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An experimental animal model of spinal root compression syndrome: an analysis of morphological changes of myelinated axons during compression radiculopathy and after decompression.

The treatment of radicular pain is mainly empirical because there are only few experimental studies dealing with morphological changes during compression radiculopathy. The goal of the study was to investigate changes in the morphology of myelinated axons during spinal root compression and the influence of decompression in a new rat model. The number of myelinated axons and their diameter were measured at 1, 2, 5, and 8 weeks during compression of the dorsal spinal root. The same approach was applied for 1-week compression followed by decompression for 1 or 2 weeks and compression for 5 weeks followed by 3-week decompression. A decrease in the number of myelinated axons (particularly those of large diameters) occurred after compression for 1 week. Continued compression for up to 8 weeks resulted in centripetal increase in the number of myelinated axons and the persistence of a small fraction of large myelinated axons at the site of compression. After that time, a decreased number of axons and a reduced fraction of large myelinated axons occurred again. Decompression after 1-week compression caused a rapid increase in the number of both small and large myelinated axons within the spinal root including the site of compression. A small fraction of regenerated axons was found after 5-week compression followed by 3-week decompression. Finally, we investigated the time course of the temporary increase in the number of regenerated myelinated axons during dorsal root compression for up to 8 weeks. The efficacy of decompression was superior when applied one week after compression or after regress of the acute phase of aseptic inflammation associated with fragility of spinal root. The results of the study verify the need for early surgical decompression to prevent irreversible damage of the spinal roots.

Animals↗

Computed chest tomography in an animal model for decompression sickness: radiologic, physiologic, and pathologic findings.

This study was conducted to investigate the early pulmonary effects of acute decompression in an animal model for human decompression sickness by CT and light microscopy. Ten test pigs were exposed to severe decompression stress in a chamber dive. Three pigs were kept at ambient pressure to serve as controls. Decompression stress was monitored by measurement of pulmonary artery pressure and arterial and venous Doppler recording of bubbles of inert gas. Chest CT was performed pre- and postdive and in addition the inflated lungs were examined after resection. Each lung was investigated by light microscopy. Hemodynamic data and bubble recordings reflected severe decompression stress in the ten test pigs. Computed tomography revealed large quantities of ectopic gas, predominantly intravascular, in three of ten pigs. These findings corresponded to maximum bubble counts in the Doppler study. The remaining test pigs showed lower bubble grades and no ectopic gas by CT. Sporadic interstitial edema was demonstrated in all animals--both test and control pigs--by CT of resected lungs and on histologic examination. A severe compression-decompression schedule can liberate large volumes of inert gas which are detectable by CT. Despite this severe decompression stress, which led to venous microembolism, CT and light microscopy did not demonstrate changes in lung structure related to the experimental dive. Increased extravascular lung water found in all animals may be due to infusion therapy.

Acute Disease↗

[Lateral orbital decompression for Graves' orbitopathy. Indication, surgical technique, and treatment success].

PURPOSE: In Graves' disease a discrepancy between volume increase of the orbital soft tissues and fixed volume of the orbital cavity leads to exophthalmos. The patients do not only feel cosmetically disfigured, they often complain about more or less painful retroorbital pressure sensation or show symptoms of compressive optic neuropathy or corneal exposure because of a significant lid lag. To solve this problem, different orbital decompression techniques have been developed. This is to report about our results with a modified Dollinger technique for lateral orbital decompression. PATIENTS AND METHODS: A total of 27 patients aged 19-76 years (mean: 45.1 years) with Grave's ophthalmopathy were recorded who had undergone orbital decompression by a lateral approach between June 1999 and April 2003. The modified Dollinger technique was performed by deepening the osteotomy to the level of the sphenoid wing and by additional resection of intraconal fat. RESULTS: The reduction of exophthalmos achieved after decompressive surgery averaged 2.9 +/- 1.1 mm. Of the patients whose indication for orbital decompression was a compressive neuropathy, the visual acuity improved postoperatively for 3 lines. Of the 16 patients with preoperative retrobulbar pressure sensation, 12 had no complaints after the operation. Remarkably no significant impairment of the ocular motility resulted after surgery. CONCLUSIONS: Decompression of the orbit by the modified Dollinger technique is a safe and effective approach to reduce exophthalmos, retrobulbar pressure sensation, and compression neuropathy as a result of diffusely elevated orbital tissue tension. In the case of direct compression of the optic nerve in the orbital apex, additional medial orbital wall decompression has to be considered.

Adult↗

A randomized trial of very early decompressive craniectomy in children with traumatic brain injury and sustained intracranial hypertension.

OBJECT: The object of our study was to determine, in children with traumatic brain injury and sustained intracranial hypertension, whether very early decompressive craniectomy improves control of intracranial hypertension and longterm function and quality of life. METHODS: All children were managed from admission onward according to a standardized protocol for head injury management. Children with raised intracranial pressure (ICP) were randomized to standardized management alone or standardized management plus cerebral decompression. A decompressive bitemporal craniectomy was performed at a median of 19.2 h (range 7.3-29.3 h) from the time of injury. ICP was recorded hourly via an intraventricular catheter. Compared with the ICP before randomization, the mean ICP was 3.69 mmHg lower in the 48 h after randomization in the control group, and 8.98 mmHg lower in the 48 hours after craniectomy in the decompression group (P=0.057). Outcome was assessed 6 months after injury using a modification of the Glasgow Outcome Score (GOS) and the Health State Utility Index (Mark 1). Two (14%) of the 14 children in the control group were normal or had a mild disability after 6 months, compared with 7 (54%) of the 13 children in the decompression group. Our conclusion was that when children with traumatic brain injury and sustained intracranial hypertension are treated with a combination of very early decompressive craniectomy and conventional medical management, it is more likely that ICP will be reduced, fewer episodes of intracranial hypertension will occur, and functional outcome and quality of life may be better than in children treated with medical management alone (P=0.046; owing to multiple significance testing P <0.0221 is required for statistical significance). This pilot study suggests that very early decompressive craniectomy may be indicated in the treatment of traumatic brain injury.

Brain Injuries↗

Design of near-optimal waveforms for chest and abdominal compression and decompression in CPR using computer-simulated evolution.

OBJECTIVE: To discover design principles underlying the optimal waveforms for external chest and abdominal compression and decompression during cardiac arrest and cardiopulmonary resuscitation (CPR). METHOD: A 14-compartment mathematical model of the human cardiopulmonary system is used to test successive generations of randomly mutated external compression waveforms during cardiac arrest and resuscitation. Mutated waveforms that produced superior mean perfusion pressure became parents for the next generation. Selection was based upon either systemic perfusion pressure (SPP = thoracic aortic minus right atrial pressure) or upon coronary perfusion pressure (CPP = thoracic aortic pressure minus myocardial wall pressure). After simulations of 64,414 individual CPR episodes, 40 highly evolved waveforms were characterized in terms of frequency, duty cycle, and phase. A simple, practical compression technique was then designed by combining evolved features with a constant rate of 80 min(-1) and duty cycle of 50%. RESULTS: All ultimate surviving waveforms included reciprocal compression and decompression of the chest and the abdomen to the maximum allowable extent. The evolved waveforms produced 1.5-3 times the mean perfusion pressure of standard CPR and greater perfusion pressure than other forms of modified CPR reported heretofore, including active compression-decompression (ACD)+ITV and interposed abdominal compression (IAC)-CPR. When SPP was maximized by evolution, the chest compression/abdominal decompression phase was near 70% of cycle time. When CPP was maximized, the abdominal compression/chest decompression phase was near 30% of cycle time. Near-maximal SPP/CPP of 60/21 mmHg (forward flow 3.8 L/min) occurred at a compromise compression frequency of 80 min(-1) and duty cycle for chest compression of 50%. CONCLUSIONS: Optimized waveforms for thoraco-abdominal compression and decompression include previously discovered features of active decompression and interposed abdominal compression. These waveforms can be used by manual (Lifestick-like) and mechanical (vest-like) devices to achieve short periods of near normal blood perfusion non-invasively during cardiac arrest.

Abdomen↗

Efficacy and side effects of 'swinging eyelid' orbital decompression in Graves' orbitopathy: a proposal for standardized evaluation of diplopia.

OBJECTIVES: To evaluate the efficacy and side effects of 'swinging eyelid' orbital decompression in patients with Graves' orbitopathy (GO). To calculate the incidence of postoperative new-onset diplopia (NOD) using a newly proposed scoring system for diplopia. METHODS: We reviewed the clinical data on proptosis, visual acuity, and diplopia in 104 consecutive patients (198 orbits) with GO, who underwent orbital decompression. A combined lateral canthal and inferior fornix incision ('swinging eyelid' approach) was used for removal of the medial wall, the orbital floor and, if indicated, the lateral wall. Indications for surgery were disfiguring/congestive GO (DGO) in 79 patients (149 orbits) and compressive optic neuropathy (CON) in 25 patients (49 orbits). Diplopia was scored according to four grades. In both groups, the incidence of new-onset (continuous) diplopia (NOD), deterioration of diplopia (DOD), and improvement of diplopia (IOD) were calculated, using strictly defined criteria. Our data on NOD were compared to those from other series, after recalculation according to our criteria. RESULTS: The mean proptosis reduction was 4.6 mm (range 0-9.5 mm) after three-wall decompression (95 patients, 180 orbits) vs 3.1 mm (range 0-7 mm) after two-wall decompression (nine patients, 18 orbits). The visual acuity improved in 98% of the patients with CON. In patients with DGO, NOD occurred in 14%. In patients with CON, NOD was not observed, but DOD occurred in 41%. Our data compare favourably to the reported incidence of NOD after either transantral or transnasal decompression. CONCLUSIONS: "Swinging eyelid' orbital decompression is efficacious for proptosis reduction as well as for optic nerve decompression. A scoring system for standardized evaluation of diplopia is proposed.

Adolescent↗

Comparison of results of core decompression and intertrochanteric osteotomy for nontraumatic osteonecrosis of the femoral head using Cox regression and survivorship analysis.

Different surgical procedures have been recommended for osteonecrosis of the femoral head to prevent or delay the need for arthroplasty. Core decompression is a commonly used treatment in the early stages of the disease, but the published efficacy has varied markedly. Only a few comparisons of different techniques have been reported. The aim of this study was to evaluate and compare the results of 2 commonly used procedures, core decompression and intertrochanteric osteotomy, using Cox regression and survivorship analysis. A total of 177 cases with a mean age of 41 years at surgery were treated for osteonecrosis (94 core decompressions, 83 osteotomies). Any further surgery was defined as failure and endpoint. Significant risk factors for treatment failure were age > 40 years at surgery (P = .022), corticosteroid intake (P < .001), advanced stage of necrosis (Steinberg stage > or =III, P=.04), and core decompression (P = .084). To analyze the influence of the surgical procedure, patients with corticosteroid treatment were excluded, and survival analysis was performed. This analysis revealed survival rates of 74% after osteotomy and 78% after core decompression 6 years postoperatively in early, precollapse stages (P = .819). In advanced stages, the rate of survival for hips after core decompression was lower (56%) than in hips after osteotomy (76%) (P = .056). Our results indicate that core decompression may be as effective as intertrochanteric osteotomy in precollapse stages but is less traumatizing and is cost-effective. For postcollapse hips, intertrochanteric osteotomy should be considered.

Adolescent↗

Effects of acute pancreatic duct obstruction on pancreatic perfusion: implication of acute pancreatic duct decompression.

BACKGROUND: Acute pancreatitis can result in pancreatic ischaemia and necrosis. Pancreatic duct (PD) obstruction may be the first step causing ischaemia in acute pancreatitis. Nitric oxide donors can attenuate acute pancreatitis through improvement in compromised pancreatic perfusion (PP). In this study, we determined if (1) PD obstruction altered PP and (2) PD decompression or L-arginine administration reversed this change. METHODS: Fifteen Australian possums were randomly assigned to two groups: Animals in group A (n = 6) were subjected to 30 min of PD obstruction and 60 min of PD decompression. Animals in group B (n = 9) were subjected to 120 min PD ligation and 60 min PD decompression. A subset group B (n = 6) were subjected to intravenous L-arginine (100 microg/kg) at the end of 120 min of ligation and at the end of PD decompression. The PP (Laser Doppler fluxmetry), PD pressure and blood pressure were continuously monitored. RESULTS: PD pressure increased from 2.9 +/- 2.5 to 18.1 +/- 4.9 mmHg following PD ligation. PP was reduced to 67.1% +/- 4.5% (P<0.01) and 46.2% +/- 7.5% (P<0.001) of baseline following 30 and 120 min of PD ligation, respectively. Following 60 min of PD decompression, PP was restored to 89.1% +/- 13.4% (P<0.02) of the baseline in the 30-min group. However, following 120 min PD ligation, PP remained depressed. L-arginine administration after 120 min of PD ligation transiently increased PP from 46.2% +/- 7.5% to 81.1% +/- 8.6% (P<0.03) of baseline. This effect was reproduced if L-arginine was administered at the end of decompression (P<0.05). CONCLUSION: In patients with acute pancreatitis due to obstructive causes, early decompression of the PD may prevent early pancreatic ischaemia.

Acute Disease↗

Immediate spinal cord decompression for cervical spinal cord injury: feasibility and outcome.

BACKGROUND: The effect of immediate surgical spinal cord decompression on neurologic outcome after spinal cord injury is controversial. Experimental models strongly suggest a beneficial effect of early decompression but there is little supportive clinical evidence. This study is designed to evaluate the feasibility and outcome of an immediate spinal cord decompression treatment protocol for cervical spinal cord injury in a tertiary treatment center. METHODS: To address this issue, 91 consecutive patients with acute, traumatic cervical spinal cord injury (1990-1997) were prospectively studied. Sixty-six patients (protocol group) underwent emergency magnetic resonance imaging (MRI) to determine the presence of persistent spinal cord compression followed, if indicated, by immediate operative decompression and stabilization. Twenty-five patients were managed outside the treatment protocol because of contraindication to magnetic resonance imaging, need for other emergency surgical procedures, or admitting surgeon preference (reference group). The protocol and reference groups had similar sex and age distributions, admitting Frankel grades, levels of neurologic injury, and Injury Severity Scores. RESULTS: Twenty-seven percent of patients seen were not enrolled in the treatment protocol because of the need for other emergent surgical treatment, contraindication to MRI, and specific surgeon bias regarding the "futility" of emergent treatment. The neurologic outcome for the patients in the reference group were similar to that in the previously reported literature. Fifty percent of protocol patients, compared with only 24% of reference patients, improved from their admitting Frankel grade. Eight protocol patients (12%), but no reference patients, improved from complete motor quadriplegia (Frankel grade A or B) to independent ambulation (Frankel grade D or E). Protocol patients required shorter intensive care unit stays, and shorter total hospital stays than reference patients. In the treatment protocol group, spinal cord decompression, confirmed by MRI, was achieved with immediate spinal column alignment and skeletal traction in 32 patients (46%). Thirty-four patients (54%) required emergent operative spinal cord decompression because of MRI-documented persistent spinal cord compression. CONCLUSION: We conclude that immediate spinal column stabilization and spinal cord decompression, based on magnetic resonance imaging, may significantly improve neurologic outcome. The feasibility of such a treatment protocol in a tertiary treatment center is well demonstrated. Additional multicenter trials are necessary to achieve definitive conclusions regarding clinical efficacy.

Adolescent↗

Reduction of diplopia following endoscopic orbital decompression: the orbital sling technique.

OBJECTIVE: Although endoscopic orbital decompression has become the surgical treatment of choice for patients with proptosis from Graves disease, postoperative diplopia requiring corrective eye muscle surgery can occur in up to 63% of patients. The purpose of the study was to evaluate a new technique intended to reduce the incidence of diplopia following endoscopic orbital decompression. STUDY DESIGN: Case-control. METHODS: Endoscopic orbital decompression was performed on 58 orbits in 37 patients with proptosis from Graves disease. The orbital sling technique, which makes use of a horizontal strip of periorbital fascia to prevent prolapse of the medial rectus muscle, was used on 20 orbits in 13 patients. Conventional endoscopic decompression was performed in 24 control subjects. The mean duration of follow-up was 3.3 +/- 1.3 years (range, 1.7-5.1 y). RESULTS: The incidence of new-onset or worsened diplopia following endoscopic decompression was significantly lower for the orbital sling group compared with control subjects (0% vs. 29.2%, respectively [ =.038]). No patients in the orbital sling group developed new-onset diplopia following surgery. Of the eight patients with pre-existing diplopia from the orbitopathy, double vision improved in four patients (50%) and was unchanged in the remaining four patients (50%). The mean reduction in proptosis was comparable for the orbital sling and control groups (5.1 +/- 1.1 mm vs. 5.0 +/- 1.9 mm, respectively [ P=.98]). CONCLUSIONS The preservation of a fascial sling overlying the medial rectus muscle during endoscopic orbital decompression appears to reduce the incidence of postoperative diplopia, while still allowing for a satisfactory reduction in proptosis. This modification of the standard decompression technique should be considered for the treatment of patients with proptosis.

Adult↗

The degree of decompressive relief and its relation to clinical outcome in patients undergoing surgery for lumbar spinal stenosis.

STUDY DESIGN: A cross-sectional, clinical study to evaluate surgical decompression of the stenotic area monitored by computed tomographic scan and its relation to clinical variables in patients operated on for lumbar spinal stenosis. OBJECTIVE: To study in patients with lumbar spinal stenosis the influence of the degree of compressive relief on the patients' clinical outcome. SUMMARY OF BACKGROUND DATA: The goal of surgical treatment in lumbar spinal stenosis is to decompress the stenotic area. Although the decompression should be adequate, there are no clear guidelines to determine the extent of necessary decompression. In fact, there is clinical evidence that there is a discrepancy between the surgical outcome in the patient with lumbar spinal stenosis and postoperative radiologic findings. METHODS: In 92 patients with lumbar spinal stenosis who had had no prior back surgery, preoperative and postoperative computed tomographic scans were obtained to determine the degree of decompression. The postoperative scan findings were classified according to the degree of decompression into a no-stenosis group (n = 35), an adjacent-stenosis group (n = 27), and a residual-stenosis group (n = 30). The postoperative instability of the lumbar spine was investigated by functional radiography. The subjective disability of the patients was assessed using the Oswestry score and the severity of pain using the visual analog scale. Walking capacity was evaluated by a treadmill test. The patients' estimations of the results of surgery were classified into groups of satisfied patients and dissatisfied patients. RESULTS: The mean Oswestry score in all 92 patients was 27.1, and mean walking capacity was 630 m. In the satisfied patients, the Oswestry score was 18.8 and in the dissatisfied patients, 34.9 (P < 0.0000). Walking capacity was 690 m and 594 m, respectively. There were 30 patients with postoperative spinal instability, but it had no influence on surgical outcome. There were no differences in the Oswestry score, walking capacity, and patients' satisfaction among the postoperative CT groups. In the linear regression analysis, the satisfied patient corresponded significantly with the Oswestry score. CONCLUSIONS: The satisfaction of the patients with the results of surgery was more important in surgical outcome than the degree of decompression detected on computed tomographic scan.

Cross-Sectional Studies↗

Effect of decompression enlargement laminoplasty for posterior shifting of the spinal cord.

STUDY DESIGN: A study to measure the shifts of the spinal cords and the effects of decompression laminoplasty in 65 patients with cervical lesions who underwent computed tomographic myelography before and after laminoplasty. OBJECTIVES: To investigate limitations of the spinal cord posterior shift after laminoplasty and to clarify the optimal decompression areas to obtain effective posterior shifting. SUMMARY OF BACKGROUND: Although several types of laminoplasty have been performed, all procedures share the common purpose of posterior decompression. No previous studies have examined the limitations of posterior decompression or the optimal decompression range. METHODS: The distance from the posterior edge of each vertebral body or disc level to the posterior edge of the spinal cord was measured by computed tomographic myelography. After the posterior shift was determined by calculating the difference between pre- and postsurgical distances, the relations between posterior shift and neck alignment, clinical results, and the areas of decompression were analyzed. RESULTS: The spinal cord shift ranged from a maximum of 6.6 mm to a minimum of 0 mm. Clinically, spinal cord shifts greater than 3 mm were associated with good clinical outcomes. Upward or downward advanced laminoplasty was related to larger spinal cord shifts at the upper or lower cervical spine. CONCLUSIONS: A mean spinal cord shift of > 3 mm was associated with good clinical outcomes after laminoplasty. In cases with compressive lesions at the upper or lower cervical spine, extension of decompression one level above or one level below likely results in a greater posterior spinal cord shift at these lesions.

Cervical Vertebrae↗

Management of isthmic spondylolisthesis with posterolateral endoscopic foraminal decompression.

STUDY DESIGN: Prospective evaluation of 24 consecutive patients with isthmic spondylolisthesis with chronic back, buttock, and leg pain treated by endoscopic foraminal decompression and followed for a minimum of 2 years. OBJECTIVES: To assess the efficacy of endoscopic foraminal decompression and mobilization of the exiting and transiting nerves, discectomy, ablation of osteophytes, and impinging pars as a means of treatment by the posterolateral approach. SUMMARY OF BACKGROUND DATA: Open decompression with or without fusion is a commonly accepted procedure for symptomatic isthmic spondylolytic spondylolisthesis in patients who fail to respond to conservative treatment. There is no published data on the outcome of endoscopic procedures for this condition. METHODS: Endoscopic foraminal decompression achieved with laser-assisted bone and soft-tissue ablation was performed on 12 males and 12 females with an average age of 42.4 years (36-72 years) followed for an average period of 34 months (28-46 months). The average preoperative duration of symptoms was 6.1 years (3-9 years). RESULTS: One hundred percent cohort integrity was maintained at the final follow-up. Results were analyzed using the percentage change in Oswestry Disability Scores and in Visual Analogue Pain scores. Using a percentage change in Oswestry Disability Score of 50 or more plus VAP scores of 50 or more to determine good and excellent outcomes, 79% (19 out of 24) exceeded this value. CONCLUSION: Laser-assisted endoscopic foraminal decompression provides a minimalist means of exploring the extraforaminal zone, the isthmic defect, the foramen and its contents, the disc and the epidural space. It allows adequate resection with decompression and discectomy, without the need for open decompression and fusion, and targets the symptomatic level effectively in patients with Grade I-III isthmic spondylolisthesis.

Adult↗

Open vertebral cement augmentation combined with lumbar decompression for the operative management of thoracolumbar stenosis secondary to osteoporotic burst fractures.

Osteoporotic burst fractures with neurologic symptoms are typically treated with neural decompression and multilevel instrumented fusion. These large surgical interventions are challenging because of patients' advanced ages, medical co-morbidities, and poor fixation secondary to osteoporosis. The purpose of this retrospective clinical study was to describe a novel technique for the treatment of osteoporotic burst fractures and symptomatic spinal stenosis via a limited thoracolumbar decompression with open cement augmentation [vertebroplasty (VP) or kyphoplasty (KP)]. Indications for decompression and cement augmentation were intractable pain at the level of a known osteoporotic burst fracture with symptoms of spinal stenosis. As such, 25 patients (mean age, 76.1 years) with low-energy, osteoporotic, thoracolumbar burst fractures (7 males, 18 females; 39 fractures) were included. In all cases, laminectomy of the stenotic level(s) was followed by vertebral cement augmentation (9 VP; 16 KP). When a spondylolisthesis at the decompressed level was present, instrumentation was applied across the listhetic level (n = 9). Clinical outcome (1 = poor to 4 = excellent) was assessed on last clinical follow-up (mean, 44.8 wks). In addition, a modified MacNab's grading criteria was used to objectively assess patient outcomes postoperatively. Radiographic analysis of sagittal contour was assessed preoperatively, immediately postoperatively, and at final follow-up. The average time from onset of symptoms to intervention was 19 weeks (range, 0.3-94 wks). A mean of 1.6 fractures/patient was augmented (range, 1-3 fractures) and 2.8 levels were decompressed (range, 1-6 levels). No statistical difference in anatomic distribution or number of fractures between the VP and KP groups or in the instrumented versus noninstrumented patients was noted (P > 0.05). An overall subjective outcome score of 3.4 was noted. Twenty of 25 patients were graded as excellent/good according to the modified MacNab's criteria. The choice of augmentation procedure or use of instrumentation did not predict outcome (P = 0.08). Overall, 1.7 degrees of sagittal correction was obtained at final follow-up. One patient was noted to have progressive kyphosis after KP. The use of a limited-posterior decompression and open cement augmentation via VP or KP is a safe treatment option for patients who have osteoporotic burst fractures and who are incapacitated from fracture pain and concomitant stenosis. After thoracolumbar decompression, open VP/KP provides direct visualization of the posterior vertebral body wall, allowing for safe cement augmentation of burst fractures, stabilizing the spine, and obviating the need for extensive spinal reconstruction. Although clinically successful, this technique warrants careful patient selection.

Aged↗

Complications associated with minimally invasive decompression for lumbar spinal stenosis.

OBJECTIVE: Surgical strategies for the decompression of lumbar spinal stenosis have evolved to include minimally invasive techniques providing for adequate and safe decompression while reducing perioperative morbidity. Retrospective case series analysis of 220 consecutive patients with lumbar spinal stenosis who underwent microscopic or microendoscopic minimally invasive decompression was performed. The objective was to evaluate the risks associated with performing a minimally invasive decompression for spinal stenosis in a large group of patients. METHODS: Two hundred twenty patients with symptomatic neurogenic claudication from lumbar spinal stenosis failing nonoperative treatment received a minimally invasive decompression surgery. Intraoperative data, postoperative data through hospital discharge, and clinical follow-up were analyzed. RESULTS: The average age was 74.2 years (range 49-98 years). There were 379 spinal levels decompressed in 220 patients. Sixty-nine patients (31.4%) had a grade 1 degenerative spondylolisthesis. One hundred sixty-eight patients (76%) received spinal anesthesia, and 52 received general anesthesia. Eighty-seven patients (40%) had a preoperative American Society of Anesthesiologists score of 3 or 4. Average operative blood loss was 92 mL. There were 17 intraoperative durotomies (4.5% rate). The average length of stay before discharge was 1.2 days. Ten patients went to inpatient rehabilitation at discharge. One hundred ninety-four patients (88.2%) were discharged within 24 hours. There were five readmissions within the first month after discharge, four of those for medical complications. There were 24 minor complications and 14 major complications. Forty-two patients (19%) took no oral or parenteral narcotic pain medications in the postanesthesia to discharge period. CONCLUSION: Minimally invasive decompression strategies for spinal stenosis seem consistently to result in short hospital lengths of stay, minimal requirements for narcotic pain medications, and a low rate of readmission and complications.

Aged↗

Decompression comparison of helium and hydrogen in rats.

The hypothesis that there are differences in decompression risk between He and H2 was examined in 1,607 unanesthetized male albino rats subjected to dives on 2% O2-balance He or 2% O2-balance H2 (depths < or = 50 ATA, bottom times < or = 60 min). The animals were decompressed to 10.8 ATA with profiles varying from rapid to slow, with up to four decompression stops of up to 60 min each. Maximum likelihood analysis was used to estimate the relative decompression risk on a per unit pressure basis (termed "potency") and the rate of gas uptake and elimination, both factors affecting the decompression sickness risk, from a specific dive profile. H2 potency for causing decompression sickness was found to be up to 35% greater than that for He. Uptake rates were unresolvable between the two gases with the time constant (TC) estimated at approximately 2-3 min, leading to saturation in both cases in < 15 min. Washout of both gases was significantly slower than uptake, with He washout (TC approximately 1.5-3 h) substantially slower than H2 washout (TC approximately 0.5 h). It is unknown whether the decompression advantage of the faster washout of H2 or the disadvantage of its increased potency, observed in the rat, would be important for human diving.

Animals↗

Gas bubbles in rats after heliox saturation and different decompression steps and rates.

Effects of pressure reduction, decompression rate, and repeated exposure on venous gas bubble formation were determined in five groups (GI, GII, GIII, GIV, and GV) of conscious and freely moving rats in a heliox atmosphere. Bubbles were recorded with a Doppler ultrasound probe implanted around the inferior caval vein. Rats were held for 16 h at 0.4 MPa (GI), 0.5 MPa (GII and GIII), 1.7 MPa (GIVa), or 1.9 MPa (GIV and GV), followed by decompression to 0.1 MPa in GI to GIII and to 1.1 MPa in GIV and GV. A greater decompression step, but at the same rate (GII vs. GI and GIVb vs. GIVa), resulted in significantly more bubbles (P < 0.01). A twofold decompression step resulted in equal amount of bubbles when decompressing to 1.1 MPa compared with 0.1 MPa. The faster decompression in GII and GVa (10.0 kPa/s) resulted in significantly more bubbles (P < 0.01) compared with GIII and GVb (2.2 kPa/s). No significant difference was observed in cumulative bubble score when comparing first and second exposure. With the present animal model, different decompression regimes may be evaluated.

Adaptation, Physiological↗

Endoscope-assisted microvascular decompression for trigeminal neuralgia: technical case report.

OBJECTIVE: Microvascular decompression may fail to relieve trigeminal neuralgia because a compressing vessel at the root entry zone may be overlooked during surgery. Alternatively, effective decompression may not always be achieved with the visualization provided by the microscope alone. We theorized that the addition of an endoscope would improve the efficacy of microvascular decompression. METHODS: We retrospectively reviewed microvascular decompression of the trigeminal nerve in 114 patients. Before closure, the endoscope was used to inspect the root entry zone. When visualization with the microscope was poor, the endoscope was used to identify an aberrant vessel and to perform or improve the subsequent decompression. RESULTS: Of 114 patients who underwent microvascular decompression, 113 successfully underwent endoscopy. In 38 patients (33%), endoscopy revealed arteries that were poorly seen (25%) or not seen at all (8%) with the microscope. At a mean follow-up period of 29 months, the pain was completely relieved in 112 patients (99.1%), all of whom were off medication. Complications included trigeminal dysesthesias in nine patients and a wound infection, partial hearing loss, and complete hearing loss in one patient each. The overall complication rate was 9%. CONCLUSION: Endoscopy is a simple and safe adjunct to microscopic exploration of the trigeminal nerve. The markedly improved visualization increases the likelihood of identifying the offending vessel and consequently of achieving satisfactory decompression of the nerve. Thus far, the success rate has been high, and the complication profile is comparable to that of other large series.

Adult↗