Interactions between the cells of the immune and nervous system: neurotrophins as neuroprotection mediators in CNS injury

Inflammatory processes in the central nervous system (CNS) are considered neurotoxic, although recent studies suggest that they also can be beneficial and confer neuroprotection (neuroprotective autoimmunity). Cells from the immune system have been detected in CNS injury and found to produce and secrete a variety of neurotrophins such as NGF, BDNF, NT-3 and NT-4/5, and to express (similarly to neuronal cells), members of the tyrosine kinase (Trk) receptor family such as TrkA, TrkB and TrkC. Indeed, autocrine and paracrine interactions are observed at the site of CNS injury, resulting in a variety of homologic-heterologic modulations of immune and neuronal cell function. The end result of the inflammatory process, neurotoxicity and/or neuroprotection, is a function of the fine balance between the two cellular systems, i.e., of the complex signaling relationships between anti-inflammatory neuroprotective factors (neurotrophins and other chemical mediators) and proinflammatory neurotoxic factors (TNF, free radicals, certain cytokines, etc.). Autoimmune neuroprotection is a novel therapeutic approach aimed at shifting the balance between the immune and neuronal cells towards survival pathways in a variety of CNS injuries. This review focuses on data supporting this concept and its future therapeutical implications for optic nerve injury and multiple sclerosis.

Application of therapeutic hypothermia in the ICU: opportunities and pitfalls of a promising treatment modality. Part 1: Indications and evidence

OBJECTIVE

Hypothermia has been used for medicinal purposes since ancient times. This paper reviews the current potential clinical applications for mild hypothermia (32-35 degrees C).

DESIGN AND SETTING

Induced hypothermia is used mostly to prevent or attenuate neurological injury, and has been used to provide neuroprotection in traumatic brain injury, cardiopulmonary resuscitation, stroke, and various other disorders. The evidence for each of these applications is discussed, and the mechanisms underlying potential neuroprotective effects are reviewed. Some of this evidence comes from animal models, and a brief overview of these models and their limitations is included in this review.

RESULTS

The duration of cooling and speed of re-warming appear to be key factors in determining whether hypothermia will be effective in preventing or mitigating neurological injury. Some other potential usages of hypothermia, such as its use in the peri-operative setting and its application to mitigate cardiac injury following ischemia and reperfusion, are also discussed.

CONCLUSIONS

Although induced hypothermia appears to be a highly promising treatment, it should be emphasized that it is associated with a number of potentially serious side effects, which may negate some or all of its potential benefits. Prevention and/or early treatment of these complications are the key to successful use of hypothermia in clinical practice. These side effects, as well as various physiological changes induced by cooling, are discussed in a separate review.

Minimizing the Risk of Neurologic Injury in Gynecologic Surgery

OBJECTIVE

The association of intraoperative neurologic injuries with gynecologic surgical procedures is well established. The sequelae of such injuries are usually transient and resolve with minimal intervention, although long-term disability can and does occasionally occur. The purpose of this study was to examine the mechanisms by which these injuries occur in order to reduce the risk of their occurrence.

DATA SOURCES

A MEDLINE search was performed cross-referencing the index terms "neurological injury" and "gynecological surgery," from January 1, 1960 to December 31, 2002.

METHODS OF STUDY SELECTION

This article, based on the data and results (Level I-III) obtained from the MEDLINE search, examined the most common neurologic injuries that occur in association with abdominal and vaginal surgical procedures routinely performed by gynecologists.

TABULATION, INTEGRATION, AND RESULTS

Neurologic injuries after pelvic surgery all generally share a common etiology, specifically injury to one or more components of the lumbosacral nerve plexus. Three major factors that predispose to neurologic injury at the time of gynecological surgery are 1) the improper placement or positioning of self-retaining or fixed retractors, particularly those with deep lateral retractor blades; 2) improper positioning of patients in lithotomy position preoperatively; and 3) radical surgical dissection resulting in autonomic nerve disruption. Level I data strongly implicate the improper placement of self-retaining or fixed retractors as the most common cause of femoral nerve injury arising in association with abdominal surgical procedures.

CONCLUSION

A thorough understanding of the anatomy of the lumbosacral nerve plexus and the mechanisms by which operative injuries to this plexus occur will enable the gynecologic surgeon to reduce the subsequent risk of their occurrence in his or her own surgical practice.

Neuroprotective activity of antazoline against neuronal damage induced by limbic status epilepticus

Imidazoline drugs exert neuroprotective effects in cerebral ischaemia models. They also have effects against mouse cerebellar and striatal neuronal death induced by N-methyl-D-aspartate (NMDA) through the blockade of NMDA currents. Here, we investigated the effects of antazoline on NMDA toxicity and current in rat hippocampal neuronal cultures, and on an in vivo model of status epilepticus. In hippocampal cultures, antazoline (30 microM) decreased NMDA-mediated neurotoxicity and also blocked the NMDA current with voltage-dependent and fast-reversible action (inhibition by 85+/-3% at -60 mV). Status epilepticus was induced by injecting pilocarpine (200 nmol) directly into the right pyriform cortex of male adult rats. The rats then received immediately three consecutive i.p. injections at 30-min intervals of either PBS (control group) or antazoline at 10 mg/kg (low-dose group) or at 45 mg/kg (high-dose group). During the 6-h recording, status epilepticus lasted more than 200 min in all groups. In the high-dose group only, seizures completely ceased 1 h after the third injection of antazoline, then started again 1 h later. Rats were killed 1 week later, and Cresyl Violet-stained sections of their brain were analysed for damage quantification. On the ipsilateral side to the pilocarpine injection, pyriform cortex and hippocampal CA1 and CA3 areas were significantly protected in both antazoline-treated groups, whilst prepyriform and entorhinal cortices were only in the high-dose group. On the contralateral side to the pilocarpine injection, only the hippocampal CA3 area was significantly protected in the low-dose group, but all investigated structures were in the high-dose group. In conclusion, antazoline is a potent neuroprotective drug in different models of neuronal primary culture, as previously shown in striatal and cerebellar granule neurons [Neuropharmacology 39 (2000) 2244], and here in hippocampal neurons. Antazoline is also neuroprotective in vivo in the intra-pyriform pilocarpine-induced status epilepticus model.

Avoiding complications of laparoscopic surgery

No matter how skilled the surgeon, the risk of complications always exists. Complications of laparoscopic surgery include anesthesia difficulties, positioning and nerve injuries, injuries due to insertion of needles and trocars, and intraoperative vascular, bowel, and urinary tract injuries. Injuries from electrosurgical equipment may also result. This article focuses on preventing such complications.

Nerve-sparing robot-assisted radical cystoprostatectomy and urinary diversion

OBJECTIVE

To develop a technique of nerve-sparing robot-assisted radical cystoprostatectomy (RRCP) for patients with bladder cancer.

PATIENTS AND METHODS

Robotic assistance should enhance the ability to preserve the neurovascular bundles during laparoscopic radical cystectomy. Thus we undertook RRCP and urinary diversion using a three-step technique. First, using a six-port approach and the da Vinci Surgical System (Intuitive Surgical, Sunnyvale, CA, USA), one surgeon carried out a complete pelvic lymphadenectomy and cystoprostatectomy using a technique developed specifically for robotic surgery. The neurovascular bundles were easily identified and dissected away, the specimen entrapped in a bag and removed through a 5-6 cm suprapubic incision. Second, a different surgical team exteriorized the bowel through this incision and created a neobladder extracorporeally. Third, the neobladder was internalized, the incision closed and the primary surgeon completed the urethro-neovesical anastomosis with robotic assistance.

RESULTS

RRCP was carried out in 14 men and three women by the primary surgeon (M.M.). The form of urinary reconstruction was ileal conduit in three, a W-pouch with a serosal-lined tunnel in 10, a double-chimney or a T-pouch with a serosal-lined tunnel in two each. The mean operative duration for robotic radical cystectomy, ileal conduit and orthotopic neobladder were 140, 120 and 168 min, respectively. The mean blood loss was < 150 mL. The number of lymph nodes removed was 4-27, with one patient having N1 disease. The margins of resection were free of tumour in all patients.

CONCLUSIONS

We developed a technique for nerve-sparing RRCP using the da Vinci system which allows precise and rapid removal of the bladder with minimal blood loss. The bowel segment can be exteriorized and the most complex form of orthotopic bladder can be created through the incision used to deliver the cystectomy specimen. Performing this part of the operation extracorporeally reduced the operative duration.

Technical advances in radical retropubic prostatectomy techniques for avoiding complications. Part II: vesico-urethral anastomosis and nerve-sparing prostatectomy

We previously reviewed different technical modifications and improvements in apical dissection in radical retropubic prostatectomy which have a considerable effect in optimizing the results. This second paper focuses on the vesico-urethral anastomosis and aspects of nerve-sparing prostatectomy.

Technical advances in radical retropubic prostatectomy techniques for avoiding complications. Part I: apical dissection

Radical retropubic prostatectomy is currently the most widely used surgical treatment for localized prostate cancer. This once cumbersome procedure has developed technically over the last 20 years, reducing dramatically the associated complications and morbidity, e.g. blood loss, incontinence and impotence. Currently the operation is safe and is the best choice for eradicating localized disease, with little loss in quality of life. However, differences in reported outcomes indicate that there is still a need for standardization and continued efforts for surgical excellence. This review focuses on the crucial steps of the procedure, in two parts: the first covers apical dissection and the second the steps related to vesico-urethral anastomosis and the nerve-sparing procedure. This evaluation of the technical modifications aims to offer a choice, to vary the procedure according to the individual situation and thus improve the results. Current trends in surgical technique are also presented.

Neuroprotective effects of bilobalide, a component of Ginkgo biloba extract (EGb 761) in global brain ischemia and in excitotoxicity-induced neuronal death

In this study, we compared the protective effect of bilobalide, a purified terpene lactone component of ginkgo biloba extract EGb 761, (definition see editorial) and EGb 761 against ischemic injury and against glutamate-induced excitotoxic neuronal death. In ischemic injury, we measured neuronal loss and the levels of mitochondrial DNA (mtDNA)-encoded cytochrome oxidase (COX) subunit III mRNA in vulnerable hippocampal regions of gerbils. At 7 days of reperfusion after 5 min of transient global ischemia, a significant increase in neuronal death and a significant decrease in COX III mRNA were observed in the hippocampal CA1 neurons. Oral administration of EGb 761 at 25, 50 and 100 mg/kg/day and bilobalide at 3 and 6 mg/kg/day for 7 days before ischemia progressively protected CA1 neurons from death and from ischemia-induced reductions in COX III mRNA. In rat cerebellar neuronal cultures, addition of bilobalide or EGb 761 protected in a dose-dependent manner against glutamate-induced excitotoxic neuronal death (effective concentration [EC (50)] = 5 microg/ml (12 microM) for bilobalide and 100 microg/ml for EGb 761. These results suggest that both EGb 761 and bilobalide are protective against ischemia-induced neuronal death in vivo and glutamate-induced neuronal death in vitro by synergistic mechanisms involving anti-excitotoxicity, inhibition of free radical generation, scavenging of reactive oxygen species, and regulation of mitochondrial gene expression.

Avoidance and management of neurovascular injuries in total hip arthroplasty

Neural injuries that occur after total hip arthroplasty (THA) can be classified as involving either the central nervous system or peripheral nerves. Central nervous system changes after THA may be attributed to increased appreciation of fat embolism syndrome associated with THA. Certain maneuvers such as impacting the acetabulum, femoral reaming, and cement pressurization can force marrow fat into the venous system. When there is an associated right to left shunt, paradoxical embolization can occur, which may account for previously unexplained cases of confusion and mental status changes after surgery. Peripheral nerve injuries are rare and can involve either distant sites or nerves in the immediate vicinity of the hip joint. Upper extremity nerve injuries are usually associated with patient positioning. Sciatic nerve injury is the most common nerve injury following THA. In comparison, femoral nerve injury is much less common and is associated with an anterior approach. Diagnosis is often delayed, and the prognosis is generally better than with sciatic nerve injury. The superior gluteal nerve is at risk during the direct lateral approach. Obturator nerve injury is the least common type of injury and has the least functional consequence. It can present as groin or inguinal pain. Vascular injuries are less common but more immediately life threatening. The mechanisms of vascular injury include occlusion associated with preexisting peripheral vascular disease and vascular injury during removal of cement during screw fixation of acetabular components, cages, or structural grafts. Perioperative assessment should include vascular evaluation of patients with absent pulses, previous vascular bypass surgery, or dysvascular limbs. A CT scan should be considered when cement or components extend medially into the pelvis.

Influence of identification and preservation of pelvic autonomic nerves in rectal cancer surgery on bladder dysfunction after total mesorectal excision

PURPOSE

Given the improvement in oncologic outcome after the introduction of total mesorectal excision for the treatment of rectal cancer, the objective of the present study was to determine the frequency of identification and preservation of the pelvic autonomic nerves and to identify a possible link between postoperative micturition disturbances and the extent of the radical resection.

METHODS

Between March 1997 and December 2001, 150 patients with adenocarcinoma of the rectum (<or=16 cm from the anal verge) underwent surgery, with sphincter preservation in 112 cases (74.7 percent). Sixty-three patients (42 percent) were classified as American Society of Anesthesiologists Stage III and two (1.3 percent) as Stage IV. The number of cases with complete identification, partial identification, or nonidentification of the autonomic nerves (superior hypogastric plexus, hypogastric nerve, and inferior hypogastric plexus) was documented and correlated with micturition disturbances (need for a long-term urinary catheter). Urine volumes were measured by ultrasound before and after surgery.

RESULTS

The pelvic autonomic nerves were identified completely in 108 patients (72 percent), partially in 16 (10.7 percent), and not at all in 26 (17.3 percent). After the initial phase of the study (n = 50 patients), complete identification was realized in 78 percent of cases. Multivariate analysis showed that of the predetermined parameters (learning curve for Group I vs. Groups II or III, gender, T stage, blood loss, curative surgery, and previous surgery), gender (P = 0.006), learning curve (P = 0.019), and depth of penetration of the rectal wall (T1/T2 vs. T3/T4; P = 0.028) exerted an independent influence on achievement of complete pelvic nerve identification. Sixteen patients (10.7 percent) were discharged from the hospital with a urinary catheter. Identification and preservation of the pelvic autonomic nerves was associated with low bladder dysfunction rates (4.5 vs. 38.5 percent; P < 0.001). In the evaluation of preoperative and postoperative bladder function, a urologic history and residual urine volume measurements by ultrasound were essential. The information obtained from urodynamic studies was of no relevance.

CONCLUSIONS

Identification and preservation of the pelvic autonomic nerves was achieved in the majority of patients and led to the prevention of urinary dysfunction. Gender (P = 0.006), learning curve (P = 0.019), and T stage are independent parameters that influence outcome.

Surgical anatomy of the thyroid and parathyroid glands

From a surgical viewpoint there are several critical anatomic structures that lie in close proximity to the thyroid gland. These critical structures include the recurrent laryngeal nerves, the superior laryngeal nerves, and the parathyroid glands. Successful thyroid surgery depends on the technical skill of the surgeon to identify and preserve these vital structures.

[First experience of intraoperative nerve root monitoring with the INS-1-device on the lumbosacral spine]

AIM

The goal of intraoperative nerve root monitoring on the lumbosacral spine is to minimize the risk of nerve root injuries during surgery by reducing the incidence of misplaced pedicle screws. In this study we hypothesized that the INS-1 device (Nuvasive) may provide more accurate information about screw placement.

METHOD

The INS-1 device provides a means for intraoperative EMG stimulation through the inside of the pedicles or the implanted screws. The readings from relevant muscles serve as a monitoring technique to detect perforated pedicles and thus can be used to prevent or detect misplaced pedicle screws and reduce the risk of nerve root injuries. We controlled 58 patients with 334 implanted pedicle screws.

RESULTS

Our first experience with 334 pedicle screws shows that nerve root injuries can be avoided by reducing the number of misplaced pedicle screws through additional intraoperative information gained by the INS-1 device. Thus we corrected 3.9 % of screws intraoperatively in cases without relevant information from fluoroscopic control.

CONCLUSION

The INS-1 device is a helpful tool to obtain additional information on misplaced pedicle drill holes or already implanted screws in the lumbosacral spine.

Somatosensory evoked potential monitoring during closed humeral nailing: a preliminary report

OBJECTIVES

To assess the role of intraoperative somatosensory evoked potential (SSEP) monitoring of the radial and median nerves in preventing iatrogenic nerve injury during closed, locked intramedullary (IM) nailing of the humerus.

DESIGN

Prospective clinical study.

SETTING

Pacific Northwest Level One trauma center and Southern California military medical center.

PATIENTS

Thirteen patients with indications for surgical stabilization of fractures of the humeral diaphysis and either unknown neurologic status of the affected limb or anticipated difficult reduction maneuvers due to fracture complexity or displacement.

INTERVENTION

Closed, antegrade or retrograde locked IM nailing of the humerus was attempted while intraoperative monitoring of the radial and median nerves with SSEP was performed.

MAIN OUTCOME MEASUREMENTS

Intraoperative radial and median nerve SSEP changes during closed fracture manipulation, guide rod insertion, reaming, and humeral nail placement.

RESULTS

Baseline recordings were obtained in twelve of thirteen patients for both the radial and median nerves. An absence of radial nerve signal in one patient with a closed head injury prompted an open procedure, revealing entrapment of the radial nerve in the fracture. Intraoperative SSEP changes were observed in two of the twelve remaining patients during fracture manipulation and distal interlocking. The signal amplitude returned after discontinuation of manipulation and traction, and alteration of the interlocking maneuver. No neurologic deficits were noted in these two patients.

CONCLUSIONS

Intraoperative radial nerve SSEP monitoring appears to reliably reflect the status of the radial nerve in those patients with a humerus fracture. In three of eleven patients, intraoperative signal changes prompted a change in surgical plan. In no patient did there appear to be evidence of iatrogenic nerve injury.

Evoked potential monitoring in anaesthesia and analgesia

Electrophysiological monitoring of selected neural pathways of the brain, brainstem, spinal cord and peripheral nervous system has become mandatory in some surgery of the nervous system where preventable neural injury can occur. Evoked potentials are relatively simple methods of testing the integrity of various aspects of the nervous system. This review covers the variety of evoked potentials that can be monitored and outlines the principles of their measurement. Their use in specific situations and how factors such as anaesthesia might affect them is presented.

Nerve injuries due to obstetric trauma

The incidence of nerve injuries among 32,637 deliveries over a period of ten years was 1.81/1000. Brachial plexus injury (1/1000) and facial nerve injury (0.74/1000) accounted for 98% of nerve injuries. Both the right and left side were involved equally. Bilateral nerve injury was not seen. Lack of antenatal care, macrosomia, abnormal presentations, and operative vaginal deliveries significantly increased the risk of nerve injuries. These babies had significantly higher incidence of meconium stained liquor and intrapartum asphyxia. Parity of the mother, gestational age and sex of the baby did not have significant role in the causation of nerve injuries. Injuries to brachial plexus and facial nerve were seen even in babies born by caesarean section, when it was performed for obstructed labour caused by cephalo-pelvic disproportion and abnormal presentations. Three babies with injuries expired and forty-three could be followed up for varying periods. None of the babies had residual defects. Detection of cephalopelvic disproportion and abnormal lie in the third trimester and their appropriate management would decrease the incidence of obstetric palsies to a significant extent.