Red blood cell-coupled tissue plasminogen activator prevents impairment of cerebral vasodilatory responses through inhibition of c-Jun-N-terminal kinase and potentiation of p38 mitogen-activated protein kinase after cerebral photothrombosis in the newborn pig.

OBJECTIVE: Pediatric ischemic stroke is a poorly understood, yet clinically important, problem. The sole approved treatment for acute stroke is tissue-type plasminogen activator. However, tissue plasminogen activator vasoactivity aggravates hypoxia/ischemia-induced impairment of cerebrovasodilation in response to hypercapnia and hypotension in newborn pigs. Mitogen-activated protein kinase (a family of 3 kinases, extracellular signal-related kinase, p38, and c-Jun-N-terminal kinase) is upregulated after hypoxia/ischemia. Coupling of tissue plasminogen activator to red blood cells prevented hypoxia/ischemia-induced impairment of dilation and suppressed extracellular signal-related kinase mitogen-activated protein kinase activation. This study investigated the differential roles of mitogen-activated protein kinase isoforms in the effects of red blood cells-tissue plasminogen activator on cerebrovasodilation in a translationally relevant injury model, photothrombosis. DESIGN: Prospective, randomized animal study. SETTING: : University laboratory. SUBJECTS: Newborn (1- to 5-day-old) pigs. INTERVENTIONS: Cerebral blood flow and pial artery diameter were determined before and after photothrombotic injury (laser 532 nm and erythrosine B) was produced in piglets equipped with a closed cranial window. Cerebral blood flow extracellular signal-related kinase, p38, and c-Jun-N-terminal kinase mitogen-activated protein kinase were determined by enzyme-linked immunosorbent assay. MEASUREMENTS AND MAIN RESULTS: Tissue plasminogen activator and red blood cells-tissue plasminogen activator alleviated reduction of cerebral blood flow after photothrombotic injury. Cerebrovasodilation was blunted by photothrombotic injury, reversed to vasoconstriction by tissue plasminogen activator, but dilation was maintained by red blood cells-tissue plasminogen activator. Cerebral blood flow c-Jun-N-terminal kinase and p38 mitogen-activated protein kinase but not extracellular signal-related kinase mitogen-activated protein kinase was elevated by photothrombotic injury, an effect potentiated by tissue plasminogen activator. Red blood cells-tissue plasminogen activator blocked c-Jun-N-terminal kinase but potentiated p38 mitogen-activated protein kinase upregulation after photothrombotic injury. A c-Jun-N-terminal kinase mitogen-activated protein kinase antagonist prevented, a p38 mitogen-activated protein kinase antagonist potentiated, whereas an extracellular signal-related kinase mitogen-activated protein kinase antagonist had no effect on dilator impairment after photothrombotic injury. CONCLUSIONS: These data indicate that in addition to restoring perfusion, red blood cells-tissue plasminogen activator prevents impairment of cerebrovasodilation after photothrombotic injury through blockade of c-Jun-N-terminal kinase and potentiation of p38 mitogen-activated protein kinase. These data suggest tissue plasminogen activator coupling to red blood cells offers a novel approach to increase the benefit/risk ratio of thrombolytic therapy to treat central nervous system ischemic disorders.

Use of O-arm With Intraoperative Arteriography for Localization and Stealth Navigation of the Vertebral Arteries During Posterior Cervical Spine Surgery.

BACKGROUND: Vertebral artery injury (VAI) can be a devastating complication during cervical spine surgery. Although considered a rare occurrence overall, incidences of VAI have been reported in the ranges of 0.07% to 8%. Such injuries have the potential for catastrophic consequences, including blood loss, permanent morbid neurologic injury, and even death. The introduction of intraoperative navigation using either preoperative or intraoperative imaging has now been widely adopted in current practice so as to try and minimize adverse outcomes while giving real-time, dynamic information of the operative field. The use of the O-arm Surgical Imaging System during cervical spine surgery allows one to obtain high-resolution, accurate intraoperative imaging, and when used in concert with forms of intraoperative navigation, it can help with instrumentation and safety. However, patients undergoing cervical spine surgery do not routinely undergo preoperative vascular imaging, particularly with regard to anterior cervical or posterior high-cervical surgeries, where the incidence of VAI, in comparison with other cervical surgeries, has been reported to be the highest. METHODS: Here we present the use of intraoperative O-arm-based arteriography for integration with navigation for vertebral artery localization during C1 to C3 posterior instrumentation and fusion of an unstable C2 fracture in a 54-year-old man. RESULTS: The patient did not experience any intraoperative VAI and was subsequently discharged with no focal neurologic deficits. CONCLUSIONS: Detailed in our report is our protocol and procedure for obtaining and using intraoperative angiographic images. CLINICAL RELEVANCE: Case report detailing O arm for intraoperative identification of vertebral arteries during C1-C3 posterior instrumentation and fusion with pre-operative unilateral vertebral artery injury.

PAI-1-derived peptide EEIIMD prevents impairment of cerebrovasodilation by augmenting p38 MAPK upregulation after cerebral hypoxia/ischemia.

Babies are frequently exposed to cerebral hypoxia and ischemia (H/I) during the perinatal period as a result of stroke, problems with delivery, or postdelivery respiratory management. The sole approved treatment for acute stroke is tissue type plasminogen activator. H/I impairs pial artery dilation (PAD) induced by hypercapnia and hypotension, the impairment aggravated by type plasminogen activator and attenuated by the plasminogen activator inhibitor-1-derived peptide EEIIMD. Mitogen-activated protein kinase (MAPK), a family of at least three kinases, ERK, p38, and JNK, is upregulated after H/I and ERK contribute to impaired cerebrovasodilation. This study determined the roles of p38 and JNK MAPK in the impairment of dilation post-H/I in pigs equipped with a closed cranial window and the relationship between alterations in MAPK isoforms and EEIIMD-mediated cerebrovascular protection. Cerebrospinal fluid-phosphorylated (activated) p38 MAPK, but not JNK MAPK, was increased after H/I, an effect potentiated by intravenous EEIIMD administered 1 h postinjury. PAD in response to hypercapnia and hypotension was blunted by H/I, but dilation was maintained by EEIIMD. PAD was further impaired by the p38 antagonist SB-203580 but unchanged by the JNK antagonist SP-600125. Isoproterenol-induced PAD was unchanged by H/I, EEIIMD, SB-203580, and SP-600125. These data indicate that postinjury treatment with EEIIMD attenuated impaired cerebrovasodilation post-H/I by upregulating p38 but not JNK. These data suggest that plasminogen activator inhibitor-1-based peptides and other approaches to upregulate p38 may offer a novel approach to increase the benefit-to-risk ratio of thrombolytic therapy for diverse central nervous system disorders associated with H/I.

Impaired cerebral blood flow autoregulation during posttraumatic arterial hypotension after fluid percussion brain injury is prevented by phenylephrine in female but exacerbated in male piglets by extracellular signal-related kinase mitogen-activated protein kinase upregulation.

OBJECTIVE: Traumatic brain injury contributes to morbidity and mortality in children and boys are disproportionately represented. Hypotension is common and worsens outcome after traumatic brain injury. Extracellular signal-related kinase mitogen-activated protein kinase is upregulated and reduces cerebral blood flow after fluid percussion brain injury in piglets. We hypothesized that increased cerebral perfusion pressure through phenylephrine sex dependently reduces impairment of cerebral autoregulation during hypotension after fluid percussion brain injury through modulation of extracellular signal-related kinase mitogen-activated protein kinase. DESIGN: Prospective, randomized animal study. SETTING: University laboratory. SUBJECTS: Newborn (1- to 5-day-old) pigs. INTERVENTIONS: Cerebral blood flow, pial artery diameter, intracranial pressure, and autoregulatory index were determined before and after fluid percussion brain injury in untreated, preinjury, and postinjury phenylephrine (1 microg/kg/min intravenously) treated male and female pigs during normotension and hemorrhagic hypotension. Cerebrospinal fluid extracellular signal-related kinase mitogen-activated protein kinase was determined by enzyme-linked immunosorbent assay. MEASUREMENTS AND MAIN RESULTS: Reductions in pial artery diameter, cerebral blood flow, cerebral perfusion pressure, and elevated intracranial pressure after fluid percussion brain injury were greater in males, which were blunted by phenylephrine pre- or postfluid percussion brain injury. During hypotension and fluid percussion brain injury, pial artery dilation was impaired more in males. Phenylephrine decreased impairment of hypotensive pial artery dilation after fluid percussion brain injury in females, but paradoxically caused vasoconstriction after fluid percussion brain injury in males. Papaverine-induced pial artery vasodilation was unchanged by fluid percussion brain injury and phenylephrine. Cerebral blood flow, cerebral perfusion pressure, and autoregulatory index decreased markedly during hypotension and fluid percussion brain injury in males but less in females. Phenylephrine prevented reductions in cerebral blood flow, cerebral perfusion pressure, and autoregulatory index during hypotension in females but increased reductions in males. Cerebrospinal fluid extracellular signal-related kinase mitogen-activated protein kinase was increased more in males than females after fluid percussion brain injury. Phenylephrine blunted extracellular signal-related kinase mitogen-activated protein kinase upregulation in females but increased extracellular signal-related kinase mitogen-activated protein kinase upregulation in males after fluid percussion brain injury. CONCLUSIONS: These data indicate that elevation of cerebral perfusion pressure with phenylephrine sex dependently prevents impairment of cerebral autoregulation during hypotension after fluid percussion brain injury through modulation of extracellular signal-related kinase mitogen-activated protein kinase. These data suggest the potential role for sex-dependent mechanisms in cerebral autoregulation after pediatric traumatic brain injury.

Novel plasminogen activator inhibitor-1-derived peptide protects against impairment of cerebrovasodilation after photothrombosis through inhibition of JNK MAPK.

The sole FDA-approved treatment for acute stroke is recombinant tissue-type plasminogen activator (rtPA). However, rtPA aggravates the impairment of cerebrovasodilation induced by global hypoxia/ischemia; this impairment is attenuated by the preinjury treatment with the plasminogen activator inhibitor derivative EEIIMD. MAPK (a family of kinases, p38, and JNK) is upregulated after cerebral ischemia. In this study, we determined whether the novel plasminogen activator inhibitor-derived peptide, Ac-RMAPEEIIMDRPFLYVVR-amide, (PAI-1-DP) given 30 min before or 2 h after, focal central nervous system injury induced by photothrombosis would preserve responses to cerebrovasodilators and the role of p38 and JNK MAPK in such effects. Cerebrospinal fluid JNK and p38 levels were elevated by photothrombotic injury, an effect potentiated by rtPA. Cerebrovasodilation was blunted by photothrombosis and reversed to vasoconstriction by rtPA but restored to dilation by PAI-1-DP pre- and posttreatment. PAI-1-DP blocked JNK, but preserved p38 MAPK upregulation after photothrombosis. The JNK MAPK antagonist SP600125 prevented, and the p38 antagonist SB203580 potentiated, impaired cerebrovasodilation after photothrombosis. These data indicate that rtPA impairs cerebrovasodilation after injury by activating JNK, while p38 MAPK is protective, and that the novel peptide PAI-1-DP protects by inhibiting activation of JNK by rtPA. JNK MAPK inhibitors, including PAI-1-DP, may offer a novel approach to increase the benefit-to-risk ratio of thrombolytic therapy and enable its use in central nervous system ischemic disorders.

Traumatic Frontal Epidural Hematoma Caused by Multiple Arterial Injuries in the Anterior Fossa.

BACKGROUND: This case report illustrates the need to evaluate the possibility of multiple arterial sources when presented with a frontal epidural hematoma associated with facial trauma. CASE DESCRIPTION: The patient presented after being struck in the face by a baseball. Computed tomography of the brain revealed a large frontal epidural hematoma. Intraoperatively, bleeding from a frontal branch of the middle meningeal artery was encountered and cauterized, and the hematoma was removed. Routine follow-up imaging performed the next day showed a residual frontal hematoma; however, the epidural hematoma was in a more medial location than the initial hematoma. The patient was taken back to the operating room; after frontal lobe retraction and extensive exploration, a different source of bleeding from posterior ethmoidal artery feeders was encountered. After the second operation, the patient's hematoma did not recur, and he was discharged home with no neurologic deficits 3 days later. CONCLUSIONS: We report a case of an epidural hematoma caused by 2 distinct arterial feeders. We discuss radiologic review and operative management of anterior fossa epidural hematomas and stress the importance of considering arterial bleeding from sources other than the middle meningeal artery in anterior fossa epidural hematomas. We discuss the utility of preoperative angiography for these patients and reinforce the need for acute postoperative imaging to ensure successful operative and patient outcomes.

Glucagon protects against impaired NMDA-mediated cerebrovasodilation and cerebral autoregulation during hypotension after brain injury by activating cAMP protein kinase A and inhibiting upregulation of tPA.

Outcome of traumatic brain injury (TBI) is impaired by hyperglycemia, hypotension, and glutamate, and improved by insulin. Insulin reduces glutamate concentration, making it uncertain whether its beneficial effect accrues from euglycemia. Glucagon decreases CNS glutamate, lessens neuronal cell injury, and improves neurological scores in mice after TBI. In vitro, glucagon limits NMDA-mediated excitotoxicity by increasing cAMP and protein kinase A (PKA). NMDA receptor activation couples cerebral blood flow (CBF) to metabolism. Dilation induced by NMDA is impaired after fluid percussion brain injury (FPI) due to upregulation of endogenous tPA, which further disturbs cerebral autoregulation during hypotension after fluid percussion injury (FPI). We hypothesized that glucagon prevents impaired NMDA receptor-mediated dilation after FPI by upregulating cAMP, which decreases release of tPA. NMDA-induced pial artery dilation (PAD) was reversed to vasoconstriction after FPI. Glucagon 30 min before or 30 min after FPI blocked NMDA-mediated vasoconstriction and restored the response to vasodilation. PAD during hypotension was blunted after FPI, but protected by glucagon. Glucagon prevented FPI-induced reductions in CSF cAMP, yielding a net increase in cAMP, and blocked FPI-induced elevation of CSF tPA. Co-administration of the PKA antagonist Rp 8Br cAMPs prevented glucagon-mediated preservation of NMDA-mediated dilation after FPI. The pKA agonist Sp 8Br cAMPs prevented impairment of NMDA-induced dilation. These data indicate that glucagon protects against impaired cerebrovasodilation by upregulating cAMP, which decreases release of tPA, suggesting that it may provide neuroprotection when given after TBI, or prior to certain neurosurgical or cardiac interventions in which the incidence of perioperative ischemia is high.

Phenylephrine infusion prevents impairment of ATP- and calcium-sensitive potassium channel-mediated cerebrovasodilation after brain injury in female, but aggravates impairment in male, piglets through modulation of ERK MAPK upregulation.

Traumatic brain injury (TBI) contributes to morbidity in children and boys, and hypotension worsens outcome. Extracellular signal-related kinase (ERK) mitogen-activated protein kinase (MAPK) is upregulated more in males and reduces cerebral blood flow (CBF) after fluid percussion injury (FPI). Increased cerebral perfusion pressure (CPP) via phenylephrine (Phe) sex-dependently improves impairment of the cerebral autoregulation seen after FPI through modulation of ERK MAPK upregulation, which is aggravated in males, but is blocked in females. Activation of ATP- and calcium-sensitive (Katp and Kca) channels produces cerebrovasodilation and contributes to autoregulation, both of which are impaired after FPI. Using piglets equipped with a closed cranial window, we hypothesized that potassium channel functional impairment after FPI is prevented by Phe in a sex-dependent manner through modulation of ERK MAPK upregulation. The Katp and Kca agonists cromakalim and NS 1619 produced vasodilation that was impaired after FPI more in males than in females. Phe prevented reductions in cerebrovasodilation after cromakalim and NS 1619 in females, but reduced dilation after these potassium channel agonists were given to males after FPI. Co-administration of U 0126, an ERK antagonist, and Phe fully restored dilation to cromakalim, calcitonin gene-related peptide (CGRP), and NS 1619, in males after FPI. These data indicate that Phe sex-dependently prevents impairment of Katp and Kca channel-mediated cerebrovasodilation after FPI in females, but aggravates impairment in males, through modulation of ERK MAPK upregulation. Since autoregulation of CBF is dependent on intact functioning of potassium channels, these data suggest a role for sex-dependent mechanisms in the treatment of cerebral autoregulation impairment after pediatric TBI.

tPA contributes to impaired NMDA cerebrovasodilation after traumatic brain injury through activation of JNK MAPK.

OBJECTIVE: N-methyl-D-aspartate (NMDA)-induced pial artery dilation (PAD) is reversed to vasoconstriction after fluid percussion brain injury (FPI). Tissue type plasminogen activator (tPA) is up-regulated and the tPA antagonist, EEIIMD, prevents impaired NMDA PAD after FPI. Mitogen-activated protein kinase (MAPK), a family of at least three kinases, ERK, p38, and JNK, is also up-regulated after traumatic brain injury (TBI). We hypothesize that tPA impairs NMDA-induced cerebrovasodilation after FPI in a MAPK isoform-dependent mechanism. METHODS: Lateral FPI was induced in newborn pigs. The closed cranial window technique was used to measure pial artery diameter and to collect cerebrospinal fluid (CSF). ERK, p38, and JNK MAPK concentrations in CSF were quantified by ELISA. RESULTS: CSF JNK MAPK was increased by FPI, increased further by tPA, but blocked by JNK antagonists SP600125 and D-JNKI1. FPI modestly increased p38 and ERK isoforms of MAPK. NMDA-induced PAD was reversed to vasoconstriction after FPI, whereas dilator responses to papaverine were unchanged. tPA, in post-FPI CSF concentration, potentiated NMDA-induced vasoconstriction while papaverine dilation was unchanged. SP 600125 and D-JNKI1, blocked NMDA-induced vasoconstriction and fully restored PAD. The ERK antagonist U 0126 partially restored NMDA-induced PAD, while the p38 inhibitor SB203580 aggravated NMDA-induced vasoconstriction observed in the presence of tPA after FPI. DISCUSSION: These data indicate that tPA contributes to impairment of NMDA-mediated cerebrovasodilation after FPI through JNK, while p38 may be protective. These data suggest that inhibition of the endogenous plasminogen activator system and JNK may improve cerebral hemodynamic outcome post-TBI.

SNP improves cerebral hemodynamics during normotension but fails to prevent sex dependent impaired cerebral autoregulation during hypotension after brain injury.

Traumatic brain injury (TBI) is a leading cause of morbidity in children and boys are disproportionately represented. Hypotension is common and worsens outcome after TBI. Previous studies show that adrenomedullin, a cerebrovasodilator, prevented sex dependent impairment of autoregulation during hypotension after piglet fluid percussion brain injury (FPI). We hypothesized that this concept was generalizable and that administration of another vasodilator, sodium nitroprusside (SNP), may equally improve CBF and cerebral autoregulation in a sex dependent manner after FPI. SNP produced equivalent percent cerebrovasodilation in male and female piglets. Reductions in pial artery diameter, cortical CBF, and cerebral perfusion pressure (CPP) concomitant with elevated intracranial pressure (ICP) after FPI were greater in male compared to female piglets during normotension which was blunted by SNP. During hypotension, pial artery dilation (PAD) was impaired more in the male than the female after FPI. However, SNP did not improve hypotensive PAD after FPI in females and paradoxically caused vasoconstriction in males. SNP did not prevent reductions in CBF, CPP or autoregulatory index during combined hypotension and FPI in either sex. SNP aggravated ERK MAPK upregulation after FPI. These data indicate that despite prevention of reductions in CBF after FPI, SNP does not prevent impairment of autoregulation during hypotension after FPI. These data suggest that therapies directed at a purely hemodynamic increase in CPP will fail to improve outcome during combined TBI and hypotension.