Ictal-Interictal Continuum in the Pediatric Intensive Care Unit.

BACKGROUND: The ictal-interictal continuum (IIC) consists of several electroencephalogram (EEG) patterns that are common in critically ill adults. Studies focused on the IIC are limited in critically ill children and have focused primarily on associations with electrographic seizures (ESs). We report the incidence of the IIC in the pediatric intensive care unit (PICU). We then compare IIC patterns to rhythmic and periodic patterns (RPP) not meeting IIC criteria looking for associations with acute cerebral abnormalities, ES, and in-hospital mortality. METHODS: This was a retrospective review of prospectively collected data for patients admitted to the PICU at Children's National Hospital from July 2021 to January 2023 with continuous EEG. We excluded patients with known epilepsy and cerebral injury prior to presentation. All patients were screened for RPP. The American Clinical Neurophysiology Society standardized Critical Care EEG terminology for the IIC was applied to each RPP. Associations between IIC and RPP not meeting IIC criteria, with clinical and EEG variables, were calculated using odds ratios (ORs). RESULTS: Of 201 patients, 21% (42/201) had RPP and 12% (24/201) met IIC criteria. Among patients with an IIC pattern, the median age was 3.4 years (interquartile range (IQR) 0.6-12 years). Sixty-seven percent (16/24) of patients met a single IIC criterion, whereas the remainder met two criteria. ESs were identified in 83% (20/24) of patients and cerebral injury was identified in 96% (23/24) of patients with IIC patterns. When comparing patients with IIC patterns with those with RPP not qualifying as an IIC pattern, both patterns were associated with acute cerebral abnormalities (IIC OR 26 [95% confidence interval {CI} 3.4-197], p = 0.0016 vs. RPP OR 3.5 [95% CI 1.1-11], p = 0.03), however, only the IIC was associated with ES (OR 121 [95% CI 33-451], p < 0.0001) versus RPP (OR 1.3 [0.4-5], p = 0.7). CONCLUSIONS: Rhythmic and periodic patterns and subsequently the IIC are commonly seen in the PICU and carry a high association with cerebral injury. Additionally, the IIC, seen in more than 10% of critically ill children, is associated with ES. The independent impact of RPP and IIC patterns on secondary brain injury and need for treatment of these patterns independent of ES requires further study.

Pediatric Moyamoya Revascularization Perioperative Care: A Modified Delphi Study.

BACKGROUND: Surgical revascularization decreases the long-term risk of stroke in children with moyamoya arteriopathy but can be associated with an increased risk of stroke during the perioperative period. Evidence-based approaches to optimize perioperative management are limited and practice varies widely. Using a modified Delphi process, we sought to establish expert consensus on key components of the perioperative care of children with moyamoya undergoing indirect revascularization surgery and identify areas of equipoise to define future research priorities. METHODS: Thirty neurologists, neurosurgeons, and intensivists practicing in North America with expertise in the management of pediatric moyamoya were invited to participate in a three-round, modified Delphi process consisting of a 138-item practice patterns survey, anonymous electronic evaluation of 88 consensus statements on a 5-point Likert scale, and a virtual group meeting during which statements were discussed, revised, and reassessed. Consensus was defined as ≥ 80% agreement or disagreement. RESULTS: Thirty-nine statements regarding perioperative pediatric moyamoya care for indirect revascularization surgery reached consensus. Salient areas of consensus included the following: (1) children at a high risk for stroke and those with sickle cell disease should be preadmitted prior to indirect revascularization; (2) intravenous isotonic fluids should be administered in all patients for at least 4 h before and 24 h after surgery; (3) aspirin should not be discontinued in the immediate preoperative and postoperative periods; (4) arterial lines for blood pressure monitoring should be continued for at least 24 h after surgery and until active interventions to achieve blood pressure goals are not needed; (5) postoperative care should include hourly vital signs for at least 24 h, hourly neurologic assessments for at least 12 h, adequate pain control, maintaining normoxia and normothermia, and avoiding hypotension; and (6) intravenous fluid bolus administration should be considered the first-line intervention for new focal neurologic deficits following indirect revascularization surgery. CONCLUSIONS: In the absence of data supporting specific care practices before and after indirect revascularization surgery in children with moyamoya, this Delphi process defined areas of consensus among neurosurgeons, neurologists, and intensivists with moyamoya expertise. Research priorities identified include determining the role of continuous electroencephalography in postoperative moyamoya care, optimal perioperative blood pressure and hemoglobin targets, and the role of supplemental oxygen for treatment of suspected postoperative ischemia.

Case Report: Successful Anterior Circulation Thrombectomy After 24 Hours in an Adolescent.

BACKGROUND: Arterial ischemic stroke in children comes with the potential for morbidity and mortality and can result in high cost of care and decreased quality of life among survivors. Children with arterial ischemic stroke are increasingly being treated with mechanical thrombectomy, but little is known about the risks and benefits 24 hours after a patient's last known well (LKW) time. METHODS: A 16-year-old female presented with acute onset of dysarthria and right hemiparesis with LKW time 22 hours prior. Pediatric National Institutes of Health Stroke Scale score was 12. Magnetic resonance imaging showed diffusion restriction and T2 hyperintensity primarily in the left basal ganglia. Magnetic resonance angiography revealed left M1 occlusion. Arterial spin labeling showed a large apparent perfusion deficit. She underwent thrombectomy with TICI3 recanalization 29.5 hours after LKW time. RESULTS: At 2-month follow-up, her examination showed moderate right-hand weakness and mild diminished sensation of the right arm. CONCLUSIONS: Adult thrombectomy trials include patients up to 24 hours from their LKW time and suggest that some patients maintain a favorable perfusion profile for over 24 hours. Without intervention many go on to experience infarct expansion. The persistence of a favorable perfusion profile likely reflects robust collateral circulation. We hypothesized our patient was relying on collateral circulation to maintain the noninfarcted areas of her left middle cerebral artery territory. Owing to concern for eventual collateral failure, thrombectomy outside of the 24-hour window was performed. This case serves as a call to action to better understand the impact of collateral circulation on cerebral perfusion in children with large vessel occlusions and delineate which children may benefit from thrombectomy in a delayed time window.

Neuromonitoring in Children with Cerebrovascular Disorders.

BACKGROUND: Cerebrovascular disorders are an important cause of morbidity and mortality in children. The acute care of a child with an ischemic or hemorrhagic stroke or cerebral sinus venous thrombosis focuses on stabilizing the patient, determining the cause of the insult, and preventing secondary injury. Here, we review the use of both invasive and noninvasive neuromonitoring modalities in the care of pediatric patients with arterial ischemic stroke, nontraumatic intracranial hemorrhage, and cerebral sinus venous thrombosis. METHODS: Narrative review of the literature on neuromonitoring in children with cerebrovascular disorders. RESULTS: Neuroimaging, near-infrared spectroscopy, transcranial Doppler ultrasonography, continuous and quantitative electroencephalography, invasive intracranial pressure monitoring, and multimodal neuromonitoring may augment the acute care of children with cerebrovascular disorders. Neuromonitoring can play an essential role in the early identification of evolving injury in the aftermath of arterial ischemic stroke, intracranial hemorrhage, or sinus venous thrombosis, including recurrent infarction or infarct expansion, new or recurrent hemorrhage, vasospasm and delayed cerebral ischemia, status epilepticus, and intracranial hypertension, among others, and this, is turn, can facilitate real-time adjustments to treatment plans. CONCLUSIONS: Our understanding of pediatric cerebrovascular disorders has increased dramatically over the past several years, in part due to advances in the neuromonitoring modalities that allow us to better understand these conditions. We are now poised, as a field, to take advantage of advances in neuromonitoring capabilities to determine how best to manage and treat acute cerebrovascular disorders in children.

The Spectrum of Quantitative EEG Utilization Across North America: A Cross-Sectional Survey.

BACKGROUND: Continuous electroencephalography (cEEG) is commonly used for neuromonitoring in pediatric intensive care units (PICU); however, there are barriers to real-time interpretation of EEG data. Quantitative EEG (qEEG) transforms the EEG signal into time-compressed graphs, which can be displayed at the bedside. A survey was designed to understand current PICU qEEG use. METHODS: An electronic survey was sent to the Pediatric Neurocritical Care Research Group and Pediatric Status Epilepticus Research Group, and intensivists in 16 Canadian PICUs. Questions addressed demographics, qEEG acquisition and storage, clinical use, and education. RESULTS: Fifty respondents from 39 institutions completed the survey (response rate 53% [39 of 74 institutions]), 76% (37 of 50) from the United States and 24% (12 of 50) from Canada. Over half of the institutions (22 of 39 [56%]) utilize qEEG in their ICUs. qEEG use was associated with having a neurocritical care (NCC) service, ≥200 NCC consults/year, ≥1500 ICU admissions/year, and ≥4 ICU EEGs/day (P < 0.05 for all). Nearly all users (92% [24 of 26]) endorsed that qEEG enhanced care of children with acute neurological injury. Lack of training in qEEG was identified as a common barrier [85% (22 of 26)]. Reviewing and reporting of qEEG was not standard at most institutions. Training was required by 14% (three of 22) of institutions, and 32% (seven of 22) had established curricula. CONCLUSIONS: ICU qEEG was used at more than half of the institutions surveyed, but review, reporting, and application of this tool remained highly variable. Although providers identify qEEG as a useful tool in patient management, further studies are needed to define clinically meaningful pediatric trends, standardize reporting, and enhance educate bedside providers.

Acute Hospital Management of Pediatric Stroke.

The field of pediatric stroke has historically been hampered by limited evidence and small patient cohorts. However the landscape of childhood stroke is rapidly changing due in part to increasing awareness of the importance of pediatric stroke and the emergence of dedicated pediatric stroke centers, care pathways, and alert systems. Acute pediatric stroke management hinges on timely diagnosis confirmed by neuroimaging, appropriate consideration of recanalization therapies, implementation of neuroprotective measures, and attention to secondary prevention. Because pediatric stroke is highly heterogenous in etiology, management strategies must be individualized. Determining a child's underlying stroke etiology is essential to appropriately tailoring hyperacute stroke management and determining best approach to secondary prevention. Herein, we review the methods of recognition, diagnosis, management, current knowledge gaps and promising research for pediatric stroke.

Cerebral Sinus Venous Thrombosis in Infants after Surgery for Congenital Heart Disease.

OBJECTIVE: To determine the prevalence of and risk factors for cerebral sinus venous thrombosis (CSVT) in neonates undergoing congenital heart disease (CHD) repair. STUDY DESIGN: Neonates who had CHD repair with cardiopulmonary bypass and postoperative brain magnetic resonance imaging (MRI) between 2013 and 2019 at a single tertiary care center were identified from institutional databases. Demographic, clinical, and surgical data were abstracted from these databases and from the medical record; 278 neonates with CHD had cardiopulmonary bypass, 184 of whom had a postoperative brain MRI. RESULTS: Eight patients (4.3%) had a CSVT. Transposition of the great arteries with an intact ventricular septum (P < .01) and interrupted aortic arch (P = .02) were associated with an increased risk for CSVT. Other risk factors for CSVT included cross-clamp time (98 [IQR, 77.5-120] minutes vs 67 [IQR, 44-102] minutes; P = .03), units of platelets (3.63 [IQR, 3-4] vs 2.17 [IQR, 1-4]; P < .01) and packed red blood cells (0.81 [IQR, 0.25-1] vs 1.21 [IQR, 1-1]; P = .03) transfused intraoperatively, and time between surgery and MRI (10 [IQR, 7-12.5] days vs 20 [IQR, 12-35] days; P < .01). Five patients (62.5%) were treated with anticoagulation. All patients had complete or partial resolution of their CSVT, regardless of treatment. CONCLUSIONS: Brain MRI after cardiopulmonary bypass in neonates revealed a low prevalence of CSVT (4.3%). Further studies are needed to establish best practices for surveillance, prevention, and treatment of CSVT in this population.

Pediatric Critical Care Neurologists in the United States and Canada: A Survey of Clinical Practice Experience.

OBJECTIVE: To describe the characteristics of pediatric intensive care neurologists and their practice in the United States and Canada. METHODS: We performed a survey-based study of child neurologists who self-identify as 'intensive care neurologists'. The survey included questions about demographics, training, pediatric neurocritical care service and job structure, teaching, academics, challenges, and views on the future of pediatric neurocritical care. RESULTS: We analyzed 55 surveys. Most respondents were 31-50 years of age with ≤10 years of practice experience. Fifty-four percent identified as female. Most completed subspecialty training after child neurology residency. The majority practice at highly resourced centers with >45 intensive care unit beds. Respondents cover a variety of inpatient (critical and noncritical care) services, at times simultaneously, for a median of 19.5 weeks/y and work >70 hours/wk when on service for pediatric neurocritical care. The top 3 challenges reported were competing demands for time, excess volume, and communication with critical care medicine. Top priorities for the "ideal pediatric neurocritical care service" were attendings with training in pediatric neurocritical care or a related field and joint rounding with critical care medicine. CONCLUSION: We report a survey-based analysis of the demographics and scope of practice of pediatric critical care neurologists. We highlight challenges faced and provide a framework for the further development of this rapidly growing field.

Pediatric Acute Stroke Protocols in the United States and Canada.

OBJECTIVE: To describe existing pediatric acute stroke protocols to better understand how pediatric centers might implement such pathways within the context of institution-specific structures. STUDY DESIGN: We administered an Internet-based survey of pediatric stroke specialists. The survey included questions about hospital demographics, child neurology and pediatric stroke demographics, acute stroke response, imaging, and hyperacute treatment. RESULTS: Forty-seven surveys were analyzed. Most respondents practiced at a large, freestanding children's hospital with a moderate-sized neurology department and at least 1 neurologist with expertise in pediatric stroke. Although there was variability in how the hospitals deployed stroke protocols, particularly in regard to staffing, the majority of institutions had an acute stroke pathway, and almost all included activation of a stroke alert page. Most institutions preferred magnetic resonance imaging (MRI) over computed tomography (CT) and used abbreviated MRI protocols for acute stroke imaging. Most institutions also had either CT-based or magnetic resonance-based perfusion imaging available. At least 1 patient was treated with intravenous tissue plasminogen activator (IV-tPA) or mechanical thrombectomy at the majority of institutions during the year before our survey. CONCLUSIONS: An acute stroke protocol is utilized in at least 41 pediatric centers in the US and Canada. Most acute stroke response teams are multidisciplinary, prefer abbreviated MRI over CT for diagnosis, and have experience providing IV-tPA and mechanical thrombectomy. Further studies are needed to standardize practices of pediatric acute stroke diagnosis and hyperacute management.

Atlanto-occipital ligament calcification: a novel imaging finding in pediatric rotational vertebral artery occlusion.

We describe a 2-year-old girl with bow hunter syndrome complicated by vertebral artery dissection and multiple ischemic infarcts. Pediatric bow hunter syndrome is a rare and likely under-recognized disorder. Interestingly, our patient had atlanto-occipital ligament calcification on CT scan, an imaging finding that has not been reported in association with bow hunter syndrome and one that might help increase recognition of this dynamic disorder of the posterior circulation.

Acute Neuromuscular Disorders in the Pediatric Intensive Care Unit.

BACKGROUND: The neuromuscular disorders encountered in the pediatric intensive care unit (PICU) encompass a broad spectrum of pathologies. These include acute disorders (eg, Guillain-Barre syndrome), acute-on-chronic disorders (eg, myasthenia gravis), progressive disorders (eg, muscular dystrophy), and disorders that develop in the PICU (eg, critical illness myopathy/polyneuropathy). Familiarity with the presenting features of these disorders is of paramount importance in facilitating timely diagnosis. METHODS: We conducted a retrospective review of the medical records of patients admitted to the PICU or Intermediate Care Program (ICP) at a single tertiary children's hospital from 2006 to 2017 with an acute or acute-on-chronic neuromuscular disorder. We did not include patients with a known progressive neuromuscular disorder or critical illness myopathy/polyneuropathy. RESULTS: Twenty-four patients were admitted to the PICU/ICP with acute or acute-on-chronic neuromuscular disorders. Diagnosis and indication for ICU/ICP admission were Guillain-Barre syndrome (n = 6; respiratory failure: 3, respiratory monitoring: 2, autonomic instability: 1), myasthenia gravis (n = 5; airway clearance: 3, respiratory failure: 2), acute flaccid myelitis (n = 3; respiratory failure: 2, respiratory monitoring: 1), periodic paralysis (n = 3; intravenous potassium replacement), rhabdomyolysis (n = 3; monitoring for electrolyte derangements), infant botulism (n = 2; respiratory failure), chronic demyelinating polyneuropathy (n = 1; respiratory failure), and congenital myasthenic syndrome (n = 1; apnea). No patients were admitted to the PICU/ICP with a diagnosis of tick paralysis, acute intermittent porphyria, or inflammatory myopathy. CONCLUSIONS: Although acute and acute-on-chronic neuromuscular disorders are encountered relatively rarely in the PICU, familiarity with the presenting features of these disorders is important in facilitating timely diagnosis. This, in turn, enables the institution of effective management strategies, thereby avoiding complications associated with diagnostic delays.

A Stroke Alert Protocol Decreases the Time to Diagnosis of Brain Attack Symptoms in a Pediatric Emergency Department.

OBJECTIVE: To determine whether a stroke alert system decreases the time to diagnosis of children presenting to the emergency department (ED) with acute-onset focal neurologic deficits. STUDY DESIGN: We performed a retrospective comparison of clinical and demographic information for patients who presented to the ED of a tertiary children's hospital with acute-onset focal neurologic deficits during the 2.5 years before (n = 14) and after (n = 65) the implementation of a stroke alert system. The primary outcome was the median time to neuroimaging analyzed using a Wilcoxon rank-sum test. RESULTS: The median time from ED arrival to neuroimaging for patients with acute-onset focal neurologic deficits decreased significantly after implementation of a stroke alert system (196 minutes; IQR, 85-230 minutes before [n = 14] vs 82 minutes; IQR, 54-123 minutes after [n = 65]; P < .01). Potential intravenous tissue plasminogen activator candidates experienced the shortest time to neuroimaging after implementation of a stroke alert system (54 minutes; IQR, 34-66 minutes [n = 13] for intravenous tissue plasminogen activator candidates vs 89.5 minutes; IQR, 62-126.5 minutes [n = 52] for non-intravenous tissue plasminogen activator candidates; P < .01). CONCLUSIONS: A stroke alert system decreases the median time to diagnosis by neuroimaging of children presenting to the ED with acute-onset focal neurologic deficits by more than one-half. Such a protocol constitutes an important step in ensuring that a greater proportion of children with arterial ischemic stroke are diagnosed in a time frame that enables hyperacute treatment.

Stroke After Cardiac Catheterization in Children.

BACKGROUND: Children with cardiac disease are at high risk for stroke. Approximately one-quarter of strokes in children with cardiac disease occur in the peri-procedural period; yet, the risk factors, clinical presentation, and treatment of post-catheterization stroke in children have not been well defined. METHODS: We conducted a retrospective review of the medical records of patients aged zero to 18 years with a new clinically-apparent arterial ischemic stroke after cardiac catheterization at a tertiary children's hospital from 2006 to 2016. We excluded patients who had cardiac surgery, a cardiac arrest, extracorporeal membrane oxygenation, a ventricular assist device, or an arrhythmia proximate to their stroke. RESULTS: Twenty children had a new clinically-apparent post-catheterization arterial ischemic stroke. The median age was one year (range, two days to 16 years). The most common procedures were balloon dilation for pulmonary vein stenosis (n = 6) and systemic pulmonary collateral closure (n = 5). The most common presenting symptoms were arm weakness (n = 10) and seizure (n = 8). The median time from catheterization to symptom discovery was 31.5 hours (interquartile range, 16.2 to 47.8 hours; n = 18). The median Pediatric Stroke Outcome Measure score 12 months post-stroke was 0.75 (range, 0 to 2; n = 6). CONCLUSIONS: Although arterial ischemic stroke after cardiac catheterization is rare, better understanding this entity is important as children with cardiac disease and stroke have ongoing morbidity. Ameliorating this morbidity requires efforts aimed at preventing and rapidly detecting stroke, thereby enabling timely institution of neuroprotective measures and treatment with hyperacute therapies.

Clinical Determination of Brain Death in Children Supported by Extracorporeal Membrane Oxygenation.

BACKGROUND/OBJECTIVE: Children supported by extracorporeal membrane oxygenation (ECMO) are at risk of catastrophic neurologic injury and brain death. Timely determination of brain death is important for minimizing psychological distress for families, resource allocation, and organ donation. Reports of successful determination of brain death in pediatric patients supported by ECMO are limited. The determination of brain death by clinical criteria requires apnea testing, which has historically been viewed as challenging in patients supported by ECMO. We report eight pediatric patients who underwent a total of 14 brain death examinations, including apnea testing, while supported by veno-arterial ECMO (VA-ECMO), resulting in six cases of clinical determination of brain death. METHODS: We performed a retrospective review of the medical records of pediatric patients who underwent brain death examination while supported by VA-ECMO between 2010 and 2018 at a single tertiary care children's hospital. RESULTS: Eight patients underwent brain death examination, including apnea testing, while supported by VA-ECMO. Six patients met criteria for brain death, while two had withdrawal of technical support after the first examination. During the majority of apnea tests (n = 13/14), the ECMO circuit was modified to achieve hypercarbia while maintaining oxygenation and hemodynamic stability. The sweep flow was decreased prior to apnea testing in ten brain death examinations, carbon dioxide was added to the circuit during three examinations, and ECMO pump flows were increased in response to hypotension during two examinations. CONCLUSIONS: Clinical determination of brain death, including apnea testing, can be performed in pediatric patients supported by ECMO. The ECMO circuit can be effectively modified during apnea testing to achieve a timely rise in carbon dioxide while maintaining oxygenation and hemodynamic stability.

Diffusion-Weighted Imaging Changes in a Child With Posterior Ischemic Optic Neuropathy.

BACKGROUND: Posterior ischemic optic neuropathy results from ischemia of the retrobulbar aspect of the optic nerve. It presents as acute loss of vision without optic disc swelling. This is rare in children, with only seven cases reported to date. Neuroimaging is frequently used to aid in the diagnosis of acute visual complaints in children; however, none of the cases described to date delineate the neuroimaging findings of this entity in children. METHODS: We retrospectively reviewed the electronic medical record. RESULTS: We describe the MRI findings in a 10-month-old boy with posterior ischemic optic neuropathy after intraophthalmic artery injection of chemotherapy for retinoblastoma. CONCLUSIONS: As targeted therapies for retinoblastoma and other diseases amenable to intravascular treatment delivery are more frequently used, the risk of grave vision-related side effects increases. Posterior ischemic optic neuropathy should be considered in the differential diagnosis of any child presenting with acute loss of vision. Dedicated imaging of the orbits can elucidate specific findings that may aid in the diagnosis of this entity in children.

An RNAi-based approach identifies molecules required for glutamatergic and GABAergic synapse development.

We report the results of a genetic screen to identify molecules important for synapse formation and/or maintenance. siRNAs were used to decrease the expression of candidate genes in neurons, and synapse development was assessed. We surveyed 22 cadherin family members and demonstrated distinct roles for cadherin-11 and cadherin-13 in synapse development. Our screen also revealed roles for the class 4 Semaphorins Sema4B and Sema4D in the development of glutamatergic and/or GABAergic synapses. We found that Sema4D affects the formation of GABAergic, but not glutamatergic, synapses. Our screen also identified the activity-regulated small GTPase Rem2 as a regulator of synapse development. A known calcium channel modulator, Rem2 may function as part of a homeostatic mechanism that controls synapse number. These experiments establish the feasibility of RNAi screens to characterize the mechanisms that control mammalian neuronal development and to identify components of the genetic program that regulate synapse formation and/or maintenance.

Ribosomal S6 kinase 2 interacts with and phosphorylates PDZ domain-containing proteins and regulates AMPA receptor transmission.

Extracellular signal-regulated kinase (ERK) signaling is important for neuronal synaptic plasticity. We report here that the protein kinase ribosomal S6 kinase (RSK)2, a downstream target of ERK, uses a C-terminal motif to bind several PDZ domain proteins in heterologous systems and in vivo. Different RSK isoforms display distinct specificities in their interactions with PDZ domain proteins. Mutation of the RSK2 PDZ ligand does not inhibit RSK2 activation in intact cells or phosphorylation of peptide substrates by RSK2 in vitro but greatly reduces RSK2 phosphorylation of PDZ domain proteins of the Shank family in heterologous cells. In primary neurons, NMDA receptor (NMDA-R) activation leads to ERK and RSK2 activation and RSK-dependent phosphorylation of transfected Shank3. RSK2-PDZ domain interactions are functionally important for synaptic transmission because neurons expressing kinase-dead RSK2 display a dramatic reduction in frequency of AMPA-type glutamate receptor-mediated miniature excitatory postsynaptic currents, an effect dependent on the PDZ ligand. These results suggest that binding of RSK2 to PDZ domain proteins and phosphorylation of these proteins or their binding partners regulates excitatory synaptic transmission.