Cadaver investigation of the usefulness of the transstyloid diaphragm approach for high-position plaque carotid endarterectomy.

OBJECTIVES: Patients sometimes present with high cervical internal carotid artery (ICA) stenosis. This study demonstrates the usefulness of the transstyloid approach to expose the distal ICA by dissection of the styloid diaphragm covering the distal cervical ICA for carotid endarterectomy (CEA). In particular, the possible exposure length achieved by this approach was investigated using cadaveric heads. METHODS: The procedure of the transstyloid diaphragm approach was confirmed in 10 cadaveric heads (20 sides). After the carotid triangle was opened, both the posterior belly of the digastric muscle (PBDM) and the stylohyoid muscle could be divided. Then, the carotid sheath was dissected, and the glossopharyngeal nerve was identified crossing over the distal ICA. The revealed length of the ICA was measured with or without dissection of both the PBDM and the stylohyoid muscle. The specimens were dissected under the surgical microscope. RESULTS: The transstyloid diaphragm approach was achieved successfully in all specimens. The revealed lengths of the ICA with and without dissection of the styloid diaphragm were 53.7 ± 5.9 mm and 38.8 ± 2.9 mm (mean ± standard deviation), respectively. Therefore, the revealed length of the distal ICA was 14.9 ± 4.5 mm greater using the transstyloid diaphragm approach compared to the regular CEA approach. CONCLUSIONS: More of the ICA can be revealed by dissection of both the PBDM and the stylohyoid muscle. The transstyloid diaphragm approach might be helpful to reveal the distal ICA in cases of high cervical ICA stenosis.

Evans Blue and Fluorescein Isothiocyanate-Dextran Double Labeling Reveals Precise Sequence of Vascular Leakage and Glial Responses After Exposure to Mild-Level Blast-Associated Shock Waves.

Abstract Blast-induced shock waves (BSWs) are responsible for several aspects of psychiatric disorders that are collectively termed mild traumatic brain injury (mTBI). The pathophysiology of mTBI includes vascular leakage resulting from blood-brain barrier (BBB) disruption. In this study, the precise sequence of BBB breakdown was examined using an Evans blue and fluorescein isothiocyanate (FITC)-dextran double labeling technique. Evans blue solution was injected into the tail vein of male C57BL6/J mice just before and 4 h, 1 day, 3 days, and 7 days after a single BSW exposure at as low as 25-kPa peak overpressure. In contrast, the FITC-dextran solution was transcardially injected just before perfusion fixation. Differences in the labeling time-point revealed that BBB breakdown was initiated after approximately 3 h, with significant remodeling by 1 day, and continued until 7 days after BSW exposure. BBB breakdown was upregulated in three distinct regions, namely the brain surface and subsurface areas facing the skull, regions closely associated with capillaries, and the circumventricular organ and choroid plexus. These regions showed distinct responses to BSW; moreover, clusters of reactive astrocytes were closely associated with the sites of BBB breakdown. In severe cases, these reactive astrocytes recruited activated microglia. Our findings provide important insights into the pathogenesis underlying mTBI and indicate that even mild BSW exposure affects the whole brain.

Computational geometry analysis of dendritic spines by structured illumination microscopy.

Dendritic spines are the postsynaptic sites that receive most of the excitatory synaptic inputs, and thus provide the structural basis for synaptic function. Here, we describe an accurate method for measurement and analysis of spine morphology based on structured illumination microscopy (SIM) and computational geometry in cultured neurons. Surface mesh data converted from SIM images were comparable to data reconstructed from electron microscopic images. Dimensional reduction and machine learning applied to large data sets enabled identification of spine phenotypes caused by genetic mutations in key signal transduction molecules. This method, combined with time-lapse live imaging and glutamate uncaging, could detect plasticity-related changes in spine head curvature. The results suggested that the concave surfaces of spines are important for the long-term structural stabilization of spines by synaptic adhesion molecules.

Synapse Elimination Triggered by BMP4 Exocytosis and Presynaptic BMP Receptor Activation.

In vitro screening of signaling molecules involved in neural circuit formation has identified a large number of synaptogenic proteins. However, factors that drive synapse elimination remain elusive. Here, we report that bone morphogenetic protein 4 (BMP4) released from axons has the ability to eliminate synapses. We found fast axonal transport of BMP4 in dense-core vesicles, its exocytosis, and subsequent cell surface clustering via type I BMP receptors near synapses. BMP4 overexpression or knockout in culture reduced or increased presynaptic structures, respectively. The destabilizing effect of surface BMP4 clusters was limited to nearby synapses. In vivo knockout of BMP4 and subsequent two-photon imaging of synapse dynamics confirmed its critical role in maintaining an appropriate density of presynaptic components along the axon. These results suggest an essential role for perisynaptic clustering of BMP4 during development in the construction of functional neuronal circuits.