Nicolas Kon Kam King

Comparison of polyetheretherketone and titanium cranioplasty after decompressive craniectomy.

OBJECTIVE To characterize complication and failure rates and outcomes of patients who underwent cranioplasty with polyetheretherketone (PEEK) and titanium implants and to compare complication and failure rates between the 2 implants. METHODS A retrospective cohort study of patients who underwent cranioplasty with PEEK patient-specific implant (PEEK Optima-LT) and preformed titanium mesh at the National Neuroscience Institute, Singapore, between January 2001 and February 2012 was performed. Data related to initial decompressive craniectomy and cranioplasty, associated complications after cranioplasty, and indication for revision or removal of implants were collected. Cranioplasty failure was defined as revision or removal of a patients implant. RESULTS Overall complication rates for PEEK and titanium cranioplasty were 25.0% and 27.8%, respectively. The combined complication rate was 27.3%. A trend toward increase in exposed implant in titanium cranioplasty compared with PEEK cranioplasty was observed (P = 0.074). There were 3 of 24 (12.5%) cranioplasty failures with PEEK, and 27 of 108 (25%) cranioplasty failures with titanium (P = 0.129). Previous deep infection in patients after decompressive craniectomy was associated with cranioplasty complications (odds ratio, 23.3; confidence interval, 3.00-180.5; P = 0.003) and failure (odds ratio, 22.5; confidence interval, 2.82-179.0; P = 0.003). CONCLUSIONS The findings from this study highlight that cranioplasty is associated with significant complications, including the necessity for reoperation. It is hoped that the information in this study will provide better understanding of the risks associated with PEEK and titanium cranioplasty and contribute to decision making by the clinician and patient.

Tractography‐Based Ventral Intermediate Nucleus Targeting: Novel Methodology and Intraoperative Validation

The ventral intermediate nucleus of the thalamus is not readily visible on structural magnetic resonance imaging. Therefore, a method for its visualization for stereotactic targeting is desirable.

Speech and language adverse effects after thalamotomy and deep brain stimulation in patients with movement disorders: A meta-analysis

Background: The thalamus has been a surgical target for the treatment of various movement disorders. Commonly used therapeutic modalities include ablative and nonablative procedures. A major clinical side effect of thalamic surgery is the appearance of speech problems.

A randomized, placebo-controlled pilot study of patients with spontaneous intraventricular haemorrhage treated with intraventricular thrombolysis

Intraventricular hemorrhage (IVH) occurring after spontaneous intracerebral hemorrhage (ICH) is an independent risk factor for mortality. The use of intraventricular urokinase (Uk) to reduce intraventricular blood clot volume and improve outcome was investigated. Patients with IVH requiring external ventricular drainage were recruited and randomized into a double-blind placebo controlled study. Assessments of collected cerebrospinal fluid (CSF) haemoglobin (Hb) and serial CT scans were performed. The study outcomes were: infection rates, length of stay in the intensive care unit, survival, National Institutes of Health Stroke Scale score; and modified Rankin Scale scores. Our results showed an increase in both the drained CSF Hb concentration in patients treated with Uk compared to placebo and in the rate of resolution clot volume. No differences were found in the other outcome measures but there was a trend towards lowered mortality in the group treated with Uk. Therefore, intraventricular Uk resulted in faster resolution of IVH with no adverse events.

The effect of dexmedetomidine on the firing properties of STN neurons in Parkinson's disease

Dexmedetomidine (an alpha‐2 adrenergic agonist) sedation is commonly used during subthalamic nucleus (STN) deep‐brain stimulation (DBS). Its effects on the electrophysiological characteristics of human STN neurons are largely unknown. We hypothesised that dexmedetomidine modulates the firing rates and bursting of human STN neurons. We analysed microelectrode recording (MER) data from patients with Parkinsons disease who underwent STN DBS. A ‘Dex bolus’ group (dexmedetomidine bolus prior to MER; 27 cells from seven patients) was compared with a ‘no sedation’ group (29 cells from 11 patients). We also performed within‐patient comparisons with varying dexmedetomidine states. Cells were classified as dorsal half or ventral half based on their relative location in the STN. Neuronal burst and oscillation characteristics were analysed using the Kaneoke–Vitek methodology and local field potential (LFP) oscillatory activity was also investigated. Dexmedetomidine was associated with a slight increase in firing rate (41.1 ± 9.9 vs. 34.5 ± 10.6 Hz, P = 0.02) but a significant decrease in burstiness (number of bursts, P = 0.02; burst index, P < 0.001; percentage of spikes in burst, P = 0.002) of dorsal but not ventral STN neurons. This was not associated with modulation of beta oscillations in the spike‐oscillations analysis(beta peak, P = 0.4; signal‐to‐noise ratio in the beta range for spikes and bursts, P = 0.3 and P = 0.5, respectively) and LFP analysis (Beta power, P = 0.17). As bursting pattern is often used to identify STN and guide electrode placement, we recommend that high‐dose dexmedetomidine should be avoided during DBS surgery.

Prior Statin Use Has No Effect on Survival After Intracerebral Hemorrhage in a Multiethnic Asian Patient Cohort

BACKGROUND Statins have been shown to reduce mortality and morbidity in ischemic stroke, subarachnoid hemorrhage, and traumatic brain injuries, but their effect on intracerebral hemorrhage (ICH) remains to be determined. This study aimed to investigate the effect of prior statin use on survival following spontaneous primary intracerebral hemorrhage in a multi-ethnic Asian population. SUBJECTS AND METHODS A study cohort of patients admitted with spontaneous primary ICH was obtained from our database. There were 1,381 patients who met the inclusion criteria. Multivariate logistic regression was used to identify independent predictors and computed odds ratios for 30-day mortality. Kaplan-Meier and Cox proportional hazard survival analyses were used to examine the effect of prior statin use on survival after ICH. RESULTS Multivariate logistic regression controlling for baseline characteristics and in-hospital interventions, did not demonstrate any effect of prior statin use (p = 0.781) on mortality. Survival analyses also failed to demonstrate any differences in survival after ICH with prior statin use. Similarly subgroup analyses showed no difference. CONCLUSION No beneficial effect on survival after ICH of prior statin use could be demonstrated in our large multi-ethnic Asian patient cohort.

Microelectrode recording findings within the tractography-defined ventral intermediate nucleus

OBJECTIVE The ventral intermediate nucleus (VIM) of the thalamus is not visible on structural MRI. Therefore, direct VIM targeting methods for stereotactic tremor surgery are desirable. The authors previously described a direct targeting method for visualizing the VIM and its structural connectivity using deterministic tractography. In this combined electrophysiology and imaging study, the authors investigated the electrophysiology within this tractography-defined VIM (T-VIM). METHODS Thalamic neurons were classified based on their relative location to the T-VIM: dorsal, within, and ventral to the T-VIM. The authors identified the movement-responsive cells (kinesthetic and tremor cells), performed spike analysis (firing rate and burst index), and local field potential analysis (area under the curve for 13-30 Hz). Tremor efficacy in response to microstimulation along the electrode trajectory was also assessed in relation to the T-VIM. RESULTS Seventy-three cells from a total of 9 microelectrode tracks were included for this analysis. Movement-responsive cells (20 kinesthetic cells and 26 tremor cells) were identified throughout the electrode trajectories. The mean firing rate and burst index of cells (n = 27) within the T-VIM are 18.8 ± 9.8 Hz and 4.5 ± 5.4, respectively. Significant local field potential beta power was identified within the T-VIM (area under the curve for 13-30 Hz = 6.6 ± 7.7) with a trend toward higher beta power in the dorsal T-VIM. The most significant reduction in tremor was also observed in the dorsal T-VIM. CONCLUSIONS The electrophysiological findings within the VIM thalamus defined by tractography, or T-VIM, correspond with the known microelectrode recording characteristics of the VIM in patients with tremor.

Comparison of Gender Differences in Intracerebral Hemorrhage in a Multi-Ethnic Asian Population

Background Intracerebral hemorrhage (ICH) accounts for 10–15% of all first time strokes and with incidence twice as high in the Asian compared to Western population. This study aims to investigate gender differences in ICH patient outcomes in a multi-ethnic Asian population. Method Data for 1,192 patients admitted for ICH were collected over a four-year period. Multivariate logistic regression was used to identify independent predictors and odds ratios were computed for 30-day mortality and Glasgow Outcome Scale (GOS) comparing males and females. Result Males suffered ICH at a younger age than females (62.2 ± 13.2 years vs. 66.3 ± 15.3 years; P<0.001). The occurrence of ICH was higher among males than females at all ages until 80 years old, beyond which the trend was reversed. Females exhibited increased severity on admission as measured by Glasgow Coma Scale compared to males (10.9 ± 4.03 vs. 11.4 ± 4.04; P = 0.030). No difference was found in 30-day mortality between females and males (F: 30.5% [155/508] vs. M: 27.0% [186/688]), with unadjusted and adjusted odds ratio (F/M) of 1.19 (P = 0.188) and 1.21 (P = 0.300). At discharge, there was a non-statistically significant but potentially clinically relevant morbidity difference between the genders as measured by GOS (dichotomized GOS of 4–5: F: 23.7% [119/503] vs. M: 28.7% [194/677]), with unadjusted and adjusted odds ratio (F/M) of 0.77 (P = 0.055) and 0.87 (P = 0.434). Conclusion In our multi-ethnic Asian population, males developed ICH at a younger age and were more susceptible to ICH than women at all ages other than the beyond 80-year old age group. In contrast to the Western population, neurological status of female ICH patients at admission was poorer and their 30-day mortality was not reduced. Although the study was not powered to detect significance, female showed a trend toward worse 30-day morbidity at discharge.

The Fluoropen: a simple low-cost device to detect intraoperative fluorescein fluorescence in stereotactic needle biopsy of brain tumors

BackgroundThe use of fluorescein fluorescence-guided stereotactic needle biopsy has been shown to improve diagnostic accuracy and to expedite operative procedure in the stereotactic needle biopsy of high-grade gliomas. We developed a device (Fluoropen) for detecting fluorescence in brain tumor tissues obtained by fluorescein fluorescence-guided stereotactic needle biopsy.MethodsThe Fluoropen is a device consisting of a light source fitted with color filters to create the required emission and visualization wavelengths. The proof-of-concept study consisted of four consecutive patients who underwent fluorescein fluorescence-guided frameless stereotactic biopsy of brain tumor. Each sample was examined for the presence of fluorescence using the Fluoropen and compared with a microscope with fluorescence visualization capability.ResultsA total of six samples were obtained from four stereotactic needle biopsy procedures. Four out of five samples (80%) taken from the contrast-enhancing part of the tumors were shown to be fluorescent under the microscope fitted with fluorescence module and the Fluoropen. One non-contrast enhancing lesion was non-fluorescent using both the microscope fitted with fluorescence module and the Fluoropen. The Fluoropen was shown to have 100% concordance with the microscope fitted with fluorescence module.ConclusionsThe Fluoropen is a low-cost and simple standalone device for the detection of fluorescein fluorescence that can expedite stereotactic needle biopsy by providing instant confirmation of the diagnostic sample and therefore avoid the need for an intraoperative frozen section. In patients with non-contrast enhancing tumors and those who were pre-treated with dexamethasone prior to surgery, fluorescein fluorescence-guided stereotactic needle biopsy will need to be used with caution.

Prediction and detection of seizures from simultaneous thalamic and scalp electroencephalography recordings

OBJECTIVE The authors explored the feasibility of seizure detection and prediction using signals recorded from the anterior thalamic nucleus, a major target for deep brain stimulation (DBS) in the treatment of epilepsy. METHODS Using data from 5 patients (13 seizures in total), the authors performed a feasibility study and analyzed the performance of a seizure prediction and detection algorithm applied to simultaneously acquired scalp and thalamic electroencephalography (EEG). The thalamic signal was obtained from DBS electrodes. The applied algorithm used the similarity index as a nonlinear measure for seizure identification, with patient-specific channel and threshold selection. Receiver operating characteristic (ROC) curves were calculated using data from all patients and channels to compare the performance between DBS and EEG recordings. RESULTS Thalamic DBS recordings were associated with a mean prediction rate of 84%, detection rate of 97%, and false-alarm rate of 0.79/hr. In comparison, scalp EEG recordings were associated with a mean prediction rate of 71%, detection rate of 100%, and false-alarm rate of 1.01/hr. From the ROC curves, when considering all channels, DBS outperformed EEG for both detection and prediction of seizures. CONCLUSIONS This is the first study to compare automated seizure detection and prediction from simultaneous thalamic and scalp EEG recordings. The authors have demonstrated that signals recorded from DBS leads are more robust than EEG recordings and can be used to predict and detect seizures. These results indicate feasibility for future designs of closed-loop anterior nucleus DBS systems for the treatment of epilepsy.