this large variety of conditions of frontotemporal cerebral degeneration into the umbrella term of frontotemporal dementia has been an evolutionary process, according to Dr. Honig. Starting with the description of Pick's disease, and later

"frontal dementia," it has continued the past 15 years with the Michigan consensus conference on FTDP17 putting together a number of genetic entities, all mapping to chromosome 17. The NIH consensus conference on FTD clinical/pathological criteria also played a role.

“Key aspects en suite were the discovery that TAU mutations caused FTD, and that abnormal tau accumulations (without amyloid accumulations) were present in Pick's disease proper, in many FTDP17, and in both PSP and CBD,” Dr. Honig says. Next was the discovery that TDP43 inclusions were present in about half of clinical FTD cases, and that in some of the cases PGN mutations were responsible. Furthermore, ALS cases with and without dementia have similar inclusions.

Thus, even though only a fraction of FTD is familial/genetic, the molecular pathology has been the principal driving force for creating an "FTD" umbrella that includes various tau disorders (Pick, CBD, PSP) and TDP43 disorders (ALSdementia and FTLD-U). But in fact there are clinical features of "frontality" common to all these disorders, in contradistinction to the relatively more posterior "parietotemporal" characteristics of AD.

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