Clinical Seizure Semiology: Lateralization & Localization PDF

CLINICAL SEIZURE SEMIOLOGY: HELPFUL HINTS FOR LATERALIZATION AND LOCALIZATION Ekrem Kutluay, MD  Introduction Ictal discharges originate from epileptogenic zone. These discharges will activate symptomatogenic zone (either within the epileptogenic zone or adja...

CLINICAL SEIZURE SEMIOLOGY: HELPFUL HINTS FOR LATERALIZATION AND LOCALIZATION Ekrem Kutluay, MD  Introduction Ictal discharges originate from epileptogenic zone. These discharges will activate symptomatogenic zone (either within the epileptogenic zone or adjacent areas via spread) Activation of symptomatogenic zone will produce clinical semiology  Introduction Resective epilepsy surgery is only successful if epileptogenic zone is completely resected. Ictal semiology gives us many clues that would improve lateralization and localization of the epileptogenic zone. Literature suggests that patients with lateralizing auras had better outcomes after surgery than without lateralizing ones.  Introduction However, it is very important to remember that semiology only reflects involvement of symptomatogenic zone. Although, the ictal onset zone may lie in the epileptogenic zone (partially or completely), ictal discharges might start in silent areas and may only produce symptoms when they spread and reach different cortical areas.  Auras Somatosensory Auras – SAs with clear somatotopic distribution are 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). Auras Somatosensory auras  Auras Somatosensory Auras – Activation of the superior bank of the Sylvian fissure may also produce SAs, however, these are usually distal and frequently bilateral. – Usually lateralizing but not necessarily localizing  Auras Painful auras – Painful auras are also mostly contralateral to seizure onset. – Symptomatogenic zone is in the postcentral gyrus and parietal lobe. – In patients with temporal lobe epilepsy, sometimes activation of secondary somatosensory area can cause ipsilateral sensation.  Auras Auditory auras – Hallucinations of simple sounds are usually indicative of Heschl gyrus (Broadmann 41 and 42) involvement. – Complex sounds (hearing voices or tunes) usually involves auditory association cortex (42 and sometimes 22-also known as auditory association area-) – Usually lateralized to the contralateral side or not clearly lateralized. Auras Auditory Auras  Auras Auditory auras – Unilateral ear plugging is also described. – Not clear if it is purely auditory in nature. – Cases were lateralized to contralateral temporal lobe (auditory cortex?)  Auras Olfactory auras – Strong localization to the mesial temporal structures. Usually involves amygdala. – Involvement of orbitofrontal cortex or insula also can lead to olfactory auras. – Non-lateralizing. Auras  Auras Gustatory auras – Usually produced by activation of parietal operculum, mesiobasal temporal lobe, insula. – Hard to differentiate from olfactory auras. – Non-lateralizing.  Auras Visual auras – Simple visual auras (static or moving lights, scotomas) are strong indications of occipital seizures (Broadman 17, 18. 19). – Simple visual auras with limited movement (static) are usually elicited by stimulation of area 17 (V1, primary visual cortex). Prominent movement suggests activation of areas 18-19 (visual association cortex). Auras  Auras Visual auras – Homonymus hemifield defects can lateralize seizure focus to contralateral hemisphere. – Restricted defects to upper or lower quadrants localize to contralateral infra- or supra-calcarine cortex.  Auras Visual auras – Complex visual hallucinations (people, scenes) are suggestive of temporo-occipital junction activation. – Visual distortions like macropsia, micropsia or metamorphopsia usually suggests activation of geniculostriate radiation. Auras  Auras Abdominal auras – Most common aura in patients with mesial temporal seizure origin. – Symptomatogenic zone is generally located in the insula. – In rare cases, frontal operculum or SMA is also involved. – Some literature suggests that if an abdominal aura evolves into complex partial seizure with oral and manual automatisms, increases the probability of TLE over 90%.  Auras Psychic auras – Can include emotional symptoms (fear, anxiety, impending doom, euphoria) or distortions of familiarity (déjà vu/jamais vu). – Fear is most characteristic activation of the amygdala but can also be seen with hippocampus or mesial frontal involvement. Auras  Auras Psychic auras – Déjà vu/jamais vu sensations are most commonly associated with the activation of uncus, enthorhinal cortex or temporal neo-cortex. – Out-of-body experience usually involves stimulation of the temporo-parietal junction.  Auras Vertiginous sensation – This includes sensation of rotation or movement in different planes. – True vertigo at the seizure onset is NOT a feature of mesial temporal epilepsy. – Possible symptomatogenic zone is temporo- parietal junction.  Auras Autonomic auras – Cardiorespiratory (palpitations, SOB), GI, genitourinary (genital sensations, urinary urge) or cutaneous (feeling warm or cold). – Elicited by activation of a number of cortical areas, including particularly the insula, anterior portion of the cingulate gyrus and the SMA.  Auras Autonomic auras – “Abdominal aura” is also type of autonomic aura. When associated with vomiting, it is suggestive of non-dominant temporal lobe. – “Ictal urge to urinate” usually signifies non-dominant hemisphere involvement. Symptomatogenic zone is in the mesial frontal region or in the medial temporal gyrus and the operculum.  Auras 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.  Auras Autonomic auras – ‘Genital sensations and orgasmic auras” are observed more in women and with right TLE. – This right sided theory is also supported by an increase in blood flow in the right prefrontal cortex in men during orgasm. – Symptomatogenic zone is usually located in the right mesiotemporal and frontal areas, likely involving amygdala.  Lateralizing Ictal Signs Head and eye deviation (Version) – “Forced and involuntary movement resulting in sustained unnatural positioning”(Wyllie, 1986) – Contralateral to the seizure onset (90% to 100% of the 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).  Lateralizing Ictal Signs Late ipsiversion – Late ipsiversion at the end of the GTC seizure (after initial contraversion) is also highly predictive of ipsilateral to seizure focus. – Most likely mechanism is exhaustion and inhibition of the Broadman area 6 in the seizure onset hemisphere and predominance of the discharges resulting in the activation of the frontal area in the hemisphere contralateral to seizure onset.  Lateralizing Ictal Signs Unilateral clonic activity – Usually contralateral to seizure focus. – Most likely caused by activation of the primary motor area (Broadman area 4)  Lateralizing Ictal Signs 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 the patients. – Possible theory explains this by metabolic or ischemic exhaustion, lack of neurotransmitters vs postictal inhibitory depression. This mechanism might end seizures more commonly in the hemisphere where it started.  Lateralizing Ictal Signs Unilateral dystonic posturing – A reliable lateralizing sign in temporal lobe epilepsy. – Almost always contralateral to the seizure onset (>95% of the patients). – Most likely explanation is spread to ipsilateral basal ganglia (by some SPECT studies)  Lateralizing Ictal Signs 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 the patients).  Lateralizing Ictal Signs 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  Lateralizing Ictal Signs 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 like in other oro-alimentary automatisms.  Lateralizing Ictal Signs 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.  Lateralizing Ictal Signs Unilateral eye blinking – Lateralizes to the ipsilateral hemisphere (usually temporal) in 80-85% of the patients. – Exact mechanism and symptomatogenic zone is unknown.  Lateralizing Ictal Signs Ictal nystagmus – Some consider it as a form of versive seizures. – 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.  Lateralizing Ictal Signs Ictal speech – Preservation of speech during complex partial seizures usually lateralizes to the non-dominant hemisphere in >80% of the patients. – Exact mechanism is unknown.  Lateralizing Ictal Signs 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 the bilateral cases were also described in literature with suspected SMA involvement.  Lateralizing Post-Ictal Signs Postictal aphasia – Epileptogenic zone is in the language-dominant hemiphere. – Need to be differentiated from post-ictal confusion. – Likely mechanism is postictal exhaustion or active inhibition of language areas.  Lateralizing Post-Ictal Signs 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 the 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?  Lateralizing Post-Ictal Signs 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.  Lateralizing Post-Ictal Signs 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.  Complex Motor Phenomena Hypermotor seizures Complex motor movements affecting proximal body parts. Appears violent in some cases. Preserved consciousness is common and duration is usually