Podcast
Questions and Answers
Which cortical areas are responsible for eliciting somatosensory auras with clear somatotopic distribution?
Which cortical areas are responsible for eliciting somatosensory auras with clear somatotopic distribution?
What is the location of the symptomatogenic zone for painful auras?
What is the location of the symptomatogenic zone for painful auras?
What is the significance of lateralizing auras in resective epilepsy surgery?
What is the significance of lateralizing auras in resective epilepsy surgery?
What is the relationship between the ictal onset zone and the epileptogenic zone?
What is the relationship between the ictal onset zone and the epileptogenic zone?
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What is the role of the supplementary sensorimotor area (SMA) in somatosensory auras?
What is the role of the supplementary sensorimotor area (SMA) in somatosensory auras?
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What is the significance of the symptomatogenic zone in seizure semiology?
What is the significance of the symptomatogenic zone in seizure semiology?
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What is the relationship between the epileptogenic zone and the symptomatogenic zone?
What is the relationship between the epileptogenic zone and the symptomatogenic zone?
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What is the importance of resecting the epileptogenic zone in resective epilepsy surgery?
What is the importance of resecting the epileptogenic zone in resective epilepsy surgery?
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What is the most likely cause of the primary motor area activation during seizures?
What is the most likely cause of the primary motor area activation during seizures?
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What is the significance of the last clonic activity in patients with temporal lobe epilepsy?
What is the significance of the last clonic activity in patients with temporal lobe epilepsy?
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What is the most likely explanation for unilateral dystonic posturing in temporal lobe epilepsy?
What is the most likely explanation for unilateral dystonic posturing in temporal lobe epilepsy?
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What is the characteristic feature of asymmetric tonic posturing during a GTC seizure?
What is the characteristic feature of asymmetric tonic posturing during a GTC seizure?
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What is the most likely lateralization of ictal spitting?
What is the most likely lateralization of ictal spitting?
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What is the location of the symptomatogenic zone in autonomic auras?
What is the location of the symptomatogenic zone in autonomic auras?
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What is the most common lateralization of ictal vomiting?
What is the most common lateralization of ictal vomiting?
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What is the predictive value of head and eye deviation for seizure localization?
What is the predictive value of head and eye deviation for seizure localization?
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What is the possible explanation for imobile limb (unilateral ictal akinesia) during seizures?
What is the possible explanation for imobile limb (unilateral ictal akinesia) during seizures?
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What is the most likely mechanism of late ipsiversion?
What is the most likely mechanism of late ipsiversion?
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What is the characteristic feature of unilateral dystonic posturing in temporal lobe epilepsy?
What is the characteristic feature of unilateral dystonic posturing in temporal lobe epilepsy?
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What is the significance of unilateral piloerection in seizure localization?
What is the significance of unilateral piloerection in seizure localization?
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What is the location of the symptomatogenic zone in genital sensations and orgasmic auras?
What is the location of the symptomatogenic zone in genital sensations and orgasmic auras?
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What is the significance of unilateral clonic activity in seizure localization?
What is the significance of unilateral clonic activity in seizure localization?
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What is the location of the frontal area involved in late ipsiversion?
What is the location of the frontal area involved in late ipsiversion?
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What is the significance of the right prefrontal cortex in orgasm?
What is the significance of the right prefrontal cortex in orgasm?
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What is the percentage of patients where unilateral eye blinking lateralizes to the ipsilateral hemisphere?
What is the percentage of patients where unilateral eye blinking lateralizes to the ipsilateral hemisphere?
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Which of the following is NOT a possible mechanism of ictal nystagmus?
Which of the following is NOT a possible mechanism of ictal nystagmus?
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In what percentage of patients does preservation of speech during complex partial seizures lateralize to the non-dominant hemisphere?
In what percentage of patients does preservation of speech during complex partial seizures lateralize to the non-dominant hemisphere?
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What is the likelihood of ictal aphasia being predictive of the dominant hemisphere involvement?
What is the likelihood of ictal aphasia being predictive of the dominant hemisphere involvement?
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What is the most likely theory for Todd's paralysis?
What is the most likely theory for Todd's paralysis?
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Which of the following brain regions is NOT involved in ictal speech arrest?
Which of the following brain regions is NOT involved in ictal speech arrest?
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What is the likely mechanism of postictal aphasia?
What is the likely mechanism of postictal aphasia?
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What is the characteristic of Todd's paralysis in rare cases?
What is the characteristic of Todd's paralysis in rare cases?
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What is the most common lateralizing post-ictal sign in patients with temporal lobe epilepsy?
What is the most common lateralizing post-ictal sign in patients with temporal lobe epilepsy?
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What is the speculated mechanism behind peri-ictal water drinking in patients with non-dominant temporal lobe epilepsy?
What is the speculated mechanism behind peri-ictal water drinking in patients with non-dominant temporal lobe epilepsy?
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Which of the following lateralizing post-ictal signs is more often associated with extra-temporal lobe epilepsy?
Which of the following lateralizing post-ictal signs is more often associated with extra-temporal lobe epilepsy?
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What is the characteristic of hypermotor seizures in terms of consciousness?
What is the characteristic of hypermotor seizures in terms of consciousness?
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What is the typical duration of hypermotor seizures?
What is the typical duration of hypermotor seizures?
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Which hemisphere is usually involved in postictal cough?
Which hemisphere is usually involved in postictal cough?
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What is the speculated mechanism behind postictal nosewiping in patients with temporal lobe epilepsy?
What is the speculated mechanism behind postictal nosewiping in patients with temporal lobe epilepsy?
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What is the typical time frame for peri-ictal water drinking in patients with epilepsy?
What is the typical time frame for peri-ictal water drinking in patients with epilepsy?
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Study Notes
Clinical Seizure Semiology: Helpful Hints for Lateralization and Localization
- Ictal discharges originate from the epileptogenic zone, which activates the symptomatogenic zone, producing clinical semiology.
- Resective epilepsy surgery is successful only if the epileptogenic zone is completely resected, and ictal semiology provides clues for lateralization and localization.
Auras
- Somatosensory auras:
- Elicited by activation of contralateral somatosensory cortex (Broadmann areas 3, 1, 2)
- Poorly defined paresthesias can also be seen with activation of the supplementary sensorimotor area (SMA)
- Usually lateralizing but not necessarily localizing
- Painful auras:
- Mostly contralateral to seizure onset
- Symptomatogenic zone is in the postcentral gyrus and parietal lobe
- Autonomic auras:
- Ictal piloerection is observed rarely (0.15% of patients undergoing vEEG monitoring studies)
- Unilateral piloerection or initially unilateral piloerection is usually ipsilateral to the seizure focus
- Symptomatogenic zone involves larger autonomic network including insula, amygdala, hypothalamus, and midbrain
- Genital sensations and orgasmic auras are observed more in women and with right TLE
Lateralizing Ictal Signs
- Head and eye deviation (version):
- Contralateral to seizure onset (90% to 100% of reported cases) if occurs immediately before secondary generalization
- Most likely caused by activation of FEF and motor areas to precentral gyrus (areas 6 and 8)
- Late ipsiversion:
- Late ipsiversion at the end of the GTC seizure is highly predictive of ipsilateral to seizure focus
- Most likely mechanism is exhaustion and inhibition of Broadman area 6 in the seizure onset hemisphere
- Unilateral clonic activity:
- Usually contralateral to seizure focus
- Most likely caused by activation of the primary motor area (Broadman area 4)
- Significance of last clonic activity:
- Few studies in patients with temporal lobe epilepsy revealed that last clonic jerk occurred ipsilateral to seizure onset in more than 80% of patients
- Possible theory explains this by metabolic or ischemic exhaustion, lack of neurotransmitters vs postictal inhibitory depression
- Unilateral dystonic posturing:
- A reliable lateralizing sign in temporal lobe epilepsy
- Almost always contralateral to seizure onset (>95% of patients)
- Most likely explanation is spread to ipsilateral basal ganglia (by some SPECT studies)
- Asymmetric tonic posturing:
- Striking asymmetry during the tonic phase of a GTC seizure
- One arm is rigidly extended at the elbow and opposite extremity is flexed at the elbow
- Also called “figure-of-4-sign”
- Extended elbow found to be contralateral to seizure onset (70 to 94% of patients)
- Immobile limb (unilateral ictal akinesia):
- Almost always contralateral in reported cases
- Most cases in literature are TLE cases
- Possible explanation is activation of the negative motor areas
- Ictal spitting:
- Almost always lateralizes to right (non-dominant) temporal lobe
- Exact mechanism is unknown but could be related to a release phenomenon or cortical activation phenomenon
- Ictal vomiting:
- Usually lateralizes to non-dominant hemisphere
- Rare left-sided cases were also reported
- Insula, mesial temporal structures, and also mesial frontal region were all associated with ictal vomiting
- Unilateral eye blinking:
- Lateralizes to the ipsilateral hemisphere (usually temporal) in 80-85% of patients
- Exact mechanism and symptomatogenic zone is unknown
- Ictal nystagmus:
- Often associated with seizures arising from posterior regions
- In almost every reported case, EEG changes were contralateral to the fast phase of the nystagmus
- Possible mechanisms:
- activation of cortical saccade areas
- activation of slow ipsiversive smooth pursuit regions
- activation of the cortical opto-kinetic regions and subsequently subcortical structures including nucleus of the optic tract
- Ictal speech:
- Preservation of speech during complex partial seizures usually lateralizes to the non-dominant hemisphere in >80% of patients
- Exact mechanism is unknown
- Ictal speech arrest (aphasia):
- Ictal aphasia can only be present in the conscious patient
- Suggestive but not predictive of the dominant hemisphere involvement (around 65%)
- Stimulation studies showed involvement of inferior frontal gyrus (Broca), supramarginal and superior temporal gyrus, and basal temporal area
Lateralizing Post-Ictal Signs
- Todd's paralysis:
- Always contralateral to seizure onset
- Most likely theory is “exhaustion of the primary motor areas”
- Rare cases of bilateral cases were also described in literature with suspected SMA involvement
- Postictal aphasia:
- Epileptogenic zone is in the language-dominant hemisphere
- Need to be differentiated from postictal confusion
- Likely mechanism is postictal exhaustion or active inhibition of language areas
- Postictal nosewiping:
- Defined as “wiping or rubbing of the nose during or within 60 seconds of seizure termination”
- Most common in patients with TLE and it is ipsilateral to seizure onset side in 75-90% of cases
- Exact mechanism is unknown:
- Activation of central autonomic network, especially amygdala, resulting in increased nasal secretions?
- Use of ipsilateral hand might be related to neglect or mild post-ictal paralysis?
- Postictal (ictal) cough:
- Can be observed during ictal or post-ictal period
- More often with temporal lobe epilepsy but can be seen with extra-temporal too
- Usually non-dominant hemisphere involvement
- Exact mechanism is unknown but postulated theories involve increased secretions or activation of the central autonomic system
- Peri-ictal water drinking (seeking):
- This behavior is described as “during a seizure or up to 2 minutes after seizure termination”
- Usually in patients with non-dominant temporal lobe epilepsy
- Speculated theory: Propagation of ictal discharges from mesial temporal structures to hypothalamus
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Description
Test your knowledge on lateralization and localization in clinical seizure semiology, including ictal discharges and epileptogenic zones. Helpful hints for resective epilepsy surgery.
