Focal Impaired Awareness Seizure

The 2017 classification by the International League Against Epilepsy has categorized seizures based on 3 key features: the location of seizure onset, level of awareness during a seizure, and other features of seizures. Focal impaired awareness seizures refer to focal seizures that start in one hemisphere of the brain and are associated with impairment in consciousness. Formerly known as "complex partial seizures," they are now called "focal impaired awareness seizure" or "focal onset impaired awareness seizure" and are typically referred to as a "focal onset seizure." Focal onset seizures refer to epileptiform activity starting in one area on one side of the brain. If awareness is impaired or affected at any time during the seizure, it is called a focal impaired awareness seizure. Focal seizures are further classified into: : Motor onset (automatisms, atonic, clonic, myoclonic, tonic, epileptic spasms, hyperkinetic) . Nonmotor onset (autonomic, emotional, sensory, cognitive, behavior arrest) . A seizure that starts on one side or one part of the brain and then spreads to both sides, previously referred to as secondarily generalized seizures, is now preferably termed a "focal to bilateral seizure." Focal onset impaired awareness seizures can present with or without an aura. Auras can last from a few seconds to 1 to 2 minutes before consciousness is impaired. Consciousness is maximally impaired in the beginning. Most of the seizures with automatisms will last longer than 30 seconds, up to 1 to 2 minutes, and sometimes can be as long as 10 minutes. Absence seizures can occasionally present with the same symptomatology; however, ictal electroencephalogram (EEG) will show generalized 3-Hz spike-wave complexes. The characteristic feature of the focal impaired awareness seizure is impaired awareness, referring to decreased overall arousal and responsiveness. Symptoms of focal onset seizures with impaired awareness depend on the area of the brain it is arising from. Simple responses like visual tracking may be preserved in focal impaired awareness seizures; however, higher-order processing tasks like verbal response decision-making are profoundly impaired. Most focal impaired awareness seizures originate in the temporal lobe, although extratemporal origin has been reported in at least 10% to 30% of patients. Temporal lobe seizures are the most common type of focal impaired awareness seizures. Stereotyped automatisms occur in about 40% to 80% of patients with temporal lobe epilepsies. Seizures with predominantly oral and manual automatism and some other motor manifestations suggest temporal lobe origin. About 60% of temporal lobe seizures spread to involve both cerebral hemispheres. Gradual recovery after several minutes of confusion occurs postictally in most patients; however, in some patients, automatic behavior like running or walking about and non-directed violent behavior may occur. Temporal lobe focal impaired seizures can have features similar to frontal seizures, but temporal lobe focal impaired seizures typically have slower onset and progression and with more pronounced confusion. Certain features can help in localizing the seizure onset to 1 hemisphere. Ictal vomiting, ictal speech, urinary urge, and automatisms with intact consciousness suggest seizure onset in the non-dominant hemisphere, and speech disturbance postictally is suggestive of seizure onset in the dominant hemisphere. Upper limb dystonia lateralizes seizure to the opposite hemisphere. In young children with focal seizures of temporal lobe onset, behavioral arrest and unresponsiveness are common. Oroalimentary automatisms tend to occur in children older than 5. The symmetric motor movement of the limbs and head nodding is typical in younger children. In infants, these seizures may be subtle with few automatisms. In very young infants, central apnea can occur. Temporal focal impaired seizures can be confused with absence seizures as both may have automatisms, but temporal seizures are usually more prolonged and are associated with postictal confusion. Seizures arising from the medial temporal lobe are characterized by auras such as epigastric sensation, deja vu, a feeling of fear, and unpleasant smells. Autonomic features like tachycardia, flushing, and pallor are common. Auras may be followed by impaired awareness and oroalimentary automatisms. Automatisms in the upper limb with or without unilateral pupillary dilatation may lateralize the seizure to the ipsilateral hemisphere. Dystonia in the upper limbs, head, and eye version on the opposite side can occur. Lateral temporal seizures may have vertigo, auditory (buzzing, ringing), or visual symptoms as initial aura symptoms. An auditory aura in only one ear may lateralize a seizure to the contralateral hemisphere. Initial aura is usually not prolonged, and impaired awareness is an early feature. Seizures are of shorter duration, and progression to bilateral convulsions is more common than those arising from the medial temporal lobe. Up to 30% of the patients with focal epilepsy have seizures arising from the frontal lobe; therefore, this is the most common extratemporal type. Seizures are accompanied by loss of consciousness in about half of the patients with frontal lobe epilepsy. Focal impaired awareness seizures can arise from various locations within the frontal lobe, except the rolandic strip. These seizures typically are brief, lasting about 30 seconds, occurring in clusters multiple times a day, are often nocturnally occurring during sleep, and have minimal postictal confusion. Motor symptoms are predominant and range from hypermotor thrashing episodes like pelvic thrusting and bicycling movements to asymmetric tonic posturing. Sexual automatisms, bizarre behavior, and vocalizations are common. These seizures often have a stereotypical pattern for each patient. Nocturnal frontal lobe seizures may be mistaken for parasomnias. The ictal EEG may be difficult to interpret because of movement artifacts. Identification based on semiology alone and differentiating from mesial temporal lobe epilepsy may be difficult; however, earliest signs and symptoms and their order of appearance may help in distinction. Seizures with hypermotor features are more likely to have an ictal focus in the orbitofrontal and frontopolar regions. Temporal lobe seizures have more oroalimentary automatisms, gesturing, and fumbling semiology. Epileptiform activity in frontal convexity can cause clonic seizures, and can cause tonic seizures in the supplementary motor area. Unique semiology of the supplementary sensorimotor cortex includes deviation of head and eye to the side contralateral to seizure onset, the asymmetrical posturing of upper limbs with an extension of arm contralateral to the side of seizure onset, and flexion of the ipsilateral arm. Orbitofrontal region seizures are auto-motor type and manifest prominently with autonomic phenomena like flushing, vocalization, and automatisms. Anterior cingulate gyrus seizures have predominant motor manifestations like hypermotor seizures and complex motor seizures. Posterior cingulate cortex epilepsies predominantly have altered consciousness and automotor seizures as the main clinical manifestations. Antero-lateral dorsal convexity seizures may manifest with auras such as dizziness, epigastric sensation, behavioral arrest, and speech arrest. Seizures from the parietal lobe may be difficult to diagnose because of their subjective nature. Sensorimotor phenomenon and vestibular hallucinations suggest onset in the parietal lobe. Positive and/or negative sensory features are common. Paresthesias, visual hallucinations, visual illusions, somatic illusions, and vertiginous features can occur. Seizures arising from the dominant hemisphere can cause receptive language impairment. Parietal lobe focal impaired awareness seizures can have auras like epigastric sensations, visual hallucinations, panic attacks, and behavioral arrest. Often, there is an involvement of other lobes as the seizure spreads. When focal seizures from the parietal lobe spread and involve the temporal lobe, loss of consciousness and automatisms may occur. A visual aura characterizes seizures with ictal origin in the occipital lobe but is difficult to diagnose, especially in young children. Visual auras, typically of elementary sensations, ictal blindness, versions of the head and eyes to the opposite side, rapid and forced blinking, and oculoclonic activity are some features suggesting the occipital lobe as an origin of focal seizure with impaired consciousness. Seizures from the primary visual cortex can cause bilateral vision loss in the form of white-out or black-out. A shorter duration of the visual aura (less than 2 minutes) can help to differentiate from a migraine aura, which is typically longer (5-15 minutes). Complex-formed visual hallucinations, like pictures of people, animals, etc., are associated with seizure onset in the extra-striate cortex. Other symptoms may result from the spread of the seizure to the temporal or parietal lobes. Seizures arising from the insula can mimic frontal, temporal, and parietal lobe seizures. Origin from the insula is suspected when viscerosensitive symptoms (nausea, vomiting, salivation), motor symptoms (tonic, hypermotor, or generalized tonic-clonic movements), and/or sensory symptoms (numbness, tightness, vibration, pain, vertigo) occur at seizure onset.