Clinical Reasoning: A 62-Year-Old Woman With Transient Vision Loss.

Transient visual loss (TVL) is a common complaint in the emergency department, with numerous possible etiologies. Prompt evaluation and management of TVL can potentially prevent progression to permanent visual loss. In this case, a 62-year-old woman presented with acute, painless, unilateral TVL. Two weeks before presentation, the patient reported bitemporal headaches and paresthesia of the distal extremities. A review of systems revealed chronic fatigue, cough, diffuse arthralgias, and decreased appetite for the previous 6 months. This case highlights the diagnostic approach to patients with TVL. Some common and rare causes associated with this clinical manifestation are briefly reviewed.

Source-sink connectivity: a novel interictal EEG marker for seizure localization.

Over 15 million epilepsy patients worldwide have drug-resistant epilepsy. Successful surgery is a standard of care treatment but can only be achieved through complete resection or disconnection of the epileptogenic zone, the brain region(s) where seizures originate. Surgical success rates vary between 20% and 80%, because no clinically validated biological markers of the epileptogenic zone exist. Localizing the epileptogenic zone is a costly and time-consuming process, which often requires days to weeks of intracranial EEG (iEEG) monitoring. Clinicians visually inspect iEEG data to identify abnormal activity on individual channels occurring immediately before seizures or spikes that occur interictally (i.e. between seizures). In the end, the clinical standard mainly relies on a small proportion of the iEEG data captured to assist in epileptogenic zone localization (minutes of seizure data versus days of recordings), missing opportunities to leverage these largely ignored interictal data to better diagnose and treat patients. IEEG offers a unique opportunity to observe epileptic cortical network dynamics but waiting for seizures increases patient risks associated with invasive monitoring. In this study, we aimed to leverage interictal iEEG data by developing a new network-based interictal iEEG marker of the epileptogenic zone. We hypothesized that when a patient is not clinically seizing, it is because the epileptogenic zone is inhibited by other regions. We developed an algorithm that identifies two groups of nodes from the interictal iEEG network: those that are continuously inhibiting a set of neighbouring nodes ('sources') and the inhibited nodes themselves ('sinks'). Specifically, patient-specific dynamical network models were estimated from minutes of iEEG and their connectivity properties revealed top sources and sinks in the network, with each node being quantified by source-sink metrics. We validated the algorithm in a retrospective analysis of 65 patients. The source-sink metrics identified epileptogenic regions with 73% accuracy and clinicians agreed with the algorithm in 93% of seizure-free patients. The algorithm was further validated by using the metrics of the annotated epileptogenic zone to predict surgical outcomes. The source-sink metrics predicted outcomes with an accuracy of 79% compared to an accuracy of 43% for clinicians' predictions (surgical success rate of this dataset). In failed outcomes, we identified brain regions with high metrics that were untreated. When compared with high frequency oscillations, the most commonly proposed interictal iEEG feature for epileptogenic zone localization, source-sink metrics outperformed in predictive power (by a factor of 1.2), suggesting they may be an interictal iEEG fingerprint of the epileptogenic zone.

Antiseizure Medications for Adults With Epilepsy: A Review.

Importance: Epilepsy affects approximately 65 million people worldwide. Persistent seizures are associated with a 20% to 40% risk of bodily injuries (eg, fractures, burns, concussions) over 12-month follow-up. The primary goal of epilepsy treatment is to eliminate seizures while minimizing adverse effects of antiseizure drugs (ASDs). Observations: An epileptic seizure is defined as a sudden occurrence of transient signs and symptoms caused by abnormal and excessive or synchronous neuronal activity in the brain. Focal and generalized epilepsy are the 2 most frequent types of epilepsy; diagnosis is based on the type of seizures. There are 26 US Food and Drug Administration-approved medications for epilepsy, of which 24 have similar antiseizure efficacy for focal epilepsy and 9 have similar efficacy for generalized epilepsy. The decision to initiate an ASD should be individualized, but should be strongly considered after 2 unprovoked seizures or after 1 unprovoked seizure that occurred during sleep and/or in the presence of epileptiform activity on an electroencephalogram and/or in the presence of a structural lesion on the brain magnetic resonance imaging. The ASDs must be selected based on the seizure and epilepsy types, the epilepsy syndrome, and the adverse effects associated with the drug. For focal epilepsy, oxcarbazepine and lamotrigine are first-line therapy, while levetiracetam can be also considered if there is no history of psychiatric disorder. For generalized epilepsy, the selection of the ASD is based on the type of epilepsy syndrome and the patient's sex, age, and psychiatric history. Seizure freedom is achieved in approximately 60% to 70% of all patients. A total of 25% to 50% of patients also experience neurologic, psychiatric, cognitive, or medical disorders, such as mood, anxiety, and attention deficit disorders and migraines. For these patients, selecting an ASD should consider the presence of these disorders and concomitant use of medications to treat them. ASDs with cytochrome P450 enzyme-inducing properties (eg, carbamazepine, phenytoin) may worsen comorbid coronary and cerebrovascular disease by causing hyperlipidemia and accelerating the metabolism of concomitant drugs used for their treatment. They can also facilitate the development of osteopenia and osteoporosis. Conclusions and Relevance: Epilepsy affects approximately 65 million people worldwide and is associated with increased rates of bodily injuries and mortality when not optimally treated. For focal and generalized epilepsy, selection of ASDs should consider the seizure and epilepsy types and epilepsy syndrome, as well as the patient's age and sex, comorbidities, and potential drug interactions.