Refined Sphenopalatine Ganglion Stimulator Placement and Intensity Setting to Augment Blood Flow and Neurologic Function

Background and Purpose- Two large, randomized trials indicated that sphenopalatine ganglion (SPG) stimulation improves final disability outcome in acute anterior circulation patients with ischemic stroke with confirmed cortical involvement. This study evaluated 2 refinements in SPG stimulation treatment technique: (1) SPG electrode placement with real-time optical tracking guidance; and (2) stimulation intensity comfortable tolerance level selection using non-noxious facial physiological markers. Methods- This study was a single, active arm trial at 4 centers, enrolling patients with anterior circulation ischemic stroke, National Institutes of Health Stroke Scale 1 to 6 including arm weakness subitem score ≥1, not receiving recanalization therapies, and within 24 hours of onset. Stimulation level was set based on ipsilateral facial tingling sensation or lacrimation. SPG stimulation effects were assessed by measuring volumetric blood flow in the ipsilateral common carotid artery by ultrasound and grasp and pinch strength in the affected hand before and during stimulation, and by change in National Institutes of Health Stroke Scale from day 1 to 7. Results- Among 50 enrolled patients, age was median 66 years (interquartile range, 60-74), 44% were female, National Institutes of Health Stroke Scale median was 5 (interquartile range, 4-5), and median onset-to-screening time was 18 hours (interquartile range, 9-20). Median implantation skin-to-skin time was 4 minutes (interquartile range, 3-7), and all 50 implants were placed correctly. Comfortable tolerance level was found based on physiological biomarkers in 96% of patients, including 86% in the optimal, low-medium intensity range. SPG stimulation significantly increased common carotid artery peak systolic and end-diastolic blood flow (44%, P<0.0001; and 52%, P<0.0001) and improved pinch strength (42%, P<0.0001) and grasp strength (26%, P<0.0001). Degree of National Institutes of Health Stroke Scale recovery by day 7 was greater than in matched historic controls, median 75% versus 50%, P=0.0003. Conclusions- SPG stimulator placement with real-time optical tracking guidance was fast and accurate, and selection of stimulation intensity levels based on non-noxious facial tingling and lacrimation was feasible in nearly all patients. SPG stimulation led to cervico-cranial blood flow augmentation and improved hand motor function. Clinical Trial Registration- URL: https://www.clinicaltrials.gov. Unique identifier: NCT03551093.

An injectable implant to stimulate the sphenopalatine ganglion for treatment of acute ischaemic stroke up to 24 h from onset (ImpACT-24B): an international, randomised, double-blind, sham-controlled, pivotal trial

BACKGROUND

Sphenopalatine ganglion stimulation increased cerebral collateral blood flow, stabilised the blood-brain barrier, and reduced infarct size, in preclinical models of acute ischaemic stroke, and showed potential benefit in a pilot randomised trial in humans. The pivotal ImpACT-24B trial aimed to determine whether sphenopalatine ganglion stimulation 8-24 h after acute ischaemic stroke improved functional outcome.

METHODS

ImpACT-24B is a randomised, double-blind, sham-controlled, pivotal trial done at 73 centres in 18 countries. It included patients (men aged 40-80 years and women aged 40-85 years) with anterior-circulation acute ischaemic stroke, not undergoing reperfusion therapy. Enrolled patients were randomly assigned via web-based randomisation to receive active sphenopalatine ganglion stimulation (intervention group) or sham stimulation (sham-control group) 8-24 h after stroke onset. Patients, clinical care providers, and all outcome assessors were masked to treatment allocation. The primary efficacy endpoint was the difference between active and sham groups in the proportion of patients whose 3-month level of disability improved above expectations. This endpoint was evaluated in the modified intention-to-treat (mITT) population (defined as all patients who received one active or sham treatment session) and the population with confirmed cortical involvement (CCI) and was analysed using the Hochberg multi-step procedure (significance in both populations if p<0·05 in both, and in one population if p<0·025 in that one). Safety endpoints at 3 months were all serious adverse events (SAEs), SAEs related to implant placement or removal, SAEs related to stimulation, neurological deterioration, and mortality. All patients who underwent an attempted sphenopalatine ganglion stimulator or sham stimulator placement procedure were included in the safety analysis. This trial is registered with ClinicalTrials.gov, number NCT00826059.

FINDINGS

Between June 10, 2011, and March 7, 2018, 1078 patients were enrolled and randomly assigned to either the intervention or the sham-control group. 1000 patients received at least one session of sphenopalatine ganglion stimulation or sham stimulation and entered the mITT population (481 [48%] received sphenopalatine ganglion stimulation, 519 [52%] were sham controls), among whom 520 (52%) patients had CCI on imaging. The proportion of patients in the mITT population whose 3-month disability level was better than expected was 49% (234/481) in the intervention group versus 45% (236/519) in the sham-control group (odds ratio 1·14, 95% CI 0·89-1·46; p=0·31). In the CCI population, the proportion was 50% (121/244) in the intervention group versus 40% (110/276) in the sham-control group (1·48, 1·05-2·10; p=0·0258). There was an inverse U-shaped dose-response relationship between attained sphenopalatine ganglion stimulation intensity and the primary outcome in the CCI population: the proportion with favourable outcome increased from 40% to 70% at low-midrange intensity and decreased back to 40% at high intensity stimulation (p=0·0034). There were no differences in mortality or SAEs between the intervention group (n=536) and the sham-control group (n=519) in the safety population.

INTERPRETATION

Sphenopalatine ganglion stimulation is safe for patients with acute ischaemic stroke 8-24 h after onset, who are ineligible for thrombolytic therapy. Although not reaching significance, the trial's results support that, among patients with imaging evidence of cortical involvement at presentation, sphenopalatine ganglion stimulation is likely to improve functional outcome.

FUNDING

BrainsGate Ltd.