Joanna Hellmuth

Oculomotor function in frontotemporal lobar degeneration, related disorders and Alzheimer's disease

Frontotemporal lobar degeneration (FTLD) often overlaps clinically with corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP), both of which have prominent eye movement abnormalities. To investigate the ability of oculomotor performance to differentiate between FTLD, Alzheimers disease, CBS and PSP, saccades and smooth pursuit were measured in three FTLD subtypes, including 24 individuals with frontotemporal dementia (FTD), 19 with semantic dementia (SD) and six with progressive non-fluent aphasia (PA), as compared to 28 individuals with Alzheimers disease, 15 with CBS, 10 with PSP and 27 control subjects. Different combinations of oculomotor abnormalities were identified in all clinical syndromes except for SD, which had oculomotor performance that was indistinguishable from age-matched controls. Only PSP patients displayed abnormalities in saccade velocity, whereas abnormalities in saccade gain were observed in PSP > CBS > Alzheimers disease subjects. All patient groups except those with SD were impaired on the anti-saccade task, however only the FTLD subjects and not Alzheimers disease, CBS or PSP groups, were able to spontaneously self-correct anti-saccade errors as well as controls. Receiver operating characteristic statistics demonstrated that oculomotor findings were superior to neuropsychological tests in differentiating PSP from other disorders, and comparable to neuropsychological tests in differentiating the other patient groups. These data suggest that oculomotor assessment may aid in the diagnosis of FTLD and related disorders.

Essential function of HIPK2 in TGFβ-dependent survival of midbrain dopamine neurons

Transforming growth factor beta (TGFβ) is a potent trophic factor for midbrain dopamine (DA) neurons, but its in vivo function and signaling mechanisms are not entirely understood. We show that the transcriptional cofactor homeodomain interacting protein kinase 2 (HIPK2) is required for the TGFβ-mediated survival of mouse DA neurons. The targeted deletion of Hipk2 has no deleterious effect on the neurogenesis of DA neurons, but leads to a selective loss of these neurons that is due to increased apoptosis during programmed cell death. As a consequence, Hipk2−/− mutants show an array of psychomotor abnormalities. The function of HIPK2 depends on its interaction with receptor-regulated Smads to activate TGFβ target genes. In support of this notion, DA neurons from Hipk2−/− mutants fail to survive in the presence of TGFβ3 and Tgfβ3−/− mutants show DA neuron abnormalities similar to those seen in Hipk2−/− mutants. These data underscore the importance of the TGFβ-Smad-HIPK2 pathway in the survival of DA neurons and its potential as a therapeutic target for promoting DA neuron survival during neurodegeneration.

Medial Versus Lateral Frontal Lobe Contributions to Voluntary Saccade Control as Revealed by the Study of Patients with Frontal Lobe Degeneration

Deficits in the ability to suppress automatic behaviors lead to impaired decision making, aberrant motor behavior, and impaired social function in humans with frontal lobe neurodegeneration. We have studied patients with different patterns of frontal lobe dysfunction resulting from frontotemporal lobar degeneration or Alzheimers disease, investigating their ability to perform visually guided saccades and smooth pursuit eye movements and to suppress visually guided saccades on the antisaccade task. Patients with clinical syndromes associated with dorsal frontal lobe damage had normal visually guided saccades but were impaired relative to other patients and control subjects in smooth pursuit eye movements and on the antisaccade task. The percentage of correct antisaccade responses was correlated with neuropsychological measures of frontal lobe function and with estimates of frontal lobe gray matter volume based on analyses of structural magnetic resonance images. After controlling for age, gender, cognitive status, and potential interactions between disease group and oculomotor function, an unbiased voxel-based morphometric analysis identified the volume of a segment of the right frontal eye field (FEF) as positively correlated with antisaccade performance (less volume equaled lower percentage of correct responses) but not with either pursuit performance or antisaccade or visually guided saccade latency or gain. In contrast, the volume of the presupplementary motor area (pre-SMA) and a portion of the supplementary eye fields correlated with antisaccade latency (less volume equaled shorter latency) but not with the percentage of correct responses. These results suggest that integrity of the presupplementary motion area/supplementary eye fields is critical for supervisory processes that slow the onset of saccades, facilitating voluntary saccade targeting decisions that rely on the FEF.

Saccade Abnormalities in Autopsy-Confirmed Frontotemporal Lobar Degeneration and Alzheimer Disease

BACKGROUND Deficits in the generation and control of saccades have been described in clinically defined frontotemporal dementia (FTD) and Alzheimer disease (AD). OBJECTIVE To determine the saccade abnormalities associated with autopsy-defined cases of frontotemporal lobar degeneration (FTLD) and of AD, because clinical FTD syndromes can correspond to a number of different underlying neuropathologic FTD and non-FTD diagnoses. DESIGN An infrared eye tracker was used to record visually guided saccades to 10° targets and antisaccades in subjects with autopsy-confirmed FTD and subjects with autopsy-confirmed AD, a mean (SE) of 35.6 (10.0) months prior to death, and age-matched normal controls. Twelve subjects with FTD had an FTLD-TAR DNA-binding protein 43 pathology, 15 had an FTLD-tau pathology, and 1 subject showed an FTLD-fused in sarcoma protein pathology. Receiver operating curve statistics were used to determine the diagnostic value of the oculomotor variables. Neuroanatomical correlates of oculomotor abnormalities were investigated using voxel-based morphometry. SETTING Memory and Aging Center, Department of Neurology, University of California, San Francisco. PARTICIPANTS A total of 28 subjects with autopsy-confirmed FTD, 10 subjects with autopsy-confirmed AD, and 27 age-matched normal controls. RESULTS All subjects with FTD or AD were impaired relative to normal controls on the antisaccade task. However, only FTLD-tau and AD cases displayed reflexive visually guided saccade abnormalities. The AD cases displayed prominent increases in horizontal saccade latency that differentiated them from the FTD cases. Impairments in velocity and gain were most severe in individuals with progressive supranuclear palsy but were also present in other tauopathies. By using vertical and horizontal saccade velocity and gain as our measures, we were able to differentiate patients with progressive supranuclear palsy from other patients. Vertical saccade velocity was strongly correlated with dorsal midbrain volume. CONCLUSION Decreased visually guided saccade velocity and gain are suggestive of underlying tau pathology in FTD, with vertical saccade abnormalities most diagnostic of progressive supranuclear palsy.

Multicenter validation of a bedside antisaccade task as a measure of executive function

Objective: To create and validate a simple, standardized version of the antisaccade (AS) task that requires no specialized equipment for use as a measure of executive function in multicenter clinical studies. Methods: The bedside AS (BAS) task consisted of 40 pseudorandomized AS trials presented on a laptop computer. BAS performance was compared with AS performance measured using an infrared eye tracker in normal elders (NE) and individuals with mild cognitive impairment (MCI) or dementia (n = 33). The neuropsychological domain specificity of the BAS was then determined in a cohort of NE, MCI, and dementia (n = 103) at UCSF, and the BAS was validated as a measure of executive function in a 6-center cohort (n = 397) of normal adults and patients with a variety of brain diseases. Results: Performance on the BAS and laboratory AS task was strongly correlated and BAS performance was most strongly associated with neuropsychological measures of executive function. Even after controlling for disease severity and processing speed, BAS performance was associated with multiple assessments of executive function, most strongly the informant-based Frontal Systems Behavior Scale. Conclusions: The BAS is a simple, valid measure of executive function in aging and neurologic disease.

Neurologic signs and symptoms frequently manifest in acute HIV infection

Objective: To determine the incidence, timing, and severity of neurologic findings in acute HIV infection (pre–antibody seroconversion), as well as persistence with combination antiretroviral therapy (cART). Methods: Participants identified with acute HIV were enrolled, underwent structured neurologic evaluations, immediately initiated cART, and were followed with neurologic evaluations at 4 and 12 weeks. Concurrent brain MRIs and both viral and inflammatory markers in plasma and CSF were obtained. Results: Median estimated HIV infection duration was 19 days (range 3–56) at study entry for the 139 participants evaluated. Seventy-three participants (53%) experienced one or more neurologic findings in the 12 weeks after diagnosis, with one developing a fulminant neurologic manifestation (Guillain-Barré syndrome). A total of 245 neurologic findings were noted, reflecting cognitive symptoms (33%), motor findings (34%), and neuropathy (11%). Nearly half of the neurologic findings (n = 121, 49%) occurred at diagnosis, prior to cART initiation, and most of these (n = 110, 90%) remitted concurrent with 1 month on treatment. Only 9% of neurologic findings (n = 22) persisted at 24 weeks on cART. Nearly all neurologic findings (n = 236, 96%) were categorized as mild in severity. No structural neuroimaging abnormalities were observed. Participants with neurologic findings had a higher mean plasma log10 HIV RNA at diagnosis compared to those without neurologic findings (5.9 vs 5.4; p = 0.006). Conclusions: Acute HIV infection is commonly associated with mild neurologic findings that largely remit while on treatment, and may be mediated by direct viral factors. Severe neurologic manifestations are infrequent in treated acute HIV.

Interactions between ageing and NeuroAIDS.

Purpose of reviewThe purpose of this study is to summarize recent advances in ageing and neuroAIDS by reviewing relevant articles from the preceding 18 months from PubMed and PsycINFO databases. Recent findingsThe success of combination antiretroviral therapy (cART) has led to ageing of the HIV-infected population, which in turn contributes to the prevalence of HIV-associated neurocognitive disorder (HAND). Biomedical advances continue to clarify the pathophysiology of HAND despite effective cART, including chronic inflammatory and neurovascular causes. In recent months, associations between HAND and nonneurological medical diseases have been identified, as well as linkage to neuroimaging in those ageing with HIV. Developing effective screening tools to detect impairment remains an important scientific gap, although promoting factors associated with successful cognitive ageing is emerging as a possible means of enhancing quality of life. SummaryA greater understanding of HAND pathophysiology among treated individuals with suppressed virus will aid in explaining the high prevalence of HAND despite effective cART and allow for development of novel targeted interventions. Neuroimaging and other biomarkers show promise in discerning HAND from age-associated cognitive disorders. Effective screening tools remain critically needed. Together, this work will inform promising strategies needed to address issues pertinent to an expanding group of older patients living with HIV.

Cognitive Impairment and Persistent CNS Injury in Treated HIV

The implementation of combination antiretroviral therapy (cART) has changed HIV infection into a chronic illness, conveying extensive benefits, including greater longevity and advantages for the central nervous system (CNS). However, studies increasingly confirm that the CNS gains are incomplete, with reports of persistent immune activation affecting the CNS despite suppression of plasma HIV RNA. The rate of cognitive impairment is unchanged, although severity is generally milder than in the pre-cART era. In this review, we discuss cognitive outcomes from recently published clinical HIV studies, review observations on HIV biomarkers for cognitive change, and emphasize longitudinal imaging findings. Additionally, we summarize recent studies on CNS viral invasion, CD8 encephalitis, and how CNS involvement during the earliest stages of infection may set the stage for later cognitive manifestations.

Progressive Brain Atrophy Despite Persistent Viral Suppression in HIV Patients Older Than 60 Years

Background: Current HIV treatments are successful at suppressing plasma HIV RNA to undetectable levels for most adherent patients. Yet, emerging evidence suggests that viral suppression will inadequately control inflammation and mitigate risk for progressive brain injury. We sought to quantify differences in longitudinal brain atrophy rates among older virally suppressed HIV-infected participants compared with that of healthy aging participants. Methods: We examined longitudinal structural brain magnetic resonance imaging atrophy rates using region of interest assessments and voxel-wise tensor-based morphometry in HIV-infected participants older than 60 years (n = 38) compared with age-matched HIV-uninfected healthy and cognitively normal controls (n = 24). Results: The mean age of participants was 63 years, the mean estimated duration of infection was 21 years, and the median duration of documented viral suppression was 3.2 years. Average proximal and nadir CD4 counts were 550 and 166, respectively; 15/38 (39%) met criteria for HIV-associated neurocognitive disorder. In models adjusting for age and sex, HIV serostatus was associated with more rapid average annualized rates of atrophy in the cerebellum (0.42% vs. 0.02%, P = 0.016), caudate (0.74% vs. 0.03%, P = 0.012), frontal lobe (0.48% vs. 0.01%, P = 0.034), total cortical gray matter (0.65% vs. 0.16%, P = 0.027), brainstem (0.31% vs. 0.01%, P = 0.026), and pallidum (0.73% vs. 0.39%, P = 0.046). Among those with HIV, atrophy rates did not differ statistically by cognitive status. Conclusions: Despite persistent control of plasma viremia, these older HIV-infected participants demonstrate more rapid progressive brain atrophy when compared with healthy aging. Either HIV or other factors that differ between older HIV-infected participants and healthy controls could be responsible for these differences.

High Number of Activated CD8+ T Cells Targeting HIV Antigens Are Present in Cerebrospinal Fluid in Acute HIV Infection

Background: Central nervous system (CNS) infiltration by CD8+ T cells is associated with neuroinflammation in many neurodegenerative diseases, including HIV-associated dementia. However, the role of CD8+ T cells in the CNS during acute HIV infection (AHI) is unknown. Methods: We analyzed the phenotype, gene expression, T cell receptor (TCR) repertoire, and HIV specificity of CD8+ T cells in cerebrospinal fluid (CSF) of a unique cohort captured during the earliest stages of AHI (n = 26), chronic (n = 23), and uninfected (n = 8). Results: CSF CD8+ T cells were elevated in AHI compared with uninfected controls. The frequency of activated CSF CD8+ T cells positively correlated to CSF HIV RNA and to markers of CNS inflammation. In contrast, activated CSF CD8+ T cells during chronic HIV infection were associated with markers of neurological injury and microglial activation. CSF CD8+ T cells in AHI exhibited increased functional gene expression profiles associated with CD8+ T cells effector function, proliferation, and TCR signaling, a unique restricted TCR Vbeta repertoire and contained HIV-specific CD8+ T cells directed to unique HIV epitopes compared with the periphery. Conclusions: These results suggest that CSF CD8+ T cells in AHI expanding in the CNS are functional and directed against HIV antigens. These cells could thus play a beneficial role protective of injury seen in chronic HIV infection if combination antiretroviral therapy is initiated early.