Distinct Beta-band Oscillatory Circuits Underlie Corticospinal Gain Modulation

Rhythmic synchronization of neurons is known to affect neuronal interactions. In the motor system, oscillatory power fluctuations modulate corticospinal excitability. However, previous research addressing phase-specific gain modulation in the motor system has resulted in contradictory findings. It remains unclear how many time windows of increased responsiveness each oscillatory cycle provides. Moreover, we still lack conclusive evidence as to whether the motor cortex entails an intrinsic response modulation along the rhythm cycle, as shown for spinal neurons. We investigated this question with single-pulse transcranial magnetic stimulation over the primary motor cortex at rest. Application of near-motor threshold stimuli revealed a frequency- and phase-specific gain modulation at both cortical and spinal level, independent of the spontaneous oscillatory power fluctuations at each level. We detected bilateral sensorimotor circuits in the lower beta-band (14–17 Hz) and unilateral corticospinal circuits in the upper beta-band (20–24 Hz). These findings provide novel evidence that intrinsic activity in the human motor cortex modulates input gain along the beta oscillatory cycle within distinct circuits. In accordance with periodic alternations of synchronous hyper- and depolarization, increased neuronal responsiveness occurred once per oscillatory beta cycle. This information may lead to new brain state-dependent and circuit-specific interventions for targeted neuromodulation.

A new scale for assessing patients with vertebrobasilar stroke—the Israeli Vertebrobasilar Stroke Scale (IVBSS): Inter-rater reliability and concurrent validity

OBJECTIVES

Most of existing stroke scoring systems have limited ability to evaluate patients with cerebrovascular events in the vertebrobasilar territory. We devised a new scale, the Israeli Vertebrobasilar Stroke Scale (IVBSS) in order to directly and more accurately assess clinical deficits of patients with vertebrobasilar stroke. The present study measured the reliability and validity of the IVBSS.

PATIENTS AND METHODS

Forty-three patients (mean age+/-S.D., 70.9+/-8.8 years, 27 males) with vertebrobasilar stroke were evaluated with the IVBSS (11 items), the NIH Stroke Scale (NIHSS) and the disability modified Rankin Scale (mRS) by independent examiners. Interobserver agreement was rated by weighted kappa statistics for each item and the total IVBSS score. Validity was examined with Spearman rank coefficients to compare the IVBSS with NIHSS and mRS.

RESULTS

Excellent reliability was demonstrated between the examiners for almost each item and the total score of the IVBSS (kappa>0.75). The total IVBSS score was strongly associated with NIHSS and mRS results (r=0.80 and 0.76, respectively; P<0.0002).

CONCLUSIONS

The IVBSS is a valid instrument that allows the assessment of patients with vertebrobasilar stroke with high reliability. Further observations are warranted to determine the predictive value of the IVBSS for stroke outcome.

Recurrent embolic strokes and cardiac valvular disease in a patient with non-small cell adenocarcinoma of lung

The etiology and mechanisms of stroke could differ in cancer compared to non-cancer patients due to altered blood coagulability and/or non-bacterial thrombotic endocarditis (NBTE). These conditions could be either missed by using inappropriate diagnostic methods or misinterpreted. For instance, certain techniques (transthoracic echocardiography, TTE) may provide false-negative results and delay appropriate therapy. On the other hand, these patients, by having atypical findings, may challenge the differential between bacterial and sterile valvular heart disease. Cerebrovascular disease in cancer patients is often aggressive with tendency to recurrent events and rapid neurological devastation. Timely diagnosis is crucial. Current treatment approach to NBTE includes anticoagulation. We report a case of multiple embolic strokes in a patient diagnosed with lung cancer. Primary and secondary stroke prevention is discussed with relevant review of the literature.

Diagnostic tools for the study of vascular cognitive dysfunction in hypertension and antihypertensive drug research

Arterial hypertension is one of the main risk factors for cerebrovascular diseases, and antihypertensive treatment has significantly reduced their associated mortality. However, morbidity has not been reduced to a similar extent and a still increasing number of patients suffers from recurring strokes and from the disabling consequences of cerebrovascular diseases and develops progressive cognitive impairment. It is still debated to what extent antihypertensive treatment may prevent the development of cognitive dysfunction, due to the lack of a focused approach to vascular cognitive impairment, to the lack of a systematic study of the early phases of dementia, and to the use of diagnostic tests that are not sensitive and specific for a slow onset clinical condition, such as dementia. The aim of the present expert consensus report is to enlist the diagnostic tools that are currently available to assess mild cognitive impairment (MCI) and early dementia and that are sensitive and specific enough to be used in observational, longitudinal, and interventional clinical research studies, aiming to investigate the impact of antihypertensive drugs on vascular dementia (VD).

Coronary artery bypass grafting (CABG) and cognitive decline: a review

Coronary artery bypass grafting (CABG) is a worldwide used myocardial revascularization procedure, which despite the modern advantages still has a spectrum of complications. The relatively old age of the patients who undergo CABG and their widespread atherosclerotic disease are possible reasons for vascular sequels particularly those leading to neurological dysfunction. Immediate, early and late cognitive decline is a known- and well-defined outcome of CABG. Whereas a lot of data was collected through the last years regarding to neuropsychological dysfunction after CABG, nevertheless etiology and mechanisms of this phenomenon remain unresolved and they are probably multifactorial. Meticulously preoperative assessment of those patients with a potential risk of adverse neurocognitive outcomes can help clinicians to select the mode of revascularization and to better counsel patients about the risks and benefits of surgery versus more conservative kinds of treatment.

Sexual dysfunction in Parkinson's disease

Sexual dysfunction is common in Parkinson's disease (PD). We investigated the premorbid and present sexual functioning of 75 people with PD (32 women and 43 men). Women reported difficulties with arousal (87.5%), with reaching orgasm (75.0%), with low sexual desire (46.9%), and wih sexual dissatisfaction (37.5%). Men reported erectile dysfunction (68.4%), sexual dissatisfaction (65.1%), premature ejaculation (40.6%), and difficulties reaching orgasm (39.5%). Premorbid sexual dysfunction may contribute to cessation of sexual activity during the course of the disease (among 23.3% men and 21.9% women). Associated illnesses, use of medications, and advanced stage of PD contributed to sexual dysfunction.