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Recent successful endovascular stroke trials have provided unequivocal support for these therapies in selected patients with large-vessel occlusive acute ischemic stroke. In this piece, we briefly review these trials and their utilization of advanced neuroimaging techniques that played a pivotal role in their success through targeted patient selection. In this context, the unique challenges and opportunity for advancement in current stroke networks' routine delivery of care created by these trials are discussed and recommendations to change current national stroke system guidelines are proposed.

Modified brain stem auditory evoked potentials in patients with intracranial mass lesions.

The authors report their experience utilizing a recently described rapid rate, binaural click and 1000-Hz tone burst modification of the brain stem auditory evoked potentials (BAEP), modified (MBP), in 27 symptomatic patients with non-brain stem compressive space-taking cerebral lesions (22), hydrocephalus (4), and pseudotumor cerebri (1).  Many presented with clinical signs suggestive of increased intracranial pressure (ICP) and focal neurological deficits. The cerebral lesions, mostly large tumors with edema, had very substantial radiological signs of mass effect. Fourteen patients were also studied following surgical decompression. A number of significant changes in the wave V and Vn latency/intensity and less so amplitude/intensity function was found in the 27 patients, compared to normal volunteers, as well as those studied pre- and postoperatively. Similar MBP changes had been noted in normal volunteers placed in a dependent head position. Possible mechanisms to explain these findings are discussed.  The MBP methodology shows promise and further development could make neuro-intensive care unit monitoring practical.

Detection of intracranial in-stent restenosis using quantitative magnetic resonance angiography.

BACKGROUND AND PURPOSE: In-stent restenosis (ISR) after angioplasty/stenting for intracranial stenosis has been reported in up to 25% to 30% of patients. Detection and monitoring of ISR relies primarily on serial catheter angiography, because noninvasive imaging methods are typically hampered by stent-related artifact. We examined the value of serial vessel flow measurements using quantitative magnetic resonance angiography (QMRA) in detection of ISR. MATERIAL AND METHODS: Records of patients undergoing stenting for intracranial symptomatic stenosis >50% between 2005 and 2009 were retrospectively reviewed. Angiographic images were graded by a blinded neurointerventionalist for stenosis pretreatment, immediately after treatment, and during follow-up. Flow in the affected vessel measured by QMRA was recorded; > 25% reduction in flow was considered indicative of an adverse change. Clinical data regarding neurological outcome were also collected. RESULTS: Twenty-eight patients underwent stenting during the time interval studied. Of these, 12 patients (mean age, 55.5 years; 8 female) had contemporaneous angiography and QMRA and were analyzed. Median follow-up was 9 months. Six patients (50%) demonstrated angiographic restenosis 2 to 12 months after treatment; all had an analogous decrease in flow in the vessel of interest. Of 3 patients with more severe flow decrement (> 50%), 2 experienced stroke. None of the patients without angiographic ISR demonstrated a flow decrease on QMRA. CONCLUSIONS: In this preliminary series, flow decrease on QMRA is highly predictive of angiographic ISR. Additionally, the degree of flow decrement correlates with symptomatic ISR. QMRA may provide a useful noninvasive tool for serial monitoring after intracranial stenting.

Near infrared technology in neuroscience: past, present and future.

OBJECTIVE: To review past, present and future applications of near-infrared spectroscopy (NIRS) in clinical neuroscience. METHODS: The literature and personal experience of the authors were critically reviewed in order to provide a balanced overview of the basic principles, clinical validation, previous experience and current use of NIRS in assessment of cerebral oxygenation in clinical neuroscience. RESULTS: Recent technological advancements in transcranial cerebral oximetry (TCCO) are opening up a new promising avenue in clinical neuroscience. With its non-invasive nature, high reliability and uniqueness of gathered data, NIRS represents a very special modality in the neuroscience intensive care unit, angiography suite and the operating room. The hurdles of using this technology in clinical practice are discussed in detail. In addition, we evaluate some known limitations of NIRS and current controversies around its use. Lastly, several commercially available cerebral oximeters are presented. CONCLUSION: Despite remarkable developments in the NIRS technology and proven reliability of the cerebral oxygenation monitoring approach, TCCO remains mostly an adjuvant tool for neuroscience applications. Newer NIRS technologies have become a source of quantitative information about brain oxygenation, cerebral blood volume and flow. However, the clinical significance of this new information in the context of clinical neuroscience will need to be determined and further validation studies will need to be performed.

Brainstem auditory evoked potentials--a review and modified studies in healthy subjects.

The authors review the brainstem auditory evoked potential (BAEP), and present studies on 40 healthy subjects. In addition to the conventional click evoked BAEP, three modified BAEP examinations were performed. The modified BAEP tests include a 1,000 Hz tone-burst BAEP, and more rapid rate binaural click and 1,000 Hz tone-burst BAEPs-each of the last two studies performed at four diminishing moderate intensities. In addition to the usual parameters, the authors examined the Wave V to Vn interpeak latency, and stimulus intensity versus Wave V latency and amplitude functions in the rapid rate binaural studies. Studies were also repeated on healthy subjects in a dependant head position in an attempt to increase intracranial pressure. Discussion centers on the BAEP, its current utility in medicine, unique neurophysiology, and literature support that the above modifications could increase the practicality of the test in patients at risk with intracranial lesions and perhaps improve the feasibility for real-time continuous or frequent monitoring in the future.

Detection of cerebral ischemia in neurovascular surgery using quantitative frequency-domain near-infrared spectroscopy.

OBJECT: There is great value in monitoring for signs of ischemia during neurovascular procedures. Current intraoperative monitoring techniques provide real-time feedback with limited accuracy. Quantitative frequency-domain near-infrared spectroscopy (Q-NIRS) allows measurement of tissue oxyhemoglobin (HbO2), deoxyhemoglobin (HHb), and total hemoglobin (tHb) concentrations and brain tissue oxygen saturation (SO2), which could be useful when monitoring for evidence of intraoperative ischemia. METHODS: Using Q-NIRS, the authors monitored 25 neurovascular procedures including aneurysm clip placement, arteriovenous malformation resection, carotid endarterectomy, superficial temporal artery-middle cerebral artery (MCA) bypass surgery, external carotid artery-MCA bypass surgery, encephaloduromyosynangiosis, and balloon occlusion testing. The Q-NIRS technology provides measurable cerebral oxygenation values independent from those of the scalp tissue. Thus, alterations in the variables measured with Q-NIRS quantitatively reflect cerebral tissue perfusion. Bilateral monitoring was performed in all cases. Five of the patients exhibited evidence of clinical ischemic events during the procedures. One patient suffered blood loss with systemic hypotension and developed diffuse brain edema intraoperatively, one patient suffered an ischemic event intraoperatively and developed an occipital stroke postoperatively, and one patient showed slowing on electroencephalography intraoperatively during carotid clamping; in two patients balloon occlusion testing failed. In all cases of ischemic events occurring during the procedure, Q-NIRS monitoring showed a decrease in HbO2, tHb, and SO2, and an increase in HHb. CONCLUSIONS: . Quantitative frequency-domain near-infrared spectroscopy provides quantifiable and continuous real-time information about brain oxygenation and hemodynamics in a noninvasive manner. This continuous intraoperative oxygenation monitoring is a promising method for detecting ischemic events during neurovascular procedures.