Evaluation of MRI criteria (1.5T) for the diagnosis of hippocampal sclerosis in healthy subjects

Prevalence of incidental meningiomas and gliomas on MRI: a meta-analysis and meta-regression analysis

BACKGROUND

The chance of incidentally detecting brain tumors is increasing as the utilization of magnetic resonance imaging (MRI) becomes more prevalent. In this background, knowledge is accumulating in relation to the prediction of their clinical sequence. However, their prevalence-especially the prevalence of glioma-has not been adequately investigated according to age, sex, and region.

METHOD

We systematically reviewed the articles according to the PRISMA statement and calculated the prevalence of meningiomas and diffuse gliomas in adults using a generalized linear mixed model. Specifically, the differences related to age, sex, and region were investigated.

RESULTS

The pooled prevalence of incidental meningiomas in MRI studies was 0.52% (95% confidence interval (CI) [0.34-0.78]) in 37,697 individuals from 36 studies. A meta-regression analysis showed that the prevalence was significantly higher in elderly individuals, women, and individuals outside Asia; this remained statistically significant in the multivariate meta-regression analysis. The prevalence reached to 3% at 90 years of age. In contrast, the prevalence of gliomas in 30,918 individuals from 18 studies was 0.064% (95%CI [0.040 - 0.104]). The meta-regression analysis did not show a significant relationship between the prevalence and age, male sex, or region. The prevalence of histologically confirmed glioma was 0.026% (95%CI [0.013-0.052]).

CONCLUSIONS

Most of meningiomas, especially those in elderlies, remained asymptomatic, and their prevalence increased with age. However, the prevalence of incidental gliomas was much lower and did not increase with age. The number of gliomas that developed and the number that reached a symptomatic stage appeared to be balanced.

Deep learning-based diagnosis of temporal lobe epilepsy associated with hippocampal sclerosis: An MRI study

PURPOSE

The currently available indicators-sensitivity and specificity of expert radiological evaluation of MRIs-to identify mesial temporal lobe epilepsy (MTLE) associated with hippocampal sclerosis (HS) are deficient, as they cannot be easily assessed. We developed and investigated the use of a novel convolutional neural network trained on preoperative MRIs to aid diagnosis of these conditions.

SUBJECTS AND METHODS

We enrolled 141 individuals: 85 with clinically diagnosed mesial temporal lobe epilepsy (MTLE) and hippocampal sclerosis International League Against Epilepsy (HS ILAE) type 1 who had undergone anterior temporal lobe hippocampectomy were assigned to the MTLE-HS group, and 56 epilepsy clinic outpatients diagnosed as nonepileptic were assigned to the normal group. We fine-tuned a modified CNN (mCNN) to classify the fully connected layers of ImageNet-pretrained VGG16 network models into the MTLE-HS and control groups. MTLE-HS was diagnosed using MRI both by the fine-tuned mCNN and epilepsy specialists. Their performances were compared.

RESULTS

The fine-tuned mCNN achieved excellent diagnostic performance, including 91.1% [85%, 96%] mean sensitivity and 83.5% [75%, 91%] mean specificity. The area under the resulting receiver operating characteristic curve was 0.94 [0.90, 0.98] (DeLong's method). Expert interpretation of the same image data achieved a mean sensitivity of 73.1% [65%, 82%] and specificity of 66.3% [50%, 82%]. These confidence intervals were located entirely under the receiver operating characteristic curve of the fine-tuned mCNN.

CONCLUSIONS

Deep learning-based diagnosis of MTLE-HS from preoperative MR images using our fine-tuned mCNN achieved a performance superior to the visual interpretation by epilepsy specialists. Our model could serve as a useful preoperative diagnostic tool for ascertaining hippocampal atrophy in patients with MTLE.

A minority of patients with functional seizures have abnormalities on neuroimaging

OBJECTIVE

Functional seizures often are managed incorrectly as a diagnosis of exclusion. However, a significant minority of patients with functional seizures may have abnormalities on neuroimaging that typically are associated with epilepsy, leading to diagnostic confusion. We evaluated the rate of epilepsy-associated findings on MRI, FDG-PET, and CT in patients with functional seizures.

METHODS

We studied radiologists' reports from neuroimages at our comprehensive epilepsy center from a consecutive series of patients diagnosed with functional seizures without comorbid epilepsy from 2006 to 2019. We summarized the MRI, FDG-PET, and CT results as follows: within normal limits, incidental findings, unrelated findings, non-specific abnormalities, post-operative study, epilepsy risk factors (ERF), borderline epilepsy-associated findings (EAF), and definitive EAF.

RESULTS

Of the 256 MRIs, 23% demonstrated ERF (5%), borderline EAF (8%), or definitive EAF (10%). The most common EAF was hippocampal sclerosis, with the majority of borderline EAF comprising hippocampal atrophy without T2 hyperintensity or vice versa. Of the 87 FDG-PETs, 26% demonstrated borderline EAF (17%) or definitive EAF (8%). Epilepsy-associated findings primarily included focal hypometabolism, especially of the temporal lobes, with borderline findings including subtle or questionable hypometabolism. Of the 51 CTs, only 2% had definitive EAF.

SIGNIFICANCE

This large case series provides further evidence that, while uncommon, EAF are seen in patients with functional seizures. A significant portion of these abnormal findings are borderline. The moderately high rate of these abnormalities may represent framing bias from the indication of the study being "seizures," the relative subtlety of EAF, or effects of antiseizure medications.

Potentially serious incidental findings on brain and body magnetic resonance imaging of apparently asymptomatic adults: systematic review and meta-analysis

OBJECTIVES

To determine prevalence and types of potentially serious incidental findings on magnetic resonance imaging (MRI) in apparently asymptomatic adults, describe factors associated with potentially serious incidental findings, and summarise information on follow-up and final diagnoses.

DESIGN

Systematic review and meta-analyses.

DATA SOURCES

Citation searches of relevant articles and authors' files in Medline and Embase (from inception to 25 April 2017).

REVIEW METHODS

Eligible studies included prevalence and types of incidental findings detected among apparently asymptomatic adults undergoing MRI of the brain, thorax, abdomen, or brain and body. Data on study population and methods, prevalence and types of incidental findings, and final diagnoses were extracted. Pooled prevalence was estimated by random effects meta-analysis, and heterogeneity by τ2 statistics.

MAIN OUTCOME MEASURES

Prevalence of potentially serious incidental findings on MRI of the brain, thorax, abdomen, and brain and body.

RESULTS

Of 5905 retrieved studies, 32 (0.5%) met the inclusion criteria (n=27 643 participants). Pooled prevalence of potentially serious incidental findings was 3.9% (95% confidence interval 0.4% to 27.1%) on brain and body MRI, 1.4% (1.0% to 2.1%) on brain MRI, 1.3% (0.2% to 8.1%) on thoracic MRI, and 1.9% (0.3% to 12.0%) on abdominal MRI. Pooled prevalence rose after including incidental findings of uncertain potential seriousness (12.8% (3.9% to 34.3%), 1.7% (1.1% to 2.6%), 3.0% (0.8% to 11.3%), and 4.5% (1.5% to 12.9%), respectively). There was generally substantial heterogeneity among included studies. About half the potentially serious incidental findings were suspected malignancies (brain, 0.6% (95% confidence interval 0.4% to 0.9%); thorax, 0.6% (0.1% to 3.1%); abdomen, 1.3% (0.2% to 9.3%); brain and body, 2.3% (0.3% to 15.4%)). There were few informative data on potential sources of between-study variation or factors associated with potentially serious incidental findings. Limited data suggested that relatively few potentially serious incidental findings had serious final diagnoses (48/234, 20.5%).

CONCLUSIONS

A substantial proportion of apparently asymptomatic adults will have potentially serious incidental findings on MRI, but little is known of their health consequences. Systematic, long term follow-up studies are needed to better inform on these consequences and the implications for policies on feedback of potentially serious incidental findings.

SYSTEMATIC REVIEW REGISTRATION

Prospero CRD42016029472.

Idiothetic signal processing and spatial orientation in patients with unilateral hippocampal sclerosis

The role of the hippocampus in spatial navigation and the presence of vestibular-responsive neurons in limbic areas are well-established from animal experiments. However, hippocampal spatial processing in humans is not fully understood. Here, we employed real whole body and head-on-trunk rotations to investigate how vestibular signals, either alone or in combination with neck-proprioceptive stimulation, shape the spatial frame of reference in patients with unilateral hippocampal sclerosis (HS). Patients were asked to point in darkness with a light spot, moved on a cylindrical screen by means of a joystick, into their visual straight-ahead direction (VSA), to remember this direction in space, and to revert back to this point after the rotations. Estimates in patients with HS were compared with those of healthy controls and of patients with epilepsy without hippocampal involvement. All groups produced similar errors after low-frequency vestibular stimuli. These errors were eliminated when rotations involved concurrent neck stimulation. Significantly increased variability was observed, however, in both the VSA and reposition estimates after the rotations in patients with HS compared with controls. These results suggest that cognitive processing of idiothetic signals for self-motion perception is inaccurate in patients with HS. Importantly, however, the responses of patients with HS showed no spatial lateralization with regard to right or left HS, suggesting that the underlying neuronal loss attenuates the precision of head-direction signal decoding in a nondirectional manner. Hence, patients are unable to use these signals as efficiently as normal subjects in the construction of a stable head-centric spatial frame of reference. NEW & NOTEWORTHY Spatial perception relies on combined processing of various idiothetic (vestibular and proprioceptive) and allothetic (visual and auditory) sensory signals. Despite the established knowledge of rodent vestibular-hippocampal interactions, human data are lacking. We investigated idiothetic orientational processing in subjects with unilateral hippocampal sclerosis using various combinations of vestibular and proprioceptive stimuli. Hippocampal impairment leads to less accurate, noisy decoding of the signal related to idiothetic orientation. However, patients did not show any lateralized deficits of visual straight-ahead perception or of target/self-displacement perception after idiothetic stimulation.

Morphological imaging of the hippocampus in epilepsy

The hippocampus is a structure frequently involved in epilepsy, especially in partial drug-resistant forms. In addition, some hippocampal pathologies are associated with specific types of epilepsy presenting specific clinical courses and requiring specific treatments. Considering these major implications for treatment, morphological investigations of the hippocampus are crucial for epileptic patients. Indeed, discovery of hippocampal sclerosis may (depending on the clinical and electrophysiological findings) lead to the diagnosis of mesial temporal lobe epilepsy (MTLE). If the diagnosis of MTLE is retained in a case of drug-resistance, surgery may be proposed without invasive phase II investigations such as stereoelectroencephalograpy. In other instances, hippocampal abnormalities may be associated with epilepsy, but without the same value for localizing the ictal onset zone. Hippocampal dysgenesis is a strong argument for non-temporo-mesial ictal onset ipsilateral to the malformation. We describe here the specific MRI modalities adapted for hippocampal investigations and the radiological signs of hippocampal pathologies associated with epilepsy (especially hippocampal sclerosis and hippocamal dysgenesis). Hippocampus morphological investigations in epilepsy require specific MRI modalities and appropriate knowledge of the specific signs of each pathology. Careful analysis is crucial since the results may have a major impact on the therapeutic management of epileptic patients.

Crossed aphasia after right anterior temporal lobectomy. A case report

The occurrence of crossed aphasia as a complication after temporal lobe epilepsy surgery is extremely rare. We report the case of a 47-year-old right-handed patient with drug-resistant mesial temporal lobe epilepsy (MTLE) who developed a transitory aphasic syndrome after a right temporal anterior lobectomy. This syndrome was characterized by anomia, poor verbal fluency, verbal perseveration, and verbal comprehension difficulties. He also showed writing difficulties, reading substitutions, and calculation task errors. The patient was regularly assessed with language tasks, and showed a spontaneous and progressive recovery of his symptoms, with remaining naming difficulties. We discuss the role that epileptogenic zone could play in cortical reorganization of the language systems.