Browsing by Author "Koivuniemi, Andrew S."

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    Central nervous system microstimulation: Towards selective micro-neuromodulation
    (Elsevier, 2017-12) Urdaneta, Morgan E.; Koivuniemi, Andrew S.; Otto, Kevin J.; Neurological Surgery, School of Medicine
    Electrical stimulation technologies capable of modulating neural activity are well established for neuroscientific research and neurotherapeutics. Recent micro-neuromodulation experimental results continue to explain neural processing complexity and suggest the potential for assistive technologies capable of restoring or repairing of basic function. Nonetheless, performance is dependent upon the specificity of the stimulation. Increasingly specific stimulation is hypothesized to be achieved by progressively smaller interfaces. Miniaturization is a current focus of neural implants due to improvements in mitigation of the body's foreign body response. It is likely that these exciting technologies will offer the promise to provide large-scale micro-neuromodulation in the future. Here, we highlight recent successes of assistive technologies through bidirectional neuroprostheses currently being used to repair or restore basic brain functionality. Furthermore, we introduce recent neuromodulation technologies that might improve the effectiveness of these neuroprosthetic interfaces by increasing their chronic stability and microstimulation specificity. We suggest a vision where the natural progression of innovative technologies and scientific knowledge enables the ability to selectively micro-neuromodulate every neuron in the brain.
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    Geniculate neuralgia successfully treated with microvascular decompression
    (Elsevier, 2020-03) Pecoraro, Nathan C.; Zaazoue, Mohamed A.; Koivuniemi, Andrew S.; Savage, Jesse J.; Neurological Surgery, School of Medicine
    Background First described by John Nottingham in 1857, geniculate neuralgia remains a rare condition associated with vascular compression of the nervus intermedius by the anterior inferior cerebellar artery (AICA), which results in paroxysmal unilateral periauricular pain. Furthermore, limited and controversial treatment options for symptom relief exist given the rarity of the condition and limited cases reported in the literature. Case description This is a case of a 37-year-old one-pack-per-day smoker with diabetes mellitus who presented to our clinic for evaluation of episodic lancinating pain localizing to the right periauricular region. The patients symptoms were attempted to be managed medically, however, remained refractory to medical management for a period greater than one year. The patient’s exam demonstrated a trigger point slightly anterior and inferior to the right tragus, and the pain was reproducible when touched or tapped. The patient was otherwise neurologically intact. Magnetic resonance imaging (MRI) was performed and demonstrated a loop of the AICA in contact with the root entry zone of the facial nerve. This patient was offered an elective microvascular decompression (MVD) for treatment of geniculate neuralgia. Conclusions Surgical microvascular decompression is a safe and effective treatment option for patients suffering from neuralgia refractory to medical therapy. Furthermore, our case report demonstrates that MVD is an effective treatment option for patients suffering from geniculate neuralgia with imaging evidence of AICA compression of the nervus intermedius that is refractory to medical management.
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    Raloxifene Enhances Material-Level Mechanical Properties of Femoral Cortical and Trabecular Bone
    (2007-08) Allen, Matthew R.; Hogan, Harry A.; Hobbs, Wesley A.; Koivuniemi, Andrew S.; Koivuniemi, Mark C.; Burr, David B.
    We have previously documented that raloxifene enhances the mechanical properties of dog vertebrae independent of changes in bone mass, suggesting a positive effect of raloxifene on material-level mechanical properties. The goal of this study was to determine the separate effects of raloxifene on the material-level mechanical properties of trabecular and cortical bone from the femur of beagle dogs. Skeletally mature female beagles (n = 12 per group) were treated daily for 1 yr with oral doses of vehicle or raloxifene (0.50 mg/kg d). Trabecular bone mechanical properties were measured at the femoral neck using reduced platen compression, a method that allows the trabecular bone to be tested without coring specimens. Cortical bone properties were assessed on prismatic beam specimens machined from the femoral diaphysis using both monotonic and dynamic (cyclic relaxation) four-point bending tests. Trabecular bone from raloxifene-treated animals had significantly higher ultimate stress (+130%), modulus (+89%), and toughness (+152%) compared with vehicle-treated animals. Cortical bone from raloxifene-treated animals had significantly greater toughness (+62%) compared with vehicle, primarily as a function of increased postyield displacement (+100%). There was no significant difference between groups in the percentage of stiffness loss during cortical bone cyclic relaxation tests. These results are consistent with previous data from the vertebrae of these same animals, showing raloxifene has positive effects on biomechanical properties independent of changes in bone volume/density. This may help explain how raloxifene reduces osteoporotic fractures despite modest changes in bone mass.