Petroclival meningiomas: radiological features essential for surgeons.

Petroclival meningiomas (PCMs) have always been a challenge for surgeons because of their difficult anatomical location. The role of radiology in providing precise indications regarding the tumour site and aggressiveness plays a major part in guiding the subsequent therapeutic process. The purpose of this review is to provide a set of the main radiological features helpful in the management of PCMs towards the most correct therapeutic approach. We aim to offer a radiological overview to allow the patient to be directed to surgery with the least possible risk of complications.

The spectral features of EEG responses to transcranial magnetic stimulation of the primary motor cortex depend on the amplitude of the motor evoked potentials.

Transcranial magnetic stimulation (TMS) of the primary motor cortex (M1) can excite both cortico-cortical and cortico-spinal axons resulting in TMS-evoked potentials (TEPs) and motor-evoked potentials (MEPs), respectively. Despite this remarkable difference with other cortical areas, the influence of motor output and its amplitude on TEPs is largely unknown. Here we studied TEPs resulting from M1 stimulation and assessed whether their waveform and spectral features depend on the MEP amplitude. To this aim, we performed two separate experiments. In experiment 1, single-pulse TMS was applied at the same supra-threshold intensity on primary motor, prefrontal, premotor and parietal cortices and the corresponding TEPs were compared by means of local mean field power and time-frequency spectral analysis. In experiment 2 we stimulated M1 at resting motor threshold in order to elicit MEPs characterized by a wide range of amplitudes. TEPs computed from high-MEP and low-MEP trials were then compared using the same methods applied in experiment 1. In line with previous studies, TMS of M1 produced larger TEPs compared to other cortical stimulations. Notably, we found that only TEPs produced by M1 stimulation were accompanied by a late event-related desynchronization (ERD-peaking at ~300 ms after TMS), whose magnitude was strongly dependent on the amplitude of MEPs. Overall, these results suggest that M1 produces peculiar responses to TMS possibly reflecting specific anatomo-functional properties, such as the re-entry of proprioceptive feedback associated with target muscle activation.

Aspergillus meningitis: a rare clinical manifestation of central nervous system aspergillosis. Case report and review of 92 cases.

OBJECTIVES: To describe the pathogenesis, clinical presentation, cerebrospinal fluid findings and outcome of Aspergillus meningitis, meningoencephalitis and arachnoiditis. METHODS: A case of Aspergillus meningitis is described. A comprehensive review of the English-language literature was conducted to identify all reported cases of Aspergillus meningitis described between January 1973 and December 2011. RESULTS: Ninety-three cases (including the one described herein) of Aspergillus meningitis were identified. Fifty-two (55.9%) were in individuals without any predisposing factor or known causes of immunosuppression. Acute and chronic meningitis was diagnosed in 65.6% of patients and meningoencephalitis in 24.7% of them with the remaining presenting with spinal arachnoiditis and ventriculitis. Cerebrospinal fluid cultures for Aspergillus spp. were positive in about 31% of cases and the galactomannan antigen test in 87%. Diagnosis during life was achieved in 52 patients (55.9%) with a case fatality rate of 50%. The overall case fatality rate was 72.1%. CONCLUSIONS: Aspergillus meningitis may occur in both immunocompetent and immunocompromised patients and run an acute or chronic course. The findings of this systematic review extend the information on this life-threatening infection and could assist physicians in achieving an improved outcome.

Interobserver agreement in the interpretation of computed tomography in acute pulmonary embolism.

Multidetector computed tomography (MDCT) is one of the best diagnostic tools for the diagnosis of pulmonary embolism (PE). However, differences in MDCT interpretation, depending on the operator personal expertise, is an important factor that could interfere with the right diagnosis and, consequently, with the more adequate and well-timed therapy. The aim of the present study was to evaluate the interobserver agreement in the interpretation of MDCT for the diagnosis of acute PE. On a blind basis, 4 radiologists with different expertise in CT interpretation evaluated 46 different MDCT executed for acute PE. They had to verify the presence or absence of PE and, in the positive case, localize (right-left) and quantify (massive, segmentarian or subsegmentarian) it. The interobserver concordance was expressed using the Cohen K statistic. The mean concordance between the 4 operators was high (0.82; range, 0.68-0.95). Ruling out the massive PE cases, the mean concordance over the other cases was only moderate (0.47; range, 0.16-0.84). We found a very good interobserver agreement in MDCT evaluation for the diagnosis of massive PE, whereas we observed a lower concordance in regard to segmentarian and subsegmentarian PE. In the case of negative or nonmassive PE diagnosis, a second evaluation of the CT performed by an expert CT radiologist would probably be effective to decrease the CT evaluation error.

Natural frequencies of human corticothalamic circuits.

The frequency tuning of a system can be directly determined by perturbing it and by observing the rate of the ensuing oscillations, the so called natural frequency. This approach is used, for example, in physics, in geology, and also when one tunes a musical instrument. In the present study, we employ transcranial magnetic stimulation (TMS) to directly perturb a set of selected corticothalamic modules (Brodmann areas 19, 7, and 6) and high-density electroencephalogram to measure their natural frequency. TMS consistently evoked dominant alpha-band oscillations (8-12 Hz) in the occipital cortex, beta-band oscillations (13-20 Hz) in the parietal cortex, and fast beta/gamma-band oscillations (21-50 Hz) in the frontal cortex. Each cortical area tended to preserve its own natural frequency also when indirectly engaged by TMS through brain connections and when stimulated at different intensities, indicating that the observed oscillations reflect local physiological mechanisms. These findings were reproducible across individuals and represent the first direct characterization of the coarse electrophysiological properties of three associative areas of the human cerebral cortex. Most importantly, they indicate that, in healthy subjects, each corticothalamic module is normally tuned to oscillate at a characteristic rate. The natural frequency can be directly measured in virtually any area of the cerebral cortex and may represent a straightforward and flexible way to probe the state of human thalamocortical circuits at the patient's bedside.

Reversible posterior leukoencephalopathy syndrome in 2 HIV-infected patients receiving antiretroviral therapy.

We describe 2 human immunodeficiency virus-infected patients who developed hypertension and severe neurological abnormalities while receiving successful antiretroviral therapy. Neuroimaging findings were characteristic of reversible posterior leukoencephalopathy syndrome, a brain-capillary leak syndrome with hypertension and endothelial damage. We discuss the role of antiretroviral therapy-associated metabolic alterations in endothelial damage, hypertension, and reversible posterior leukoencephalopathy syndrome.