Edward D. Huey

Focal brain damage protects against post-traumatic stress disorder in combat veterans

Post-traumatic stress disorder (PTSD) is an often debilitating mental illness that is characterized by recurrent distressing memories of traumatic events. PTSD is associated with hypoactivity in the ventromedial prefrontal cortex (vmPFC), hyperactivity in the amygdala and reduced volume in the hippocampus, but it is unknown whether these neuroimaging findings reflect the underlying cause or a secondary effect of the disorder. To investigate the causal contribution of specific brain areas to PTSD symptoms, we studied a unique sample of Vietnam War veterans who suffered brain injury and emotionally traumatic events. We found a substantially reduced occurrence of PTSD among those individuals with damage to one of two regions of the brain: the vmPFC and an anterior temporal area that included the amygdala. These results suggest that the vmPFC and amygdala are critically involved in the pathogenesis of PTSD.

A systematic review of neurotransmitter deficits and treatments in frontotemporal dementia.

Objective: To evaluate neurotransmitter deficiencies and neurotransmitter-based treatments for frontotemporal dementia (FTD). Methods: The authors conducted a systematic review of the literature on the mechanism and treatment of FTD and a meta-analysis of treatment studies of antidepressants for the behavioral symptoms of FTD. Results: Patients with FTD show deficiencies in the serotonin and dopamine neurotransmitter systems, while the acetylcholine system appears relatively intact. Antidepressant treatment significantly improves behavioral symptoms in FTD, but most studies are small and uncontrolled. Serotonergic treatments appear to improve the behavioral but not cognitive symptoms of FTD. Conclusions: Studies of neurotransmitter deficiencies in frontotemporal dementia (FTD) can be helpful in developing treatments. Treatment studies on FTD are scarce, given the prevalence and severity of this illness. Larger, well-controlled treatment studies are required to reach more definitive conclusions about treatment efficacy. Multicenter studies are likely the best way to complete treatment studies in a timely manner.

Phenotypic variability associated with progranulin haploinsufficiency in patients with the common 1477C→T (Arg493X) mutation: an international initiative

BACKGROUND The progranulin gene (GRN) is mutated in 5-10% of patients with frontotemporal lobar degeneration (FTLD) and in about 20% of patients with familial FTLD. The most common mutation in GRN is Arg493X. We aimed to establish the contribution of this mutation to FTLD and related disorders. METHODS We measured the frequency of Arg493X in 3405 unrelated patients with various neurodegenerative diseases using Taqman single-nucleotide polymorphism (SNP) genotyping. Clinicopathological characterisation and shared haplotype analysis were done for 30 families with FTLD who carry Arg493X. To investigate the effect of potential modifying loci, we did linear regression analyses with onset age as the covariate for GRN variants, for genotypes of the apolipoprotein E gene (APOE), and for haplotypes of the microtubule-associated protein tau gene (MAPT). FINDINGS Of 731 patients with FTLD, 16 (2%) carried Arg493X. This mutation was not detected in 2674 patients who did not have FTLD. In 37 patients with Arg493X from 30 families with FTLD, clinical diagnoses included frontotemporal dementia, primary progressive aphasia, corticobasal syndrome, and Alzheimers disease. Range of onset age was 44-69 years. In all patients who came to autopsy (n=13), the pathological diagnosis was FTLD with neuronal inclusions that contained TAR DNA-binding protein or ubiquitin, but not tau. Neurofibrillary tangle pathology in the form of Braak staging correlated with overall neuropathology in the Arg493X carriers. Haplotype analyses suggested that Arg493X arose twice, with a single founder for 27 families. Linear regression analyses suggested that patients with SNP rs9897528 on their wild-type GRN allele have delayed symptom onset. Onset ages were not associated with the MAPT H1 or H2 haplotypes or APOE genotypes, but early memory deficits were associated with the presence of an APOE epsilon4 allele. INTERPRETATION Clinical heterogeneity is associated with GRN haploinsufficiency, and genetic variability on the wild-type GRN allele might have a role in the age-related disease penetrance of GRN mutations.

Apathy and disinhibition in frontotemporal dementia Insights into their neural correlates

Background: Aberrant social behavior is a defining symptom of frontotemporal dementia (FTD) and may eventually occur in all syndromes composing the FTD spectrum. Two main behavioral abnormalities have been described: apathy and disinhibition, but their neuroanatomical correlates remain underspecified. Methods: Sixty-two patients with a clinical diagnosis of FTD participated in the study. Voxel-based morphometry of MRI data was performed to explore the association between gray matter loss and severity of the two behavioral profiles as measured by the Apathy and Disinhibition subscales of the Frontal Systems Behavior Scale. Results: Compared with a group of controls, the FTD group showed extensive bilateral atrophy predominantly involving frontal and temporal lobes. Within the FTD group, the severity of apathy correlated with atrophy in the right dorsolateral prefrontal cortex. The severity of disinhibition correlated with atrophy in the right nucleus accumbens, right superior temporal sulcus, and right mediotemporal limbic structures. Conclusions: Prefrontal and temporal regions are differentially associated with apathy and disinhibition. Our results support the view that successful execution of complex social behaviors relies on the integration of social knowledge and executive functions, represented in the prefrontal cortex, and reward attribution and emotional processing, represented in mesolimbic structures.

Distinct Regions of Prefrontal Cortex Mediate Resistance and Vulnerability to Depression

The neuroanatomical correlates of depression remain unclear. Functional imaging data have associated depression with abnormal patterns of activity in prefrontal cortex (PFC), including the ventromedial (vmPFC) and dorsolateral (dlPFC) sectors. If vmPFC and dlPFC are critical neural substrates for the pathogenesis of depression, then damage to either area should affect the expression of depressive symptoms. Using patients with brain lesions we show that, relative to nonfrontal lesions, bilateral vmPFC lesions are associated with markedly low levels of depression, whereas bilateral dorsal PFC lesions (involving dorsomedial and dorsolateral areas in both hemispheres) are associated with substantially higher levels of depression. These findings demonstrate that vmPFC and dorsal PFC are critically and causally involved in depression, although with very different roles: vmPFC damage confers resistance to depression, whereas dorsal PFC damage confers vulnerability.

The role of the Met66 brain-derived neurotrophic factor allele in the recovery of executive functioning after combat-related traumatic brain injury.

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, promotes survival and synaptic plasticity in the human brain. The Val66Met polymorphism of the BDNF gene interferes with intracellular trafficking, packaging, and regulated secretion of this neurotrophin. The human prefrontal cortex (PFC) shows lifelong neuroplastic adaption implicating the Val66Met BDNF polymorphism in the recovery of higher-order executive functions after traumatic brain injury (TBI). In this study, we examined the effect of this BDNF polymorphism on the recovery of executive functioning after TBI. We genotyped a sample of male Vietnam combat veterans consisting of a frontal lobe lesion group with focal penetrating head injuries and a non-head-injured control group for the Val66Met BDNF polymorphism. The Delis–Kaplan Executive Function System as a standardized psychometric battery was administrated to examine key domains of executive functions. The results revealed that the Met allele but not the hypothesized Val allele promotes recovery of executive functioning. Overall, the Met66 carriers in the lesion group performed as well as the Met66 carriers in the control group. The Met66 allele accounted for 6.2% of variance for executive functioning independently of other significant predictors including preinjury intelligence, left hemisphere volume loss, and dorsolateral PFC volume loss. The findings point to different mechanisms of the Val66Met BDNF gene in complex phenotypes under normal and pathological conditions. A better understanding of these mechanisms could be instrumental in the development and application of effective therapeutic strategies to facilitate recovery from TBI.

Analysis of IFT74 as a candidate gene for chromosome 9p-linked ALS-FTD

BackgroundA new locus for amyotrophic lateral sclerosis – frontotemporal dementia (ALS-FTD) has recently been ascribed to chromosome 9p.MethodsWe identified chromosome 9p segregating haplotypes within two families with ALS-FTD (F476 and F2) and undertook mutational screening of candidate genes within this locus.ResultsCandidate gene sequencing at this locus revealed the presence of a disease segregating stop mutation (Q342X) in the intraflagellar transport 74 (IFT74) gene in family 476 (F476), but no mutation was detected within IFT74 in family 2 (F2). While neither family was sufficiently informative to definitively implicate or exclude IFT74 mutations as a cause of chromosome 9-linked ALS-FTD, the nature of the mutation observed within F476 (predicted to truncate the protein by 258 amino acids) led us to sequence the open reading frame of this gene in a large number of ALS and FTD cases (n = 420). An additional sequence variant (G58D) was found in a case of sporadic semantic dementia. I55L sequence variants were found in three other unrelated affected individuals, but this was also found in a single individual among 800 Human Diversity Gene Panel samples.ConclusionConfirmation of the pathogenicity of IFT74 sequence variants will require screening of other chromosome 9p-linked families.

FTD and ALS: a tale of two diseases

The first reports of disorders that in terms of cognitive and behavioral symptoms resemble frontotemporal dementia (FTD) and in terms of motor symptoms resemble amyotrophic lateral sclerosis (ALS) bring us back to the second half of the 1800s. Over the last 150 years, and especially in the last two decades, there has been growing evidence that FTD signs can be seen in patients primarily diagnosed with ALS, implying clinical overlap among these two disorders. In the last decade pathological investigations and genetic screening have contributed tremendously in elucidating the pathology and genetic variability associated with FTD and ALS. To the most important recentdiscoveries belong TAR DNA binding protein [TARDBP or TDP-43] and the fused in sarcoma gene [FUS] and their implication in these disorders.FTD and ALS are the focus of this review which aims to 1. summarize clinical features by describing the diagnostic criteria and specific symptomatology, 2. describe the morphological aspects and related pathology, 3. describe the genetic factors associated with the diseases and 4. summarize the current status of clinical trials and treatment options. A better understanding of the clinical, pathological and genetic features characterizing FTD and ALS will shed light into overlaps among these two disorders and the underpinning mechanisms that contribute to the onset and development. Nevertheless, advancements in the knowledge of the biology of these two disorders will help developing novel and, hopefully, more effective diagnostic and treatment options.

Clinicopathologic features of frontotemporal dementia with Progranulin sequence variation

Background: Frontotemporal lobar degeneration with ubiquitin-immunoreactive (ub-ir) inclusions (FTLD-U) has been associated with frontotemporal dementia (FTD) and ALS. Recently, mutations in Progranulin (PGRN), predicted to cause premature truncation of the PGRN coding sequence, were found in patients with inherited FTLD-U and ub-ir neuronal intranuclear inclusions (NII). Objective: To describe clinical, pathologic, and genetic features of three FTD patients having either a family history of FTD (A.III.1 and B.II.1) or of ALS (C.III.1). Methods: Patients underwent a single clinical assessment, MRI, and [18F]fluorodeoxyglucose PET brain scan. Neuropathologic examination and genetic analyses were carried out. Results: Patients presented clinically with the behavioral variant of FTD. Language dysfunctions were marked with comprehension being particularly affected. Neuroimaging revealed frontotemporal atrophy and glucose hypometabolism, with predominant left-side involvement, in Patients A.III.1 and B.II.1. Subject C.III.1 displayed mild atrophy and symmetric anterior hypometabolism. All patients were neuropathologically diagnosed with FTLD-U. Ub-ir NII were noted in Patients A.III.1 and B.II.1 but were absent in Patient C.III.1. The following PGRN sequence variations were found: IVS6-2A→G (A.III.1), R493X (B.II.1), and R433W (C.III.1). IVS6-2A→G may lead to skipping of exon 7 with consequent frameshift of the coding sequence and premature termination of PGRN translation. Conclusions: We have found two PGRN mutations associated with FTD, in affected individuals who are members of families with possible autosomal dominant FTD. A third PGRN sequence variation (R433W) was found in an FTD patient with family history of ALS.

Executive dysfunction in frontotemporal dementia and corticobasal syndrome

Objective: To determine the pattern of executive dysfunction in frontotemporal dementia (FTD) and corticobasal syndrome (CBS) and to determine the brain areas associated with executive dysfunction in these illnesses. Method: We administered the Delis-Kaplan Executive Function System (D-KEFS), a collection of standardized executive function tests, to 51 patients with behavioral-variant FTD and 50 patients with CBS. We also performed a discriminant analysis on the D-KEFS to determine which executive function tests best distinguished the clinical diagnoses of FTD and CBS. Finally, we used voxel-based morphometry (VBM) to determine regional gray matter volume loss associated with executive dysfunction. Results: Patients with FTD and patients with CBS showed executive dysfunction greater than memory dysfunction. Executive function was better preserved in the patients with CBS than the patients with FTD with the exception of tests that required motor, visuospatial ability, or both. In patients with CBS, dorsal frontal and parietal and temporal-parietal cortex was associated with executive function. In FTD, tests with a language component (Verbal Fluency) were associated with left perisylvian cortex, sorting with the left dorsolateral prefrontal cortex, and reasoning (the Twenty Questions task) with the left anterior frontal cortex. The Twenty Questions test best distinguished the clinical diagnoses of CBS and FTD. Conclusions: The neuroanatomic findings (especially in frontotemporal dementia [FTD]) agree with the previous literature on this topic. Patients with FTD and patients with corticobasal syndrome (CBS) show disparate performance on higher-order executive functions, especially the Twenty Questions test. It may be difficult to distinguish motor and visuospatial ability from executive function in patients with CBS using tests with significant motor and visuospatial demands such as Trail Making.