Induced neural phase precession through exogeneous electric fields.

The gradual shifting of preferred neural spiking relative to local field potentials (LFPs), known as phase precession, plays a prominent role in neural coding. Correlations between the phase precession and behavior have been observed throughout various brain regions. As such, phase precession is suggested to be a global neural mechanism that promotes local neuroplasticity. However, causal evidence and neuroplastic mechanisms of phase precession are lacking so far. Here we show a causal link between LFP dynamics and phase precession. In three experiments, we modulated LFPs in humans, a non-human primate, and computational models using alternating current stimulation. We show that continuous stimulation of motor cortex oscillations in humans lead to a gradual phase shift of maximal corticospinal excitability by ~90°. Further, exogenous alternating current stimulation induced phase precession in a subset of entrained neurons (~30%) in the non-human primate. Multiscale modeling of realistic neural circuits suggests that alternating current stimulation-induced phase precession is driven by NMDA-mediated synaptic plasticity. Altogether, the three experiments provide mechanistic and causal evidence for phase precession as a global neocortical process. Alternating current-induced phase precession and consequently synaptic plasticity is crucial for the development of novel therapeutic neuromodulation methods.

Impedance Plethysmography as an Alternative Measure of Reactive Hyperemia.

Peripheral vascular flow in response to induced reactive hyperemia of the radial artery is used as a benchmark for non-invasive assessment of the endothelial function. As an alternative to standard modalities, this study investigates the suitability of impedance plethysmography to estimate peripheral vascular flow variations associated with the reactive hyperemia process. Results indicate a consistent variation of bio-impedance during the reactive hyperemia process at higher measurement frequencies and these variations are compatible with a standard tissue impedance model. Further, calculated features of bioimpedance has shown the capability of differentiating healthy and diabetic groups which is useful in estimating the endothelial dysfunction.

Comparison of risk factors, severity and outcome between lacunar and non-lacunar stroke in a tertiary care center in Sri Lanka: a descriptive study.

This study compares demography, risk factors and outcome of lacunar (LAC) and non-lacunar (non-LAC) strokes from the prospective hospital based stroke registry at Colombo South Teaching Hospital from 1st March 2012 to 30th June 2013. Data on admission, discharge and at 28 days after discharge were analysed. There were 229 ischaemic stroke (IS) patients. Average age was 65.7 years (SD 12.2, range 34-94) and 116 (50.7%) were males. LAC (n=130, 56.8%) were common than non-LAC (n=99, 43.2%). There were 75 (64.7%) males and 55 (48.7%) females in the LAC group (adjusted OR 2.1, 95% CI 1.08-4.29). Atrial fibrillation was less frequent among LAC stroke (OR 0.3, 95% CI 0.09-0.99). Hypertension, diabetes, smoking, dyslipidaemia did not differ in the two groups. Lower NIHSS (5.34 Vs 6.6, p= 0.053), higher GCS (14.7 Vs 13.3, p=0.001) were seen in LAC. Disability (MRS, Barthel index) on discharge, at 28 days and mortality during hospital stay and within 28 days was lower in the LAC group (p <0.001).

Minimal access is not maximal safety: pelviureteric necrosis following percutaneous chemical lumbar sympathectomy.

Lumbar sympathectomy remains popular in the treatment of a variety of painful and circulatory conditions of the lower extremities. Although percutaneous chemical lumbar sympathectomy (PCLS) under radiographic guidance is minimally invasive and has decreased the need for open surgical sympathectomy, inadvertent damage to neighbouring structures is a matter for concern. We report the case of a 38-year-old man with thromboangiitis obliterans who had PCLS under radiographic guidance for relief of ischaemic rest pain that was complicated by necrotic disruption of the left pelviureteric region. The kidney was salvaged with an ureterocalycostomy and he remains well 4 years later. Such complications point to imprecise and unpredictable spread of the injected chemical too far beyond the needle tip. It is possible that such complications are often under reported and, therefore, not taken into consideration during informed consent. Precise neurolysis with laser and radiofrequency may be a safer alternative.

Trans rectal ultra sound guided prostate biopsies: a single centre experience in Sri Lanka.

BACKGROUND: Trans rectal ultrasound guided prostate biopsy (TRUS) was introduced to Sri Lanka in 2002. OBJECTIVES: 1. To study clinicopathological features of males subjected to TRUS biopsy 2. To compare estimation of tumour burden by two methods in carcinoma prostate (CaP). METHODS: 749 symptomatic males subjected to TRUS biopsy over 64 months at a single centre. Information was retrieved from case records. Tumour burden in CaP was calculated as: 1. Calculated tumour burden (CTB)--total percentage tumour in each core/total number of cores 2. Percentage positive biopsy cores (PPBC)--number of positive cores/total number of cores X 100. SPSS 15.0, student's t test and Spearman's rank correlation coefficients were used for statistical analysis. RESULTS: 35.2% had CaP, microacinar in type. 34.88% were poorly differentiated. CaP was frequent among older patients (P<0.00001). The prostate volume in CaP was significantly lower than in the benign group (P<0.05). Prostate specific antigen (PSA) level was significantly higher in CaP (P<0.00001). A 99.6% sensitivity and 4.7% specificity was observed at PSA of 4 ng/ml for detecting CaP. Specificity was 98% at 25.5 ng/ml, with a sensitivity of 44.4%. CTB and PPBC had similar correlations with biochemical/histological parameters of CaP and were strongly correlated (0.786). INTERPRETATION: Males with CaP were older, had higher PSA levels and smaller prostates. A cut off level of PSA >4 ng/ml could be used for directing symptomatic patients for TRUS biopsy to detect CaP, keeping in mind that specificity is 98% only at 25.5 ng/ml. Both CTB and PPBC could be used to calculate tumour burden in TRUS with CaP.

Erectile and ejaculatory failure after transurethral prostatectomy.

OBJECTIVES: To evaluate the clinical incidence of sexual dysfunction after transurethral resection of the prostate (TURP) and to identify risk factors. SETTING: Havering Hospitals NHS Trust, Essex, UK. PATIENTS AND METHODS: 253 patients who underwent TURP were assessed using a standard proforma regarding pre- and post-operative erectile and ejaculatory functions. The patients who developed post-operative erectile failure were compared with the unaffected group. RESULTS: 126 patients completed the study; 22 were pre-operatively impotent and remained so post-operatively. Of 104 patients who were sexually active 18 developed post-operative erectile impairment. Five patients (4.8%) had total erectile failure. Only 7% of patients retained ejaculation after the operation. Significant risk factors in the patients with post-operative erectile failure, were presentation with acute retention and development of profuse primary hemorrhage. CONCLUSION: The study reaffirmed that there is a low but significant clinical incidence (4.8%) of erectile failure after TURP which is associated with certain risk factors. Ejaculatory failure was higher in incidence but carried a lower clinical significance.

The value of percutaneous nephrostomy; Sri Lankan experience.

OBJECTIVE: To identify the most useful indications for image-guided percutaneous nephrostomy (PCN). DESIGN: Retrospective analysis of immediate outcome of the procedure in 46 patients. SETTING: Department of Radiology, The National Hospital of Sri Lanka, Colombo. PATIENTS: 46 patients on whom 59 PCNs done between June 1995 and August 1996. RESULTS: 57 PCNs were successful and 2 failed. Clinical improvement was observed in all patients with acute obstructive renal failure, pyorenephrosis and fistulae. Benefits were minimal in patients with chronic obstruction and none with terminal malignancy.