Cognitive performance of GBA mutation carriers with early-onset PD: the CORE-PD study

OBJECTIVE

To assess the cognitive phenotype of glucocerebrosidase (GBA) mutation carriers with early-onset Parkinson disease (PD).

METHODS

We administered a neuropsychological battery and the University of Pennsylvania Smell Identification Test (UPSIT) to participants in the CORE-PD study who were tested for mutations in PARKIN, LRRK2, and GBA. Participants included 33 GBA mutation carriers and 60 noncarriers of any genetic mutation. Primary analyses were performed on 26 GBA heterozygous mutation carriers without additional mutations and 39 age- and PD duration-matched noncarriers. Five cognitive domains, psychomotor speed, attention, memory, visuospatial function, and executive function, were created from transformed z scores of individual neuropsychological tests. Clinical diagnoses (normal, mild cognitive impairment [MCI], dementia) were assigned blind to genotype based on neuropsychological performance and functional impairment as assessed by the Clinical Dementia Rating (CDR) score. The association between GBA mutation status and neuropsychological performance, CDR, and clinical diagnoses was assessed.

RESULTS

Demographics, UPSIT, and Unified Parkinson's Disease Rating Scale-III performance did not differ between GBA carriers and noncarriers. GBA mutation carriers performed more poorly than noncarriers on the Mini-Mental State Examination (p = 0.035), and on the memory (p = 0.017) and visuospatial (p = 0.028) domains. The most prominent differences were observed in nonverbal memory performance (p < 0.001). Carriers were more likely to receive scores of 0.5 or higher on the CDR (p < 0.001), and a clinical diagnosis of either MCI or dementia (p = 0.004).

CONCLUSION

GBA mutation status may be an independent risk factor for cognitive impairment in patients with PD.

The relation between depression and parkin genotype: the CORE-PD study

BACKGROUND

Mutations in parkin are a known genetic risk factor for early onset Parkinson's disease (EOPD) but their role in non-motor manifestations is not well established. Genetic factors for depression are similarly not well characterized. We investigate the role of parkin mutations in depression among those with EOPD and their relatives.

METHODS

We collected psychiatric information using the Patient Health Questionnaire and Beck Depression Inventory II on 328 genotyped individuals including 88 probands with early onset PD (41 with parkin mutations, 47 without) and 240 first and second-degree relatives without PD.

RESULTS

Genotype was not associated with depression risk among probands. Among unaffected relatives of EOPD cases, only compound heterozygotes (n = 4), and not heterozygotes, had significantly increased risk of depressed mood (OR = 14.1; 95% CI 1.2-163.4), moderate to severe depression (OR = 17.8; 95% CI 1.0-332.0), depression (score ≥ 15) on the Beck Depression Inventory II (BDI-II) (OR = 51.9; 95% CI 4.1-657.4), and BDI-II total depression score (β = 8.4; 95% CI 2.4-11.3) compared to those without parkin mutations.

CONCLUSIONS

Relatives of EOPD cases with compound heterozygous mutations and without diagnosed PD may have a higher risk of depression compared to relatives without parkin mutations. These findings support evidence of a genetic contribution to depression and may extend the phenotypic spectrum of parkin mutations to include non-motor manifestations that precede the development of PD.

Olfaction in Parkin heterozygotes and compound heterozygotes: the CORE-PD study

BACKGROUND

While Parkinson disease (PD) is consistently associated with impaired olfaction, one study reported better olfaction among Parkin mutation carriers than noncarriers. Whether olfaction differs between Parkin mutation heterozygotes and carriers of 2 Parkin mutations (compound heterozygotes) is unknown.

OBJECTIVE

To assess the relationship between Parkin genotype and olfaction in PD probands and their unaffected relatives.

METHODS

We administered the University of Pennsylvania Smell Identification Test (UPSIT) to 44 probands in the Consortium on Risk for Early-Onset Parkinson Disease study with PD onset ≤50 years (10 Parkin mutation heterozygotes, 9 compound heterozygotes, 25 noncarriers) and 80 of their family members (18 heterozygotes, 2 compound heterozygotes, 60 noncarriers). In the probands, linear regression was used to assess the association between UPSIT score (outcome) and Parkin genotype (predictor), adjusting for covariates. Among family members without PD, we compared UPSIT performance in heterozygotes vs noncarriers using generalized estimating equations, adjusting for family membership, age, gender, and smoking.

RESULTS

Among probands with PD, compound heterozygotes had higher UPSIT scores (31.9) than heterozygotes (20.1) or noncarriers (19.9) (p < 0.001). These differences persisted after adjustment for age, gender, disease duration, and smoking. Among relatives without PD, UPSIT performance was similar in heterozygotes (32.5) vs noncarriers (32.4), and better than in heterozygotes with PD (p = 0.001).

CONCLUSION

Olfaction is significantly reduced among Parkin mutation heterozygotes with PD but not among their heterozygous relatives without PD. Compound heterozygotes with PD have olfaction within the normal range. Further research is required to assess whether these findings reflect different neuropathology in Parkin mutation heterozygotes and compound heterozygotes.

Attention modulates beta oscillations during prolonged tactile stimulation

The inter-play between changes in beta-band (14-30-Hz) cortical rhythms and attention during somatosensation informs us about where and when relevant processes occur in the brain. As such, we investigated the effects of attention on somatosensory evoked and induced responses using vibrotactile stimulation and magnetoencephalographic recording. Subjects received trains of vibration at 23 Hz to the right index finger while watching a movie and ignoring the somatosensory stimuli or paying attention to the stimuli to detect a change in the duration of the stimulus. The amplitude of the evoked 23-Hz steady-state response in the contralateral primary somatosensory cortex (SI) was enhanced by attention and the underlying dipole source was located 2 mm more medially, indicating top-down recruitment of additional neuronal populations for the functionally relevant stimulus. Attentional modulation of the somatosensory evoked response indicates facilitation of early processing of the tactile stimulus. Beta-band activity increased after vibration offset in the contralateral primary motor cortex (MI) [event-related synchronization (ERS)] and this increase was larger for attended than ignored stimuli. Beta-band activity decreased in the ipsilateral SI prior to stimulus offset [event-related desynchronization (ERD)] for attended stimuli only. Whereas attention modulation of the evoked response was confined to the contralateral SI, event-related changes of beta-band activity involved contralateral SI-MI and inter-hemispheric SI-SI connections. Modulation of neural activity in such a large sensorimotor network indicates a role for beta activity in higher-order processing.

Evaluation of quantitative liver function tests in HIV-positive patients under anti-retroviral therapy

Background and aims

Quantitative tests of liver function (QTLF) which are based on the hepatic metabolism or clearance of test substances have been successfully used to predict prognosis of a variety of different liver diseases. Still sufficient data in HIV-patients under anti-retroviral therapy (ART) are lacking. Therefore, the aim of this prospective study was to investigate if and to what extent ART influences a broad panel of quantitative tests of liver function in patients with HIV-infection.

Patients and methods

Nineteen patients (14 males, 5 females, mean age 40 years) with HIV-infection underwent QTLF including lidocaine half-life test (LHT), galactose elimination capacity (GEC), and indocyanine green clearance (IGC). These tests were performed before and 3 to 6 months after initiation of anti-retroviral therapy. Twenty age-matched healthy, medication-and virus-free adults served as controls.

Results

Lidocaine half-life was significantly lower in HIV-patients without ART. Combining anti-retroviral therapies shifted cytochrome p450 activity back into standard ranges. Galactose elimination capacity as a parameter of cytosolic liver function and indocyanine green clearance as a parameter of liver perfusion were not affected by ART.

Conclusions

QTLF may be a tool to predict prognosis or hepatic complications in HIV-infected patients with liver disease. Early determination of lidocaine half-life seems to be useful - this should be considered during the treatment of HIV-positive individuals.

Magnetoencephalographic study of vibrotactile evoked transient and steady-state responses in human somatosensory cortex

Somatosensory responses to vibrotactile stimulation applied to the index fingertip were recorded with whole-head MEG in eleven healthy young adult participants. Stimulus trains were produced by a pneumatically driven membrane oscillating at 22 Hz for a trial duration of 1 s, separated by interstimulus intervals (ISIs) of 0.5, 1.0, 3.0, and 7.0 s. Data analysis was performed in two frequency bands. Transient onset responses in the lower frequency band (<20 Hz) contained a clearly expressed P50 component. The higher frequency band (18-30 Hz) revealed a gamma-band response (GBR) within the first 200 ms followed by rhythmic activity at the stimulus frequency that continued throughout the stimulus duration, known as the steady-state response (SSR). Dipoles associated with the transient responses and SSRs were localized in two distinct regions within the primary somatosensory cortex (SI), with transient responses located on average 3 mm more medial and inferior than the SSRs. The transient and GBR peak amplitudes increased with ISI, whereas the SSR amplitude showed no ISI dependence. These results may reflect functionally and spatially distinct neural populations. Further investigations are required to assess the implications of these findings for probing the somatosensory system using other functional neuroimaging methods such as fMRI.

Correlates of eye blinking as determined by synthetic aperture magnetometry

OBJECTIVE

To evaluate the spatiotemporal characteristics of ocular and cerebral current sources during voluntary eyeblinking.

METHODS

Whole-head magnetoencephalographic (MEG) recordings were acquired during voluntary blinking in eight healthy adults and analysed using synthetic aperture magnetometry (SAM).

RESULTS

Fronto-temporal MEG sensors showed a large slow wave lasting approximately 400 ms and a small burst of activity with frequencies above 30 Hz at the initiation of the blink. Group maps of blink-related oscillatory activity at frequencies between 1-18 Hz and 32-64 Hz showed increased activity in and around the orbits during the 400 ms following blink onset. Increased oscillatory activity occurred in occipital regions 200 ms after blink onset at frequencies between 18 and 64 Hz.

CONCLUSIONS

Blink-related MEG signals are recorded in the regions of the eyes and in the occipital cortex. The anterior activation is likely a combination of muscle contraction and eyelid currents. Occipital activation likely represents neural processes concerned with re-establishing the visual image after transient ocular occlusion.

SIGNIFICANCE

The possibility of eyeblink-related fields should be considered when interpreting frontal and occipital source activities during SAM analyses.

Efficiency and efficacy of multi-channel gastric electrical stimulation

Gastric electrical stimulation (GES) using single channel has been under investigation for its therapeutic potential for gastroparesis. The aim of this study was to study the efficacy and efficiency of multi-channel GES in accelerating gastric emptying in dogs. The study was performed in eight dogs, and gastric emptying of liquid was assessed in three randomized sessions of control, one-channel GES and four-channel GES. It was found that (i) GES of both one-channel and four-channel was able to completely entrain the slow waves in the entire stomach. However, the stimulation energy required by four-channel GES was only 1% of that required by one-channel GES. (ii) Four-channel, but not one-channel, GES significantly and substantially accelerated gastric emptying. An increase of 121.0 and 93.9% was noted with four-channel GES at 30 and 60 min after the meal, respectively. It was concluded that four-channel GES is substantially more efficient and effective than conventional single-channel GES in improving gastric emptying. It is worthy to explore its therapeutic potential for gastroparesis in clinical settings.

Stimulus Induced Desynchronization of Human Auditory 40-Hz Steady-State Responses

The hypothesis that gamma-band oscillations are related to the representation of an environmental scene in the cerebral cortex after binding of corresponding perceptual elements is currently under discussion. One question is how the sensory system reacts to a fast change in the scene if perceptual elements are rigidly bound together. A reset of the gamma-band oscillation forced by a change in sensory input may dissolve the binding, which then would be re-established for the new sensation. We studied the reset of gamma-band oscillations on the 40-Hz auditory steady-state responses (ASSR) by means of whole-head magnetoencephalography (MEG). The rhythm of 40-Hz AM of a 500-Hz tone evoked the ASSR, and a short noise burst served as a concurrent stimulus. Possible direct interactions of the auditory stimuli were excluded by presenting the noise impulse in a different frequency channel (2,000–3,000 Hz) to the contralateral ear. The concurrent stimulus induced a considerable decrement in the amplitude of ASSR, which was localized in primary auditory cortices. This decrement lasted 250 ms and was significantly longer than the duration of the transient gamma-band response evoked by the noise burst. Thus it could not be explained by any linear superimposition of the responses. The time courses of ASSR amplitude and phase during recovery from the decrement resembled those after stimulus onset, indicating that a new ASSR was built up after the resetting stimulus. The results are discussed as reset of oscillations in human thalamocortical networks.

Dilated cardiomyopathy in two adult human immunodeficiency positive (HIV+) patients possibly related to highly active antiretroviral therapy (HAART)

Human immunodeficiency virus (HIV) and acute immunodeficiency syndrome are known to be associated with cardiac involvement. In this respect, a relation between HIV and dilated cardiomyopathy has been described. Additionally, highly active antiretroviral therapy (HAART) may independently contribute to cardiac impairment. We here report two cases of severely reduced left ventricular function detected in the context of a recent standardized screening of 132 HIV+ individuals of the German heart failure network. Both patients presented in a poor overall condition and progressive exercise-induced dyspnea accompanied by edema or angina pectoris, respectively. Subsequent examinations revealed left bundle-branch blockade, ventricular arrhythmia, elevated serum BNP-levels as well as pathologic transthoracic echocardiography, left ventricular angiography, electron beam tomography and cardiac magnetic resonance imaging without significant coronary stenoses or immunohistological signs of an ongoing or prior myocarditis. Clinical signs of progressive chronic heart failure developed slowly but constantly following initiation of the HAART regimen. Patients were treated by an implantation of a biventricular implantable cardioverter defibrillator beside conventional conservative standard therapy followed by a significant improvement of clinical symptoms. Antiviral medication could be maintained in both patients. Taking all data into account, the diagnosis of a HAART-associated dilated cardiomyopathy could be assessed. Even though the pathogenesis of secondary heart failure after HAART is still object of investigation a mitochondrial impairment by antiviral drugs is thought to contribute the development of dilated cardiomyopathy. However, due to the coexistence of an eminent HIV infection, a direct effect of the HI virus itself can not be completely excluded.