Efficacy of MR vs CT in epilepsy

ACR Appropriateness Criteria® Seizures and Epilepsy

Seizures and epilepsy are a set of conditions that can be challenging to diagnose, treat, and manage. This document summarizes recommendations for imaging in different clinical scenarios for a patient presenting with seizures and epilepsy. MRI of the brain is usually appropriate for each clinical scenario described with the exception of known seizures and unchanged semiology (Variant 3). In this scenario, it is unclear if any imaging would provide a benefit to patients. In the emergent situation, a noncontrast CT of the head is also usually appropriate as it can diagnose or exclude emergent findings quickly and is an alternative to MRI of the brain in these clinical scenarios. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

New-onset seizures in adults with tuberculous meningitis during long-term follow-up: Characteristics, functional outcomes and risk factors

OBJECTIVE

This study aimed to determine the characteristics and risk factors of adult new-onset seizure patients with tuberculous meningitis (TBM) during long-term follow-up.

METHODS

Patients with TBM who were seen between June 2012 and January 2018 were retrospectively reviewed and categorized into two groups based on the presence or absence of new-onset seizures. Seizure characteristics, functional outcomes and risk factors were assessed.

RESULTS

A total of 223 patients with TBM were enrolled, including 20.6% (46/223) with seizures. In all, 39.1% (18/46) of the patients with new-onset seizures and 14.1% (25/177) of the patients without seizures died (p < 0.001). Seizures were classified as single (n = 14/46, 30.4%), repetitive (n = 25/46, 54.3%), or status epilepticus (n = 7/46, 15.2%). We found that non-single seizures (repetitive seizures and status epilepticus) were associated with mortality (P = 0.002, P = 0.022), while single seizures were not (P = 0.834). The independent risk factors associated with non-single seizures were cortical involvement (p = 0.007) and epileptiform discharges (p = 0.001).

CONCLUSIONS

Non-single seizures were associated with poor functional outcomes and should be noted by the clinic. Cortical involvement and epileptiform discharges are independent risk factors for non-single seizures.

Modified periinsular hemispherotomy: operative anatomy and technical nuances

Surgical options for pediatric patients with marked dysfunction of a single epileptogenic hemisphere have evolved over time. Complications resulting from highly resective operations such as anatomical hemispherectomy, including superficial siderosis and secondary hydrocephalus, have led to the development of less resective and more disconnective functional hemispherectomy. Functional hemispherectomy has recently given rise to hemispherotomy, the least resective operation primarily aimed at disconnecting the abnormal hemisphere. Hemispherotomy is effective in decreasing seizure frequency and most likely decreases the risk of postoperative complications when compared with its predecessors. Hemispherotomy is a technically challenging operation that requires a thorough understanding of 3D cerebral anatomy to ensure adequate hemispheric disconnection without placing important structures at risk. The details of germane operative anatomy are not currently available because of the difficulty in exposing this operative anatomy adequately in cadavers to prepare detailed instructive illustrations. Using 3D graphic models, the authors have prepared 2D overlay illustrations to discuss the relevant operative nuances for a modified form of this procedure. Through hemispherotomy, experienced surgeons can effectively treat patients with unilateral epileptogenic hemisphere dysfunction while limiting potential complications.

Diffusion imaging in epilepsy

Epilepsy is the most common serious neurological disease. Seizures are refractory to medication in approximately 30% of patients with focal epilepsy, and surgical treatment is potentially curative should the epileptic focus be accurately localized. MRI has revolutionized the investigation of such patients; however, up to 20% of patients with refractory focal epilepsy have an undetermined etiological basis for their epilepsy despite extensive investigation. Diffusion imaging is an advanced MRI technique that is sensitive to the molecular displacement of water molecules and provides additional information on the microstructural arrangement of tissue. Both qualitative and quantitative analyses of the interictal and peri-ictal states are possible and provide valuable insights into the epileptic brain in vivo. Furthermore, advanced postacquisition processing can reveal additional information on, for example, anatomical connectivity. The description, application and limitations of diffusion imaging in epilepsy are the focus of this review. Future directions of research required in this area are also discussed in the context of existing literature.

Cancer risks associated with external radiation from diagnostic imaging procedures

The 600% increase in medical radiation exposure to the US population since 1980 has provided immense benefit, but increased potential future cancer risks to patients. Most of the increase is from diagnostic radiologic procedures. The objectives of this review are to summarize epidemiologic data on cancer risks associated with diagnostic procedures, describe how exposures from recent diagnostic procedures relate to radiation levels linked with cancer occurrence, and propose a framework of strategies to reduce radiation from diagnostic imaging in patients. We briefly review radiation dose definitions, mechanisms of radiation carcinogenesis, key epidemiologic studies of medical and other radiation sources and cancer risks, and dose trends from diagnostic procedures. We describe cancer risks from experimental studies, future projected risks from current imaging procedures, and the potential for higher risks in genetically susceptible populations. To reduce future projected cancers from diagnostic procedures, we advocate the widespread use of evidence-based appropriateness criteria for decisions about imaging procedures; oversight of equipment to deliver reliably the minimum radiation required to attain clinical objectives; development of electronic lifetime records of imaging procedures for patients and their physicians; and commitment by medical training programs, professional societies, and radiation protection organizations to educate all stakeholders in reducing radiation from diagnostic procedures.

Evaluation of the efficiency of inpatient 24-hour VEEG combined with MRI in consecutive patients with newly diagnosed epilepsies

A total of 128 patients were recruited into this study to evaluate the cost efficiency of 24-hour video electroencephalography (VEEG) combined with magnetic resonance imaging (MRI) in people with newly diagnosed epilepsies. The rate of neuroimaging abnormalities detected was 14.8% higher with MRI than with computed tomography (CT), whereas 25.7% more EEG abnormalities were detected with inpatient 24-hour VEEG than with outpatient EEG. In the partial seizure (PS) group, MRI combined with 24-hour VEEG revealed that 20 of 73 (27.4%) patients had local epileptogenic lesions, whereas CT with outpatient EEG revealed a rate of 10 in 73 (13.7%). With respect to the economic impact, 27.3% of the patients spent more than 17.8% of their annual household income for 24-hour VEEG and MRI. However, 82.7% of the patients spent less than that, and among these patients, only 16.4% spent less than 5.9% of their annual household income. Hence, we conclude that the combination of MRI and 24-hour VEEG as a compulsory tool should be popularized in less developed countries.

Pre-surgical evaluation and surgical treatment in children with extratemporal epilepsy

INTRODUCTION

This review summarizes some patterns of pre-surgical evaluation and surgical treatment of extratemporal epilepsy in pediatric patients with medically refractory seizures, whose ictal behavior is variable. The most effective treatment for intractable partial epilepsy is a focal cortical resection with excision of the epileptogenic zone (the area of ictal onset and initial seizure propagation). This might be risky, though, in the case of a widespread lesion, sometimes encroaching one or more lobes, given the risk to the functional cerebral cortex. An anterior temporal lobectomy might prove more effective then in preventing seizures with fewer potential complications. If partial extratemporal epilepsy is associated with pharmaco-resistant seizures, the preoperative evaluation and operative strategy are determined according to the epileptogenic zone and to the relationship between a substrate-directed disorder and eloquent areas. The pediatric treatment of extratemporal epilepsy is aimed at controlling the seizures, avoiding morbidity, and improving the patient's quality of life through psychosocial integration. Since the immature brain is more plastic than when mature, the recovery of functions after surgery is greater in children than in adults.

RECOMMENDATION

Early surgery is recommended for children with intractable epilepsy, and is now accepted as an important therapeutic modality also for children with chronic epilepsy.

CONCLUSION

Technological advances in the last two decades, mainly in neuroimaging, have led many medical centers to consider surgical treatment of epilepsy, accuracy being granted by MRI-based neuronavigation systems-an interface between the lesion seen in the preoperative magnetic resonance imaging (MRI) and the operative field, often invisible to the surgeon.

Regional distribution of interictal 31P metabolic changes in patients with temporal lobe epilepsy

PURPOSE

We compared the 31P metabolites in different brain regions of patients with temporal lobe epilepsy (TLE) with those from controls.

METHODS

Ten control subjects and 11 patients with TLE were investigated with magnetic resonance imaging (MRI) and [31P]MR spectroscopic imaging (MRSI). [31P]MR spectra were selected from a variety of brain regions inside and outside the temporal lobe.

RESULTS

There were no asymmetries of inorganic phosphate (Pi), pH, or phosphomonoesters (PME) between regions in the left and right hemispheres of controls. In patients with TLE, Pi and pH were higher and PME was lower throughout the entire ipsilateral temporal lobe as compared with the contralateral side and there were no significant asymmetries outside the temporal lobe. The degree of ipsilateral/contralateral asymmetry for all three metabolites was substantially greater for the temporal lobe than for the frontal, occipital, and parietal lobes, and these asymmetries provided additional data for seizure localization. As compared with levels in controls, Pi and pH were increased and PME were decreased on the ipsilateral side in patients with TLE. There were changes in Pi, pH, and PME on the contralateral side in persons with epilepsy as compared with controls, contrary to changes on the ipsilateral side.

CONCLUSIONS

Our findings provide some insight into the metabolic changes that occur in TLE and may prove useful adjuncts for seizure focus lateralization or localization.

Economic impact of replacing CT with MR imaging for refractory epilepsy

PURPOSE

To evaluate the economic costs of using computed tomography (CT) vs. magnetic resonance (MR) imaging in the preoperative evaluation of refractory epilepsy patients.

METHODS

Preoperative CT and MR imaging findings from 117 patients who underwent surgery for medically refractory epilepsy during a 3.5-year period were reviewed. Cost savings were based on the paradigm that intracranial electroencephalogram monitoring (costing about $50,000) would have been necessary for preoperative localization of the epileptogenic zone in those patients without positive imaging findings. Savings attributed to replacing CT with MR were based on patients with positive MR and normal CT. A similar paradigm was used to calculate savings for replacing MR with CT. National savings were based solely on patients with neoplasms or vascular lesions because paradigms for other lesions vary considerable depending on institutional philosophy.

RESULTS

Replacing CT with MR imaging would have eliminated preoperative intracranial electrode procedures in 29 of 117 patients, with potential savings of $1,450,000 at our institution. In the 37 patients with neoplastic or vascular substrates, MR would have eliminated 10 invasive electrode procedures with estimated savings of $0.5 million institutionally and $3 to $4 million per year nationally. There were no cases to support replacing MR with CT.

CONCLUSION

Replacing CT with MR decreases health costs associated with preoperative evaluation of intractable epilepsy requiring surgical amelioration.

EEG investigation of temporal lobe epilepsy

We report the results of the study assessing the role of electroencephalogram (EEG) in the evaluation of patients with temporal lobe epilepsy (TLE). A prospective interictal EEG study was performed in 80 patients with TLE, and the results were compared with those of neuroimaging magnetic resonance imaging (MRI) and computed tomography (CT). All patients had interictal scalp-recorded electroencephalographic monitoring with a full array of electrodes placed according to the International 10-20 Placement System, CT and MRI. Scalp EEG had a success rate of 70% in TLE patients, this rate was 50% for MRI and 15% for CT. Epileptiform EEG abnormalities were unilateral in 25 (31%) and bilateral in 31 (39%) patients. In 56% of patients with unilateral interictal activity and 97% of patients with bilateral interictal activity, epileptiform activity was localized at the temporal electrodes. The wave morphology which we most frequently saw in our study was the sharp, sharp-slow wave or spike, or spike-wave. A correlation was observed between the focal MRI-CT abnormalities and the EEG findings. We found abnormal imaging incidence in patients with unilateral EEG findings to be significantly greater than in patients with bilateral EEG findings (chi 2 = 4.62, p = .032). EEG showed abnormality in 28 (70%) of 40 patients whose neuroimaging (NI) tests were found abnormal and also did in 70% of 40 patients whose NI tests were normal. In our study EEG has remained as the most efficient test in the localization of an epileptogenic focus.

Intractable epilepsy in children

Although most children with epilepsy have a good prognosis, a small but significant minority have seizures that either do not respond to conventional antiepileptic drugs (AEDs) or have significant adverse reactions to AEDs. Many children may benefit from epilepsy surgery. Surgical treatment of epilepsy is becoming a well-established therapy for infants and young children with severe, medically intractable seizures. As in older children and adults, the presurgical evaluations of possible surgical candidates typically consist of a detailed history, neurologic and neuropsychologic examination, and anatomic and functional neuroimaging. The "gold standard" test, however, is the recording of ictal events by using simultaneous EEG and videomonitoring. Although temporal lobe resection is the most commonly performed surgery in older children and adults, nontemporal lobe resection, corpus callosotomy, and hemispherectomy are commonly performed in younger children. Efficacy of surgery in children compares favorably with results from adult patients. In addition, because the immature brain is more plastic than the mature brain, recovery of function is often greater after surgery in children than in adults. Early surgery in children with intractable epilepsy is recommended.