The influence of cage positioning and cage type on cage migration and fusion rates in patients with monosegmental posterior lumbar interbody fusion and posterior fixation.

In posterior lumbar interbody fusion, cage migrations and lower fusion rates compared to autologous bone graft used in the anterior lumbar interbody fusion procedure are documented. Anatomical and biomechanical data have shown that the cage positioning and cage type seem to play an important role. Therefore, the aim of the present study was to evaluate the impact of cage positioning and cage type on cage migration and fusion. We created a grid system for the endplates to analyze different cage positions. To analyze the influence of the cage type, we compared "closed" box titanium cages with "open" box titanium cages. This study included 40 patients with 80 implanted cages. After pedicle screw fixation, 23 patients were treated with a "closed box" cage and 17 patients with an "open box" cage. The follow-up period averaged 25 months. Twenty cages (25%) showed a migration into one vertebral endplate of <3 mm and four cages (5%) showed a migration of > or =3 mm. Cage migration was highest in the medio-medial position (84.6%), followed by the postero-lateral (42.9%), and the postero-medial (16%) cage position. Closed box cages had a significantly higher migration rate than open box cages, but fusion rates did not differ. In conclusion, cage positioning and cage type influence cage migration. The medio-medial cage position showed the highest migration rate. Regarding the cage type, open box cages seem to be associated with lower migration rates compared to closed box cages. However, the cage type did not influence bone fusion.

The effect of N-acetylcysteine on posttraumatic changes after controlled cortical impact in rats.

OBJECTIVE: The antioxidant potential N-Acetylcysteine (NAC) and its improvement of posttraumatic mitrochondrial dysfunction have been reported. This study investigated the effect of NAC on posttraumatic changes after controlled cortical Impact (CCI) injury. DESIGN AND SETTING: Prospective randomized controlled animal study. METHODS: A moderate left focal cortical contusion was induced using CCI. Either NAC (163 mg/kg bw) or physiological saline was administered intraperitoneally immediately and 2 and 4 h after trauma. Blood gases, temperature, mean arterial blood pressure (MABP), and intracranial pressure (ICP) were monitored. Twenty-four hours after trauma brains were removed and either posttraumatic edema was quantified gravimetrically (n=24], or contusion volume was determined morphometrically using slices staining and computerized image analysis (n=24]. Laser Doppler flowmetry was used to assess pericontusional cortical perfusion before trauma, 30 min and 4 and 24 h after trauma (n=14]. MEASUREMENTS AND RESULTS: Physiological parameters remained within normal limits. ICP measurements and water content in traumatized hemispheres did not differ between the groups. Relative contusion volume of the left hemisphere was slightly but nonsignificantly diminished in NAC-treated animals (4.7+/-0.4% vs. 5.9+/-0.5% in controls). In both groups pericontusional perfusion was significantly reduced at 4 h followed by a state of hyperperfusion at 24 h with no differences between the groups. CONCLUSIONS: Despite previously reported neuroprotective abilities of NAC, no positive effect on posttraumatic perfusion, brain edema formation, or contusion volume after focal brain injury was observed in this study.

A spine frame for intra-operative fixation to increase accuracy in spinal navigation and robotics.

OBJECTIVE: Intra-operative movements due to mechanical ventilation or manipulations are a limiting factor for accurate spinal navigation or robotic-assisted spinal surgery. The purpose of this study was to assess the accuracy of an intra-operative spinal fixation device in an experimental setup. MATERIALS AND METHODS: We developed a fixation device, attached to the operating table, that combines soft tissue retraction with spinal process fixation. Using a lumbar spine cadaver, tightness of fixation was evaluated using two measurement systems. Accuracy measurements using changes in spatial co-ordinates of implanted reference markers were performed in three segments, following different manipulations of the spine. In addition, for intra-operative movements of the spine during mechanical ventilation, the range of motion was determined in 10 patients during lumbar interbody fusion. RESULTS: The spine frame was easy to use and did not restrict screw insertion. Mean deviations of the markers' in all segments were measured at between 0.35 and 0.8 mm, following pedicle screw insertion and lateral traction. Intra-operative range of motion of the spine was measured with a mean value of 8.7 +/- 3.3 mm. CONCLUSION: Using our spine frame, a rigid fixation following manipulation of the spine was demonstrated. By overcoming the intra-operative movement-dependent inaccuracy, safety in navigated spine surgery and robotic-assisted procedures might be improved.

Degenerative spondylolisthesis of the cervical spine--symptoms and surgical strategies depending on disease progress.

BACKGROUND: Degenerative spondylolisthesis of the cervical spine is rare. Patients show signs of progredient myelopathy, radiculopathy and pain. Treatment strategies include ventral, dorsal and combined fusion techniques with or without repositioning and decompression. METHODS: In this study, we present 16 patients with degenerative cervical spondylolisthesis. The leading symptom was severe myelopathy in 8 patients, radiculomyelopathy in 5 patients and neck pain in 3 patients. However, neck pain was the initial symptom in all the patients and decreased when neurological symptoms became more evident. Radiographic examinations included plain radiography, MRI, CT, myelography and lateral tomography. RESULTS: Spondylolisthesis was located five times at level C3/4, C4/5 and C5/6. In three cases spondylolisthesis was located at level C7/T1. There were two patients with spondylolisthesis on two levels. Instability could be demonstrated by flexion/extension radiography in five cases. Patients were divided into three groups according to a newly introduced classification system. The surgical approach corresponded to this classification. In ten patients the spondylolisthesis could be corrected by extension and positioning, so discectomy and fusion on one or two levels with cage, plate and screws was sufficient. In five cases a corpectomy was necessary due to severe spondylosis. In one case a combined approach with dorsal decompression and release followed by ventral fusion was applied due to additional dorsal spinal cord compression. The follow-up period was 6-52 months. After surgery, none of the patients showed any signs of neurological deterioration. In all cases, a stable fusion was achieved with no signs of instability on flexion/extension radiographs. Neurological improvement was seen in 6 of 8 patients with myelopathy and 4 of 5 patients with radiculomyelopathy. The others showed stable disease. Pain relief was seen in all patients who complained of pain preoperatively. CONCLUSION: The aims of treatment for cervical spondylolisthesis are spinal cord decompression (ventral, dorsal or both), correction and fusion. The used procedure should depend on the severity of the cervical deformity, degree and side of the spinal cord compression, and the possibility of correction by extension and positioning.

Small volume resuscitation with HyperHaes improves pericontusional perfusion and reduces lesion volume following controlled cortical impact injury in rats.

The hyperosmolar and hyperoncotic properties of HyperHaes (HHES) might improve impaired posttraumatic cerebral perfusion. Possible beneficial effects on pericontusional perfusion, brain edema, and contusion volume were investigated in rats subjected to controlled cortical impact (CCI). Male Sprague-Dawley rats (n = 60) anesthetized with isoflurane were subjected to a left temporoparietal CCI. Thereafter, rats were randomized to receive HHES (10% hydroxyethylstarch, 7.5% NaCl) or physiological saline solution (4 mL/kg body weight) intravenously. Mean arterial blood pressure (MABP) and intracranial pressure (ICP) were determined before and following CCI, after drug administration and 24 h later. Regional pericontusional cortical perfusion was determined by scanning laser Doppler flowmetry before CCI, and 30 min, 4 and 24 h after injury. At 24 h brain swelling and water content were measured gravimetrically. At 7 days, cortical contusion volume was determined planimetrically. MABP was not influenced by HHES. ICP was significantly decreased immediately after HHES infusion (5.7 +/- 0.4 vs. 7.1 +/- 1.0 mm Hg; p < 0.05). Pericontusional cortical perfusion was significantly decreased by 44% compared to pre-injury levels (p < 0.05). HHES significantly improved cortical perfusion at 4 h after CCI, approaching baseline values (85 +/- 12%). While increased posttraumatic brain edema was not reduced by HHES at 24 h, cortical contusion volume was significantly decreased in the HHES-treated rats at 7 days after CCI (23.4 +/- 3.5 vs. 39.6 +/- 6.2 mm3; p < 0.05). Intravaneous administration of HHES within 15 min after CCI has a neuroprotective potential, as it significantly attenuated impaired pericontusional perfusion and markedly reduced the extent of induced structural damage.

Effects of early and late intravenous norepinephrine infusion on cerebral perfusion, microcirculation, brain-tissue oxygenation, and edema formation in brain-injured rats.

OBJECTIVES: Reduction of cerebral perfusion during the early phase after traumatic brain injury is followed by a later phase of normal to increased perfusion. Thus, pharmacologically elevating mean arterial blood pressure with the aim of improving cerebral perfusion may exert different time-dependent effects on cortical perfusion, microcirculation, tissue oxygenation and brain edema formation after traumatic brain injury. DESIGN: Randomized, placebo-controlled trial. SETTING: Experimental laboratory at a university hospital. SUBJECTS: A total of 37 male Sprague-Dawley rats subjected to a focal cortical contusion. INTERVENTIONS: At 4 or 24 hrs after focal traumatic brain injury, mean arterial blood pressure was increased to 120 mm Hg for 90 mins by infusing norepinephrine. In rats receiving physiologic saline, mean arterial blood pressure remained unchanged. In the first series, pericontusional cortical perfusion was measured using the laser Doppler flowmetry scanning technique before injury and before, during, and after the infusion period. In a second series, intracranial and cerebral perfusion pressure and intraparenchymal perfusion and tissue oxygen measured within the contused and pericontusional cortex were recorded continuously before, during, and after norepinephrine infusion. Changes in cortical microcirculation were investigated by orthogonal polarization spectral imaging. At the end of each experiment, hemispheric swelling and water content were determined gravimetrically. MEASUREMENTS AND MAIN RESULTS: At 4 and 24 hrs after traumatic brain injury, intravenous norepinephrine significantly increased pericontusional cortical perfusion, which was also reflected by an increase in diameters and flow velocities of pericontusional arterioles and venules. Cerebral perfusion pressure and intraparenchymal perfusion and tissue oxygen were significantly increased during norepinephrine infusion at 4 and 24 hrs. Hemispheric swelling and water content showed no difference between the groups. CONCLUSIONS: After cortical impact injury, early and late intravenous norepinephrine infusion pressure-dependently increased cerebral perfusion and tissue oxygenation without aggravating or reducing brain edema formation. Future studies are warranted to determine long-term changes of short and prolonged norepinephrine-induced increases in mean arterial blood pressure and cerebral perfusion pressure.

Effects of LY379268, a selective group II metabotropic glutamate receptor agonist on EEG activity, cortical perfusion, tissue damage, and cortical glutamate, glucose, and lactate levels in brain-injured rats.

Activating presynaptic group II metabotropic glutamate (mGlu II) receptors reduces synaptic glutamate release. Attenuating glutamatergic transmission without blocking ionotropic glutamate receptors, thus avoiding unfavorable psychomimetic side effects, makes mGlu II receptor agonists a promising target in treating brain-injured patients. Neuroprotective effects of LY379268 were investigated in rats following controlled cortical impact injury (CCI). At 30 min after CCI, rats received a single intraperitoneal injection of LY379268 (10 mg/kg/body weight) or NaCl. Changes in EEG activity and pericontusional cortical perfusion were determined before trauma, at 4, 24, and 48 h, and 7 days after CCI. Brain edema and contusion volume were determined at 24 h and 7 days after CCI, respectively. Before brain removal pericontusional cortical glutamate, glucose, and lactate were measured via microdialysis. During the early period following CCI, EEG activity and cortical perfusion were significantly reduced in rats receiving LY379268. At 7 days, cortical perfusion was significantly increased in rats treated with LY379268, while EEG activity was depressed as in control rats. While brain edema remained unchanged at 24 h, cortical contusion was significantly decreased by 56% at 7 days after CCI. Cortical glutamate, glucose, and lactate were not influenced. Significant reductions in EEG activity and contusion volume by LY379268 do not appear mediated by attenuated excitotoxicity and energetic impairment. Overall, an additional decrease in cortical perfusion seems to interfere with the anti-edematous potential of LY379268 during the early period following CCI, while an increase in perfusion in LY379268-treated rats at 7 days might contribute to tissue protection.

Tentorial dural arteriovenous fistula presenting with various visual symptoms related to anterior and posterior visual pathway dysfunction: case report.

OBJECTIVE AND IMPORTANCE: Dural arteriovenous fistulae (DAVFs) not directly shunting into the cavernous sinus are an infrequent cause of visual dysfunction. An unusual case of a tentorial DAVF associated with visual symptoms related to dysfunction of the anterior and posterior visual pathway is presented. CLINICAL PRESENTATION: A 38-year-old woman with a history of long-standing bilateral proptosis experienced a sudden onset of headache and visual disturbances. Ocular examination revealed bilateral episcleral and retinal venous congestion, optic disc paleness, right superior homonymous quadrantanopsia in both eyes, and concentric narrowing of the visual field of the right eye. Angiography revealed a DAVF supplied by a falx branch arising from the left vertebral artery and both middle meningeal arteries, which drained directly into the markedly dilated vein of Galen via the basal vein of Rosenthal and the cavernous sinus into both superior ophthalmic veins. INTERVENTION: Endovascular treatment was performed in two consecutive sessions by transarterial embolization with n-butylcyanoacrylate, which resulted in occlusion of the fistula and complete clinical cure, confirmed at the 6-month follow-up examination. CONCLUSION: Various neuro-ophthalmological findings may be caused by an arteriovenous lesion remote from the optic organ as a result of rerouting of venous drainage compromising the visual pathway at different locations. Transarterial embolization of a DAVF may result in complete cure if advantageous arterial anatomy allows for flow control and occlusion of the fistulous connection with liquid adhesives.

Pineal region lesion masquerading choroid plexus papilloma: case report.

BACKGROUND: Choroid plexus papillomas (CPPs) are rare intracranial neoplasms, especially in the third ventricle. We report a patient with a posterior third ventricular CPP extending into the pineal that radiographically and clinically presented as a pineal region lesion. CASE DESCRIPTION: In a 51-year-old female with headache and upward gaze impairment radiological examination showed a mass in the pineal region obstructing the aqueduct of Sylvius and causing hydrocephalus. After ventriculoperitoneal shunting the tumor was approached through the infratentorial-supracerebellar approach and pathological examination revealed a typical CPP. CONCLUSIONS: This case represents an unusual presentation of an intracranial CPP. This entity should be considered an extremely rare cause of a lesion in the pineal region.

Influence of norepinephrine and dopamine on cortical perfusion, EEG activity, extracellular glutamate, and brain edema in rats after controlled cortical impact injury.

Following traumatic brain injury, catecholamines given to ameliorate cerebral perfusion may induce brain damage via cerebral arteriolar constriction and increased neuronal excitation. In the present study the acute effects of norepinephrine and dopamine on pericontusional cortical perfusion (rCBF), electroencephalographic (EEG) activity, extracellular glutamate, and brain edema were investigated in rats following controlled cortical impact injury (CCI). rCBF, cerebral perfusion pressure (CPP), EEG activity, and glutamate were determined before, during, and after infusing norepinephrine or dopamine, increasing MABP to 120 mm Hg for 90 min at 4 h after CCI. Control rats received physiological saline. At 8 h after CCI, hemispheric swelling and water content were determined gravimetrically. Following CCI, rCBF was significantly decreased. In parallel to elevating MABP and CPP, rCBF was significantly increased by norepinephrine and dopamine, being mostly pronounced with norepinephrine (+44% vs. +29%). In controls, rCBF remained diminished (-45%). EEG activity was significantly increased by norepinephrine and dopamine, while pericontusional glutamate was only elevated by norepinephrine (28 +/- 6 vs. 8 +/- 4 microM). Brain edema was not increased compared to control rats. Despite significantly increasing MABP and CPP to the same extent, norepinephrine and dopamine seem to differentially influence pericontusional cortical perfusion and glutamatergic transmission. In addition to the pressure-passive increase in CPP local cerebral effects seem to account for the sustained norepinephrine-induced increase in pericontusional cortical perfusion. The significantly elevated pericontusional glutamate concentrations in conjunction with the increased EEG activity suggest a sustained metabolically driven increase in cortical perfusion during norepinephrine infusion.

Osteochondroma of the cervical spine--a surprising finding in a liver transplanted patient with polyneuropathy and polyradiculitis: case report.

BACKGROUND: Osteochondroma of the spine is a rare condition. We report a case of a patient with a cervical osteochondroma presenting with a polyneuropathy and polyradiculitis simultaneously. CASE DESCRIPTION: In a liver-transplant patient with progressive neurological deficits a polyneuropathy and a polyradiculitis were diagnosed. Eventually the patient became quadraparetic and an osteochondroma compressing the cervical spinal cord was found. The patient's neurological symptoms markedly improved after gross total tumor resection and antibiotic therapy. CONCLUSIONS: Review of the literature reveals this case to be an unusual presentation of a cervical osteochondroma, its diagnosis being delayed because of concomitant neurological diseases.

Temporal profile of cortical perfusion and microcirculation after controlled cortical impact injury in rats.

Impaired cerebral perfusion contributes to evolving posttraumatic tissue damage. Spontaneous reversibility of reduced perfusion within the first days after injury could make a persisting impact on secondary tissue damage less likely and needs to be considered for possible therapeutic approaches. The present study was designed to characterize the temporal profile and impact of trauma severity on cortical perfusion and microcirculation during the first 48 h after controlled cortical impact injury (CCI). In 10 rats, pericontusional cortical perfusion and microcirculation using laser Doppler flowmetry (LDF) and orthogonal polarization spectral (OPS) imaging were assessed before, and at 4, 24, and 48 h after CCI. Influence of trauma severity was studied by varying the penetration depth of the impactor rod (0.5 vs. 1 mm), thereby inducing a less and a more severe contusion. Mean arterial blood pressure (MABP), arterial blood gases, and blood glucose were monitored. With unchanged MABP and paCO2, cortical perfusion and microcirculation were significantly impaired during the first 48 h following CCI. Hypoperfusion observed at 4 h related to vasoconstriction and microcirculatory stasis preceded a long-lasting phase of hyperperfusion at 24 and 48 h reflected by vasodilation and increased flow velocity in arterioles and venules. Hyperperfusion was mostly pronounced in rats with a less severe contusion. Following CCI, trauma severity markedly influences changes in pericontusional cortical perfusion and microcirculation. Overall, pericontusional cortical hypoperfusion observed within the early phase preceded a long lasting phase of hyperperfusion up to 48 h after CCI.