E. Lui

Minimally invasive endovascular stent-electrode array for high-fidelity, chronic recordings of cortical neural activity

High-fidelity intracranial electrode arrays for recording and stimulating brain activity have facilitated major advances in the treatment of neurological conditions over the past decade. Traditional arrays require direct implantation into the brain via open craniotomy, which can lead to inflammatory tissue responses, necessitating development of minimally invasive approaches that avoid brain trauma. Here we demonstrate the feasibility of chronically recording brain activity from within a vein using a passive stent-electrode recording array (stentrode). We achieved implantation into a superficial cortical vein overlying the motor cortex via catheter angiography and demonstrate neural recordings in freely moving sheep for up to 190 d. Spectral content and bandwidth of vascular electrocorticography were comparable to those of recordings from epidural surface arrays. Venous internal lumen patency was maintained for the duration of implantation. Stentrodes may have wide ranging applications as a neural interface for treatment of a range of neurological conditions.

Validation of Conventional Fluoroscopic and ECG Criteria for Right Ventricular Pacemaker Lead Position Using Cardiac Computed Tomography

It is hypothesized that pacing the right ventricular (RV) septum is associated with less deleterious outcomes than RV apical pacing. Our aim was to validate fluoroscopic and electrocardiography (ECG) criteria for describing pacemaker and implantable cardioverter defibrillator RV “septal” lead position against the proposed gold standard: cardiac computed tomography (CT).

MRI-identified pathology in adults with new-onset seizures

Objective: To determine the frequency and nature of potentially epileptogenic lesions on MRI in adults with new-onset seizures. Methods: We prospectively studied a consecutive series of 993 patients (597 males [61%]; mean [SD] age: 42.2 [18.8] years, range 14.3–94.3 years) who presented to an adult First Seizure Clinic over a 10-year period. The MRI scans, performed clinically on 3- and 1.5-tesla scanners, were reviewed for their diagnostic yield, nature of abnormalities, and their association with abnormal electrical activity on EEG. Results: MRI scans were acquired in 764 patients (77%); potentially epileptogenic lesions were detected in 177 (23%). The frequency of potentially epileptogenic lesions was higher in patients who were diagnosed as having an epileptic seizure (28%) than in those with a nonepileptic event (8%) (p < 0.001), and highest in those who had focal-onset seizures (53%) (p < 0.001). The most common lesion type in patients with focal seizures was gliosis or encephalomalacia (49%). Other common lesion types were tumors (15%), cavernomas (9%), and mesial temporal sclerosis (9%). Abnormal MRI and EEG were concordant in 18% of patients, with EEG being normal in 55% of patients with epileptogenic lesions. Conclusions: MRI reveals potentially epileptogenic lesions in a minority of patients with a newly diagnosed seizure disorder. Lesions are most common in patients who have experienced focal seizures. The presence of a potentially epileptogenic MRI lesion did not influence the chance of having an abnormal EEG.

Pacing and implantable cardioverter defibrillator lead perforation as assessed by multiplanar reformatted ECG-gated cardiac computed tomography and clinical correlates.

We aimed to assess the utility of cardiac computed tomography (CT) in the evaluation of right atrial (RA) and right ventricular (RV) pacemaker and implantable cardiac defibrillator lead perforation.

Proximity of Pacemaker and Implantable Cardioverter‐Defibrillator Leads to Coronary Arteries as Assessed by Cardiac Computed Tomography

There have been rare case reports of damage to adjacent coronary arteries by screw‐in pacemaker and implantable cardioverter‐defibrillator (ICD) leads. Our aim was to assess the proximity of pacemaker and ICD leads to the major coronary anatomy using cardiac computed tomography (CT).

Assessment of patient dose and image quality for cardiac CT with breast shields

Breast shielding can reduce dose to the female breast, a radiosensitive organ receiving significant radiation during computed tomography (CT) chest examinations, particularly in cardiac CT, where Electrocardiogram dose modulation currently precludes the use of radial dose modulation to reduce breast dose. However, breast shields may produce artefacts affecting interpretation of coronary arteries. This study explores the dose savings and the effect of breast shields on image quality with torso and CT dose index body phantoms and an organ dose calculator. Change in dose calculated: 53-63 % (female breast), 82-85 % (lung), 79-84 % (oesophagus) and 76-80 % (effective dose) with larger dose reductions at lower kVp. Image quality is preserved when breast shields are placed after the scout no closer than 10 mm from the skin. Therefore, breast shields can be used in cardiac CT to reduce breast dose without compromising image quality. Revised conversion factors for dose length product to effective dose are suggested for cardiac CT without and with breast shields.

Fibre-specific white matter changes in multiple sclerosis patients with optic neuritis

Long term irreversible disability in multiple sclerosis (MS) is thought to be primarily driven by axonal degeneration. Axonal degeneration leads to degenerative atrophy, therefore early markers of axonal degeneration are required to predict clinical disability and treatment efficacy. Given that additional pathologies such as inflammation, demyelination and oedema are also present in MS, it is essential to develop axonal markers that are not confounded by these processes. The present study investigated a novel method for measuring axonal degeneration in MS based on high angular resolution diffusion magnetic resonance imaging. Unlike standard methods, this novel method involved advanced acquisition and modelling for improved axonal sensitivity and specificity. Recent work has developed analytical methods, two novel axonal markers, fibre density and cross-section, that can be estimated for each fibre direction in each voxel (termed a “fixel”). This technique, termed fixel-based analysis, thus simultaneously estimates axonal density and white matter atrophy from specific white matter tracts. Diffusion-weighted imaging datasets were acquired for 17 patients with a history of acute unilateral optic neuritis (35.3 ± 10.2 years, 11 females) and 14 healthy controls (32.7 ± 4.8 years, 8 females) on a 3 T scanner. Fibre density values were compared to standard diffusion tensor imaging parameters (fractional anisotropy and mean diffusivity) in lesions and normal appearing white matter. Group comparisons were performed for each fixel to assess putative differences in fibre density and fibre cross-section. Fibre density was observed to have a comparable sensitivity to fractional anisotropy for detecting white matter pathology in MS, but was not affected by crossing axonal fibres. Whole brain fixel-based analysis revealed significant reductions in fibre density and fibre cross-section in the inferior fronto-occipital fasciculus (including the optic radiations) of patients compared to controls. We interpret this result to indicate that this fixel-based approach is able to detect early loss of fibre density and cross-section in the optic radiations in MS patients with a history of optic neuritis. Fibre-specific markers of axonal degeneration should be investigated further for use in early stage therapeutic trials, or to monitor axonal injury in early stage MS.

Magnetic resonance imaging in adults with epilepsy: A pictorial essay

This pictorial essay highlights the role of the radiologist as a member of the adult epilepsy multidisciplinary team, and gives an overview of MRI‐evident epileptogenic lesions.

Efficacy of patient questionnaire in predicting renal dysfunction in outpatients older than 60 years of age prior to contrast-enhanced computed tomography

Introduction: Contrast‐induced nephropathy (CIN), a common iatrogenic cause of acute renal failure, is preventable. Identification of impaired renal function prior to intravenous contrast is important. Questionnaire screening has been useful to negate the need for cumbersome and costly renal function testing on all patients prior to contrast‐enhanced CT (CECT). The Royal Australian and New Zealand College of Radiologists guidelines include age older than 60 as a risk marker requiring renal function testing. The aim of this retrospective study is to assess the efficacy of the pre‐CT questionnaire in identifying patients with pre‐existing renal impairment even in this older than 60 age group.

Psychosis with obsessive-compulsive symptoms in tuberous sclerosis

We present a case of tuberous sclerosis complex (TSC) diagnosed in adulthood in a man initially referred for specialist neuropsychiatric assessment with psychosis and obsessive-compulsive symptoms (OCS) on a background of epilepsy and intellectual disability. To our knowledge, this is the first reported patient with TSC featuring both psychosis and OCS. This patient highlights the importance of comprehensive re-evaluation of atypical presentations of intellectual disability, epilepsy and associated neuropsychiatric symptoms, even in adulthood. This is particularly relevant in the context of significant advances in genetics, neuroscience, imaging and treatments for heritable neurogenetic disorders.