Correlation between hippocampal volume and excessive daytime sleepiness in obstructive sleep apnea syndrome.

BACKGROUND/AIM: The limbic system, specifically the hippocampus, plays a key role in controlling the sleep-wake cycle. Changes in these particular structures of the central nervous system have been suggested to be related to obstructive sleep apnea syndrome (OSAS). We hypothesized that reduced hippocampal volume is a risk factor for excessive daytime sleepiness (EDS) in OSAS. PATIENTS AND METHODS: Twenty-two patients with newly diagnosed OSAS and 20 healthy controls were included in the present study. Polysomnography was performed for each participant to determine the presence of OSAS. EDS was defined based on the Epworth sleepiness scale (ESS) score, and patients were grouped as sleepy or non-sleepy according to this score. The hippocampal volume was calculated by MR volumetry using a manual tracing technique. RESULTS: There was no significant difference between groups in demographic variables. The hippocampus was markedly smaller in the OSAS groups than in controls (p < 0.001 Hippocampal volume was negatively correlated with the ESS score (r = -0.631, p = 0.002). CONCLUSIONS: Our findings suggest that EDS is associated with reduced hippocampal volume in OSAS.

Solitary metastases and high-grade gliomas: radiological differentiation by morphometric analysis and perfusion-weighted MRI.

AIM: To evaluate the value of morphometric analysis and perfusion-weighted magnetic resonance imaging (MRI) in differentiating solitary metastases from high-grade gliomas. MATERIALS AND METHODS: Forty-eight tumours (22 high-grade gliomas and 26 solitary hemispheric metastases) were evaluated using conventional and perfusion-weighted MRI. T2-weighted, gradient-echo, echo-planar sequences were used for perfusion-weighted MRI. Relative cerebral blood volume (rCBV) ratios were calculated by dividing the rCBV of the intratumoural and peritumoural areas with the average CBV value of the normal white matter areas. Morphometric analysis was carried out by proportioning the area of peritumoural oedema to the mass area. Mann-Whitney U test and ROC curve analysis were applied for statistical analysis. P<0.05 was accepted as statistically significant. RESULTS: Mean rCBV ratios of intratumoural areas of high-grade gliomas and metastases were 5.02+/-2.47 and 4.62+/-2.46, respectively. No statistically significant difference was found (p=0.515). rCBV ratios of peritumoural oedema were 0.89+/-0.51 in high-grade gliomas and 0.31+/-0.12 in metastases. The difference was statistically significant (p<0.001). According to the results of morphometric analysis, a statistically significant difference was present between the two tumour types (p<0.001). CONCLUSION: Measuring the oedema: mass and rCBV ratios of the oedema surrounding the tumour prior to operation in solitary masses proved to be useful for differentiating metastases from high-grade gliomas.

Diffusion-weighted MR imaging of pleural fluid: differentiation of transudative vs exudative pleural effusions.

The aim of this study was to evaluate the ability of diffusion-weighted MRI in differentiating transudative from exudative pleural effusions. Fifty-seven patients with pleural effusion were studied. Diffusion-weighted imaging (DWI) was performed with an echo-planar imaging (EPI) sequence (b values 0, 1000 s/mm(2)) in 52 patients. The apparent diffusion coefficient (ADC) values were reconstructed from three different regions. Subsequently, thoracentesis was performed and the pleural fluid was analyzed. Laboratory results revealed 20 transudative and 32 exudative effusions. Transudates had a mean ADC value of 3.42+/-0.76 x 10(-3) mm(2)/s. Exudates had a mean ADC value of 3.18+/-1.82 x 10(-3) mm(2)/s. The optimum cutoff point for ADC values was 3.38 x 10(-3) mm(2)/s with a sensitivity of 90.6% and specificity of 85%. A significant negative correlation was seen between ADC values and pleural fluid protein, albumin concentrations and lactate dehydrogenase (LDH) measurements ( r=-0.69, -0.66, and -0.46, respectively; p<0.01). The positive predictive value, negative predictive value, and diagnostic accuracy of ADC values were determined to be 90.6, 85, and 88.5%, respectively. The application of diffusion gradients to analyze pleural fluid may be an alternative to the thoracentesis. Non-invasive characterization of a pleural effusion by means of DWI with single-shot EPI technique may obviate the need for thoracentesis with its associated patient morbidity.

Proton MRS in Behçet's disease with and without neurological findings.

Our aim was to investigate whether neurological impairment in Behçet's disease (BD) can be assessed by means of proton MRS and whether it can assist in prognosis. We used single-voxel MRS to measure metabolites in regions of normal-appearing pons, basal ganglia and periventricular white matter (PWM) in 32 patients with chronic BD patients with and without neurological deficits and 29 control subjects. Patients had significantly higher N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios in the basal ganglia than the controls. The Cho/Cr ratio in the PWM was also significantly higher in the patients. MRS enabled clear discrimination of patients and controls and also revealed spectral differences between non-neuro-Behçet's disease and neuro-Behçet's disease in the basal ganglia. MRS can be used to assess brain involvement in BD even if structural changes are absent.