Background and Purpose: The primary aim of this study was to investigate the diagnostic accuracy and time frames for neurological and transcranial color-coded sonography (TCCS) assessments in a prehospital ‘911’ emergency stroke situation by using portable duplex ultrasound devices to visualize the bilateral middle cerebral arteries (MCAs). Methods: This study was conducted between May 2010 and January 2011. Patients who had sustained strokes in the city of Regensburg and the surrounding area in Bavaria, Germany, were enrolled in the study. After a ‘911 stroke code’ call had been dispatched, stroke neurologists with expertise in ultrasonography rendezvoused with the paramedic team at the site of the emergency. After a brief neurological assessment had been completed, the patients underwent TCCS with optional administration of an ultrasound contrast agent in cases of insufficient temporal bone windows or if the agent had acute therapeutic relevance. The ultrasound studies were performed at the site of the emergency or in the ambulance during patient transport to the admitting hospital. Relevant timelines, such as the time from the stroke alarm to patient arrival at the hospital and the duration of the TCCS, were documented, and positive and negative predictive values for the diagnosis of major MCA occlusion were assessed. Results: A total of 113 patients were enrolled in the study. MCA occlusion was diagnosed in 10 patients. In 9 of these 10 patients, MCA occlusion could be visualized using contrast-enhanced or non-contrast-enhanced TCCS during patient transport and was later confirmed using computed tomography or magnetic resonance angiography. One MCA occlusion was missed by TCCS and 1 atypical hemorrhage was misdiagnosed. Overall, the sensitivity of a ‘field diagnosis’ of MCA occlusion was 90% [95% confidence interval (CI) 55.5–99.75%] and the specificity was 98% (95% CI 92.89–99.97%). The positive predictive value was 90% (95% CI 55.5–99.75%) and the negative predictive value was 98% (95% CI 92.89–99.97%). The mean time (standard deviation) from ambulance dispatch to arrival at the patient was 12.3 min (7.09); the mean time for the TCCS examination was 5.6 min (2.2); and the overall mean transport time to the hospital was 53 min (18). Conclusion: Prehospital diagnosis of MCA occlusion in stroke patients is feasible using portable duplex ultrasonography with or without administration of a microbubble contrast agent. Prehospital neurological as well as transcranial vascular assessments during patient transport can be performed by a trained neurologist with high sensitivity and specificity, perhaps opening an additional therapeutic window for sonothrombolysis or neuroprotective strategies.

Background and PurposeTranscranial near-infrared laser therapy (TLT) is a promising and novel method to promote neuroprotection and clinical improvement in both acute and chronic neurodegenerative diseases such as acute ischemic stroke (AIS), traumatic brain injury (TBI), and Alzheimer’s disease (AD) patients based upon efficacy in translational animal models. However, there is limited information in the peer-reviewed literature pertaining to transcranial near-infrared laser transmission (NILT) profiles in various species. Thus, in the present study we systematically evaluated NILT characteristics through the skull of 4 different species: mouse, rat, rabbit and human.ResultsUsing dehydrated skulls from 3 animal species, using a wavelength of 800nm and a surface power density of 700 mW/cm2, NILT decreased from 40.10% (mouse) to 21.24% (rat) to 11.36% (rabbit) as skull thickness measured at bregma increased from 0.44 mm in mouse to 0.83 mm in rat and then 2.11 mm in rabbit. NILT also significantly increased (p<0.05) when animal skulls were hydrated (i.e. compared to dehydrated); but there was no measurable change in thickness due to hydration.In human calvaria, where mean thickness ranged from 7.19 mm at bregma to 5.91 mm in the parietal skull, only 4.18% and 4.24% of applied near-infrared light was transmitted through the skull. There was a slight (9.2-13.4%), but insignificant effect of hydration state on NILT transmission of human skulls, but there was a significant positive correlation between NILT and thickness at bregma and parietal skull, in both hydrated and dehydrated states.ConclusionThis is the first systematic study to demonstrate differential NILT through the skulls of 4 different species; with an inverse relationship between NILT and skull thickness. With animal skulls, transmission profiles are dependent upon the hydration state of the skull, with significantly greater penetration through hydrated skulls compared to dehydrated skulls. Using human skulls, we demonstrate a significant correlation between thickness and penetration, but there was no correlation with skull density. The results suggest that TLT should be optimized in animals using novel approaches incorporating human skull characteristics, because of significant variance of NILT profiles directly related to skull thickness.

BackgroundTranscranial color-coded sonography (TCCS) has proved to be a fast and reliable tool for the detection of middle cerebral artery (MCA) occlusions in a hospital setting. In this feasibility study on prehospital sonography, our aim was to investigate the accuracy of TCCS for neurovascular emergency diagnostics when performed in a prehospital setting using mobile ultrasound equipment as part of a neurological examination.MethodsFollowing a ‘911 stroke code’ call, stroke neurologists experienced in TCCS rendezvoused with the paramedic team. In patients with suspected stroke, TCCS examination including ultrasound contrast agents was performed. Results were compared with neurovascular imaging (CTA, MRA) and the final discharge diagnosis from standard patient-centered stroke care.ResultsWe enrolled ‘232 stroke code’ patients with follow-up data available in 102 patients with complete TCCS examination. A diagnosis of ischemic stroke was made in 73 cases; 29 patients were identified as ‘stroke mimics’. MCA occlusion was diagnosed in ten patients, while internal carotid artery (ICA) occlusion/high-grade stenosis leading to reversal of anterior cerebral artery flow was diagnosed in four patients. The initial working diagnosis ‘any stroke’ showed a sensitivity of 94% and a specificity of 48%. ‘Major MCA or ICA stroke’ diagnosed by mobile ultrasound showed an overall sensitivity of 78% and specificity of 98%.ConclusionsThe study demonstrates the feasibility and high diagnostic accuracy of emergency transcranial ultrasound assessment combined with neurological examinations for major ischemic stroke. Future combination with telemedical support, point-of-care analysis of blood serum markers, and probability algorithms of prehospital stroke diagnosis including ultrasound may help to speed up stroke treatment.

c-TCCS is a sensitive noninvasive method for detecting cardiac right-to-left shunt and is as sensitive as c-TEE.

This bioeffects study gives further evidence of the safety of ultrasonic destruction of Levovist and Optison microbubbles by diagnostic transcranial color-coded sonography. However, more subtle local effects may have been missed by gadolinium-enhanced magnetic resonance imaging. Studies on diagnostic contrast-enhanced transcranial color-coded sonography as well as microbubble-based drug delivery strategies should consider ultrasonic contrast agent microbubble characteristics and concentration as well as ultrasound transmission power levels.