We acquired a rapidly preserved human surgical sample from the temporal lobe of the cerebral cortex. We stained a 1 mm3 volume with heavy metals, embedded it in resin, cut more than 5000 slices at ~30 nm and imaged these sections using a high-speed multibeam scanning electron microscope. We used computational methods to render the three-dimensional structure of 50,000 cells, hundreds of millions of neurites and 130 million synaptic connections. The 1.3 petabyte electron microscopy volume, the segmented cells, cell parts, blood vessels, myelin, inhibitory and excitatory synapses, and 100 manually proofread cells are available to peruse online. Despite the incompleteness of the automated segmentation caused by split and merge errors, many interesting features were evident. Glia outnumbered neurons 2:1 and oligodendrocytes were the most common cell type in the volume. The E:I balance of neurons was 69:31%, as was the ratio of excitatory versus inhibitory synapses in the volume. The E:I ratio of synapses was significantly higher on pyramidal neurons than inhibitory interneurons. We found that deep layer excitatory cell types can be classified into subsets based on structural and connectivity differences, that chandelier interneurons not only innervate excitatory neuron initial segments as previously described, but also each others initial segments, and that among the thousands of weak connections established on each neuron, there exist rarer highly powerful axonal inputs that establish multi-synaptic contacts (up to ~20 synapses) with target neurons. Our analysis indicates that these strong inputs are specific, and allow small numbers of axons to have an outsized role in the activity of some of their postsynaptic partners.
Both two-dimensional and three-dimensional techniques provide acceptably accurate measurement of mandibular anatomy. Cone beam computed tomography measurement was not significantly influenced by variation in skull orientation during image acquisition.
In assessing post-treatment stability in a group of treated patients, most of the change usually occurs in just a few of them. For this reason, it is highly misleading to use statistics based on normal distribution to describe posttreatment changes. With a normal distribution, the mean is the most likely indicator of what a patient would experience, and the clinician tends to think of it in just that way. But if essentially no change occurred in three fourths of the patients who underwent a certain type of treatment, and relatively large changes occurred in the one fourth who experienced change, the mean is highly misleading as an expectation of treatment response.It is even more misleading to describe stability in terms of the percentage of treatment change that was retained at some follow-up time, as was done in many early articles on stability after orthognathic surgery. Reporting such percentages implies that the amount of relapse is directly related to the amount of treatment change: the more you changed it, the more it would relapse. In dentofacial patients, that almost never is the case. You simply cannot say that 80% of the amount of typical mandibular advancement will be retained, for instance, because, up to 8-10 mm, posttreatment change (in the few patients who experience it) is relatively independent of the amount of advancement.So how should stability data be reported? The best way is in terms of the percentage of the patients who have changes of a given magnitude. From that perspective, responses can be grouped as:• Highly stable-less than a 10% chance of significant posttreatment change• Stable-less than a 20% chance of significant post-treatment change and almost no chance of major posttreatment change• Stable if modified in a specific way (eg, rigid internal fixation [RIF] after surgery)• Problematic: a considerable probability of major posttreatment changeIn the real world, nothing is 100% successful, and high-risk procedures sometimes are quite successful. The clinician needs to know the odds of long-term stability and predictability with the possible treatment approaches, so that this information can guide the choice of treatment. The hierarchy of stabilityThe data for this article are taken from the University of North Carolina (UNC) Dentofacial Program database, which now contains over 3000 patients with initial records and over 1400 with at least 1 year follow-up. The database includes only patients with developmental deformities (no craniofacial anomalies or syndromes) treated with maxillary or mandibular orthognathic procedures.Current data make it clear that, although modern orthognathic surgery can move the jaws and dentoalveolar segments, within limits, in any desired direction, there are major differences in stability and predictability. Based on this, it is possible to construct a hierarchy of procedures (Fig 1) and to group procedures into 4 major categories. 1Superior repositioning of the maxilla is the most stable orthognathic procedure, closely followed by mandibular advancement...
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