Bilateral lesions of the basal ganglia and thalami (central grey matter)-pictorial review.

The basal ganglia and thalami are paired deep grey matter structures with extensive metabolic activity that renders them susceptible to injury by various diseases. Most pathological processes lead to bilateral lesions, which may be symmetric or asymmetric, frequently showing characteristic patterns on imaging studies. In this comprehensive pictorial review, the most common and/or typical genetic, acquired metabolic/toxic, infectious, inflammatory, vascular and neoplastic pathologies affecting the central grey matter are subdivided according to the preferential location of the lesions: in the basal ganglia, in the thalami or both. The characteristic imaging findings are described with emphasis on the differential diagnosis and clinical context.

Cerebral abscesses imaging: A practical approach.

Brain abscesses (BAs) are focal infections of the central nervous system (CNS) that start as a localised area of weakening of the brain parenchyma (cerebritis) and develops into a collection of pus surrounded by a capsule. Pyogenic (bacterial) BAs represent the majority of all BAs; in some cases, the diagnostic and therapeutic management can be challenging. Imaging has a primary role in differentiating BAs from other lesions. Conventional magnetic resonance imaging (cMRI) is essential for the identification of the lesion, its localisation and its morphological features. However, cMRI does not allow to reliably differentiate BAs from other intracranial mass lesions such as necrotic tumours. Advanced sequences, such as diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI) and proton MR spectroscopy (1H-MRS) are very useful in the differential diagnosis from other brain lesions, such as non-pyogenic abscesses or necrotic tumours, and provide essential information on structural, vascular and metabolic characteristics allowing greater neuroradiological confidence. The aim of this pictorial review is to provide a practical approach showing the added value of more advanced MRI techniques in their diagnostic management.

Magnetic Resonance Imaging Derived Biomarkers of IDH Mutation Status and Overall Survival in Grade III Astrocytomas.

The evaluation of the isocitrate dehydrogenase (IDH) mutation status in the glioma decision-making process has diagnostic, prognostic and therapeutic implications. The aim of this study was to evaluate whether conventional magnetic resonance imaging (MRI) and apparent diffusion coefficient (ADC) can noninvasively predict the most common IDH mutational status (R132H) in GIII-astrocytomas and the overall survival (OS). Hence, twenty-two patients (9-F, 13-M) with a histological diagnosis of GIII-astrocytoma and evaluation of IDH-mutation status (12-wild type, 10-mutant) were retrospectively evaluated. Imaging studies were reviewed for the morphological feature and mean ADC values (ADCm). Statistics included a Fisher's exact test, Student's t-test, Spearman's Test and receiver operating characteristic analysis. A p ≤ 0.05 value was considered statistically significant for all the tests. A younger age and a frontal location were more likely related to mutational status. IDH-wild type (Wt) exhibited a slight enhancement (p = 0.039). The ADCm values in IDH-mutant (Mut) patients were higher than those of IDH-Wt patients (p < 0.0004). The value of ADC ≥ 0.99 × 10-3 mm2/s emerged as a "cut-off" to differentiate the mutation state. In the overall group, a positive relationship between the ADCm values and OS was detected (p = 0.003; r = 0.62). Adding quantitative measures of ADC values to conventional MR imaging could be used routinely as a noninvasive marker of specific molecular patterns.

Brain stones revisited-between a rock and a hard place.

OBJECTIVES AND METHODS: Large intracranial calcifications are occasionally encountered in routine computed tomography (CT) scans of the brain. These calcifications, also known as "brain stones", can be classified according to location and aetiology. Combining imaging findings with relevant clinical history and physical examination can help narrow down the differential diagnosis and may allow confident diagnosis in certain situations. RESULTS: This article provides a pictorial review illustrating various clinical entities resulting in brain stones. DISCUSSION: Based on location, brain stones can be classified as extra- or intra-axial. Extra-axial brain stones comprise tumours and exaggerated physiological calcifications. Intra-axial brain stones can further be classified according to aetiology, namely neoplastic, vascular, infectious, congenital and endocrine/metabolic. Imaging findings combined with essential clinical information can help in narrowing the differential diagnosis, determining disease state and evaluating effect of therapy. TEACHING POINTS: • Based on location, brain stones can be either extra- or intra-axial. • Extra-axial brain stones comprise tumours and exaggerated physiological calcifications. • Intra-axial aetiologies include neoplastic, vascular, infectious, congenital and endocrine/metabolic. • CT scan is the mainstay in identifying and characterising brain stones. • Certain MRI sequences (gradient echo T2* and susceptibility-weighted imaging) are considered adjunctive.

Diffusion tensor imaging provides an insight into the microstructure of meningiomas, high-grade gliomas, and peritumoral edema.

OBJECTIVE: Fractional anisotropy (FA) is a measure for the degree of microstructural organization. Several studies have used FA values to assess microstructural organization of brain tumors and peritumoral edema. The purpose of our study was to validate FA and apparent diffusion constant (ADC) values in the diagnosis of meningiomas versus high-grade glial tumors, with the focus on the ability of diffusion tensor imaging (DTI) to reveal tumor ultrastructure. Our hypothesis was that FA and ADC values significantly differ between high-grade gliomas and meningiomas, and in the peritumoral edema. METHODS: Diffusion tensor imaging values were obtained from 20 patients with meningiomas (21 tumors) and 15 patients with high-grade gliomas. Regions of interest were outlined in FA and ADC maps for solid-enhancing tumor tissue and peritumoral edema. Fractional anisotropy and ADC values were normalized by comparison to normal-appearing white matter (NAWM) in the contralateral hemisphere. Differences between meningiomas and high-grade gliomas were statistically analyzed. RESULTS: Meningiomas showed a significantly higher FA tumor/FA NAWM ratio (P = 0.0001) and lower ADC tumor/ADC NAWM ratio (P = 0.0008) compared to high-grade gliomas. On average, meningiomas also showed higher FA values in peritumoral edema than high-grade gliomas (P = 0.016). Apparent diffusion constant values of peritumoral edema for the 2 tumor groups did not differ significantly (P = 0.5). CONCLUSIONS: Diffusion tensor imaging can be used to reveal microstructural differences between meningiomas and high-grade gliomas and may contribute toward predicting the histopathology of intracranial tumors. We advocate that diffusion tensor imaging should be included in the standard imaging protocol for patients with intracranial tumors.

Cerebrotendinous xanthomatosis presenting with asymmetric parkinsonism: a case with I-123-FP-CIT SPECT imaging.

Cerebrotendinous xanthomatosis (CTX) is a rare inherited neurometabolic disease. Clinical symptoms are caused by increased deposition of cholestanol and cholesterol in various tissues. Progressive neurological symptoms are one of the principal manifestations. We report the case of a 44-year-old man who presented with asymmetric parkinsonism. In addition, there were mild bilateral pyramidal signs and a mild polyneuropathy. Brain MRI showed bilateral lesions in the dentate nucleus of the cerebellum and in the substantia nigra. Nuclear brain imaging using I-123-FP-CIT demonstrated an asymmetric reduced presynaptic dopaminergic function of the putamen and caudate nucleus, correlating well with his lateralized bradykinetic-rigid syndrome. CTX was diagnosed based on an increased plasma level of cholestanol, typical cerebellar brain lesions and the causative genetic mutation. CTX presenting with parkinsonism is considered rare and data on the neuroimaging of the dopaminergic deficit are limited.

Does intratympanic gadolinium injection predict efficacy of gentamicin partial chemolabyrinthectomy in Menière's disease patients?

Using actual diagnostic criteria, the diagnosis of certain Menière's disease remains impossible during life without histopathologic confirmation. Assessing the value of a diagnostic test is difficult due to the lack of a gold standard. Recent studies reported on the use of MRI after intratympanic gadolinium injection to demonstrate endolymphatic hydrops in vivo. We evaluate whether MRI after intratympanic gadolinium administration is useful for predicting the effect and outcome of intratympanic gentamicin therapy. The correlation between transtympanic electrocochleographic (TT-ECoG) results and hydrops grade on MRI images is also investigated. Twelve definite Menière's disease patients with incapacitating vertigo attacks, not responding to drug and behavioral treatment, were selected for partial chemolabyrinthectomy with intratympanic gentamicin. All patients underwent transtympanic electrocochleography followed by surgical middle ear inspection, partial chemolabyrinthectomy (gentamicin solution 40 mg/ml applied during 60 min) and intratympanic gadolinium injection with clear exposure of the round window membrane. The MR images were reviewed and a hydrops grade was assigned. Correlation between the hydrops grade and the electrocochleographic data was assessed. Only 5 of 12 patients showed gadolinium enhancement in the inner ear. However, 6 of the 7 patients that did not show postoperative intracochlear or intralabyrinthine gadolinium distribution did report the clinical improvement after intratympanic gentamicin therapy. Hydrops grade correlated with the result of transtympanic electrocochleography in four of five cases that showed gadolinium enhancement. We conclude that the use of intratympanic gadolinium has no added value in predicting the clinical outcome of intratympanic gentamicin application. However, based on these data, a correlation between the result of TT-ECoG and hydrops grading on MRI images can be suggested.