Activity-dependent ectopic action potentials in regular-spiking neurons of the neocortex.

Introduction: Action potentials usually travel orthodromically along a neuron's axon, from the axon initial segment (AIS) toward the presynaptic terminals. Under some circumstances action potentials also travel in the opposite direction, antidromically, after being initiated at a distal location. Given their initiation at an atypical site, we refer to these events as "ectopic action potentials." Ectopic action potentials (EAPs) were initially observed in pathological conditions including seizures and nerve injury. Several studies have described regular-spiking (RS) pyramidal neurons firing EAPs in seizure models. Under nonpathological conditions, EAPs were reported in a few populations of neurons, and our group has found that EAPs can be induced in a large proportion of parvalbumin-expressing interneurons in the neocortex. Nevertheless, to our knowledge there have been no prior reports of ectopic firing in the largest population of neurons in the neocortex, pyramidal neurons, under nonpathological conditions. Methods: We performed in vitro recordings utilizing the whole-cell patch clamp technique. To elicit EAPs, we triggered orthodromic action potentialswith either long, progressively increasing current steps, or with trains of brief pulses at 30, 60, or 100 Hz delivered in 3 different ways, varying in stimulus and resting period duration. Results: We found that a large proportion (72.7%) of neocortical RS cells from mice can fire EAPs after a specific stimulus in vitro, and that most RS cells (56.1%) are capable of firing EAPs across a broad range of stimulus conditions. Of the 37 RS neurons in which we were able to elicit EAPs, it took an average of 863.8 orthodromic action potentials delivered over the course of an average of ~81.4 s before the first EAP was seen. We observed that some cells responded to specific stimulus frequencies while less selective, suggesting frequency tuning in a subset of the cells. Discussion: Our findings suggest that pyramidal cells can integrate information over long time-scales before briefly entering a mode of self-generated firing that originates in distal axons. The surprising ubiquity of EAP generation in RS cells raises interesting questions about the potential roles of ectopic spiking in information processing, cortical oscillations, and seizure susceptibility.

Risk Factors for Opioid Utilization in Patients with Intracerebral Hemorrhage.

BACKGROUND: Headache is a common presenting symptom of intracerebral hemorrhage (ICH) and often necessitates treatment with opioid medications. However, opioid prescribing patterns in patients with ICH are not well described. We aimed to characterize the prevalence and risk factors for short and longer-term opioid use in patients with ICH. METHODS: We conducted a retrospective cohort study using data from a single-center registry of patients with nontraumatic ICH. This registry included data on demographics, ICH-related characteristics, and premorbid, inpatient, and postdischarge medications. After excluding patients who died or received end-of-life care, we used multivariable regression models adjusted for premorbid opioid use to determine demographic and ICH-related risk factors for inpatient and postdischarge opioid use. RESULTS: Of 468 patients with ICH in our cohort, 15% (n = 70) had premorbid opioid use, 53% (n = 248) received opioids during hospitalization, and 12% (n = 53) were prescribed opioids at discharge. The most commonly used opioids during hospitalization were fentanyl (38%), oxycodone (30%), morphine (26%), and hydromorphone (7%). Patients who received opioids during hospitalization were younger (univariate: median [interquartile range] 64 [53.5-74] vs. 76 [67-83] years, p < 0.001; multivariable: odds ratio [OR] 0.96 per year, 95% confidence interval [CI] 0.94-0.98) and had larger ICH volumes (univariate: median [interquartile range] 10.1 [2.1-28.6] vs. 2.7 [0.8-9.9] cm3, p < 0.001; multivariable: OR 1.05 per cm3, 95% CI 1.03-1.08) than those who did not receive opioids. All patients who had external ventricular drain placement and craniotomy/craniectomy received inpatient opioids. Additional risk factors for increased inpatient opioid use included infratentorial ICH location (OR 4.8, 95% CI 2.3-10.0), presence of intraventricular hemorrhage (OR 3.9, 95% CI 2.2-7.0), underlying vascular lesions (OR 3.0, 95% CI 1.1-8.1), and other secondary ICH etiologies (OR 7.5, 95% CI 1.7-32.8). Vascular lesions (OR 4.0, 95% CI 1.3-12.5), malignancy (OR 5.0, 95% CI 1.5-16.4), vasculopathy (OR 10.0, 95% CI 1.8-54.2), and other secondary etiologies (OR 7.2, 95% CI 1.8-29.9) were also risk factors for increased opioid prescriptions at discharge. Among patients who received opioid prescriptions at discharge, 43% (23 of 53) continued to refill their prescriptions at 3 months post discharge. CONCLUSIONS: Inpatient opioid use in patients with ICH is common, with some risk factors that may be mechanistically connected to primary headache pathophysiology. However, the lower frequency of opioid prescriptions at discharge suggests that inpatient opioid use does not necessarily lead to a high rate of long-term opioid dependence in patients with ICH.

Gender Disparities in Stroke Code Activation in Patients with Intracerebral Hemorrhage.

OBJECTIVES: Routine implementation of protocol-driven stroke "codes" results in timelier and more effective acute stroke management. However, it is unclear if patient demographics contribute to disparities in stroke code activation. We aimed to explore these demographic factors in a retrospective cohort study of patients with intracerebral hemorrhage (ICH). MATERIALS AND METHODS: We identified consecutive patients with non-traumatic ICH who presented directly to our Comprehensive Stroke Center over 2 years and collected data on demographics, clinical features, and stroke code activation. We used multivariable logistic regression to examine differences in stroke code activation based on patient demographics while adjusting for initial clinical features (NIH Stroke Scale, FAST [facial drooping, arm weakness, speech difficulties] vs. non-FAST symptoms, time from last-known-well [LKW], and systolic blood pressure [SBP]). RESULTS: Among 265 patients, 68% (n=179) had a stroke code activation. Stroke codes occurred less frequently in women (62%) than men (72%) and in non-white (57%) vs. white patients (70%). Non-stroke code patients were less likely to have FAST symptoms (37% vs. 87%) and had lower initial SBP (mean±SD 159.3±34.2 vs. 176.0±31.9 mmHg) than stroke code patients. In our primary multivariable models, neither age nor race were associated with stroke code activation. However, women were significantly less likely to have stroke codes than men (OR 0.49 [95% CI 0.24-0.98]), as were non-FAST symptoms (OR 0.11 [95% CI 0.05-0.22]). CONCLUSIONS: Our data suggest gender disparities in emergency stroke care that should prompt further investigations into potential systemic biases. Increased awareness of atypical stroke symptoms is also warranted.