12/1/2023 0 Comments Spike definition mri![]() ![]() It is possible that deeper structures, such as the thalamus, may be involved with generalized discharges. Typically found with primary or symptomatic generalized epilepsies, generalized discharges begin in such a widespread fashion that they effectively involve the entire cortex simultaneously. First of all, generalized discharges cannot be localized. However, there are a few fine details or caveats to this rule. For example, a discharge at T4 suggests right mid-temporal hyperexcitability / epileptogenic potential. Generally speaking, the location of an epileptiform (or interictal) discharge suggests cortical irritability of that region. If you see a single discharge without a field, its good to make note of it but you probably shouldn't call it an interictal discharge (do, however, look for more of them and remain suspicious). The left temporal discharge above, for example, has a good field throughout the left temporal region, with the surrounding tracings "pointing to" the discharge site, as expected in bipolar montages. Whether an interictal has an appreciable slow wave or not, it should always disrupt the background and have a field this is to say, you should see "ripples" of a discharge in the surrounding EEG electrodes (as discussed in the technical section). Slow waves always immediately follow, and are often higher amplitude than, their precedent spikes or sharps. Realistically, the cutoff between them is not very important clinically, as one isn't known to be any more "severe" than the other.Īfter a spike or sharp, there is typically a slow wave, which represents the refractory period of the affected neuron population after the large and synchronized EPSPs that led to the spike or sharp itself. A spike is very similar to a sharp but faster, with a duration from 20-70ms. ![]() A sharp is a single epileptiform discharge defined by its duration lasting between 70-200ms, and by its disruption of the EEG background. doi:10.2214/ajr.09.Any epileptiform discharge is a disruption of the usual functioning of the brain, and sharps and spikes are perhaps the most classic type. MRI Nomenclature for Musculoskeletal Infection. Alaia E, Chhabra A, Simpfendorfer C et al. Glossary of Terms for Musculoskeletal Radiology. Imaging of Periosteal Reactions Associated with Focal Lesions of Bone. Radiologic and Pathologic Analysis of Solitary Bone Lesions. Symmetrical periosteal reaction carries a separate differential diagnosis. Unilateral periosteal reaction is non-specific and can be due to localized 7: More specific classification of periosteal reactions can be made to narrow the differential diagnosis: ![]() Morphological classification of periosteal reactions The cortex may appear lamellated, amorphous, or sunburst-like.Īggressive periosteal reactions can not only be seen with malignant tumors, but also with more benign processes like infection, eosinophilic granuloma (Langerhans cell histiocytosis), aneurysmal bone cyst, osteoid osteoma, hemophilia 4, and trauma. Rapid irritative processes do not allow the periosteum time to lay down and consolidate new bone to form normal cortex. The cortex will be thick and dense and have a wavy or uniform appearance.īenign periosteal reactions can be seen in callus formation in a fracture or with slowly growing tumors. Low-grade chronic irritation allows time for the formation of normal or near-normal cortex. Periosteal reactions may be classified as benign or aggressive (note: not benign and malignant) based on the time course of the initiating process. Periosteal reaction is the recommended term over periostitis/ periosteitis and periosteal new bone formation, although all three are used synonymously 6. ![]()
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