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FRONTAL

Overview

The frontal lobe is the largest lobe and gives rise to seizures with distinctive features depending on the area of the frontal lobe involved. Motor features are prominent and range from hypermotor thrashing attacks with pelvic thrusting and bipedal automatisms to asymmetric tonic posturing. Frontal lobe seizures may begin with a brief aura, even when seizures occur from sleep. Seizures are typically brief, and can have prominent vocalization, bizarre behavior, urinary incontinence, and head and eye deviation. Frontal lobe seizures may be exclusively nocturnal and often cluster. The ictal EEG may not show ictal patterns or may be obscured by movement artifact.


CAUTION When consciousness is impaired, frontal dyscognitive seizures can be difficult to distinguish from absence seizures.


CAUTION Nocturnal frontal lobe seizures can be mistaken for parasomnias, however:


  • Frontal lobe seizures are usually brief events (< 2 minutes), with stereotyped features seen from seizure to seizure and preserved awareness. Parasomnias are usually longer in duration (> 10 minutes), have variable features from event to event and are characterized by a confusional state with the patient having no memory of the event afterwards.
  • In parasomnias, clustering is rare and the common non-REM parasomnias typically occur 1-2 hours after falling asleep, in the first cycle of deep slow wave sleep. Nocturnal frontal lobe seizures typically occur throughout the night, and more frequently within half an hour of falling asleep or awakening.

CAUTION Frontal lobe seizures may be mis-diagnosed as non-epileptic seizures as there may be bilateral motor phenomena with preserved awareness, and the ictal EEG can be normal.


Subtypes of frontal lobe seizures

  1. Primary sensorimotor cortex

    Seizures are characterized by localized convulsive, tonic or myoclonic activity. They may exhibit features of a Jacksonian march where unilateral convulsive movements start in one muscle group and spread systematically to adjacent groups reflecting the spread of ictal activity through the motor cortex according to the homunculus. There may be sensory features alone such as unilateral tingling, or in combination with motor features. Negative motor features such as atonic features may also occur.

  2. Supplementary sensorimotor cortex

    Seizures are characterized by an abrupt onset and offset of asymmetric tonic posturing, lasting 10-40 seconds with minimal postictal confusion. Asymmetric posturing of the upper limbs occurs, with extension of the upper limb contralateral to the hemisphere of seizure onset and flexion of the ipsilateral upper limb. Loud vocalization or speech arrest can occur at seizure onset. The head and eyes are often turned to the side contralateral to the hemisphere of seizure onset. There may be a somatosensory aura.

    CAUTION The supplementary sensorimotor area is highly connected to other brain regions and asymmetric posturing may be seen in seizures from other regions through rapid spread to the supplementary sensorimotor area.

  3. Orbitofrontal cortex

    Dyscognitive features, initial repetitive gestural automatisms, olfactory hallucinations and illusions and autonomic signs may occur.

  4. Frontopolar cortex

    Seizures may be characterized by forced thoughts, dyscognitive features, initial ipsilateral head and eye version with possible progression to contralateral version, autonomic features and axial convulsive movements resulting in falls.

  5. Dorsolateral frontal cortex

    In the dominant hemisphere, a seizure occurring in or near Broca's area can result in aphasia or dysphasia in a patient who is otherwise awake and responsive. Motor features occur, most commonly tonic features, and are accompanied by contralateral head and eye version. 'Forced thinking' or 'forced acts' may be described.

  6. Cingulate cortex

    Seizures are characterized by gestural automatisms at onset with loss of awareness, affective aura and autonomic features. Gelastic automatisms can occur.

  7. Fronto-parietal operculum

    Seizures are characterized by facial (mouth and tongue) clonic movements (which may be unilateral), laryngeal symptoms, articulation difficulty, swallowing or chewing movements and hyper-salivation. Sensory (e.g. epigastric) and experiential (e.g. fear) aura and autonomic (urogenital, gastrointestinal, cardiovascular or respiratory) features are common. Gustatory hallucinations are particularly common.

    NOTE the terms fronto-parietal opercular, centrotemporal, sylvian and rolandic seizures are synonymous, referring to seizures involving the region around the central sulcus, particularly in the lower central sulcus.

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