Adherence with psychotherapy and treatment outcomes for psychogenic nonepileptic seizures

OBJECTIVE

We conducted a prospective cohort study of patients with psychogenic nonepileptic seizures (PNES) to examine the association between adherence with psychotherapy and outcomes, including significant (≥50%) reduction in PNES frequency, PNES freedom, improvement in quality of life, and reduction in emergency department (ED) utilization.

METHODS

A total of 105 participants were referred to receive psychotherapy either at Brigham and Women's Hospital or with a local therapist. We called participants at 12-24 months follow-up and obtained detailed follow-up data from 93 participants (89%). Participants were considered adherent with psychotherapy if they attended at least 8 sessions within a 16-week period starting at the time of referral.

RESULTS

Adherence with psychotherapy was associated with reduction in seizure frequency (84% in adherent group vs 61% in nonadherent, p = 0.021), improvement in quality of life (p = 0.044), and reduction in ED utilization (p = 0.040), with medium effect sizes; there was no difference in PNES freedom. The association between adherence and ≥50% reduction in PNES frequency persisted when controlling for potential confounders in a multivariate model. Psychotherapy nonadherence was associated with baseline characteristics of self-identified minority status (odds ratio 7.47, p = 0.019) and history of childhood abuse (odds ratio 3.30, p = 0.023).

CONCLUSIONS

Our study is limited in that it cannot establish a causal relationship between adherence with psychotherapy and outcomes, and the results may not generalize beyond the single quaternary care center study site. Among participants with documented PNES, adherence with psychotherapy was associated with reduction in PNES frequency, improvement in quality of life, and decrease in ED visits.

Prevalence and predictors of seizure clusters: A prospective observational study of adult patients with epilepsy

OBJECTIVE

The purpose of this prospective observational study was to describe the prevalence and adverse outcomes associated with seizure clusters (defined as ≥2 seizures in a 6-hour period) in a large sample of adult patients with a range of epilepsy severities and to identify clinical characteristics predictive of clustering.

METHODS

Patients maintained a seizure diary and were contacted monthly to verify compliance and data accuracy. Logistic regression models were utilized to test associations between individual patient demographic/clinical characteristics and seizure clustering. Fisher's exact test was utilized to test associations between rescue medication use and adverse seizure-related outcomes.

RESULTS

A total of 300 patients were followed prospectively for one year; 247 patients qualified for final analysis. Six-hour seizure clusters occurred in 45.8% of patients with active epilepsy at enrollment, including 62.7% of those with prior day-clusters and 30.0% of those without prior day-clusters. The odds of clustering were markedly greater among patients who reported a higher seizure frequency (>4 seizures per year vs. 1-4 seizures per year) (adjusted odds ratio (OR): 8.9; 95% confidence interval (CI): 3.2-24.6; p < 0.0001) and among patients with prior day-clusters (adjusted OR: 11.0; 95% CI: 1.2-104.2; p = 0.036). Rescue medication use was associated with significantly fewer injuries and emergency department visits, but rescue medication was underutilized.

CONCLUSIONS

Seizure clusters are common, occurring in nearly half of adult patients with active epilepsy followed prospectively over one year, and are more frequent in those with higher seizure frequencies and prior day-clusters. Although underutilized, rescue medication was associated with fewer injuries and emergency department visit.

Seizure susceptibility and infraslow modulatory activity in the intracranial electroencephalogram

OBJECTIVE

Studies of infraslow amplitude modulations (<0.15 Hz) of band power time series suggest that these envelope correlations may form a basis for distant spatial coupling in the brain. In this study, we sought to determine how infraslow relationships are affected by antiepileptic drug (AED) taper, time of day, and seizure.

METHODS

We studied intracranial electroencephalographic (icEEG) data collected from 13 medically refractory adult epilepsy patients who underwent monitoring at Yale-New Haven Hospital. We estimated the magnitude-squared coherence (MSC) at <0.15 Hz of traditional EEG frequency band power time series for all electrode contact pairs to quantify infraslow envelope correlations between them. We studied, first, hour-long background icEEG epochs before and after AED taper to understand the effect of taper. Second, we analyzed the entire record for each patient to study the effect of time of day. Finally, for each patient, we reviewed the clinical record to find all seizures that were at least 6 hours removed from other seizures and analyzed infraslow envelope MSC before and after them.

RESULTS

Infraslow envelope MSC increased slightly, but significantly, after AED taper, and increased on average during the night and decreased during the day. It was also increased significantly in all frequency bands up to 3 hours preseizure and 1 hour postseizure as compared to background icEEG (61 seizures studied). These changes occurred for both daytime and nighttime seizures (28 daytime, 33 nighttime). Interestingly, there was significant spatial variability to these changes, with the seizure onset area peaking at 3 hours preseizure, then showing progressive desynchronization from 3 hours preseizure to 1 hour postseizure.

SIGNIFICANCE

Infraslow envelope analysis may be used to understand long-term changes over the course of icEEG monitoring, provide unique insight into interictal electrophysiological changes related to ictogenesis, and contribute to the development of novel seizure forecasting algorithms.

Bilateral independent periodic discharges are associated with electrographic seizures and poor outcome: A case-control study

OBJECTIVE

To determine the clinical correlates bilateral independent periodic discharges (BIPDs) and their association with electrographic seizures and outcome.

METHODS

Retrospective case-control study of patients with BIPDs compared to patients without periodic discharges ("No PDs") and patients with lateralized periodic discharges ("LPDs"), matched for age, etiology and level of alertness.

RESULTS

We included 85 cases and 85 controls in each group. The most frequent etiologies of BIPDs were stroke, CNS infections, and anoxic brain injury. Acute bilateral cerebral injury was more common in the BIPDs group than in the No PDs and LPDs groups (70% vs. 37% vs. 35%). Electrographic seizures were more common with BIPDs than in the absence of PDs (45% vs. 8%), but not than with LPDs (52%). Mortality was higher in the BIPDs group (36%) than in the No PDs group (18%), with fewer patients with BIPDs achieving good outcome (moderate disability or better; 18% vs. 36%), but not than in the LPDs group (24% mortality, 26% good outcome). In multivariate analyses, BIPDs remained associated with mortality (OR: 3.0 [1.4-6.4]) and poor outcome (OR: 2.9 [1.4-6.2]).

CONCLUSION

BIPDs are caused by bilateral acute brain injury and are associated with a high risk of electrographic seizures and of poor outcome.

SIGNIFICANCE

BIPDs are uncommon but their identification in critically ill patients has potential important implications, both in terms of clinical management and prognostication.

Association between death and loss of stage N2 sleep features among critically Ill patients with delirium

PURPOSE

Critically ill patients experience significant sleep disruption. In this study of ICU patients with delirium, we evaluated associations between the loss of stage N2 features (K-complexes, sleep spindles), grade of encephalopathy based on electroencephalography (EEG), and intensive care unit (ICU) outcomes. We hypothesized that loss of stage N2 features is associated with more severe grades of encephalopathy and worse ICU outcomes including death.

MATERIALS AND METHODS

This was an observational cohort study of 93 medical ICU patients without primary acute brain injury who underwent continuous EEG. Type and severity of critical illness, sedative-hypnotic use, length of stay, modified Rankin Scale at hospital discharge, and death during hospitalization were abstracted from the medical record. EEG was evaluated for grade of encephalopathy and sleep features.

RESULTS

Patients without K-complexes or without sleep spindles had more severe encephalopathy and higher odds of death. The odds ratio for patients without K-complexes was 18.8 (p = .046). The odds ratio for patients without sleep spindles was 6.3 (p = .036).

CONCLUSIONS

Loss of stage N2 features is common and associated with more severe encephalopathy and higher odds of death. The absence of either Stage N2 feature, K complexes or sleep spindles, may have important prognostic value.

Seizures, periodic and rhythmic patterns in primary intraventricular hemorrhage

Objective

Primary intraventricular hemorrhage (pIVH) uncommonly presents with seizures. There are no prior data regarding the frequency of seizures, periodic and rhythmic patterns on continuous electroencephalography (EEG), (cEEG) in these patients.

Methods

We retrospectively assessed frequency of seizures, periodic discharges, and rhythmic patterns in pIVH patients undergoing cEEG monitoring. We reviewed indications for cEEG, demographics, GCS at presentation and during cEEG, modified Graeb score (mGS), presence of hydrocephalus, cEEG duration, findings and use of antiseizure medications (ASM). cEEG patterns were classified according to location and morphology. All patterns were considered “hyperexcitable” except GRDA. The ictal‐interictal continuum (IIC) was defined as LRDA, PDs, and/or SW >1 Hz but <2.5 Hz, not meeting criteria for definite electrographic seizures.

Results

Eleven patients had pIVH with median age of 81 (46–87) years and median mGS of 15 (9–23). Hydrocephalus was present in 7 (63.6%) and all underwent external ventricular drain (EVD) placement. Median cEEG recording was 19 (12–156) hours. Periodic or rhythmic EEG patterns were seen in 7 of 11 (64%), 5 of which were “hyperexcitable”. For the 5 patients with pIVH, EVDs, and hyperexcitable patterns, 4 (80%) were lateralized contralateral to the EVD and 1 (20%) was generalized to the EVD. The only significant difference between the hyperexcitable and non‐hyperexcitable group was duration of cEEG monitoring (P = 0.007).

Interpretation

Hyperexcitable patterns were common in our cases. Further research is warranted to assess prevalence of hyperexcitable patterns, their risk factors, underlying pathophysiology, and association with neuronal injury in pIVH.

Presurgical language fMRI: Technical practices in epilepsy surgical planning

Little is known about how language functional MRI (fMRI) is executed in clinical practice in spite of its widespread use. Here we comprehensively documented its execution in surgical planning in epilepsy. A questionnaire focusing on cognitive design, image acquisition, analysis and interpretation, and practical considerations was developed. Individuals responsible for collecting, analyzing, and interpreting clinical language fMRI data at 63 epilepsy surgical programs responded. The central finding was of marked heterogeneity in all aspects of fMRI. Most programs use multiple tasks, with a fifth routinely using 2, 3, 4, or 5 tasks with a modal run duration of 5 min. Variants of over 15 protocols are in routine use with forms of noun–verb generation, verbal fluency, and semantic decision‐making used most often. Nearly all aspects of data acquisition and analysis vary markedly. Neither of the two best‐validated protocols was used by more than 10% of respondents. Preprocessing steps are broadly consistent across sites, language‐related blood flow is most often identified using general linear modeling (76% of respondents), and statistical thresholding typically varies by patient (79%). The software SPM is most often used. fMRI programs inconsistently include input from experts with all required skills (imaging, cognitive assessment, MR physics, statistical analysis, and brain–behavior relationships). These data highlight marked gaps between the evidence supporting fMRI and its clinical application. Teams performing language fMRI may benefit from evaluating practice with reference to the best‐validated protocols to date and ensuring individuals trained in all aspects of fMRI are involved to optimize patient care.

Electro-clinical characteristics and prognostic significance of post anoxic myoclonus

OBJECTIVE

To systematically examine the electro-clinical characteristics of post anoxic myoclonus (PAM) and their prognostic implications in comatose cardiac arrest (CA) survivors.

METHODS

Fifty-nine CA survivors who developed myoclonus within 72 h of arrest and underwent continuous EEG monitoring were included in the study. Retrospective chart review was performed for all relevant clinical variables including time of PAM onset ("early onset" when within 24 h) and semiology (multi-focal, facial/ocular, whole body and limbs only). EEG findings including background, reactivity, epileptiform patterns and EEG correlate to myoclonus were reviewed at 6, 12, 24, 48 and 72 h after the return of spontaneous circulation (ROSC). Outcome was categorized as either with recovery of consciousness (Cerebral Performance Category (CPC) 1-3) or without recovery of consciousness (CPC 4-5) at the time of discharge.

RESULTS

Seven of the 59 patients (11.9%) regained consciousness, including 6/51 (11.8%) with early onset PAM. Patients with recovery of consciousness had shorter time to ROSC, and were more likely to have preserved brainstem reflexes and normal voltage background at all times. No patient with suppression burst or low voltage background (N = 52) at any point regained consciousness. In the subset where precise electro-clinical correlation was possible, all (5/5) those with recovery of consciousness had multi-focal myoclonus and most (4/5) had midline-maximal spikes over a continuous background. No patient with any other semiology (N = 21) regained consciousness.

CONCLUSIONS

Early onset PAM is not always associated with lack of recovery of consciousness. EEG can help discriminate between patients who may or may not regain consciousness by the time of hospital discharge.

Presurgical language fMRI: Clinical practices and patient outcomes in epilepsy surgical planning

The goal of this study was to document current clinical practice and report patient outcomes in presurgical language functional MRI (fMRI) for epilepsy surgery. Epilepsy surgical programs worldwide were surveyed as to the utility, implementation, and efficacy of language fMRI in the clinic; 82 programs responded. Respondents were predominantly US (61%) academic programs (85%), and evaluated adults (44%), adults and children (40%), or children only (16%). Nearly all (96%) reported using language fMRI. Surprisingly, fMRI is used to guide surgical margins (44% of programs) as well as lateralize language (100%). Sites using fMRI for localization most often use a distance margin around activation of 10mm. While considered useful, 56% of programs reported at least one instance of disagreement with other measures. Direct brain stimulation typically confirmed fMRI findings (74%) when guiding margins, but instances of unpredicted decline were reported by 17% of programs and 54% reported unexpected preservation of function. Programs reporting unexpected decline did not clearly differ from those which did not. Clinicians using fMRI to guide surgical margins do not typically map known language‐critical areas beyond Broca's and Wernicke's. This initial data shows many clinical teams are confident using fMRI not only for language lateralization but also to guide surgical margins. Reported cases of unexpected language preservation when fMRI activation is resected, and cases of language decline when it is not, emphasize a critical need for further validation. Comprehensive studies comparing commonly‐used fMRI paradigms to predict stimulation mapping and post‐surgical language decline remain of high importance.

Abstract 35: Hyperexcitability and Seizures in Primary Intraventricular Hemorrhage

Introduction: While seizures are uncommon but reported in primary intraventricular hemorrhage (IVH), little evidence is available on the prevalence of hyperexcitable patterns on long term EEG monitoring.

Methods: We sought to determine the prevalence of hyperexcitable patterns and seizures in patients with primary IVH who were extracted from a cohort consisting of patients with spontaneous intracerebral hemorrhage (sICH) who underwent continuous electroencephalogram (cEEG) monitoring between January 2013 and December 2016 at Yale-New Haven Hospital. Indications for cEEG monitoring included fluctuation of or depressed mental status, abnormal movements and a limited clinical exam. We recorded demographics, radiologic hydrocephalus, duration of EEG recording and EEG findings. Hyperexcitable patterns comprised generalized, bilateral independent or lateralized periodic discharges (PDs), lateralized rhythmic delta activity (RDA), brief potentially ictal rhythmic discharges (B(I)RDs), and spike-and-wave discharges (SW).

Results: Of 196 adults with sICH who had cEEG performed, 13 patients (54% female) had primary IVH. Hydrocephalus was present in 9 patients (69%). Patients were monitored for a mean duration of 22.4 (± 14.7) hours. 9 patients had hyperexcitable patterns and/or electrographic seizures (70%): Electrographic seizures and co-existent hyperexcitable patterns were captured in 2 of 13 patients (16%) and hyperexcitable patterns without seizures in 7 of 13 patients (54%). Hyperexcitable patterns included periodic discharges (PDs) (4) (generalized, lateralized and bilateral independent, with and without rhythmicity), rhythmic delta activity (RDA) (5) (both lateralized and generalized, with and without sharps), brief potentially ictal rhythmic discharges(B(I)RDs) (1) and spike-and-wave discharges (SW) (1). There was no significant difference between patients with and without hydrocephalus and hyperexcitability or electrographic seizures (p= 0.76).

Conclusion: Both electrographic seizures and/or patterns of hyperexcitability on EEG are common in our cohort of primary IVH patients. The exclusion or detection of non-convulsive seizures offers an opportunity for therapeutic intervention.

Commonalities in epileptogenic processes from different acute brain insults: Do they translate?

The most common forms of acquired epilepsies arise following acute brain insults such as traumatic brain injury, stroke, or central nervous system infections. Treatment is effective for only 60%-70% of patients and remains symptomatic despite decades of effort to develop epilepsy prevention therapies. Recent preclinical efforts are focused on likely primary drivers of epileptogenesis, namely inflammation, neuron loss, plasticity, and circuit reorganization. This review suggests a path to identify neuronal and molecular targets for clinical testing of specific hypotheses about epileptogenesis and its prevention or modification. Acquired human epilepsies with different etiologies share some features with animal models. We identify these commonalities and discuss their relevance to the development of successful epilepsy prevention or disease modification strategies. Risk factors for developing epilepsy that appear common to multiple acute injury etiologies include intracranial bleeding, disruption of the blood-brain barrier, more severe injury, and early seizures within 1 week of injury. In diverse human epilepsies and animal models, seizures appear to propagate within a limbic or thalamocortical/corticocortical network. Common histopathologic features of epilepsy of diverse and mostly focal origin are microglial activation and astrogliosis, heterotopic neurons in the white matter, loss of neurons, and the presence of inflammatory cellular infiltrates. Astrocytes exhibit smaller K+ conductances and lose gap junction coupling in many animal models as well as in sclerotic hippocampi from temporal lobe epilepsy patients. There is increasing evidence that epilepsy can be prevented or aborted in preclinical animal models of acquired epilepsy by interfering with processes that appear common to multiple acute injury etiologies, for example, in post-status epilepticus models of focal epilepsy by transient treatment with a trkB/PLCγ1 inhibitor, isoflurane, or HMGB1 antibodies and by topical administration of adenosine, in the cortical fluid percussion injury model by focal cooling, and in the albumin posttraumatic epilepsy model by losartan. Preclinical studies further highlight the roles of mTOR1 pathways, JAK-STAT3, IL-1R/TLR4 signaling, and other inflammatory pathways in the genesis or modulation of epilepsy after brain injury. The wealth of commonalities, diversity of molecular targets identified preclinically, and likely multidimensional nature of epileptogenesis argue for a combinatorial strategy in prevention therapy. Going forward, the identification of impending epilepsy biomarkers to allow better patient selection, together with better alignment with multisite preclinical trials in animal models, should guide the clinical testing of new hypotheses for epileptogenesis and its prevention.

Association of an Electroencephalography-Based Risk Score With Seizure Probability in Hospitalized Patients

Importance

Continuous electroencephalography (EEG) use in critically ill patients is expanding. There is no validated method to combine risk factors and guide clinicians in assessing seizure risk.

Objective

To use seizure risk factors from EEG and clinical history to create a simple scoring system associated with the probability of seizures in patients with acute illness.

Design, Setting, and Participants

We used a prospective multicenter (Emory University Hospital, Brigham and Women's Hospital, and Yale University Hospital) database containing clinical and electrographic variables on 5427 continuous EEG sessions from eligible patients if they had continuous EEG for clinical indications, excluding epilepsy monitoring unit admissions. We created a scoring system model to estimate seizure risk in acutely ill patients undergoing continuous EEG. The model was built using a new machine learning method (RiskSLIM) that is designed to produce accurate, risk-calibrated scoring systems with a limited number of variables and small integer weights. We validated the accuracy and risk calibration of our model using cross-validation and compared its performance with models built with state-of-the-art logistic regression methods. The database was developed by the Critical Care EEG Research Consortium and used data collected over 3 years. The EEG variables were interpreted using standardized terminology by certified reviewers.

Exposures

All patients had more than 6 hours of uninterrupted EEG recordings.

Main Outcomes and Measures

The main outcome was the average risk calibration error.

Results

There were 5427 continuous EEGs performed on 4772 participants (2868 men, 49.9%; median age, 61 years) performed at 3 institutions, without further demographic stratification. Our final model, 2HELPS2B, had an area under the curve of 0.819 and average calibration error of 2.7% (95% CI, 2.0%-3.6%). It included 6 variables with the following point assignments: (1) brief (ictal) rhythmic discharges (B[I]RDs) (2 points); (2) presence of lateralized periodic discharges, lateralized rhythmic delta activity, or bilateral independent periodic discharges (1 point); (3) prior seizure (1 point); (4) sporadic epileptiform discharges (1 point); (5) frequency greater than 2.0 Hz for any periodic or rhythmic pattern (1 point); and (6) presence of "plus" features (superimposed, rhythmic, sharp, or fast activity) (1 point). The probable seizure risk of each score was 5% for a score of 0, 12% for a score of 1, 27% for a score of 2, 50% for a score of 3, 73% for a score of 4, 88% for a score of 5, and greater than 95% for a score of 6 or 7.

Conclusions and Relevance

The 2HELPS2B model is a quick accurate tool to aid clinical judgment of the risk of seizures in critically ill patients.

Psychiatric and behavioral side effects of antiepileptic drugs in adults with epilepsy

PURPOSE

Psychiatric and behavioral side effects (PBSEs) are common, undesirable effects associated with antiepileptic drug (AED) use. The objective of the study was to compare the PBSE profiles of older and newer AEDs in a large specialty practice-based sample of patients diagnosed with epilepsy.

METHODS

As part of the Columbia and Yale AED Database Project, we reviewed patient records including demographics, medical history, AED use, and side effects for 4085 adult patients (age: 18 years) newly started on an AED regimen. Psychiatric and behavioral side effects were determined by patient or physician report in the medical record, which included depressive mood, psychosis, anxiety, suicidal thoughts, irritability, aggression, and tantrum. Significant non-AED predictors of PBSE rate were first determined from 83 variables using logistic regression. Predictors were then controlled for in the comparison analysis of the rate of PBSEs and intolerable PBSEs (PBSEs that led to dosage reduction or discontinuation) between 18 AEDs.

RESULTS

Psychiatric and behavioral side effects occurred in 17.2% of patients and led to intolerability in 13.8% of patients. History of psychiatric condition(s), secondary generalized seizures, absence seizures, and intractable epilepsy were associated with increased incidence of PBSE. Levetiracetam (LEV) had the greatest PBSE rate (22.1%). This was statistically significant when compared with the aggregate of the other AEDs (P<0.001, OR=6.87). Levetiracetam was also significantly (P<0.001) associated with higher intolerability rate (17.7%), dose decreased rate (9.4%), and complete cessation rate (8.3%), when compared with the aggregate of the other AEDs. Zonisamide (ZNS) was also significantly associated with a higher rate of PBSE (9.7%) and IPBSE (7.9%, all P<0.001). On the other hand, carbamazepine (CBZ), clobazam (CLB), gabapentin (GBP), lamotrigine (LTG), oxcarbazepine (OXC), phenytoin (PHT), and valproate (VPA) were significantly associated with a decreased PBSE rates (P<0.001). Carbamazepine, GBP, LTG, PHT, and VPA were also associated with lower IPBSE rates when compared individually with the aggregate of other AEDs. All other AEDs were found to have intermediate rates that were not either increased or decreased compared with other AEDs. When each AED was compared to LTG, only CBZ had a significantly lower PBSE rate. The main limitations of this study were that the study design was retrospective and not blinded, and the AEDs were not randomly assigned to patients.

CONCLUSIONS

Psychiatric and behavioral side effects occur more frequently in patients taking LEV and ZNS than any other AED and led to higher rates of intolerability. Lower PBSE rates were seen in patients taking CBZ, CLB, GBP, LTG, OXC, PHT, and VPA. Our findings may help facilitate the AED selection process.

Time-dependent risk of seizures in critically ill patients on continuous electroencephalogram

OBJECTIVE

Find the optimal continuous electroencephalographic (CEEG) monitoring duration for seizure detection in critically ill patients.

METHODS

We analyzed prospective data from 665 consecutive CEEGs, including clinical factors and time-to-event emergence of electroencephalographic (EEG) findings over 72 hours. Clinical factors were selected using logistic regression. EEG risk factors were selected a priori. Clinical factors were used for baseline (pre-EEG) risk. EEG findings were used for the creation of a multistate survival model with 3 states (entry, EEG risk, and seizure). EEG risk state is defined by emergence of epileptiform patterns.

RESULTS

The clinical variables of greatest predictive value were coma (31% had seizures; odds ratio [OR] = 1.8, p < 0.01) and history of seizures, either remotely or related to acute illness (34% had seizures; OR = 3.0, p < 0.001). If there were no epileptiform findings on EEG, the risk of seizures within 72 hours was between 9% (no clinical risk factors) and 36% (coma and history of seizures). If epileptiform findings developed, the seizure incidence was between 18% (no clinical risk factors) and 64% (coma and history of seizures). In the absence of epileptiform EEG abnormalities, the duration of monitoring needed for seizure risk of <5% was between 0.4 hours (for patients who are not comatose and had no prior seizure) and 16.4 hours (comatose and prior seizure).

INTERPRETATION

The initial risk of seizures on CEEG is dependent on history of prior seizures and presence of coma. The risk of developing seizures on CEEG decays to <5% by 24 hours if no epileptiform EEG abnormalities emerge, independent of initial clinical risk factors. Ann Neurol 2017;82:177-185.