Alexander Taghva

Obesity and brain addiction circuitry: implications for deep brain stimulation.

Obesity is a growing health problem worldwide and is responsible for a significant proportion of health expenditures in developed nations. It is also notoriously difficult to treat. Prior attempts at pharmacological or neurological modulation, including deep brain stimulation, have primarily targeted homeostatic mechanisms of weight control centered in the hypothalamus. To date, these attempts have had limited success. Multiple lines of independent data suggest that dysregulated reward circuitry in the brain underlies behaviors leading to obesity. Here, we review the existing data and related neurocircuitry, as well as the scope of obesity and currently available treatments. Finally, we suggest a neuromodulation strategy geared toward regulating these dysfunctional circuits, primarily by alteration of frontolimbic circuits.

Minimally invasive circumferential spinal decompression and stabilization for symptomatic metastatic spine tumor: Technical case report

OBJECTIVEMetastatic epidural spinal cord compression is a potentially devastating complication of cancer and is estimated to occur in 5% to 14% of all cancer patients. It is best treated surgically. Minimally invasive spine surgery has the potential benefits of decreased surgical approach–related morbidity, blood loss, hospital stay, and time to mobilization. CLINICAL PRESENTATIONA 36-year-old man presented with worsening back pain and lower extremity weakness. Workup revealed metastatic adenocarcinoma of the lung with spinal cord compression at T4 and T5. INTERVENTION AND TECHNIQUET4 and T5 vertebrectomy with expandable cage placement and T1–T8 pedicle screw fixation and fusion were performed using minimally invasive surgical techniques. RESULTThe patient improved neurologically and was ambulatory on postoperative day 1. At the 9-month follow-up point, he remained neurologically intact and pain free, and there was no evidence of hardware failure. CONCLUSIONMinimally invasive surgical circumferential decompression may be a viable option for the treatment of metastatic epidural spinal cord compression.

Posttraumatic stress disorder: neurocircuitry and implications for potential deep brain stimulation.

Posttraumatic stress disorder (PTSD) is a prevalent and highly disabling psychiatric disorder that is notoriously difficult to treat. At some point in their lifetimes, 5-8% of men, 10-14% of women, and up to a quarter of combat veterans carry this diagnosis. Despite pharmacological and behavioral therapies, up to 30% of patients are still symptomatic 10 years after initial diagnosis. Recent advances in imaging have implicated changes in the limbic and autonomic corticostriatopallidothalamocortical (CSPTC) circuitry in the pathogenesis of this disease. Deep brain stimulation modulates CSPTC circuits in movement and other neuropsychiatric disorders. In this review, we discuss the salient clinical features and neurocircuitry of PTSD and propose a neuromodulation strategy for the disorder.

Hidden semi-Markov models in the computerized decoding of microelectrode recording data for deep brain stimulator placement.

OBJECTIVE To describe an approach to the analysis of deep brain stimulation (DBS) of the subthalamic nucleus (STN) using a hidden semi-Markov model (HsMM) and early results of the analysis of microelectrode recordings for STN DBS. METHODS The author simulated the anatomy and electrophysiology of STN DBS and built a seven-state model to compare Hidden Markov model (HMM) and HsMM approaches. RESULTS Accuracy of these competing models was similar for correctly identifying brain nuclei; however, HsMMs showed superior specificity in detecting microelectrode passes traversing the STN. CONCLUSIONS Further clinical work must be done; however, based on these data, HsMMs may be best suited to computer-assisted anatomic delineation for DBS.

Posttraumatic Human Cerebral Myiasis

OBJECTIVE Only eight cases of cerebral myiasis in humans have been reported worldwide and only one in the United States. Presented here is a case of cerebral myiasis in the setting of head trauma in suburban Los Angeles. METHODS The article includes chart review and description of a clinical case presentation. RESULTS A 42-year-old HIV-positive man was found in a ditch after 2 weeks, the victim of apparent assault. He had multiple facial fractures along with open depressed bifrontal sinus fractures with necrotic bone, eroded dura, exposed cortex, and extensive maggot infestation of the left frontal lobe. The patient was taken urgently to the operating room, where the maggots where evacuated by irrigation and suction. Debridement of necrotic bone, dura, and brain was performed, the frontal sinuses were exenterated, and skull defects plated with titanium mesh. Intraoperative cultures revealed a polymicrobial meningitis/encephalitis, which was treated postoperatively with antibiotics. The patients neurologic exam stabilized and the patient was transferred to a rehabilitation facility for further care, ultimately achieving functionality and holding a job. CONCLUSION This is the first published case of cerebral myiasis secondary to trauma, and to our knowledge, the first documented long-term survivor of extensive cerebral myiasis. Wide debridement to normal brain followed by 6 weeks of broad-spectrum antibiotic treatment is effective in managing this condition. A well-functioning outcome can be expected with prompt recognition and treatment of the disease. Larval infestation may have a protective effect against bacterial infection and may allow for greater tolerance of treatment delay.

From Atom to Brain: Applications of Molecular Imaging to Neurosurgery

Molecular imaging is a field born out of the happy marriage of molecular biology and radiology. The first installment of this two-part series on molecular imaging demonstrated basic principles for practitioners in the field of the neurosciences. This installment seeks to provide some illustrative examples, insights, and specific applications to the neurosciences. The fields of functional neurosurgery including the treatment of neuropsychiatric disorders, novel treatments and imaging of tumors, neuroregenerative medicine, and nanotechnology in vascular disorders are covered. Finally, we give some parting thoughts on the future of molecular imaging, including advances in the imaging of neurodegenerative disorders.

An automated navigation system for deep brain stimulator placement using hidden Markov models.

OBJECTIVE Placement of deep brain stimulators (DBSs) currently involves the use of both image-based stereotaxy and intraoperative microelectrode recording (MER). Interpretations of MER data and integration with anatomical data are currently manual processes. Hidden Markov models (HMMs) are commonly used in signal processing, speech recognition, and a wide array of biologic applications. METHODS A 6-state HMM was designed and trained for evaluation in simulated surgery for subthalamic nucleus (STN) DBS. RESULTS The accuracy of identifying the correct brain location was 98.5%. Sensitivity of detecting passes intersecting the STN was 100%, and specificity was 84.9%. Anatomical location of the MER passes was calculated with a mean error of 0.06 mm (95% confidence interval, −0.54 to 0.42 mm) in the medial-lateral axis. CONCLUSION Automated DBS intraoperative navigation using HMMs may be feasible based on promising results of this prototype system.

Symptomatic vertebral artery compression by the rod of a C1-C2 posterior fusion construct: case report and review of the literature.

Study Design. Case report. Objective. To report a rare complication of atlantoaxial fusion. Summary of Background Data. Vertebral artery injury is a serious complication of screw-based atlantoaxial fusion. To our knowledge, injury to the vertebral artery has only been described as a result of screw placement. We describe the first case of atlantoaxial fixation complicated by symptomatic and reversible external compression of the vertebral artery by the rod in a Harms construct. Methods. Medical records and imaging reports were reviewed. Results. A neurologically intact 84-year-old woman presented after a ground-level fall. Imaging revealed a nondisplaced type II odontoid fracture associated with a C1 ring fracture. She underwent a minimally invasive Harms atlantoaxial fusion. After surgery, she developed fluctuating level of consciousness in the setting of an otherwise normal neurologic and metabolic workup. A computed tomographic angiogram was obtained and showed good screw placement except for compression of the right vertebral artery from the right transfixing rod causing 75% luminal narrowing. She underwent a revision with rod shortening, and after surgery, improved neurologically, without any further episodes of altered mental status. Conclusion. In atlantoaxial fusion, the incidence of vertebral artery compression by the rod component of fusion construct may be underreported because it is difficult to detect with noncontrast computed tomography without computed tomographic angiography, which is not routinely obtained unless there is a high suspicion for vascular injury. We recommend inserting the rods with the cut (sharp) end pointing inferiorly, to avoid lacerating the vertebral artery. A vertebral artery compression from the rod in the absence of screw violation of the foramen transversarium should be considered in a patient with altered mental status after atlantoaxial fusion.

Molecular imaging, part 1: apertures into the landscape of genomic medicine.

Conventional imaging paradigms rely on the detection of anatomical changes in disease that are preceded by molecular genetic changes that go otherwise undetected. With the advent of molecular imaging, it will be possible to detect these changes prior to the manifestation of disease. Molecular imaging is the amalgamation of molecular biology and imaging technology that was spawned by parallel advances in the two fields. Fundamental to this technique is the ability to directly image biological processes that precede the anatomical changes detected by conventional imaging techniques. The two main strategies for imaging of biologic processes are direct and indirect imaging techniques. Direct techniques use molecules that have specific affinities for targets of interest that can be radiolabeled or otherwise detected on imaging. Indirect imaging uses reporter genes that are coexpressed with therapeutic proteins or other proteins of interest to image vector-transfected cells. Optical imaging and nanotechnology paradigms will also prove to be important additions to the imaging armamentarium. The first installment of this two-part series on molecular imaging seeks to demonstrate basic principles and illustrative examples for the uninitiated neophyte to this field.

Minimally Invasive Posterior Atlantoaxial Fusion: A Cadaveric and Clinical Feasibility Study

OBJECTIVE Minimally invasive surgical (MIS) techniques have several potential advantages for the patient over open techniques, including decreased loss of blood, postoperative pain, and recovery time. We aimed to demonstrate atlantoaxial fusion by using the MIS techniques, shown previously in only two reports. A smaller operating corridor with MIS may increase difficulty of instrumentation placement and risk of instrumentation-related complications. METHODS Five cadaveric specimens were studied presurgically with computed tomography (CT) to determine bony anatomy, vertebral artery course, and the trajectory for C1/C2 screw placement. Four specimens had adequate C2 pedicle sizes to accommodate screw placement. Specimens were used to perform C1-2 instrumentation through minimal access tubular retractors. After procedures, specimens were re-examined with CT to assess accuracy of MIS C1-2 screw placement. RESULTS Through minimal access expandable tubular retractors, C1-lateral mass and C2 pedicle screws were placed in all four specimens. Postinstrumentation CT analysis demonstrated no violation of the foramen transversarium in all cases. There was one grade 1 medial breach from C1 lateral mass screw placement. Two patients with type-2 odontoid fractures were treated with MIS C1-2 fusion with follow-up 4-24 months. Average operating time was 3.5 hours, and average surgical blood loss was 125 mL. Both cases were examined with CT scan postsurgically, and there were no bony breaches with screw placement. Both patients remained neurologically intact postoperatively, with significant improvement revealed in pain scores. Follow-up imaging at two years demonstrated union of odontoid fracture. CONCLUSIONS Minimally invasive atlantoaxial fixation is feasible and safe. Preoperative CT is paramount for preoperative evaluation of the vertebral artery anatomy in relation to C1/2 vertebra.