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Ictal abnormalities.pptxvbcvbcbcbcbcbcbcbc
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- 2. Seizures Ictal recordingsare very important for making a confirmatory diagnosis of seizures from other movements, localize it accurately and for pre-surgical planning. Seizures can be recognized on EEG as a distinct electrophysiological change from the background that may or may not have a clinical correlate. Therefore, to recognize seizures, it is of utmost importance that you know what the background of the EEG is.
- 3. There aretwo patterns of seizures: 1) Metamorphic: Seizures that have an onset, offset, and evolution (defined as a change in the frequency and spatial spread). Generally, the change in the morphology alone of the waveform does not qualify as seizures. This the most common pattern seen in focal seizures. 2) Isomorphic: Here a single or run of epileptiform discharges produce clinical change without any evolution. Most commonly you will see in genetic generalized epilepsy. Ex: myoclonic jerks time- locked to 3 seconds of generalized spike and wave discharges. Or in childhood absence seizures, a 10 second run of 3 Hz generalized spike and wave discharges is associated with staring and unresponsiveness.
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- 6. Facts about seizures 1. For an electrographic seizure, the ictal activity must last a minimum of 10 seconds. The exception to this rule is when you have isomorphic seizures where a single spike and wave or epileptiform discharge produces a clinical correlate, which then becomes a seizure. 2. There are multiple clinical seizure types depending on their behavior change, however, the EEG changes are not always distinct in each type.
- 7. 3. TheEEG onset of seizures can be variable as below, however, barring some exceptions are not specific to the site of origin or type of seizure. • Rhythmic theta/delta/alpha • bullet • Low voltage fast beta activity • bullet • Diffuse attenuation • bullet • Irregular slowing (theta/delta) • bullet • Spike and wave discharges • bullet • Periodic discharges
- 8. Seizure classification: Seizurescan be classified based on their origin (focal vs generalized) and the behavioral changes associated with them. Please review the ILAE 2017 classification for seizures types which can be done with a combination of clinical features and EEG.
- 10. Seizures of FocalOnset Seizures of temporal lobe origin 1. Depending on the exact location of origin within the temporal lobe ( mesial, lateral, basal, or temporal pole), you can have different semiology and EEG onset patterns. 2. While no particular patterns are definitively suggestive of onset in a given area, seizures arising from the medial temporal region (hippocampus, entorhinal cortex) typically onset with rhythm theta (4-8 Hz) over the anterior temporal channels (F7/T3 or F8/T8) whereas neocortical onset seizures have onset with low voltage fast activity or delta pattern over the entire temporal chains /entire hemisphere or sometimes localized to the posterior temporal lobe (neocortical lateral)
- 11. 3. Thesemiology can vary as well. Typical medial temporal onset seizures will have an epigastric aura or Deja Vu sensation followed by oral automatism, behavioral arrest and may/may not be followed by secondary generalization to whole body. 4. Lastly, remember that focal seizure with retained awareness (eg. Deja Vu alone) may not have an ictal scalp EEG correlate or there may be subtle slowing (either focal or generalized).
- 12. Example of temporalseizures
- 13. Seizures offrontal lobe origin 1. Frontal lobe seizures can be variable as well depending on the onset location. The semiology often consists of hypermotor behavior, asymmetric tonic seizure or complex motor behavior. They tend to be nocturnal in nature. 2. They are notorious for not necessarily having a scalp EEG correlate since much of the medial and orbitofrontal lobe is located deep inside and located far away from scalp electrodes. Therefore observing the video in these cases is crucial is to make a definitive diagnosis.
- 14. 3. Frontallobe seizures often show rapid spread, appear bilateral onset, and can be difficult to lateralize. They can also show a phenomenon called "pseudo-lateralization" whereby the ictal rhythms are seen on the opposite side of the site of origin. Therefore, changing the montages and correlating semiology are critical in these patients.
- 15. Example of frontallobe seizure
- 17. Seizures ofoccipital lobe origin 1. Occipital onset epilepsy is the less common compared to the temporal and frontal lobe. 2. Seizures arising from the occipital lobe often have a visual aura which can be elementary (flashes of light) or more complex depending on the area of onset.
- 18. Example of occipitallobe seizure
- 20. Generalized Onset seizures •Generalized tonic-clonic • Tonic • Atonic • Myoclonic • Typical and atypical absence seizures 1. In generalized onset seizures, the EEG onset is widespread involving the bilateral cerebral hemisphere rapidly. 2. There are no lateralizing signs on semiology in most cases and no aura (with some rare exceptions). 3. Most often these present early in life in childhood, adolescence, and early adulthood.
- 21. Generalized Tonic-ClonicSeizure (GTC) GTC can be seen as patients with various epilepsy syndrome such as juvenile myoclonic epilepsy (ME), GTC upon awakening or Lenox Gastaut Syndrome (LGS).
- 22. Example of GTCEEG Generalized tonic seizure Tonic seizures of generalized onset are most commonly seen in Lenox Gastaut Syndrome however other types of static encephalopathy as well.
- 24. Generalized myoclonicseizure In myoclonic seizure, the patient has a brief jerk of the body/extremities/head. These seizures are typically seen as part of juvenile myoclonic epilepsy (JME) syndrome.
- 26. Generalized non-motor- Absence Seizure Typical absence seizure •Onset age 3-8 year of age with normal development, multiple sz per day •Prognosis: Good, resolves by teens
- 28. Reading material foryour exam: Wyllie’s Treatment of epilepsy, chapter 10, 11. Tatum WO. Handbook of EEG interpretation. Video EEG and adult seizures (chapter 8).
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