Subthalamic deep brain stimulation induces finely-tuned gamma oscillations in the absence of levodopa.

Finely-tuned gamma (FTG) oscillations can be recorded from cortex or the subthalamic nucleus (STN) in patients with Parkinson's disease (PD) on dopaminergic medication, and have been associated with dyskinesias. When recorded during deep brain stimulation (DBS) on medication the FTG is entrained to half the stimulation frequency. We investigated whether these characteristics are shared off medication by recording local field potentials (LFP) from the STN from externalised DBS leads in 14 PD patients after overnight withdrawal of medication. FTG was induced de-novo by DBS in the absence of dyskinesias in a third of our cohort. The FTG could outlast stimulation or arise only after DBS ceased. FTG frequencies decreased during and across consecutive DBS blocks, but did not shift with changing stimulation frequency off medication. Together with the sustained after-effects this argues against simple entrainment by DBS in the off medication state. We also found significant coherence between STN-LFP and electroencephalogram (EEG) signals at FTG frequencies. We conclude that FTG is a network phenomenon that behaves differently in the off medication state, when it is neither associated with dyskinesias nor susceptible to entrainment.

Local field potential activity dynamics in response to deep brain stimulation of the subthalamic nucleus in Parkinson's disease.

Local field potentials (LFPs) may afford insight into the mechanisms of action of deep brain stimulation (DBS) and potential feedback signals for adaptive DBS. In Parkinson's disease (PD) DBS of the subthalamic nucleus (STN) suppresses spontaneous activity in the beta band and drives evoked resonant neural activity (ERNA). Here, we investigate how STN LFP activities change over time following the onset and offset of DBS. To this end we recorded LFPs from the STN in 14 PD patients during long (mean: 181.2 s) and short (14.2 s) blocks of continuous stimulation at 130 Hz. LFP activities were evaluated in the temporal and spectral domains. During long stimulation blocks, the frequency and amplitude of the ERNA decreased before reaching a steady state after ~70 s. Maximal ERNA amplitudes diminished over repeated stimulation blocks. Upon DBS cessation, the ERNA was revealed as an under-damped oscillation, and was more marked and lasted longer after short duration stimulation blocks. In contrast, activity in the beta band suppressed within 0.5 s of continuous DBS onset and drifted less over time. Spontaneous activity was also suppressed in the low gamma band, suggesting that the effects of high frequency stimulation on spontaneous oscillations may not be selective for pathological beta activity. High frequency oscillations were present in only six STN recordings before stimulation onset and their frequency was depressed by stimulation. The different dynamics of the ERNA and beta activity with stimulation imply different DBS mechanisms and may impact how these activities may be used in adaptive feedback.

Cortical structural involvement and cognitive dysfunction in early Parkinson's disease.

Magnetic resonance imaging (MRI) studies in early Parkinson's disease (PD) have shown promise in the detection of disease-related brain changes in the white and deep grey matter. We set out to establish whether intrinsic cortical involvement in early PD can be detected with quantitative MRI. We collected a rich, multi-modal dataset, including diffusion MRI, T1 relaxometry and cortical morphometry, in 20 patients with early PD (disease duration, 1.9 ± 0.97 years, Hoehn & Yahr 1-2) and in 19 matched controls. The cortex was reconstructed using FreeSurfer. Data analysis employed linked independent component analysis (ICA), a novel data-driven technique that allows for data fusion and extraction of multi-modal components before further analysis. For comparison, we performed standard uni-modal analysis with a general linear model (GLM). Linked ICA detected multi-modal cortical changes in early PD (p = 0.015). These comprised fractional anisotropy reduction in dorsolateral prefrontal, cingulate and premotor cortex and the superior parietal lobule, mean diffusivity increase in the mesolimbic, somatosensory and superior parietal cortex, sparse diffusivity decrease in lateral parietal and right prefrontal cortex, and sparse changes to the cortex area. In PD, the amount of cortical dysintegrity correlated with diminished cognitive performance. Importantly, uni-modal analysis detected no significant group difference on any imaging modality. We detected microstructural cortical pathology in early PD using a data-driven, multi-modal approach. This pathology is correlated with diminished cognitive performance. Our results indicate that early degenerative processes leave an MRI signature in the cortex of patients with early PD. The cortical imaging findings are behaviourally meaningful and provide a link between cognitive status and microstructural cortical pathology in patients with early PD.

Venoplasty and stenting of a jugular foramen meningioma.

The authors describe a novel approach to relieving major venous sinus stenosis at the level of the jugular bulb caused by a petrous meningioma. A balloon-expandable renovascular stent was deployed via a jugular approach to restore venous outflow and thus reduce visual and vestibulocochlear symptoms. Endovascular balloon venoplasty and stenting may assess and restore cranial outflow in veins compressed by soft tumours in anatomical locations challenging to surgical resection, even in the absence of intracranial hypertension.

Oral Verruciform Xanthoma of lateral border of tongue - a sheep in wolf's clothing.

Oral Verruciform Xanthoma (OVX) is an uncommon benign lesion of the oral cavity. Most authors consider it to develop as a response to chronic local irritation. It usually presents as a pink, yellow or greyish flat mass occurring on the gingiva, alveolar ridge or hard palate. This paper reports to you the management of a case of Oral Verruciform Xanthoma occurring on the latero-ventral border of the tongue in a young male patient, which is a rare location for this lesion. It goes on to discuss the etiopathogenesis and clinical features of this rare lesion and emphasizes the importance of having a broad knowledge of oral pathologic lesions especially for lesions that resemble malignant or pre-malignant pathologies in the oral cavity.

Transcranial magnetic stimulation: from neurophysiology to pharmacology, molecular biology and genomics.

Noninvasive plasticity paradigms, both physiologically induced and artificially induced, have come into their own in the study of the effects of genetic variation on human cortical plasticity. These techniques have the singular advantage that they enable one to study the effects of genetic variation in its natural and most relevant context, that of the awake intact human cortex, in both health and disease. This review aims to introduce the currently available artificially induced plasticity paradigms, their putative mechanisms-both in the traditional language of the systems neurophysiologist and in the evolving (and perhaps more relevant for the purposes of stimulation genomics) reinterpretation in terms of molecular neurochemistry, and highlights recent studies employing these techniques by way of examples of applications.

C reactive protein and immunoglobulin G in synovial fluid and serum in joint disease.

C reactive protein (CRP) and immunoglobulin G (IgG) were measured in synovial fluid and serum of 72 patients (29 with rheumatoid arthritis (RA), 17 with osteoarthritis, 11 with crystal synovitis, seven with undifferentiated arthritis, and eight with seronegative arthritis). The synovial fluid:serum (SF:S) ratios were compared with those calculated from the SF:S ratios of transferrin, caeruloplasmin, and alpha 2 macroglobulin, using the binomial test within groups and the Mann-Whitney test between groups. In RA synovial fluid CRP concentrations were lower than expected and IgG concentrations higher than expected. In osteoarthritis CRP concentrations were higher than expected. In seronegative arthritis IgG concentrations were raised. The ratio of CRP:IgG was depressed in RA. These findings are consistent with a role for CRP in the inflammatory process of RA, while the CRP:IgG ratio may be of value in the differential diagnosis of joint disease.