Cortical and thalamic hyper-perfusion in non-convulsive status epilepticus. Relationship between perfusion CT patterns and Salzburg EEG criteria

Pragmatic computerised perfusion diagnostics for non-convulsive status epilepticus: a prospective observational study

BACKGROUND

Non-convulsive status epilepticus (NCSE) is a time-dependent neurological disorder often misdiagnosed in the emergency setting. Electroencephalography (EEG) is often not available on a 24/7 basis, and Salzburg criteria may at times miss the diagnosis. Here, we tested the accuracy of hyperperfusion on CT perfusion imaging (CTP) in the identification of NCSE against Salzburg criteria, to define its potential role in a pragmatic diagnostic workflow.

METHODS

We enrolled consecutive patients with suspected acute seizure or seizure disorder undergoing brain imaging with CTP and EEG from January 2021 to March 2023. EEG recordings, Salzburg criteria and CTP hyperperfusion were rated and adjudicated by two independent experts blinded to patient status. A reference standard including all clinical, lab, imaging, EEG and therapeutic data was used to adjudicate NCSE diagnosis. Sensitivity, specificity, diagnostic accuracy, positive and negative predictive values (NPV) were calculated for CTP hyperperfusion and Salzburg criteria versus NCSE adjudicated according to reference standard.

RESULTS

Seventy-seven patients were enrolled. Among 21 NCSE cases, 17 were adjudicated according to Salzburg criteria (81%) and 4 received NCSE diagnosis according to reference standard. Agreement between EEG and CTP emerged in 16/21 NCSE cases, reaching sublobar level in 37.5% of cases. Receiver operator curve analysis suggested good accuracy for CTP hyperperfusion for the diagnosis of NCSE (AUROC 0.79, 95% CI 0.69 to 0.89). CTP hyperperfusion had a high NPV for NCSE (NPV 0.97, 95% CI 0.86 to 1).

CONCLUSION

CTP hyperperfusion may be implemented in the emergency fast-track to rule out NCSE, given very high NPV. Further validation studies are needed to evaluate CTP application in real-world setting for NCSE codes.

Neuroimaging correlation with EEG in status epilepticus

PURPOSE

This study was to correlate EEG patterns with peri‑ictal perfusion CT abnormality (PCA) or peri‑ictal MR abnormality (PMA) in patients with status epilepticus (SE).

METHODS

This is a retrospective study done with SE patients from January 2016 to December 2021. We defined the PCA as single or multi-territorial cortical and/or thalamic hyper-perfusion. The PMA was defined as increased signal intensity in multiple brain regions including the cortex and subcortical regions. EEG patterns were categorized into electrographic seizure (ESz)/electroclinical seizure (ECSz), ictal-interictal continuum (IIC), and lateralized periodic discharges (LPDs) per the American Clinical Neurophysiology Society's guideline. We analyzed the association between the patterns of EEG and the presence of PCA or PMA.

RESULTS

Among 73 patients, 26 % (19/73) showed PCA and 25 % (18/73) demonstrated PMA. The patterns of EEG were as follows; ESz/ECSz in 25 % (18/73), IIC in 34 % (25/73), and LPD in 12 % (9/73). There was a significant correlation between the patterns of EEG and the presence of PMA, but not PCA. 48 % (12/25) had both PMA and PCA whereas 52 % (13/25) showed either PMA (6/25) or PCA (7/25).

CONCLUSION

Although PCA did not reveal an electro-radiographical correlation, PMA was strongly linked to ESz, ECSz, IIC, and LPD.

The role of fetal-type posterior cerebral artery in mediating occipital and thalamic perfusion: An arterial spin labeling MRI study

BACKGROUND

The posterior cerebral artery (PCA) is key in supplying blood to the occipital lobes and significant portions of the thalamus. Some individuals present with a 'fetal-type' posterior cerebral artery (fPCA), which is associated with a higher risk of neurological disorders such as ischemic stroke. This study investigates the relationship between the presence of fPCA and arterial spin labeling (ASL) hyperperfusion patterns in the medial occipital cortex and thalami.

METHODS

MRI scans from 84 patients with no detectable radiological evidence of brain pathology were retrospectively analyzed. We investigated the association between PCA type (normal vs. fetal) and perfusion pattern (hyperperfused vs. non-hyperperfused) using Fisher's exact test.

RESULTS

Hyperperfusion in the medial occipital cortex and thalami was absent in all patients with fPCA, but present in 69% of those with normal PCA. In patients with unilateral fPCA, hyperperfusion was exclusively observed on the side with the normal PCA.

CONCLUSION

The study suggests a consistent relationship between PCA type and ASL perfusion patterns in the medial occipital cortex and thalami. Further research is warranted to explore the physiological underpinnings of these findings and their potential clinical implications. Understanding this relationship could improve the interpretation of ASL MRI and contribute to a better understanding of pathophysiological mechanisms associated with PCA variants.

FDA-approved machine learning algorithms in neuroradiology: A systematic review of the current evidence for approval

Over the past decade, machine learning (ML) and artificial intelligence (AI) have become increasingly prevalent in the medical field. In the United States, the Food and Drug Administration (FDA) is responsible for regulating AI algorithms as "medical devices" to ensure patient safety. However, recent work has shown that the FDA approval process may be deficient. In this study, we evaluate the evidence supporting FDA-approved neuroalgorithms, the subset of machine learning algorithms with applications in the central nervous system (CNS), through a systematic review of the primary literature. Articles covering the 53 FDA-approved algorithms with applications in the CNS published in PubMed, EMBASE, Google Scholar and Scopus between database inception and January 25, 2022 were queried. Initial searches identified 1505 studies, of which 92 articles met the criteria for extraction and inclusion. Studies were identified for 26 of the 53 neuroalgorithms, of which 10 algorithms had only a single peer-reviewed publication. Performance metrics were available for 15 algorithms, external validation studies were available for 24 algorithms, and studies exploring the use of algorithms in clinical practice were available for 7 algorithms. Papers studying the clinical utility of these algorithms focused on three domains: workflow efficiency, cost savings, and clinical outcomes. Our analysis suggests that there is a meaningful gap between the FDA approval of machine learning algorithms and their clinical utilization. There appears to be room for process improvement by implementation of the following recommendations: the provision of compelling evidence that algorithms perform as intended, mandating minimum sample sizes, reporting of a predefined set of performance metrics for all algorithms and clinical application of algorithms prior to widespread use. This work will serve as a baseline for future research into the ideal regulatory framework for AI applications worldwide.

"It's not mine!" First description of somatoparaphrenia possibly reflecting an undergoing ictal epileptic activity

Content available: Video

Hyperperfusion Tmax mapping for nonconvulsive status epilepticus in the acute setting: A pilot case-control study

OBJECTIVE

Nonconvulsive status epilepticus (NCSE) is misdiagnosed in >50% of cases in the emergency department. Computed tomographic perfusion (CTP) has been implemented in the hyperacute setting to detect seizure-induced hyperperfusion. However, the diagnostic value of CTP is limited by the lack of thresholds for hyperperfusion and high interrater variability. This pilot case-control study aims at identifying the diagnostic value of reverse Tmax (rTmax) in differentiating NCSE from acute ischemic stroke in the hyperacute setting.

METHODS

We enrolled patients with NCSE (Salzburg criteria-based diagnosis) and stroke cases 1:1 matched for clinical features and time of presentation. CTP standard maps (mean transit time [MTT]-cerebral blood volume-cerebral blood flow [CBF]) and rTmax maps were elaborated and rated by two experts in CTP blinded to the final diagnosis. Hyperperfusion was adjudicated for standard CTP maps as an increase in CBF and a decrease in MTT, and for rTmax as the presence of a black area on 3-, 2-, and 1-s threshold maps. Cronbach alpha was used for interrater agreement; receiver operating curve analysis was run to measure accuracy with area under the curve.

RESULTS

Overall, 34 patients were included (17 NCSE, 17 stroke; time from onset to imaging = 2 h for both groups). People with NCSE were older and more frequently had a history of epilepsy. NCSE patients had hyperperfusion on rTmax maps in 11 of 17 cases versus zero of 17 in stroke. Intra- and interrater reliability was higher for rTmax than for standard CTP maps (κ = 1 vs. κ = .6). rTmax was 82% (95%CI = 67-97%) accurate in predicting NCSE versus stroke in the hyperacute setting. Agreement between neuroimaging and electroencephalography (EEG) was limited at a hemispheric level for standard CTP maps, whereas rTMax had agreement with EEG largely reaching the sublobar level.

SIGNIFICANCE

rTmax mapping might represent a reliable tool to spot NCSE-induced hyperperfusion with a threshold-based reproducible approach. Further studies are needed for validation and implementation in the differential diagnosis of focal neurological deficit in the hyperacute setting.

Epileptic seizures in the emergency room: clinical and electroencephalographic findings associated with brain perfusion patterns on computed tomography

Background

Diagnosis of epileptic seizures, particularly regarding status epilepticus (SE), may be challenging in an emergency room setting. The aim of the study was to study the diagnostic yield of perfusion computed tomography (pCT) in patients with single epileptic seizures and SE.

Methods

We retrospectively reviewed the records of patients who followed an acute ischemic stroke pathway during a 9-month period and who were finally diagnosed with a single epileptic seizure or SE. Perfusion maps were visually analyzed for the presence of hyperperfusion and hypoperfusion. Clinical data, EEG patterns, and neuroimaging findings were compared.

Results

We included 47 patients: 20 (42.5%) with SE and 27 (57.5%) with single epileptic seizure. Of 18 patients who showed hyperperfusion on pCT, 12 were ultimately diagnosed with SE and eight had EEG findings compatible with an SE pattern. Focal hyperperfusion on pCT had a sensitivity of 60% (95% CI 36.4–80.2) and a specificity of 77.8% (95% CI 57.2–90.6) for predicting a final diagnosis of SE. The presence of cerebral cortical and thalamic hyperperfusion had a high specificity for predicting SE presence. Of note, 96% of patients without hyperperfusion on pCT did not show an SE pattern on early EEG.

Conclusions

In acute settings, detection by visual analysis of focal cerebral cortical hyperperfusion on pCT in patients with epileptic seizures, especially if accompanied by the highly specific feature of thalamic hyperperfusion, is suggestive of a diagnosis of SE and requires clinical and EEG confirmation. The absence of focal hyperperfusion makes a diagnosis of SE unlikely.

Usefulness of arterial spin labeling perfusion as an initial evaluation of status epilepticus

This study aimed to evaluate the sensitivity and prognostic value of arterial spin labeling (ASL) in a large group of status epilepticus (SE) patients and compare them with those of other magnetic resonance (MR) sequences, including dynamic susceptibility contrast (DSC) perfusion imaging. We retrospectively collected data of patients with SE in a tertiary center between September 2016 and March 2020. MR images were visually assessed, and the sensitivity for the detection of SE and prognostication was compared among multi-delay ASL, DSC, fluid-attenuated inversion recovery (FLAIR), and diffusion-weighted imaging (DWI). We included 51 SE patients and 46 patients with self-limiting seizures for comparison. Relevant changes in ASL were observed in 90.2% (46/51) of SE patients, a percentage higher than those for DSC, FLAIR, and DWI. ASL was the most sensitive method for initial differentiation between SE and self-limiting seizures. The sensitivity of ASL for detecting refractory SE (89.5%) or estimating poor outcomes (100%) was higher than those of other MR protocols or electroencephalography and comparable to those of clinical prognostic scores, although the specificity of ASL was very low as 9.4% and 15.6%, respectively. ASL showed a better ability to detect SE and predict the prognosis than other MR sequences, therefore it can be valuable for the initial evaluation of patients with SE.