Shabbar F. Danish

Deep brain stimulation in the treatment of obesity

Obesity is a growing global health problem frequently intractable to current treatment options. Recent evidence suggests that deep brain stimulation (DBS) may be effective and safe in the management of various, refractory neuropsychiatric disorders, including obesity. The authors review the literature implicating various neural regions in the pathophysiology of obesity, as well as the evidence supporting these regions as targets for DBS, in order to explore the therapeutic promise of DBS in obesity. The lateral hypothalamus and ventromedial hypothalamus are the appetite and satiety centers in the brain, respectively. Substantial data support targeting these regions with DBS for the purpose of appetite suppression and weight loss. However, reward sensation associated with highly caloric food has been implicated in overconsumption as well as obesity, and may in part explain the failure rates of conservative management and bariatric surgery. Thus, regions of the brains reward circuitry, such as the nucleus accumbens, are promising alternatives for DBS in obesity control. The authors conclude that deep brain stimulation should be strongly considered as a promising therapeutic option for patients suffering from refractory obesity.

Magnetic resonance thermometry-guided laser-induced thermal therapy for intracranial neoplasms: initial experience.

BACKGROUND: Laser-induced thermal therapy is a promising tool in the neurosurgeons armamentarium. This methodology has seen a resurgence in application as a result of advances in technology. OBJECTIVE: To report our initial experience with the procedure after treating 20 consecutive patients, the largest series to date. METHODS: Patients were selected for laser therapy if they had failed conventional therapies, were unable to tolerate an open cranial procedure, or the tumor was deemed otherwise inoperable. In this series, 980-nm diode laser catheters were placed stereotactically in the operating room. The patients were then transferred to the magnetic resonance imaging suite for thermal ablation. RESULTS: A total of 31 laser applicators were placed in 20 patients with intracranial neoplasms. The majority of patients (17 of 20) had prior treatment for their tumors. The overall accuracy of laser insertion was 83.9%, improving with increased experience. The average lesion volume treated was 7.0 ± 9.0 cm3. With the use of damage estimates from the software provided, the treatment continued until the entire tumor had been irreversibly ablated. The average length of hospitalization was 2.27 days, with the majority of patients going home on postoperative day 1. Complications occurred in 4 patients, typically in those who were in poor health preoperatively. CONCLUSION: Laser-induced thermal therapy is an intuitive procedure for treating difficult intracranial neoplasms. As with any other procedure, patient selection and lesion selection are important factors in determining outcome. ABBREVIATIONS: LITT, laser-induced thermal therapy Nd:YAG, neodymium-doped yttrium aluminum garnet PAD, precision aiming device

Choosing the best operation for chronic subdural hematoma: a decision analysis

OBJECT Chronic subdural hematoma (CSDH), a condition much more common in the elderly, presents an increasing challenge as the population ages. Treatment strategies for CSDH include bur-hole craniostomy (BHC), twist-drill craniostomy (TDC), and craniotomy. Decision analysis was used to organize existing data and develop recommendations for effective treatment. METHODS A Medline search was used to identify articles about treatment of CSDH. Direct assessment by health care professionals of the relative health impact of common complications and recurrences was used to generate utility values for treatment outcomes. Monte Carlo simulation and sensitivity analyses allowed comparisons across treatment strategies. A second simulation examined whether intraoperative irrigation or postoperative drainage affect the outcomes following BHC. RESULTS On a scale from 0 to 1, the utility of BHC was found to be 0.9608, compared with 0.9202 for TDC (p = 0.001) and 0.9169 for craniotomy (p = 0.006). Sensitivity analysis confirmed the robustness of these values. Craniotomy yielded fewer recurrences, but more frequent and more serious complications than did BHC. There were no significant differences for BHC with or without irrigation or postoperative drainage. CONCLUSIONS Bur-hole craniostomy is the most efficient choice for surgical drainage of uncomplicated CSDH. Bur-hole craniostomy balances a low recurrence rate with a low incidence of highly morbid complications. Decision analysis provides statistical and empirical guidance in the absence of well-controlled large trials and despite a confusing range of previously reported morbidity and recurrence.

Brain shift during deep brain stimulation surgery for Parkinson's disease.

Background: Brain shift may occur during deep brain stimulation (DBS) surgery, which may affect the position of subcortical structures, compromising target localization. Methods: We retrospectively evaluated pre- and postoperative magnetic resonance imaging in 50 Parkinson’s disease patients who underwent bilateral subthalamic nucleus (STN) DBS. Patients were separated into two groups: group A – those with <2 mm cortical displacement (66 leads) and group B – those with ≧2 mm cortical displacement (34 leads). Pre and post-op coordinates of anterior (AC) and posterior commissures (PC), as well as the boundaries of red nucleus (RN) were compared. Results: AC-PC shortening due to posterior displacement of AC correlated with cortical displacement (p < 0.02) and was significantly greater in group B (0.41 ± 0.68 mm) than A (0.04 ± 0.76 mm; p < 0.005). Posterior shift of AC and RN’s center positively correlated (p < 0.0001). Shift appeared to impact the number of microelectrode tracks made to optimize STN targeting. AC-PC shortening also correlated with age (p < 0.003) and duration of surgery (p < 0.04). Conclusions: Subcortical structures shift during DBS surgery. This shift appears to be gravity-dependent since structures only shifted posteriorly, and patients were primarily in the supine position. Posterior shift of RN may indicate STN displacement. Such positional change may compromise target localization, requiring multiple microelectrode adjustments. This may provide indirect justification for the necessity of microelectrode recordings during DBS surgery.

Prophylaxis for deep venous thrombosis in craniotomy patients: A decision analysis

OBJECTIVE: We sought to determine the most efficient perioperative prophylactic strategy for deep venous thrombosis (DVT) in craniotomy patients by use of a decision analysis model. METHODS: We conducted a structured review of the relevant literature and compiled the reported incidences of DVT, pulmonary embolism, and postoperative intracranial hemorrhage (ICH) in craniotomy patients. We also obtained from the literature estimates of the likelihood and the impact of various outcomes of these complications. Data from 810 craniotomies performed at our own institution were also examined. The decision analytic model was then used to compare the effectiveness of pneumatic compression boots with pneumatic compression boots combined with either unfractionated or low-molecular-weight heparin. The model dealt with variability by using both sensitivity analysis and Monte Carlo simulation. RESULTS: As expected, the addition of heparin lowered the incidence of both DVT and pulmonary embolism, but at the cost of increasing ICH. Because the deleterious effects of ICH were so much greater than the benefits from heparinization, overall outcomes were best with mechanical prophylaxis alone. This was especially true for low-molecular-weight heparin, which is associated with a relatively high risk of ICH. Our own institutional data support the findings in the literature. Although the differences are modest, they reach statistical significance in the case of low-molecular-weight heparin. CONCLUSION: Using decision analytic modeling, we have shown that mechanical prophylaxis yields outcomes in craniotomy patients superior to those of either unfractionated or low-molecular-weight heparin.

Magnetic Resonance-Guided Laser Ablation Improves Local Control for Postradiosurgery Recurrence and/or Radiation Necrosis

BACKGROUND Enhancing lesions that progress after stereotactic radiosurgery are often tumor recurrence or radiation necrosis. Magnetic resonance-guided laser-induced thermal therapy (LITT) is currently being explored for minimally invasive treatment of intracranial neoplasms. OBJECTIVE To report the largest series to date of local control with LITT for the treatment of recurrent enhancing lesions after stereotactic radiosurgery for brain metastases. METHODS Patients with recurrent metastatic intracranial tumors or radiation necrosis who had previously undergone radiosurgery and had a Karnofsky performance status of >70 were eligible for LITT. Sixteen patients underwent a total of 17 procedures. The primary end point was local control using magnetic resonance imaging scans at intervals of >4 weeks. Radiographic outcomes were followed up prospectively until death or local recurrence (defined as >25% increase in volume compared with the 24-hour postprocedural scan). RESULTS Fifteen patients (age, 46-82 years) were available for follow-up. Primary tumor histology was non-small-cell lung cancer (n = 12) and adenocarcinoma (n = 3). On average, the lesion size measured 3.66 cm (range, 0.46-25.45 cm); there were 3.3 ablations per treatment (range, 2-6), with 7.73-cm depth to target (range, 5.5-14.1 cm), ablation dose of 9.85 W (range, 8.2-12.0 W), and total ablation time of 7.43 minutes (range, 2-15 minutes). At a median follow-up of 24 weeks (range, 4-84 weeks), local control was 75.8% (13 of 15 lesions), median progression-free survival was 37 weeks, and overall survival was 57% (8 of 14 patients). Two patients experience recurrence at 6 and 18 weeks after the procedure. Five patients died of extracranial disease progression; 1 patient died of neurological progression elsewhere in the brain. CONCLUSION Magnetic resonance imaging-guided LITT is a well-tolerated procedure and may be effective in treating tumor recurrence/radiation necrosis.

Quality of life after hemicraniectomy for traumatic brain injury in adults. A review of the literature.

Decompressive hemicraniectomy is well accepted for the surgical treatment of intractable intracranial hypertension in cases in which medical management fails. Although it is performed as a life-saving procedure when death is imminent from intracranial hypertension, little is known about the functional outcomes for these patients on long-term follow-up. In this study, the authors performed a systematic review of the literature to examine neurological outcome after hemicraniectomy. A literature search revealed 29 studies that reported outcomes using GOS scores. The GOS scores were transformed to utility values for quality of life using a conversion method based on decision analysis modeling. Based on the literature, 1422 cases were analyzed. The average 6-month-postoperative mortality rate was 28.2%. The mean QOL value among survivors was 0.592, which corresponds roughly to a GOS score of 4. Although more studies are needed for validation of long-term neurological outcome after hemicraniectomy, the assumption that most patients remain in a vegetative state after this intervention is clearly incorrect.

Intramedullary low-grade astrocytomas: Long-term outcome following radical surgery

The management of low-grade intramedullary astrocytomas is controversial. Unlike ependymomas, which have a distinct cleavage plane, astrocytomas are diffuse infiltrative tumors. The intramedullary tumor database at NYU Medical Center was searched to identify all patients with intramedullary astrocytoma from 1988 to 1994. Seventeen patients presented with a low-grade diffuse astrocytoma. The medical, surgical and office records were reviewed retrospectively and statistically analyzed. All patients underwent a radical resection of the intramedullary tumor; of these, 12 patients had gross-total removal and 5 had subtotal removal. Nine patients received adjuvant radiotherapy. The median follow-up period was 7.4 years. Fourteen patients are alive and have stable disease. Eleven patients (79%) are functionally independent at last follow-up. The remaining patients are at functional Grade III. The 5-year overall survival was 82% for this group.These results indicate that aggressive surgery is associated with a prolonged survival for patients with intramedullary astrocytomas. Radiation therapy should only be reserved for patients who have radiographic progression or inoperable disease.

Cognition following bilateral deep brain stimulation surgery of the subthalamic nucleus for Parkinson's disease.

Parkinsons disease (PD) is a neurodegenerative disorder characterized by significant motor dysfunction and various non‐motor disturbances, including cognitive alterations. Deep brain stimulation (DBS) is an increasingly utilized therapeutic option for patients with PD that yields remarkable success in alleviating disabling motor symptoms. DBS has additionally been associated with changes in cognition, yet the evidence is not consistent across studies. The following review sought to provide a clearer understanding of the various cognitive sequelae of bilateral subthalamic nucleus (STN) DBS while taking into account corresponding neuroanatomy and potential confounding variables.

Functional localization and visualization of the subthalamic nucleus from microelectrode recordings acquired during DBS surgery with unsupervised machine learning.

Microelectrode recordings are a useful adjunctive method for subthalamic nucleus localization during deep brain stimulation surgery for Parkinsons disease. Attempts to quantitate and standardize this process, using single computational measures of neural activity, have been limited by variability in patient neurophysiology and recording conditions. Investigators have suggested that a multi-feature approach may be necessary for automated approaches to perform within acceptable clinical standards. We present a novel data visualization algorithm and several unique features that address these shortcomings. The algorithm extracts multiple computational features from the microelectrode neurophysiology and integrates them with tools from unsupervised machine learning. The resulting colour-coded map of neural activity reveals activity transitions that correspond to the anatomic boundaries of subcortical structures. Using these maps, a non-neurophysiologist is able to achieve sensitivities of 90% and 95% for STN entry and exit, respectively, to within 0.5 mm accuracy of the current gold standard. The accuracy of this technique is attributed to the multi-feature approach. This activity map can simplify and standardize the process of localizing the subthalamic nucleus (STN) for neurostimulation. Because this method does not require a stationary electrode for careful recording of unit activity for spike sorting, the length of the operation may be shortened.