FRONTAL LOBE SEIZURE

Overview

The frontal lobe is the largest lobe. Seizures involving frontal lobe network have distinctive features depending on the area of the frontal lobe involved. Motor features are prominent and may be hyperkinetic (e.g. pelvic thrusting, bipedal kicking or pedalling) or asymmetric tonic in nature. The motor feature may not be the initial sign and the seizure may be a focal aware non-motor seizure with the prominent motor phase occurring a brief period after seizure onset. Seizures are typically brief overall, and can have prominent vocalization, bizarre behavior, urinary incontinence, and head and eye deviation. 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 awareness is impaired, focal impaired awareness seizures of frontal origin 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 focal motor seizures characterized by localized clonic, tonic-clonic, tonic or myoclonic activity. They may exhibit features of a Jacksonian march where unilateral tonic-clonic 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 focal somatosensory features alone, such as unilateral tingling, or in combination with motor features. Negative motor features such as focal atonic features may also occur.

2. Supplementary sensorimotor cortex

   Seizures are focal bilateral motor seizures 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 focal somatosensory seizure prior to onset of the motor features.

   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

   Impaired awareness, initial repetitive automatisms, olfactory hallucinations and illusions and autonomic features may be seen.

4. Frontopolar cortex

   Seizures may be characterized by forced thoughts, impaired awareness, ipsilateral head and eye version with possible progression to contralateral version, autonomic features and axial tonic-clonic 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 thoughts may be described.

6. Cingulate cortex

   Seizures are characterized by automatisms at onset with impaired awareness, emotion/mood and autonomic features. Focal emotional seizures with laughter (gelastic seizures) may occur.

7. Fronto-parietal operculum

   Seizures are characterized by mouth and tongue sensorimotor symptoms (which may evolve to the unilateral face), speech difficulty (dysarthria) and drooling. Autonomic (e.g. epigastric, urogenital, gastrointestinal, cardiovascular or respiratory), emotional (e.g. fear) and cognitive (e.g. gustatory) symptoms are 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.