Jeremy D. W. Greenlee

Human auditory cortical activation during self-vocalization

During speaking, auditory feedback is used to adjust vocalizations. The brain systems mediating this integrative ability have been investigated using a wide range of experimental strategies. In this report we examined how vocalization alters speech-sound processing within auditory cortex by directly recording evoked responses to vocalizations and playback stimuli using intracranial electrodes implanted in neurosurgery patients. Several new findings resulted from these high-resolution invasive recordings in human subjects. Suppressive effects of vocalization were found to occur only within circumscribed areas of auditory cortex. In addition, at a smaller number of sites, the opposite pattern was seen; cortical responses were enhanced during vocalization. This increase in activity was reflected in high gamma power changes, but was not evident in the averaged evoked potential waveforms. These new findings support forward models for vocal control in which efference copies of premotor cortex activity modulate sub-regions of auditory cortex.

Chiari malformation Type I in children younger than age 6 years: presentation and surgical outcome

OBJECT The authors conducted a study to evaluate the unique presenting signs and symptoms of Chiari malformation Type I (CM-I) in children younger than 6 years of age and highlight the benefits of early surgical treatment in this patient population. METHODS The authors reviewed the medical records of patients who presented to the neurosurgery department before their 6th birthday and subsequently underwent surgery for CM-I. They identified 39 patients who had been evaluated between 1984 and 2007 and examined the medical records for presentation, surgical intervention, and outcome. RESULTS Children aged 0-2 years commonly presented with oropharyngeal dysfunction (77.8%). Children aged 3-5 years more frequently presented with syringomyelia (85.7%), scoliosis (38.1%), and/or headache (57.1%). All patients underwent posterior fossa craniectomy. Additionally, in many patients cervical laminectomy and/or duraplasty was performed. A few patients required transoral decompression and occipitocervical fusion. In most cases, surgery led to resolution or dramatic improvement of initial symptoms. CONCLUSIONS Early recognition and surgical treatment of CM-I in young children leads to good outcomes in the majority of patients. Additional therapies for oropharyngeal dysfunction, syringomyelia, and scoliosis can frequently be avoided.

Purely endoscopic resection of colloid cysts.

OBJECTIVE To further assess the safety and long-term efficacy of endoscopic resection of colloid cysts of the third ventricle. METHODS A retrospective review of a series of 35 consecutive patients (18 male, 17 female) with colloid cysts treated by endoscopic surgery was undertaken. RESULTS The mean patient age was 32.4 years (range, 11–54 yr). Headache was the most common presenting symptom (22 patients). The average tumor size was 18 mm (range, 3–50 mm). The endoscopic technique could not be completed in six patients, necessitating conversion to an open craniotomy and a transcortical approach to the colloid cyst. All patients had histologically confirmed colloid cysts of the third ventricle, and complete resection of the lesion was confirmed macroscopically and radiologically in all patients. There were no deaths. Two patients developed aseptic meningitis without any permanent sequelae. One patient developed unilateral hydrocephalus attributable to obstruction of the foramen of Monro, which was treated with endoscopic septum pellucidotomy. The median follow-up period was 88 months (range, 10–132 mo). There was one asymptomatic radiological recurrence. No seizures occurred after surgery. CONCLUSION The results of this study support the role of endoscopic resection in the treatment of patients with colloid cysts as a safe and effective modality. In some cases, conversion to an open procedure may be required. Additional follow-up will be required to continue to address the duration of lesion-free survival.

O2⋅− and H2O2-Mediated Disruption of Fe Metabolism Causes the Differential Susceptibility of NSCLC and GBM Cancer Cells to Pharmacological Ascorbate

Pharmacological ascorbate has been proposed as a potential anti-cancer agent when combined with radiation and chemotherapy. The anti-cancer effects of ascorbate are hypothesized to involve the autoxidation of ascorbate leading to increased steady-state levels of H2O2; however, the mechanism(s) for cancer cell-selective toxicity remain unknown. The current study shows that alterations in cancer cell mitochondrial oxidative metabolism resulting in increased levels of O2⋅- and H2O2 are capable of disrupting intracellular iron metabolism, thereby selectively sensitizing non-small-cell lung cancer (NSCLC) and glioblastoma (GBM) cells to ascorbate through pro-oxidant chemistry involving redox-active labile iron and H2O2. In addition, preclinical studies and clinical trials demonstrate the feasibility, selective toxicity, tolerability, and potential efficacy of pharmacological ascorbate in GBM and NSCLC therapy.

Sensory-motor networks involved in speech production and motor control: An fMRI study

Speaking is one of the most complex motor behaviors developed to facilitate human communication. The underlying neural mechanisms of speech involve sensory-motor interactions that incorporate feedback information for online monitoring and control of produced speech sounds. In the present study, we adopted an auditory feedback pitch perturbation paradigm and combined it with functional magnetic resonance imaging (fMRI) recordings in order to identify brain areas involved in speech production and motor control. Subjects underwent fMRI scanning while they produced a steady vowel sound /a/ (speaking) or listened to the playback of their own vowel production (playback). During each condition, the auditory feedback from vowel production was either normal (no perturbation) or perturbed by an upward (+600 cents) pitch-shift stimulus randomly. Analysis of BOLD responses during speaking (with and without shift) vs. rest revealed activation of a complex network including bilateral superior temporal gyrus (STG), Heschls gyrus, precentral gyrus, supplementary motor area (SMA), Rolandic operculum, postcentral gyrus and right inferior frontal gyrus (IFG). Performance correlation analysis showed that the subjects produced compensatory vocal responses that significantly correlated with BOLD response increases in bilateral STG and left precentral gyrus. However, during playback, the activation network was limited to cortical auditory areas including bilateral STG and Heschls gyrus. Moreover, the contrast between speaking vs. playback highlighted a distinct functional network that included bilateral precentral gyrus, SMA, IFG, postcentral gyrus and insula. These findings suggest that speech motor control involves feedback error detection in sensory (e.g. auditory) cortices that subsequently activate motor-related areas for the adjustment of speech parameters during speaking.

Elevated body mass index and risk of postoperative CSF leak following transsphenoidal surgery

OBJECT Postoperative CSF leakage can be a serious complication after a transsphenoidal surgical approach. An elevated body mass index (BMI) is a significant risk factor for spontaneous CSF leaks. However, there is no evidence correlating BMI with postoperative CSF leak after transsphenoidal surgery. The authors hypothesized that patients with elevated BMI would have a higher incidence of CSF leakage complications following transsphenoidal surgery. METHODS The authors conducted a retrospective review of 121 patients who, between August 2005 and March 2010, underwent endoscopic endonasal transsphenoidal surgeries for resection of primarily sellar masses. Patients requiring extended transsphenoidal approaches were excluded. A multivariate statistical analysis was performed to investigate the association of BMI and other risk factors with postoperative CSF leakage. RESULTS In 92 patients, 96 endonasal endoscopic transsphenoidal surgeries were performed that met inclusion criteria. Thirteen postoperative leaks occurred and required subsequent treatment, including lumbar drainage and/or reoperation. The average BMI of patients with a postoperative CSF leak was significantly greater than that in patients with no postoperative CSF leak (39.2 vs 32.9 kg/m(2), p = 0.006). Multivariate analyses indicate that for every 5-kg/m(2) increase in BMI, patients undergoing a transsphenoidal approach for a primarily sellar mass have 1.61 times the odds (95% CI 1.10-2.29, p = 0.016, by multivariate logistic regression) of having a postoperative CSF leak. CONCLUSIONS Elevated BMI is an independent predictor of postoperative CSF leak after an endonasal endoscopic transsphenoidal approach. The authors recommend that patients with BMI greater than 30 kg/m(2) have meticulous sellar reconstruction at surgery and close monitoring postoperatively.

Cervical decompression and reconstruction without intraoperative neurophysiological monitoring.

OBJECT The primary goal of this study was to review the immediate postoperative neurological function in patients surgically treated for symptomatic cervical spine disease without intraoperative neurophysiological monitoring. The secondary goal was to assess the economic impact of intraoperative monitoring (IOM) in this patient population. METHODS This study is a retrospective review of 720 consecutively treated patients who underwent cervical spine procedures. The patients were identified and the data were collected by individuals who were not involved in their care. RESULTS A total of 1534 cervical spine levels were treated in 720 patients using anterior, posterior, and combined (360°) approaches. Myelopathy was present preoperatively in 308 patients. There were 185 patients with increased signal intensity within the spinal cord on preoperative T2-weighted MR images, of whom 43 patients had no clinical evidence of myelopathy. Three patients (0.4%) exhibited a new neurological deficit postoperatively. Of these patients, 1 had a preoperative diagnosis of radiculopathy, while the other 2 were treated for myelopathy. The new postoperative deficits completely resolved in all 3 patients and did not require additional treatment. The Current Procedural Terminology (CPT) codes for IOM during cervical decompression include 95925 and 95926 for somatosensory evoked potential monitoring of the upper and lower extremities, respectively, as well as 95928 and 95929 for motor evoked potential monitoring of the upper and lower extremities. In addition to the charge for the baseline [monitoring] study, patients are charged hourly for ongoing electrophysiology testing and monitoring using the CPT code 95920. Based on these codes and assuming an average of 4 hours of monitoring time per surgical case, the savings realized in this group of patients was estimated to be

Sensory-Motor Interactions for Vocal Pitch Monitoring in Non-Primary Human Auditory Cortex

1,024,754. CONCLUSIONS With the continuing increase in health care costs, it is our responsibility as providers to minimize expenses when possible. This should be accomplished without compromising the quality of care to patients. This study demonstrates that decompression and reconstruction for symptomatic cervical spine disease without IOM may reduce the cost of treatment without adversely impacting patient safety.

Endoscopic approach for pituitary surgery improves rhinologic outcomes.

The neural mechanisms underlying processing of auditory feedback during self-vocalization are poorly understood. One technique used to study the role of auditory feedback involves shifting the pitch of the feedback that a speaker receives, known as pitch-shifted feedback. We utilized a pitch shift self-vocalization and playback paradigm to investigate the underlying neural mechanisms of audio-vocal interaction. High-resolution electrocorticography (ECoG) signals were recorded directly from auditory cortex of 10 human subjects while they vocalized and received brief downward (−100 cents) pitch perturbations in their voice auditory feedback (speaking task). ECoG was also recorded when subjects passively listened to playback of their own pitch-shifted vocalizations. Feedback pitch perturbations elicited average evoked potential (AEP) and event-related band power (ERBP) responses, primarily in the high gamma (70–150 Hz) range, in focal areas of non-primary auditory cortex on superior temporal gyrus (STG). The AEPs and high gamma responses were both modulated by speaking compared with playback in a subset of STG contacts. From these contacts, a majority showed significant enhancement of high gamma power and AEP responses during speaking while the remaining contacts showed attenuated response amplitudes. The speaking-induced enhancement effect suggests that engaging the vocal motor system can modulate auditory cortical processing of self-produced sounds in such a way as to increase neural sensitivity for feedback pitch error detection. It is likely that mechanisms such as efference copies may be involved in this process, and modulation of AEP and high gamma responses imply that such modulatory effects may affect different cortical generators within distinctive functional networks that drive voice production and control.

Functional connections within the human inferior frontal gyrus.

Objectives: We hypothesized that the endoscopic approach to pituitary surgery improves rhinology-specific quality of life and has satisfactory tumor outcomes compared with the open approach. Methods: Cases of pituitary surgery from the Department of Neurosurgery database included an inception cohort of all patients who had endoscopic procedures and consecutive patients who had open procedures between January 1998 and February 2008. The Sino-Nasal Outcome Test-22 was mailed. Results: Since January 1998, 71 endoscopic and 122 open pituitary surgeries had been performed. The mean follow-up was longer for open procedures (49.3 months) than for endoscopic procedures (18.8 months). Recurrence was more common after open surgery (28.4%) than after endoscopic surgery (18.2%; p = 0.219). The most common diagnosis was macroadenoma (77.1% of endoscopic procedures and 93.4% of open procedures). The mean hospital stay was shorter for endoscopic procedures (4.1 days) than for open procedures (6.0 days; p < 0.001). Of patients who presented with visual deterioration, 53.8% with endoscopic surgery and 46.7% with open surgery had improvement. Among patients with normal preoperative hormonal function, 27.5% of patients in the endoscopy group and 29.4% of patients in the open group required medication for more than 2 months after surgery. Complications occurred in 33.3% of endoscopic procedures and 43.4% of open procedures. Cerebrospinal fluid leaks were more common in the endoscopy group (p = 0.035), and diabetes insipidus lasting more than 30 days was more common in the open group (p = 0.017). The mean Sino-Nasal Outcome Test-22 score was lower for patients in the endoscopy group (20.4) than for those in the open group (23.2; p = 0.41). Patients in the endoscopy group had a significantly lower rhinology-specific mean score (6.5) than did patients in the open group (9.2; p = 0.03). Conclusions: The endoscopic approach to pituitary surgery offers tumor outcomes comparable to those of open surgery, with no greater incidence of complications and an improved rhinology-specific quality of life.