A Modified Two-Way Active Avoidance Test for Combined Contextual and Auditory Instrumental Conditioning

Available two-way active avoidance paradigms do not provide contextual testing, likely due to challenges in performing repetitive trials of context exposure. To incorporate contextual conditioning in the two-way shuttle box, we contextually modified one of the chambers of a standard two-chamber rat shuttle box with visual cues consisting of objects and black and white stripe patterns. During the 5 training days, electrical foot shocks were delivered every 10 s in the contextually modified chamber but were signaled by a tone in the plain chamber. Shuttling between chambers prevented an incoming foot shock (avoidance) or aborted an ongoing one (escape). During contextual retention testing, rats were allowed to freely roam in the box. During auditory retention testing, visual cues were removed, and tone-signaled shocks were delivered in both chambers. Avoidance gradually replaced escape or freezing behaviors reaching 80% on the last training day in both chambers. Rats spent twice more time in the plain chamber during contextual retention testing and had 90% avoidance rates during auditory retention testing. Our modified test successfully assesses both auditory and contextual two-way active avoidance. By efficiently expanding its array of outcomes, our novel test will complement standard two-way active avoidance in mechanistic studies and will improve its applications in translational research.

Potentiating Hemorrhage in a Periadolescent Rat Model of Closed-Head Traumatic Brain Injury Worsens Hyperexcitability but Not Behavioral Deficits

Post-traumatic epilepsy (PTE) and neurocognitive deficits are devastating sequelae of head injuries that are common in adolescents. Investigating desperately needed treatments is hindered by the difficulties in inducing PTE in rodents and the lack of established immature rat models of pediatric PTE. Hemorrhage is a significant risk factor for PTE, but compared to humans, rats are less prone to bleeding because of their rapid blood coagulation system. In this study, we promoted bleeding in the controlled cortical impact (CCI) closed-head injury model with a 20 min pre-impact 600 IU/kg intraperitoneal heparin injection in postnatal day 35 (P35) periadolescent rats, given the preponderance of such injuries in this age group. Temporo-parietal CCI was performed post-heparin (HTBI group) or post-saline (TBI group). Controls were subjected to sham procedures following heparin or saline administration. Continuous long-term EEG monitoring was performed for 3 months post-CCI. Sensorimotor testing, the Morris water maze, and a modified active avoidance test were conducted between P80 and P100. Glial fibrillary acidic protein (GFAP) levels and neuronal damage were also assessed. Compared to TBI rats, HTBI rats had persistently higher EEG spiking and increased hippocampal GFAP levels (p < 0.05). No sensorimotor deficits were detected in any group. Compared to controls, both HTBI and TBI groups had a long-term hippocampal neuronal loss (p < 0.05), as well as contextual and visuospatial learning deficits (p < 0.05). The hippocampal astrogliosis and EEG spiking detected in all rats subjected to our hemorrhage-promoting procedure suggest the emergence of hyperexcitable networks and pave the way to a periadolescent PTE rat model.

High-Dose Levetiracetam for Neonatal Seizures: A Retrospective Review

BACKGROUND

Neonatal seizures are frequently encountered in the neonatal intensive care unit and may be associated with serious long-term neurological sequelae. Response to treatment continues to be modest, and treatment guidelines remain unclear. The use of levetiracetam has been on the rise in the past several years due to its favorable safety profile in the face of limited data on its efficacy and optimal dosing regimens. Unlike the older age groups, the benefit of escalating to high-dose levetiracetam of 80-100 mg/kg/day in neonates not responding to the standard used dosing regimen (40-60 mg/kg/day) is not studied. We sought to investigate the safety and efficacy of levetiracetam escalation to high dose regimens for neonatal seizures.

METHODS

A retrospective chart review over a 7-year period was conducted at the American University of Beirut to identify neonates with electrographically proven seizures treated with levetiracetam. Data was collected on electroclinical seizure characteristics, underlying etiology, seizure control, other anti-seizure medications, and adverse effects.

RESULTS

Electronic chart review revealed a total of 15 neonates with electrographically confirmed seizures treated with levetiracetam, with escalation to high doses in seven. As a first line drug, levetiracetam monotherapy terminated seizures in six out 10 neonates, two of whom had complete seizure cessation only after escalation to high doses of 80 or 100 mg/kg/day. When used in combination with other anti-seizure medications, four out of five neonates achieved complete seizure cessation upon escalation to high doses of levetiracetam. No adverse effects were noted.

CONCLUSIONS

In neonates not responding to the standard used levetiracetam doses, incremental increases to 80-100 mg/kg/day may be considered. Prospective studies are needed to confirm the promising role of such high dosing regimens, and to better elucidate the role of levetiracetam in neonatal seizures.

Anatomic relations between the lumbar pedicle and the adjacent neural structures

STUDY DESIGN

The authors analyzed anatomic parameters between the lumbar pedicles and the dural sac as well as the spinal nerve roots.

OBJECTIVES

To determine quantitatively the anatomic relations between the lumbar pedicle and adjacent dural sac and nerve roots.

SUMMARY OF BACKGROUND DATA

Posterior transpedicular screw fixation is the most commonly used method of instrumentation for stabilization of the unstable lumbar spine. A thorough knowledge of the unique anatomy of the lumbar pedicle and adjacent neural structures may avoid or minimize neurologic complications with pedicular screw placement.

METHODS

Fifteen adult cadavers were obtained to evaluate quantitatively the anatomic relations of the lumbar pedicle to the adjacent neural structures. After removal of the laminas and facets, the lumbar pedicles, dural sac, and nerve roots were exposed. Direct measurements were taken from the pedicle to the dural sac medially, to the nerve roots superiorly and inferiorly, and between the pedicles. Also, the superoinferior diameter of the nerve root and the frontal angle of the nerve root were measured. Symmetric structures were measured bilaterally.

RESULTS

No consistent changes from L1 to L5 were found in all parameters. The mean distances from the lumbar pedicle to the dural sac medially and to the adjacent nerve roots superiorly and inferiorly for all levels were 1.5 mm, 5.3 mm, and 1.5 mm, respectively. The mean interpedicular distance ranged from 23.2 to 24.4 mm. The mean superoinferior diameter of the nerve root ranged from 3.8 to 4.6 mm. The mean nerve root angle ranged from 33.7 degrees to 39.2 degrees.

CONCLUSIONS

On the basis of this study, improper placement of the pedicle screw medially or caudally in the lumbar spine should be avoided.

[Hydroelectrolytic requirements during the first week of life in premature infants weighing less than 1000 g. Physiopathology and recommendations]

Fluid and electrolyte maintenance in very low birth weight infants during the first week of life must be adapted to their physiological characteristics and to pathological events. Insensible water losses are elevated and may reach 100 mL/kg/24 h depending upon many factors, such as type of incubator, phototherapy, presence of respiratory distress syndrome, changes in transepidermal water losses and renal water and electrolyte regulation (prediuretic, diuretic and postdiuretic phases); there is also a major risk of hypernatremia and hyperkaliema. In cases of insufficient fluid intake the main complication is dehydration with hypernatremia. Excessive fluid intake results in increased incidence of bronchopulmonary dysplasia, patent ductus arteriosus and necrotizing enterocolitis. Hypernatremia is a major risk factor of intracranial hemorrhage. A careful management of water and electrolyte requirements is therefore mandatory in very low birth weight infants. Guidelines on daily maintenance and management are presented.

Open reduction and internal fixation with bone grafting of clavicular nonunion

BACKGROUND

Although clavicular fractures are common, nonunion of the clavicle is a rare complication. However, it can be disabling, presenting mainly with pain, limitation of shoulder movement, and/or compression of the brachial plexus. The technical difficulty in securing adequate skeletal stabilization and the unique anatomic features of the clavicle pose a challenge for the orthopedic surgeon.

METHODS

Sixteen patients with symptomatic nonunion of the clavicle were studied. They were nine men and seven women with a median age of 34 years (range, 15-52 years). The average follow-up was 12.9 months (range, 9-24 months). The nonunion was hypertrophic in 11 cases, atrophic in five cases, and showed pseudoarthrosis in one case. The primary indication for performing the operation was pain in all cases. Five of the 16 cases had previous operations. All cases were treated with open reduction and internal fixation using a reconstruction plate or a dynamic compression plate. Double plating was used in three cases. Autogenous bone grafting was applied in 14 cases and corraline hydroxyapatite in one case.

RESULTS

Fifteen of the 16 fractures eventually healed with complete resolution of the preoperative pain, except in two cases who had persistent mild pain. The hardware was removed after union in one case. One hardware failure required revision and eventually went on to heal. Another hardware failure required removal because of pain. The pain subsided despite the persistent nonunion. The same patient had hematoma at the site of the bone graft and continued to have pain until the last follow-up.

CONCLUSION

Plating and bone grafting of the clavicle is an effective method of management of painful nonunion, and it has minimal complications.

Effects of early indomethacin administration on oxygenation and surfactant requirement in low birth weight infants

A previous study found that early intravenous indomethacin administration prolonged respiratory support in very low birth weight infants. We have, therefore, designed a randomized, double blind controlled study to evaluate the oxygenation, and surfactant requirements in preterm low birth weight infants receiving early indomethacin administration. Premature neonates who received surfactant therapy and on mechanical ventilation were prospectively randomized to receive either placebo or indomethacin (0.2 mg/kg intravenously at 12 postnatal hours and every 24 h for two more doses). Oxygenation was assessed by FiO2 required and arterial/alveolar oxygen (a/A O2) ratio during the first 48 h of life. The doses of surfactant were compared between the two groups. Twenty-seven infants (n = 14 of early indomethacin and n = 13 of placebo group) fulfilled inclusion criteria. At admission to the study, there were no differences in the birth weight, gestational age, sex, Apgar scores, a/A O2 ratio, and FiO2. The control group exhibited a significant improvement in oxygenation (FiO2 requirement and a/A O2 compared with the early indomethacin group at 24 (P = 0.026 and 0.02, respectively) and 48 h of life (P = 0.037 and 0.026, respectively). The requirement of surfactant was significantly larger in the early indomethacin group (P = 0.029). Early indomethacin administration increases oxygen and surfactant requirement.