Gavin W. Britz

Magnesium sulfate for neuroprotection after traumatic brain injury: a randomised controlled trial

BACKGROUND Traumatic brain injuries represent an important and costly health problem. Supplemental magnesium positively affects many of the processes involved in secondary injury after traumatic brain injury and consistently improves outcome in animal models. We aimed to test whether treatment with magnesium favourably affects outcome in head-injured patients. METHODS In a double-blind trial, 499 patients aged 14 years or older admitted to a level 1 regional trauma centre between August, 1998, and October, 2004, with moderate or severe traumatic brain injury were randomly assigned one of two doses of magnesium or placebo within 8 h of injury and continuing for 5 days. Magnesium doses were targeted to achieve serum magnesium ranges of 1.0-1.85 mmol/L or 1.25-2.5 mmol/L. The primary outcome was a composite of mortality, seizures, functional measures, and neuropsychological tests assessed up to 6 months after injury. Analyses were done according to the intention-to-treat principle. This trial is registered with , number . FINDINGS Magnesium showed no significant positive effect on the composite primary outcome measure at the higher dose (mean=55 average percentile ranking on magnesium vs 52 on placebo, 95% CI for difference -7 to 14; p=0.70). Those randomly assigned magnesium at the lower dose did significantly worse than those assigned placebo (48 vs 54, 95% CI -10.5 to -2; p=0.007). Furthermore, there was higher mortality with the higher magnesium dose than with placebo. Other major medical complications were similar between groups, except for a slight excess of pulmonary oedema and respiratory failure in the lower magnesium target group. No subgroups were identified in which magnesium had a significantly positive effect. INTERPRETATION Continuous infusions of magnesium for 5 days given to patients within 8 h of moderate or severe traumatic brain injury were not neuroprotective and might even have a negative effect in the treatment of significant head injury.

Ulnar nerve entrapment at the elbow: Correlation of magnetic resonance imaging, clinical, electrodiagnostic, and intraoperative findings

The diagnosis of ulnar nerve entrapment at the elbow has relied primarily on clinical and electrodiagnostic findings. Recently, magnetic resonance imaging (MRI) has been used in the evaluation of peripheral nerve entrapment disorders to document signal and configuration changes in nerves. We performed a prospective study on a population of 31 elbows in 27 patients with ulnar nerve entrapment at the elbow. The study correlated MRI findings with clinical, electrodiagnostic, and operative findings. A control population consisting of 10 asymptomatic subjects also was studied by MRI. Electrodiagnostic evaluation confirmed ulnar neuropathy in 24 (77%) elbows of the 31, with localization to the elbow region in 21 (68%). MRI, using a short tau inversion recovery sequence, demonstrated increased signal of the ulnar nerve in 30 (97%) elbows of the 31 and enlargement of the ulnar nerve in 23 (74%). No MRI abnormalities were found in the control population. MRI signal increase of the ulnar nerve occurred an average of 27 mm proximal to the distal humerus and extended distally an average of 4 mm below the distal humerus. The mean total length of increased ulnar nerve signal was 34 mm. Ulnar nerve enlargement occurred an average of 19 mm proximal to the distal humerus and extended distally an average of 8 mm above the distal humerus. The mean total length of ulnar nerve enlargement was 12 mm. The 12 patients who underwent a surgical procedure for ulnar nerve entrapment were found to have ulnar nerve compression, with 9 (75%) having excellent and 3 (25%) having good postoperative results. In this study, MRI was both sensitive and specific in diagnosing ulnar nerve entrapment at the elbow as defined by clinical, electrodiagnostic, and operative findings.

The utility of magnetic resonance imaging in evaluating peripheral nerve disorders

The evaluation of peripheral nerve injuries has traditionally relied primarily on information gained from the clinical history, physical examination, and electrodiagnostic testing. Taken together, all of this clinical and diagnostic information often allows one to determine the location and severity of the underlying peripheral nerve problem. However, it may not be sufficient in diagnosing a focal entrapment neuropathy superimposed upon a more generalized peripheral neuropathy; localizing a focal lesion along a long segment of nerve which may be difficult to assess accurately with electrodiagnostic sutdies; distinguishing early between an axonotmetic grade of injury, which can recover through axonal regeneration, and a neurotmetic grade which cannot and therefore may benefit from a surgical exploration and repair procedure; and noninvasively diagnosing and determining the surgical resectability of peripheral nerve mass lesions such as tumors. The goal of this review is to illustrate how standard and evolving magnetic resonance imaging techniques can provide additional information in dealing with some of these problems.

Multimodality treatment of brain arteriovenous malformations with microsurgery after embolization with Onyx: Single-center experience and technical nuances

OBJECTIVETo report our experience with the treatment of brain arteriovenous malformations (AVM) with microsurgical resection after embolization with Onyx liquid embolic agent (eV3, Irvine, CA). METHODSBetween August 2005 and December 2006, 28 patients were treated by the same surgical-endovascular team. Twenty-eight AVMs were embolized preoperatively in 55 sessions (71 pedicles) with Onyx. We analyzed the AVM size, volume, number of embolization sessions, degree of preoperative obliteration, time to embolization and resection after the bleed, intraprocedural complications, intraoperative blood loss, other complications, and postoperative outcome at 6 months. Technical nuances of the embolization and surgical resection of the embolized AVMs are illustrated in illustrative cases. RESULTSThe average size and volume of AVMs treated with Onyx were 3.56 cm (largest, 7.6 cm), and 13.03 ml, respectively. The average Spetzler-Martin grade was 2.75. The average preoperative volumetric obliteration was 74.1%. The average blood loss during resection of embolized AVMs was 348 ml. Complications related to embolization were stuck microcatheter (two patients), proximal vessel perforation (one patient), and anterior choroidal territory stroke (one patient). Surgical complications included wound infection (one patient), residual AVM nidus (one patient), normal pressure perfusion breakthrough with worsening of neurological deficit caused by embolization (one patient), and new-onset motor deficits in five patients. At the time of the 6-month follow-up examination, four patients with new-onset motor deficits had recovered completely or nearly completely, and one patient was disabled. One patient died, never recovering from the initial poor condition due to the bleed. Pathological examination of resected AVMs showed angionecrosis in 42.9%, foreign body giant cells in 39.3%, and evidence of recanalization of Onyx-embolized vessels in 14.3% of specimens. CONCLUSIONMultimodality treatment with microsurgery is safe and effective after embolization with Onyx. High occlusion rates and low complication rates were observed after Onyx embolization and were comparable to those in previous reports. Superselective intranidal or perinidal catheter positions and slow, controlled injections that protect the draining veins make the therapy safe even in complex AVMs and critical locations. We recommend resection of the AVM despite apparently complete embolization with Onyx. Team work and coordination between the surgeon and the interventional neuroradiologist are important to achieve a good outcome.

Balloon Guide Catheter Improves Revascularization and Clinical Outcomes With the Solitaire Device Analysis of the North American Solitaire Acute Stroke Registry

Background and Purpose— Efficient and timely recanalization is an important goal in acute stroke endovascular therapy. Several studies demonstrated improved recanalization and clinical outcomes with the stent retriever devices compared with the Merci device. The goal of this study was to evaluate the role of the balloon guide catheter (BGC) and recanalization success in a substudy of the North American Solitaire Acute Stroke (NASA) registry. Methods— The investigator-initiated NASA registry recruited 24 clinical sites within North America to submit demographic, clinical, site-adjudicated angiographic, and clinical outcome data on consecutive patients treated with the Solitaire Flow Restoration device. BGC use was at the discretion of the treating physicians. Results— There were 354 patients included in the NASA registry. BGC data were reported in 338 of 354 patients in this subanalysis, of which 149 (44%) had placement of a BGC. Mean age was 67.3±15.2 years, and median National Institutes of Health Stroke Scale score was 18. Patients with BGC had more hypertension (82.4% versus 72.5%; P=0.05), atrial fibrillation (50.3% versus 32.8%; P=0.001), and were more commonly administered tissue plasminogen activator (51.6% versus 38.8%; P=0.02) compared with patients without BGC. Time from symptom onset to groin puncture and number of passes were similar between the 2 groups. Procedure time was shorter in patients with BGC (120±28.5 versus 161±35.6 minutes; P=0.02), and less adjunctive therapy was used in patients with BGC (20% versus 28.6%; P=0.05). Thrombolysis in cerebral infarction 3 reperfusion scores were higher in patients with BGC (53.7% versus 32.5%; P<0.001). Distal emboli and emboli in new territory were similar between the 2 groups. Discharge National Institutes of Health Stroke Scale score (mean, 12±14.5 versus 17.5±16; P=0.002) and good clinical outcome at 3 months were superior in patients with BGC compared with patients without (51.6% versus 35.8%; P=0.02). Multivariate analysis demonstrated that the use of BGC was an independent predictor of good clinical outcome (odds ratio, 2.5; 95% confidence interval, 1.2–4.9). Conclusions— Use of a BGC with the Solitaire Flow Restoration device resulted in superior revascularization results, faster procedure times, decreased need for adjunctive therapy, and improved clinical outcome.

Magnetic resonance neurography of peripheral nerve lesions in the lower extremity

OBJECTIVE We describe the clinical application and utility of high-resolution magnetic resonance neurography (MRN) techniques to image the normal fascicular structure of peripheral nerves and its distortion by mass lesions or trauma in the lower extremity. METHODS MRN images were obtained using a standard 1.5 Tesla magnet and custom built phased-array coils. Patients were imaged using T1-weighted spin echo without and with gadolinium, T2-weighted fast spin echo with fat peripheral nerve tumors (three neurofibromas and one schwannoma), two with intraneural cysts, and three with traumatic peripheral nerve lesions. Six patients with peripheral nerve mass lesions underwent surgery, thereby allowing MRN images to be correlated with intraoperative and pathological findings. RESULTS Preoperative MRN accurately imaged the normal fascicular anatomy of peripheral nerves and precisely depicted its relation to tumor and cystic lesions. Increased signal on T2-weighted fast spin-echo and short tau inversion recovery fast spin-echo pulse sequences was seen in the peripheral nerve fascicles of patients with clinical and electrodiagnostic evidence of nerve injury. CONCLUSION MRN proved useful in the preoperative evaluation and planning of surgery in patients with peripheral nerve lesions.

Carpal tunnel syndrome: Correlation of magnetic resonance imaging, clinical, electrodiagnostic, and intraoperative findings

We undertook a prospective study of 43 wrists in 32 patients who had been clinically diagnosed as having carpal tunnel syndrome (study group) and 5 wrists in people who had no symptoms (control group), correlating the clinical, electrodiagnostic, intraoperative, and magnetic resonance imaging (MRI) findings. MRI of the carpal tunnel and thenar eminence was performed, using coronal and axial T1- and T2-weighted, proton density, and short tau inversion recovery sequences. Abnormalities of the median nerve, as revealed by MRI, were found in 43 of 43 (100%) wrists in the study group and in 0 of 5 (0%) wrists in the control group. Increased signal of the median nerve was seen in 41 of 43 (95%) wrists, increased signal of the flexor tendon sheath in 41 of 43 (95%), volar bowing of the flexor retinaculum in 39 of 43 (91%), increased distance between the flexor tendons in 37 of 43 (86%), and abnormal nerve configuration in 28 of 43 (65%). Increased short tau inversion recovery signal of the thenar muscles was found in 5 of 43 (12%) wrists, all of which had undergone severe denervation changes, as revealed by electromyography. Operative release was performed for 27 of 43 (63%) wrists, and follow-up was obtained for 42 of 43 (98%). A good or excellent postoperative outcome resulted for 20 of 27 (74%) patients, a fair outcome for 2 of 27 (7%), and a poor outcome for 4 of 27 (15%), and 1 of 27 (4%) patients was lost to follow-up. For patients undergoing carpal tunnel release whose MRI revealed an abnormal nerve configuration, the outcome was improved, with good or excellent results in 15 of 18 (83%) patients. No association with outcome was seen with median nerve or flexor tendon signal changes, increased interspace between the flexor tendons, or flexor retinaculum bowing. Our results indicate that MRI is a sensitive diagnostic modality that can demonstrate signal and configurational abnormalities of the median nerve in patients diagnosed with carpal tunnel syndrome. Increased signal of the thenar muscles, as revealed by MRI, using short tau inversion recovery sequences, occurs only in muscles that have undergone severe denervation changes, as revealed by electromyography.

Long-term outcome of superficial temporal artery-middle cerebral artery bypass for patients with moyamoya disease in the US

OBJECT The authors report the long-term results of a series of direct superficial temporal artery-middle cerebral artery (STA-MCA) bypass procedures in patients with moyamoya disease from the western US. METHODS All patients with moyamoya disease treated at the University of Washington from 1990 through 2004 (39 patients) were included in this study. Patients underwent pre- and postoperative evaluation of cerebral perfusion dynamics. Surgical revascularization procedures were performed in all patients with impaired cerebral blood flow (CBF) findings. RESULTS The mean age of patients at diagnosis was 34 years (range 10-55 years). All 39 patients had impaired CBF and/or vasomotor reserve and underwent revascularization procedures: 26 patients underwent bilateral operations, 13 unilateral (65 total procedures). An STA-MCA bypass was technically possible in 56 procedures (86.2%); saphenous vein interposition grafts were required in 3 procedures (4.6%); encephaloduroarteriosynangiosis was performed in 6 procedures (9.2%). Three patients died due to postoperative complications, yielding a procedure-related mortality rate of 4.61%, and 8 experienced non-life threatening complications (for a procedure-related rate of 12.3%). Long-term follow-up appeared to indicate a reduction in further ischemic events in surviving patients compared with the natural history. Cerebral perfusion dynamics improved postoperatively in all 36 surviving patients. CONCLUSIONS Moyamoya disease may differ in the US and Asia, and STA-MCA bypass procedures may prevent future ischemic events in patients with this condition.

North American Solitaire Stent Retriever Acute Stroke registry: post-marketing revascularization and clinical outcome results

Background Limited post-marketing data exist on the use of the Solitaire FR device in clinical practice. The North American Solitaire Stent Retriever Acute Stroke (NASA) registry aimed to assess the real world performance of the Solitaire FR device in contrast with the results from the SWIFT (Solitaire with the Intention for Thrombectomy) and TREVO 2 (Trevo versus Merci retrievers for thrombectomy revascularization of large vessel occlusions in acute ischemic stroke) trials. Methods The investigator initiated NASA registry recruited North American sites to submit retrospective angiographic and clinical outcome data on consecutive acute ischemic stroke (AIS) patients treated with the Solitaire FR between March 2012 and February 2013. The primary outcome was a Thrombolysis in Myocardial Ischemia (TIMI) score of ≥2 or a Treatment in Cerebral Infarction (TICI) score of ≥2a. Secondary outcomes were 90 day modified Rankin Scale (mRS) score, mortality, and symptomatic intracranial hemorrhage. Results 354 patients underwent treatment for AIS using the Solitaire FR device in 24 centers. Mean time from onset to groin puncture was 363.4±239 min, mean fluoroscopy time was 32.9±25.7 min, and mean procedure time was 100.9±57.8 min. Recanalization outcome: TIMI ≥2 rate of 83.3% (315/354) and TICI ≥2a rate of 87.5% (310/354) compared with the operator reported TIMI ≥2 rate of 83% in SWIFT and TICI ≥2a rate of 85% in TREVO 2. Clinical outcome: 42% (132/315) of NASA patients demonstrated a 90 day mRS ≤2 compared with 37% (SWIFT) and 40% (TREVO 2). 90 day mortality was 30.2% (95/315) versus 17.2% (SWIFT) and 29% (TREVO 2). Conclusions The NASA registry demonstrated that the Solitaire FR device performance in clinical practice is comparable with the SWIFT and TREVO 2 trial results.

Multimodality treatment of intracranial dural arteriovenous fistulas in the Onyx era: a single center experience.

BACKGROUND The results of treatment of intracranial dural arteriovenous fistulas (DAVFs) since Onyx became available as an embolic agent at our institution is reported. An algorithm is presented for treatment of DAVFs with Onyx, and the role of endovascular transvenous, surgical, and radiosurgical approaches are presented. METHODS Thirty-two patients with DAVFs treated between November 2005 and November 2008 by endovascular embolization, surgery, or radiosurgery were identified by a retrospective chart review. Treatment strategies were based on the location or complexity of the fistula and the patients clinical status. Data collected included DAVF characteristics, obliteration rates, complications, and outcomes. The results were analyzed and correlated with the treatment modality. RESULTS Presenting symptoms were as follows: hemorrhage (n = 12 patients), headaches (n = 12), tinnitus (n = 5), orbital symptoms (n = 7), and seizures (n = 1). Thirty patients were treated by endovascular embolization (transarterial only with Onyx-21, transvenous only with platinum coils-6, transarterial [Onyx] and transvenous [coils]-3). Five patients (4 after incomplete/failed embolization) had surgical excision of the fistula. Three patients were treated with Gamma Knife radiosurgery (primary-1, 2 after incomplete/failed embolization). The locations of the fistulas were transverse sigmoid (10 patients), petrotentorial (7 patients), indirect carotid cavernous fistula (7 patients), parasagittal/falcine (3 patients), middle fossa dura (3 patients), torcula (1 patient), and anterior fossa dura (1 patient). The distribution of patients according to Borden classification was I-6, II-13, and III-13. Complete obliteration of the fistula was achieved in 26/32 (81%) patients after multimodal treatment. All surgical cases had complete obliteration. In the high-risk group with cortical venous reflux, 23/26 (89%) patients were cured. Endovascular complications included a stuck microcatheter tip with fracture of the tip in two patients and cranial nerves V and VII palsies in one patient. At last follow-up (range 1-36 months), 24 patients had modified Rankin score of 0-2, 5 patients had modified Rankin score of 3-5, and 3 patients were dead. Two patients died during admission due to the insult of the hemorrhage, and one died after an accidental fall with subsequent traumatic subdural hematoma. CONCLUSIONS Multimodality treatment of DAVFs has high success rates for cure at our center. Transarterial embolization with Onyx has become the primary treatment for intracranial DAVFs at our center and is associated with high safety profile and efficacy. Transvenous coil embolization is still preferred in DAVFs with supply from arterial branches supplying cranial nerves, predominant internal carotid artery feeders and potential extracranial-intracranial collateral anastomosis. In our series, patients with incompletely treated DAVFs were treated with surgery and those with partially treated type I fistulas had radiosurgery for palliation.