Ronald L. A. W. Bleys

Changes in neuronal connectivity after stroke in rats as studied by serial manganese-enhanced MRI.

Loss of function and subsequent spontaneous recovery after stroke have been associated with physiological and anatomical alterations in neuronal networks in the brain. However, the spatiotemporal pattern of such changes has been incompletely characterized. Manganese-enhanced MRI (MEMRI) provides a unique tool for in vivo investigation of neuronal connectivity. In this study, we measured manganese-induced changes in longitudinal relaxation rate, R(1), to assess the spatiotemporal pattern of manganese distribution after focal injection into the intact sensorimotor cortex in control rats (n=10), and in rats at 2 weeks after 90-min unilateral occlusion of the middle cerebral artery (n=10). MEMRI data were compared with results from conventional tract tracing with wheat-germ agglutinin horseradish peroxidase (WGA-HRP). Distinct areas of the sensorimotor pathway were clearly visualized with MEMRI. At 2 weeks after stroke, manganese-induced changes in R(1) were significantly delayed and diminished in the ipsilateral caudate putamen, thalamus and substantia nigra. Loss of connectivity between areas of the sensorimotor network was also identified from reduced WGA-HRP staining in these areas on post-mortem brain sections. This study demonstrates that MEMRI enables in vivo assessment of spatiotemporal alterations in neuronal connectivity after stroke, which may lead to improved insights in mechanisms underlying functional loss and recovery after stroke.

Manganese-enhanced MRI of brain plasticity in relation to functional recovery after experimental stroke.

Restoration of function after stroke may be associated with structural remodeling of neuronal connections outside the infarcted area. However, the spatiotemporal profile of poststroke alterations in neuroanatomical connectivity in relation to functional recovery is still largely unknown. We performed in vivo magnetic resonance imaging (MRI)-based neuronal tract tracing with manganese in combination with immunohistochemical detection of the neuronal tracer wheat-germ agglutinin horseradish peroxidase (WGA-HRP), to assess changes in intra- and interhemispheric sensorimotor network connections from 2 to 10 weeks after unilateral stroke in rats. In addition, functional recovery was measured by repetitive behavioral testing. Four days after tracer injection in perilesional sensorimotor cortex, manganese enhancement and WGA-HRP staining were decreased in subcortical areas of the ipsilateral sensorimotor network at 2 weeks after stroke, which was restored at later time points. At 4 to 10 weeks after stroke, we detected significantly increased manganese enhancement in the contralateral hemisphere. Behaviorally, sensorimotor functions were initially disturbed but subsequently recovered and plateaued 17 days after stroke. This study shows that manganese-enhanced MRI can provide unique in vivo information on the spatiotemporal pattern of neuroanatomical plasticity after stroke. Our data suggest that the plateau stage of functional recovery is associated with restoration of ipsilateral sensorimotor pathways and enhanced interhemispheric connectivity.

The influence of diffuse idiopathic skeletal hyperostosis on bone mineral density measurements of the spine

OBJECTIVES BMD has been described to be increased in patients with DISH. The contribution of the ossified anterior longitudinal ligament (ALL) on vertebral body BMD is currently unknown. We investigated the influence of DISH on BMD measurements using an experimental DXA scanning protocol. METHODS Ten DISH specimens and 10 matched human cadaveric spines were used. After assessment of the localization and orientation of the ossified ALL with CT, BMD was measured using an experimental DXA protocol, exploiting the asymmetry of DISH in the thoracic spine. For controls, identical orientations were used and both groups were compared for differences in BMD. RESULTS Specimens with DISH displayed a significantly higher BMD than their matched controls when the ossified ALL was present in the scanning field. Measurements of the left half of the spine were comparable for DISH specimens and controls (P = 0.446). The right-left difference in anteroposterior view was statistically significant within DISH specimens (P = 0.001), but not in controls (P = 0.825). CONCLUSIONS The variability in measurements in different scanning orientations suggests a substantial contribution of the ossified ALL to the total BMD in DISH specimens, ranging from 23.6 to 39.0%. Vertebral body BMD does not seem to be increased, as demonstrated by comparable BMDs in the unaffected left half of the spine. It is suggested that routine anteroposterior DXA scanning may overestimate the true vertebral body BMD in DISH patients.

Anatomy of the carotid sinus nerve and surgical implications in carotid sinus syndrome

BACKGROUND The carotid sinus syndrome (CSS) is characterized by syncope and hypotension due to a hypersensitive carotid sinus located in the carotid bifurcation. Some patients ultimately require surgical sinus denervation, possibly by transection of its afferent nerve (carotid sinus nerve [CSN]). The aim of this study was to investigate the anatomy of the CSN and its branches. METHODS Twelve human carotid bifurcations were microdissected. Acetylcholinesterase (ACHE) staining was used to identify location, side branches, and connections of the CSN. RESULTS A distinct CSN originating from the glossopharyngeal (IX) nerve was identified in all specimens. A duplicate CSN was incidentally present (2/12). Mean CSN length measured from the hypoglossal (XII) nerve to the carotid sinus was 29 +/- 4 mm (range, 15-50 mm). The CSN was frequently located on anterior portions of the internal carotid artery, either laterally (5/12) or medially (6/12). Separate connections to pharyngeal branches of the vagus (X) nerve (6/12), vagus nerve itself (3/12), sympathetic trunk (2/12), as well as the superior cervical ganglion (2/12) were commonly observed. The CSN always ended in a network of small separate branches innervating both carotid sinus and carotid body. CONCLUSION Anatomical position of the CSN and its side branches and communications is diverse. From a microanatomical standpoint, CSN transection as a single treatment option for patients with CSS is suboptimal. Surgical denervation at the carotid sinus level is probably more effective in CSS. CLINICAL RELEVANCE Some patients suffering from CSS ultimately require surgical carotid sinus denervation, possibly by transection of its afferent nerve (CSN). This study was performed to investigate the anatomy of the CSN using a nerve-specific ACHE staining technique. Microdissection demonstrated a great variability of the CSN and its branches. Simple high transection of the CSN may lead to an incomplete sinus denervation in patients with CSS. Surgical denervation at the level of the carotid sinus itself may be more effective in CSS.

Coronary Artery Calcification Scoring with State-of-the-Art CT Scanners from Different Vendors Has Substantial Effect on Risk Classification

PURPOSE To determine the intervendor variability of Agatston scoring determined with state-of-the-art computed tomographic (CT) systems from the four major vendors in an ex vivo setup and to simulate the subsequent effects on cardiovascular risk reclassification in a large population-based cohort. MATERIALS AND METHODS Research ethics board approval was not necessary because cadaveric hearts from individuals who donated their bodies to science were used. Agatston scores obtained with CT scanners from four different vendors were compared. Fifteen ex vivo human hearts were placed in a phantom resembling an average human adult. Hearts were scanned at equal radiation dose settings for the systems of all four vendors. Agatston scores were quantified semiautomatically with software used clinically. The ex vivo Agatston scores were used to simulate the effects of different CT scanners on reclassification of 432 individuals aged 55 years or older from a population-based study who were at intermediate cardiovascular risk based on Framingham risk scores. The Friedman test was used to evaluate overall differences, and post hoc analyses were performed by using the Wilcoxon signed-rank test with Bonferroni correction. RESULTS Agatston scores differed substantially when CT scanners from different vendors were used, with median Agatston scores ranging from 332 (interquartile range, 114-1135) to 469 (interquartile range, 183-1381; P < .05). Simulation showed that these differences resulted in a change in cardiovascular risk classification in 0.5%-6.5% of individuals at intermediate risk when a CT scanner from a different vendor was used. CONCLUSION Among individuals at intermediate cardiovascular risk, state-of the-art CT scanners made by different vendors produced substantially different Agatston scores, which can result in reclassification of patients to the high- or low-risk categories in up to 6.5% of cases.

Landmarks for parotid gland surgery

Many surgical landmarks have been suggested to help the surgeon identify the facial nerve when performing parotid gland surgery. There is no conclusive evidence that any one landmark is better than the rest. In this study distances from the most frequently used surgical landmarks to the main trunk of the facial nerve were measured in 30 halves of cadaver heads. Two ENT surgeons assessed the best landmark in each case. The tympanomastoid suture was nearest to the main trunk and was therefore considered the most reliable landmark. Its average distance to the main trunk of the facial nerve was 2.7 mm. This result was consistent with the subjective best score given by two ENT surgeons.

Computed tomography radiation dose reduction: effect of different iterative reconstruction algorithms on image quality.

Objective We evaluated the effects of hybrid and model-based iterative reconstruction (IR) algorithms from different vendors at multiple radiation dose levels on image quality of chest phantom scans. Methods A chest phantom was scanned on state-of-the-art computed tomography scanners from 4 vendors at 4 dose levels (4.1 mGy, 3.0 mGy, 1.9 mGy, and 0.8 mGy). All data were reconstructed with filtered back projection (FBP) and reduced-dose data also with IR (iDose4, Adaptive Iterative Dose Reduction 3D, Adaptive Statistical Iterative Reconstruction, Sinogram-Affirmed Iterative Reconstruction, prototype Iterative Model Reconstruction, and Veo). Computed tomography numbers and noise were measured in the spine and lungs. Signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were calculated and differences were analyzed with the Friedman test. Results For all vendors, radiation dose reduction with FBP resulted in significantly increased noise levels (⩽148%) as well as decreased SNR (⩽57%) and CNR (⩽58%) (P < 0.001). Conversely, IR resulted in decreased noise levels (⩽48%) as well as increased SNR (⩽94%) and CNR (⩽94%). The SNRs and CNRs of the model-based algorithms at 80% reduced dose were similar to reference-dose FBP. Conclusions Hybrid IR algorithms have the potential to reduce radiation dose with 27% to 54% and model-based IR algorithms with up to 80%.

Intraneural or Extraneural Diagnostic Accuracy of Ultrasound Assessment for Localizing Low-Volume Injection

Background and Objectives When one is performing ultrasound-guided peripheral nerve blocks, it is common to inject a small amount of fluid to confirm correct placement of the needle tip. If an intraneural needle tip position is detected, the needle can then be repositioned to prevent injection of a large amount of local anesthetic into the nerve. However, it is unknown if anesthesiologists can accurately discriminate intraneural and extraneural injection of small volumes. Therefore, this study was conducted to determine the diagnostic accuracy of ultrasound assessment using a criterion standard and to compare experts and novices in ultrasound-guided regional anesthesia. Methods A total of 32 ultrasound-guided infragluteal sciatic nerve blocks were performed on 21 cadaver legs. The injections were targeted to be intraneural (n = 18) or extraneural (n = 14), and 0.5 mL of methylene blue 1% was injected. Cryosections of the nerve and surrounding tissue were assessed by a blinded investigator as “extraneural” or “intraneural.” Ultrasound video clips of the injections were reviewed by 10 blinded observers (5 experts, 5 novices) independently who scored each injection as either “intraneural,” “extraneural,” or “undetermined.” Results The mean sensitivity of experts and novices was measured to be 0.84 (0.80–0.88) and 0.65 (0.60–0.71), respectively (P = 0.006), whereas mean specificity was 0.97 (0.94–0.98) and 0.98 (0.96–0.99) (P = 0.53). Conclusions Discrimination of intraneural or extraneural needle tip position based on an injection of 0.5mL is possible, but even experts missed 1 of 6 intraneural injections. In novices, the sensitivity of assessment was significantly lower, highlighting the need for focused education.

Carotid baroreceptors are mainly localized in the medial portions of the proximal internal carotid artery

AIM To visualize baroreceptors in the human carotid bifurcation by light microscopy. Baroreceptor location is investigated in order to provide recommendations for the extent of adventitial stripping in the treatment for carotid sinus syndrome (CSS). METHODS Human carotid specimens were transversely cut in 20 μm sections. After immunohistochemical staining using antibodies to vesicular glutamate transporter 2 (VGLUT2) and protein gene product 9.5 (PGP 9.5), the presence of baroreceptor tissue was studied using light microscopic techniques. RESULTS Visual assessment indicated that VGLUT2 and PGP 9.5 immunoreactivity was present in the adventitia of the carotid arteries and that nerve density was highest in the medial wall of the proximal first cm of the internal carotid artery (ICA). CONCLUSION Human carotid baroreceptors, as reflected in immunoreactivity for VGLUT2 and PGP 9.5, are mainly localized in the medial portions of the proximal ICA. If surgical carotid denervation is indicated in patients suffering from carotid sinus syndrome, adventitial stripping of the proximal portion of the ICA should be sufficient.

Neural connections in and around the cavernous sinus in rat, with special reference to cerebrovascular innervation.

There is a confluence in and around the cavernous sinus of neural pathways innervating the intracranial structures. To determine the patterns of innervation, particularly of the cerebral arteries, we stained whole‐mount preparations of the cavernous sinus and adjacent regions of the rat for acetylcholinesterase. The cavernous nerve plexus, with several small ganglia, mainly occupied the lateral wall of the sinus and extended laterally above the ophthalmic and maxillary divisions of the trigeminal nerve, in relation to the oculomotor and trochlear nerves. The cavernous plexus was connected to the pterygopalatine ganglion, the trigeminal ganglion, and the abducens nerve. The elongated pterygopalatine ganglion consisted of an orbital part, from which parasympathetic fibers ran to the cerebral arteries, and a cavernous part. Nerves from the lateral extension of the cavernous plexus ran rostrally into the orbit along the oculomotor, trochlear, and ophthalmic nerves, and caudally to the pineal gland along the trochlear nerve. Several branches also ran over the dura mater. Caudal to the cavernous sinus, we found two large nerves and a number of small nerves that ran between the nerves surrounding the internal carotid artery and the abducens nerve. These nerves may represent additional parasympathetic and/or sensory pathways to the cerebral arteries.