Seizures: Semiology

by Roy Strowd, MD

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    00:01 So if that's how the seizures develop, how do seizures spread throughout the brain? Well typically seizures start in the gray matter in the cell bodies of the gray matter and spread along typical white matter tracts.

    00:15 And so the spread of the seizure is dependent upon where that seizure starts.

    00:20 With that being said, there's some typical zones that we tend to see that are related to seizure spread, that help us to evaluate patients clinically, and see the seizures with EEG.

    00:31 The smallest area, the initial seizure focus is called the ictal-onset zone.

    00:37 And this is the brain area that's resulting in the observed scalp EEG abnormalities that drive the seizure, this is where the seizure starts in the scalp or where the seizure starts on the brain.

    00:50 This is surrounded by a symptomatic zone, the area of brain surrounding that ictal-onset zone, this is typically gray matter that's responsible for the symptoms that the patient has at the onset of the seizure.

    01:04 That symptomatic zone is often the zone that contributes to aura formation.

    01:08 And what we ask patients about are here, when patients are describing their aura.

    01:13 This is surrounded by the functional-deficit zone, the area of surrounding brain that may be responsible for interictal clinical deficits, not the deficits during the seizure but the findings between seizures or interictally.

    01:26 And similarly, this is also the territory of brain that we call the irritative zone.

    01:32 The area of surrounding brain that may be responsible for the interictal EEG discharges.

    01:38 Those are spikes and waves that we look for in between seizures that tell us that this is where the seizure focus may be.

    01:44 We know that that area where the spike is coming from is a little bit bigger than actually where the seizure itself has started.

    01:52 And then lastly, we see the epileptic zones, the brain areas involved in seizure, generation and spread.

    01:58 And typically, that's the area, the smallest individual area where that seizure begins.

    02:04 That's that green area on the chart here, that's not something that we can see on EEG or even on MRI, but biochemically, that's where the seizure will start.

    02:15 We can use this information when we evaluate patients and that's when we're talking to patients throughout history, we're evaluating the seizure semiology, how the seizure begins, how it progresses and how it ends, and that semiology can tell us about where the seizure is starting can define some of those clinical zones.

    02:34 The seizure focus determines the seizure symptoms.

    02:36 And so seizures that begin in the primary sensory cortex present with paresthesias often not negative sensory findings but positive sensory findings, tingling or electric shock or electric discharges that occur in a region of the body.

    02:50 Seizures that begin in the primary motor cortex will cause clonic activity and that's movement of jerking of the arms or legs or face or a certain part of the body or tonic activity that will be a stiff and posturing.

    03:04 Tonic activity can also be seen from other frontal seizures.

    03:08 The frontal lobe is the motor lobe.

    03:10 And areas in the anterior frontal lobe are involved in planning motor movements, the supplementary motor area which we call the SMA is particularly susceptible to causing dystonic posturing of the body.

    03:23 And we can see that type of semiology from seizures from high frontal epileptic areas.

    03:30 Ictal vomit or vomiting during a seizure can come from the temporal lobe.

    03:35 We can also divide the sides of the brain into those that are associated with parasympathetic activity and the side of the brain with sympathetic activity.

    03:43 Typically, when we think of the left brain is being parasympathetic and the right brain is driving sympathetic activity.

    03:50 And so ictal spitting or urinary urge incontinence or urinary urgency is seen with left sided, medial temporal ictal onset or seizures.

    04:00 Olfactory auras, olfactory symptoms can be seen with bifrontal seizures or seizures in the orbital frontal cortices, on either side of the brain.

    04:08 Piloerection is seen in dominant hemisphere typically medial temporal lobe seizures.

    04:16 Déjà vu is a symptom we can see from seizures that develop from the lateral temporal lobe and that can be either temporal lobes.

    04:24 The dominant or non-dominant temporal lobes.

    04:27 Déjà vu is not uncommon aura for temporal lobe epilepsy, as you see here.

    04:32 In the medial temporal lobe again, either medial temporal lobes the right or left, we can see abdominal symptoms or rising nausea or abdominal fear.

    04:41 A fear that's associated with abdominal discomfort and that can be a symptom we see from seizures arising from the medial temporal lobes.

    04:50 About 60% of auras involve sensory symptoms.

    04:53 So sensory symptoms are extremely common and somewhere around 90% of patients with frontal lobe epilepsy will have contralateral dystonic posturing.

    05:01 So some of these frequencies can help us when we're evaluating patients.

    05:05 Fencing is a really cool posture that we can see with SMA (supplementary motor area) seizures.

    05:11 You think of someone who comes in and says, "I wake up at night in this fencing posture", or a bed partner may say that.

    05:18 They sound crazy and those actually can be seizures arising from the supplementary motor area.

    05:24 Early head tilting or head movement, early version of the head can be seen with seizures on the ipsilateral frontal lobe, whereas late head turning can be seen with seizures from the contralateral frontal lobe.

    05:37 So if the head early in the seizure is turning to the right, that may suggest a right frontal seizure onset.

    05:43 If the head is turning to the right late in the seizure process that suggests a left sided frontal onset.

    05:51 So you can see how we use the patient's symptoms to guide where the seizure may be coming from.

    05:55 And ultimately, if we consider seizure surgery, those symptoms and that localization is critical.

    06:01 Pain is thought to come from the contralateral sensory hemisphere.

    About the Lecture

    The lecture Seizures: Semiology by Roy Strowd, MD is from the course Seizures and Epilepsy.

    Included Quiz Questions

    1. The symptomatic zone is the area of gray matter that is responsible for aura symptoms.
    2. The epileptic zone can be visualized on EEG.
    3. The ictal onset zone is the smallest zone that pinpoints the seizure’s origin.
    4. The functional deficit zone of the brain is impacted during the ictal phase of a seizure.
    5. Irritative zone and symptomatic zone are different names for the same region.
    1. Seizures in the primary sensory cortex produce positive sensory findings.
    2. Seizures in the primary motor cortex produce negative sensory findings.
    3. Frontal lobe seizures do not cause motor symptoms.
    4. Right hemisphere seizures are more likely to cause parasympathetic symptoms.
    5. Lateral temporal lobe seizures result in abdominal discomfort and nausea.
    1. Temporal lobe
    2. Supplemental motor area
    3. Olfactory region of the frontal lobe
    4. Right hemisphere
    5. Occipital lobe

    Author of lecture Seizures: Semiology

     Roy Strowd, MD

    Roy Strowd, MD

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