Faculty Bibliography

BACKGROUND:Intrathecal baclofen is widely accepted as a treatment option for severe spasticity through its γ-Aminobutyric acid-B (GABAB ) agonist properties. Abrupt cessation can lead to severe and life-threatening withdrawal characterized by altered mental status, autonomic dysreflexia, rigidity, and seizures. This symptomatic presentation is similar to alcohol withdrawal, which is mediated by modification of GABAA expression. Use of the α2-adrenergic agonist dexmedetomidine for the treatment of ethanol withdrawal has been widely reported, raising the question of its potential role in baclofen withdrawal. We present a case of the successful treatment of acute severe baclofen withdrawal with a dexmedetomidine infusion. METHODS:A 15-year-old patient with spastic quadriparesis and cerebral palsy underwent unexpected removal of his baclofen pump due to an infection that was encountered during a planned pump revision. Following removal, he was placed on high dose enteral baclofen every 6 h. Despite further benzodiazepine supplementation, he had progressive hemodynamic instability, severe rebound spasticity, and intermittent spontaneous clonus consistent with baclofen withdrawal. A dexmedetomidine infusion was titrated to a peak dose of 16 mcg per hour with successful treatment of withdrawal symptoms. RESULTS:The patient became normotensive without tachycardia. Tone and agitation improved. CONCLUSION/CONCLUSIONS:Dexmedetomidine is to our knowledge a previously unreported option for treatment of acute severe baclofen withdrawal. We report a case of safe and efficacious use in a patient with spastic quadriparesis on chronic intrathecal baclofen. Scientifically rigorous comparison with other options remains to be performed.

BACKGROUND:Neurointerventionalists do not agree about the optimal imaging protocol when evaluating patients with acute stroke for potential endovascular revascularization. Preintervention cerebrovascular blood volume (CBV) has been shown to predict outcomes in patients undergoing intra-arterial stroke therapies. OBJECTIVE:To determine whether CBV can predict hemorrhagic transformation and clinical outcomes in patients selected for endovascular therapy for acute ischemic middle cerebral artery (MCA) stroke using a CT perfusion (CTP)-based imaging protocol. METHODS:We retrospectively reviewed cases of acute ischemic stroke due to MCA M1 segment occlusion and correlated favorable clinical outcomes (modified Rankin scale (mRS) ≤2) and radiographic outcomes with preintervention CBV values. All patients underwent whole-brain (320-detector-row) CTP imaging, and absolute CBV values of the affected and contralateral MCA territories were obtained separately for the cortical and basal ganglia regions. RESULTS:Relative CBV (rCBV) of the MCA cortical regions was significantly lower in patients with poor clinical outcomes than in those with favorable clinical outcomes (0.87±0.21 vs 1.02±0.09, p=0.0003), and a negative correlation was found between rCBV values and mRS score severity. rCBV of the basal ganglia region was significantly lower in patients with hemorrhagic infarction (p=0.004) and parenchymal hematoma (p=0.04) than in those without hemorrhagic transformation. CONCLUSIONS:We found that cortical CBV loss is predictive of poor clinical outcomes, whereas basal ganglia CBV loss is predictive of hemorrhagic transformation but without translation into poor clinical outcomes. Our study findings support published results of baseline preintervention CBV as a predictor of outcomes in patients undergoing intra-arterial stroke therapies.

BACKGROUND:Thrombus characteristics, including Hounsfield unit (HU) value to measure density and thrombus volume and length, can predict successful recanalization following IV thrombolysis with recombinant tissue plasminogen activator. Conflicting and limited data exist regarding the value of assessing thrombus properties in acute stroke cases treated with endovascular IA approaches. METHODS:We retrospectively reviewed cases of anterior circulation acute ischemic stroke in which a Solitaire stent retriever (ev3-Covidien) was the primary treatment device. We measured the following thrombus characteristics: absolute and corrected HU values; thrombus length and volume; clot burden score; and vessel bifurcation involvement. Fisher's exact test and the t test were used to study the association between these clot characteristics and successful recanalization (Thrombolysis in Cerebral Infarction (TICI) score 2b-3). RESULTS:We identified 41 patients with anterior circulation stroke treated with the Solitaire stent retriever as the primary treatment device. Successful recanalization (TICI score 2b-3) was achieved in 59% of cases. Higher absolute and corrected HU values were strongly predictive of successful recanalization (49.9±7.6 vs 43.8±6.6, p=0.01 for absolute HU values and 1.2±0.2 vs 1.0±0.1, p=0.03 for HU ratio in TICI 2b-3 and TICI 0-2a groups, respectively). There was no significant difference between recanalization and non-recanalization groups in the other thrombus characteristics studied. CONCLUSIONS:In acute stroke treated with Solitaire stent retriever thrombectomy, higher thrombus HU values are predictive of successful recanalization. Such information can be used in decision making when estimating recanalization success rate with different endovascular treatment approaches.

Carotid artery stenting technologies are rapidly evolving. Options for endovascular surgeons and interventionists who treat occlusive carotid disease continue to expand. We here present an update and overview of carotid stenting devices. Evidence supporting carotid stenting includes randomized controlled trials that compare endovascular stenting to open surgical endarterectomy. Carotid technologies addressed include the carotid stents themselves as well as adjunct neuroprotective devices. Aspects of stent technology include bare-metal versus covered stents, stent tapering, and free-cell area. Drug-eluting and cutting balloon indications are described. Embolization protection options and new direct carotid access strategies are reviewed. Adjunct technologies, such as intravascular ultrasound imaging and risk stratification algorithms, are discussed. Bare-metal and covered stents provide unique advantages and disadvantages. Stent tapering may allow for a more fitted contour to the caliber decrement between the common carotid and internal carotid arteries but also introduces new technical challenges. Studies regarding free-cell area are conflicting with respect to benefits and associated risk; clinical relevance of associated adverse effects associated with either type is unclear. Embolization protection strategies include distal filter protection and flow reversal. Though flow reversal was initially met with some skepticism, it has gained wider acceptance and may provide the advantage of not crossing the carotid lesion before protection is established. New direct carotid access techniques address difficult anatomy and incorporate sophisticated flow-reversal embolization protection techniques. Carotid stenting is a new and exciting field with rapidly advancing technologies. Embolization protection, low-risk deployment, and lesion assessment and stratification are active areas of research. Ample room remains for further innovations and developments.

The minimally destructive lateral transpsoas approach to the spine has been used in the treatment of various lumbar spinal pathologies. Approach-specific complications have been reported due to the unique surgical corridor and lateral anatomical structures. The authors report a case of complex regional pain syndrome (CRPS) following interbody cage placement utilizing the lateral lumbar transpsoas approach. A review of the literature is discussed. Further clarification of the mechanism of CRPS and its treatments remains crucial for the fine-tuning of novel surgical techniques and complication avoidance during the development of these techniques.

Local soft tissue compression of fractures enhances fracture healing. The mechanism remains uncertain. Past studies have focused on intermittent soft tissue compression. We report a preliminary study assessing the relationship between constant soft tissue compression and enhanced fracture healing in an osteotomy model designed to minimize confounding variables. Fibulae of nine New Zealand white rabbits were bilaterally osteotomized, openly stabilized, and fitted with spandex stockinets. Soft tissue at the osteotomy site was unilaterally compressed using a deforming element (load = 26 mmHg). The contralateral side was saved as the control and was not compressed. Osteotomies were monitored with weekly radiographs. All fibulae in both groups were healed 6 weeks postoperatively. Micro-CT analysis of bone mineral density (BMD) and bone volume (BV) was then performed on both the experimental and control sides. Radiographic measurement of transverse callus-to-shaft ratios (TCSR) was compared. BMD of the experimental callus was greater than the noncompressed controls. BV and TCSR were not different between controls and experimental osteotomies. Constant local soft tissue compression produced significant increases in BMD, but not in BV or transverse callus size, indicating significant measurable increases in callus composition without significant change in gross dimensions. Our experimental design minimizes confounding factors, such as micromotion, immobilization, and altered venous flow, suggesting that these are not the primary mechanisms for fracture healing enhancement. Further studies with more animals and study groups are necessary to confirm efficacy and identify optimal compression pressures and schedules.

Animal fracture models have been extensively applied to preclinical research as a platform to identify and characterize normal and abnormal physiological processes and to develop specific maneuvers that alter the biology and biomechanics being examined. The choice of animal model employed in a study bears a direct relationship to the specific intervention being analyzed. The animal models employed should be described clearly, control-group data should be established, and reproducibility should be defined from experiment to experiment and from institution to institution so that quantitative and qualitative outcomes can be reliably compared and contrasted to other related studies.

INTRODUCTION/BACKGROUND:Different forms of water vary in calcium content. High divalent ion (i.e., Ca(2+), Mg(2+), etc.) concentration is deleterious to the absorption and efficacy of the bisphosphonate group of drugs in osteoporosis treatment. Water with high calcium concentration may also present an alternate pathway of calcium administration. In either case, knowing the actual concentration is critical. HYPOTHESIS/OBJECTIVE:The current paper is a surveillance study. We hypothesize that there is considerable variation in the calcium concentrations in the various water sources: tap water from US and Canadian cities of different regions and purified, spring, and mineral bottled waters. In addition, we hypothesize that the water filter removes a significant amount of minerals including calcium from the water. METHODOLOGY/METHODS:Calcium concentrations in various city tap waters, as well as an assorted number of bottled waters, were determined through the direct inspection of scientific data. The effect of filtering was also determined by mineral analysis of mineral water directly before and after filtration. RESULT/RESULTS:The calcium concentration of water varies from 1 to 135 mg/L across the USA and Canada. Most spring waters were found to have a relatively low calcium concentration, with an average of 21.8 mg/L. Purified waters contain a negligible calcium concentration. Mineral waters, on the other hand, were generally found to contain higher calcium concentrations, an average of 208 mg/L of calcium. Filtration was found to remove a considerable amount of calcium from the water, removing 89% on average. CONCLUSION/CONCLUSIONS:Calcium concentration in water varied substantially from different sources in the USA and Canada. Bottled waters presented with concentrations of calcium covering a very large range. Certain tap and bottled waters present with concentrations of calcium sufficient to exhibit a deleterious effect on bisphosphonate treatment. Alternatively, certain waters may be used as a source of calcium that may provide over 40% of the recommended daily intake for calcium.