MRI Findings in Acute Tonsillar Infections

BACKGROUND AND PURPOSE

Previous literature is vague on the prevalence and exact nature of abscesses in tonsillar infections, ranging from intratonsillar and peritonsillar collections to deep extension involving the parapharyngeal and retropharyngeal spaces. MR imaging has excellent diagnostic accuracy in detecting neck infections and can potentially clarify this issue. We sought to characterize the spectrum of MR imaging findings regarding tonsillar infections.

MATERIALS AND METHODS

We conducted a retrospective cohort study of emergency neck MR imaging scans of patients with tonsillar infections. Imaging data were assessed in terms of signs of infection and the location of abscesses and were compared with clinical findings, final diagnoses, and surgical findings as reference standards.

RESULTS

The study included 132 patients with tonsillar infection. Of these, 110 patients (83%) had ≥1 abscess (99 unilateral, 11 bilateral; average volume, 3.2 mL). Most abscesses were peritonsillar, and we found no evidence of intratonsillar abscess. Imaging showed evidence of parapharyngeal and retropharyngeal extension in 36% and 10% of patients, respectively. MR imaging had a high positive predictive value for both abscesses (0.98) and deep extension (0.86). Patients with large abscesses and widespread edema patterns had a more severe course of illness.

CONCLUSIONS

Emergency neck MR imaging can accurately describe the extent and nature of abscess formation in tonsillar infections.

Improving the performance of the signal space separation method by comprehensive spatial sampling

Biomagnetic instruments usually employ sensors with approximately radial normal vectors arranged on a near-spherical surface. The multipole expansion employed in the recently introduced signal space separation method (SSS) reveals limitations in this traditional sensor array design. Specifically, we show that the excessive symmetry of the sensor array impedes separation of multipole components arising from inside and outside of the array. This motivates consideration of novel instrument designs that would sample the field in a more comprehensive way. We evaluated several simulated sensor arrays that employ vector sensors in one or two layers, giving information on multiple field components and the radial dependence of the field. Our results indicate that this kind of sensor array design could significantly improve SSS performance, leading to enhanced shielding against external interference and reduced noise after signal reconstruction. The best two-layer array evaluated here attains a shielding factor of nearly 1000 or 60 dB with about 400 sensors. Due to limited spatial coverage, a traditional reference array geometry does not give the same level of improvement. In addition to improved software shielding, enhanced detection of different multipole components increases the information obtained about the magnetic field, which has fundamental importance.

Effects of sensor calibration, balancing and parametrization on the signal space separation method

Signal space separation (SSS) is a novel method for processing multichannel biomagnetic data. It is useful for a variety of applications including interference suppression, movement compensation and conversion of measurements between sensor arrays. The performance of SSS has been examined mainly on a 306-channel whole-head magnetoencephalography system. To facilitate the adaptation of the method to other biomagnetometer systems, the effect of various properties of the sensor array on its performance needs to be studied. To this end, we examined the effects of gradiometer imbalance, sensor calibration errors and erroneous sensor geometry information on SSS using simulations. The results indicate that depending on the application, gradiometer balance on the level of 0.1% to 0.5% may be needed for satisfactory SSS performance. For wire-wound gradiometers, this requires very careful attention in manufacturing. Errors in calibration coefficients and geometry information were found to have less significance.

Serum p97 levels as an aid to identifying Alzheimer's disease

Background: The application of formal clinical diagnostic criteria for the identification of Alzheimer's Disease (AD) has improved diagnostic sensitivity. However, there remains a need for non-invasive biological markers and laboratory tests, which can facilitate case identification, and the assessment of treatment response. The p97 protein is a secreted protein specifically expressed by amyloid plaque associated reactive microglia that may have AD diagnostic ability. Methods: A quantitative radioimmunoassay was developed to measure serum p97. This study, under a double blind protocol, evaluated the utility of serum p97 as diagnostic test for AD. All subjects were referred to the UBC Clinic for Alzheimer's Disease and Related Disorders (CADRD) for clinical assessment of dementia. A serum p97 sample was obtained at the time of assessment but diagnosis of disease was determined independently of p97 examination. Results: "Possible" and "probable" AD cases (n = 41) and cognitively normal controls (n = 64) showed a highly significant difference in mean p97 concentration (41 vs. 20 ng/ml, p<0.001). There was some overlap in p97 distributions between AD cases and control subjects. The area under the curve (AUC) for the receiver operator curve (ROC) was 0.812. Conclusions: These results further support the specificity of high serum p97 levels in AD and its potential utility as a biological marker in AD. The reproducible elevation of serum p97 in AD underlines the need to further determine its role as a biological marker and diagnostic adjunct for AD.

Four fatal cases of nephropathia epidemica

Four serologically confirmed fatal cases of nephropathia epidemica (NE), the mild form of hemorrhagic fever with renal syndrome (HFRS) are described. All the patients had disseminated intravascular coagulation. Autopsies revealed hemorrhage and necrotic areas of their pituitary glands, myocarditis, venous congestion and hemorrhage of the kidneys as well as pulmonary edema and hemorrhage of the lungs in all patients. This report provides new evidence that NE can be a fatal disease.

Esophagitis and findings of long-term esophageal pH recording in children with repeated lower respiratory tract symptoms

Esophagoscopy was performed on 116 children with recurrent lower respiratory tract symptoms; esophagitis of various degrees was detected in 45% of the cases. The presence of verified esophagitis correlated with endoscopic findings of bile-stained gastric contents, suggesting a role of bile reflux in the pathogenesis. Esophageal pH recordings covering an 18-24-h period were performed on 22 patients with esophagitis and 19 patients without esophagitis. Gastroesophageal reflux (GER) during the sleeping period was detected in 95% of children with esophagitis, as compared to 42% in children with no esophagitis (p less than 0.001). The percentage of time with esophageal pH below 4 of the total registration time was significantly greater (p less than 0.05) in children with esophagitis (9.5%) than in those with no esophagitis (4.0%)--the difference being due to a greater share of nocturnal GER of the recording time. These criteria could be applied to a search for clinically significant GER in children with recurrent lower respiratory tract symptoms and to select patients for esophagoscopy.