A seizure is a symptom that refers to episodic, excessive and disorderly neuronal activity in the brain. Traditionally seizures have been classified into partial and generalized. Partial seizure refers to abnormal neural activity localized to one area of the cerebral hemisphere and having a discernible focal or localized onset. When there is no associated impairment in consciousness, it is called simple partial seizure, and when it is associated with impairment in consciousness, it is called a complex partial seizure. When a partial seizure becomes generalized, it is referred to as a "partial seizure with secondary generalization." New terminology for a simple partial seizure is "focal onset aware seizure."
Partial seizures are the most common type of seizures in patients with epilepsy. Complex partial seizures occur more often than simple partial seizures, although most complex partial seizures start as simple partial seizures.
Patients with simple partial seizure remain awake and aware throughout the seizure, and some patients can even talk during the episode. It may be difficult to distinguish them from complex partial seizure in infants and patients with cognitive and speech difficulties, as impairment in consciousness can be difficult to assess in these patients.
The term "aura" refers to signs and symptoms that occur with a seizure before consciousness is lost and for which memory is intact afterward. Auras that are not followed by seizure should be considered focal aware seizures or simple partial seizures.
Depending on clinical signs, symptoms, and EEG localization, focal seizures can be further subdivided into four types: (1) focal motor seizures, (2) focal sensory seizures, (3) autonomic seizures, and (4) psychological seizures.
Focal Motor Seizures
Focal or partial motor seizure occurs due to an epileptogenic lesion on the contralateral frontal lobe. Motor symptoms constitute the primary clinical manifestation. Typically, consciousness is not impaired in seizures of discrete motor areas. They usually originate from the supplementary motor area and cause turning movements of head and neck to the opposite side and sometimes tonic contractions of the limbs and trunk on the same side. This may or may not be followed by generalized clonic movements. Subdivisions of ictal motor symptoms include elementary (tonic, clonic, dystonic, versive) and automatism (coordinated, repetitive motor activity like lip smacking, tapping, and swallowing). Another classification based on clinical symptomatology uses the terms like focal clonic, focal tonic, or versive seizures.
Focal motor seizures are more common on the face, hands, and toes because these areas have disproportionately large cortical representation. The excitatory focus is usually around the rolandic (motor) cortex. If there are accompanying sensory symptoms, the focus may be on post-rolandic convolution. Temporal lobe origin seizures sometimes have head-turning movements on the same side followed by the forceful contraversive turning of the head and body.
Following convulsions with predominant focal motor symptoms, patients may have transient, functional, and localized paralysis of the affected limbs. This is known as Todd paralysis and can last minutes to hours, usually in proportion to the duration of the convulsion. This postepileptic paralysis occurs due to persistent focal dysfunction of the affected epileptogenic area and is the signature of a focal seizure. It has significant clinical value in lateralizing the hemisphere of seizure onset.
Jacksonian march seizure
Jacksonian march seizure starts with tonic contractions in one hand or on one side of the face or the muscles of one foot. This is followed by clonic movements in these parts and sometimes a series of clonic movements with increasing frequency that builds up to a tonic contraction. These movements may spread ("march") from the muscles affected to the other muscles on the same side of the body. In classic Jacksonian march, the seizure spreads from hand to arm to face and then down the leg ipsilaterally, or if it started in the foot, then seizure marches up the leg, down the arm, and then to the face. This typically happens over a short time (20 to 30 seconds). There can be other associated symptoms like automatism (lip smacking or tapping movements), hallucinations, muscle cramping, head-turning, etc. Symptoms are usually mild. These seizures rarely become generalized, and typically consciousness remains intact. Jacksonian march seizure can be mistaken for a transient ischemic attack, migraine, or other condition.
Focal Somatosensory Seizures
Sensory seizures present as numbness, tingling, crawling sensation, "pins and needles" feeling, and rarely, as pain or thermal sensations. They can be focal or can march to other ipsilateral body parts and usually have focus in or around post-rolandic convolution of the contralateral cerebral hemisphere.
Autonomic seizures manifest with predominantly altered autonomic function. Some common autonomic signs and symptoms include diaphoresis, shivering, piloerection, rising sensation in epigastrium, nausea, changes in blood pressure and heart rate (commonly tachycardia), and pupillary changes. Autonomic features are common in several nonepileptic conditions, making autonomic seizures harder to diagnose.
Some specific epilepsy syndromes with prominent autonomic features include neonatal seizures, epilepsy of infancy with migrating focal seizures, Dravet syndrome, benign epilepsy with centrotemporal spikes, and early-onset benign occipital epilepsy.
Psychological seizures manifest with affective and cognitive symptoms like memory flashback, dream-like events, Deja Vu feeling, hallucinations, anxiety, agitation, and uncontrolled laughter or crying. They arise commonly from the temporal area rather than extratemporal.
Etiology of seizures can sometimes be difficult to find. Some known causes of seizures include the following:
Seizures can be brought on by certain situations or triggers. Some common triggers include tiredness and lack of sleep, stress, alcohol, fever, acute medical illness, substance abuse, and medication noncompliance.
A common cause of seizures in childhood is a perinatal hypoxic brain injury. In adolescents, seizures are most commonly caused by head trauma and encephalitis. Brain tumors are the most common etiology of seizures in middle-aged adults, and vascular dementia and encephalopathies are the most common etiology in older adults.
After the first year of life, partial seizures are the most common seizure type in patients with epilepsy. The incidence of all partial seizures is approximately 20 cases per 100,000 population between the age of 1 to 65 years in the United States. It is estimated that around 6% to 12% of patients with epilepsy have simple partial seizures; these are frequently associated with other types of seizures. There is no reported predilection for gender, race, or ethnicity. Incidence has been increasing in older people, especially those with cerebrovascular disease.
Seizures are caused by episodic, excessive, and disorderly neuronal activity in the brain. Ordinarily, electrical impulses are transmitted by action potential that involves a net positive inward ion influx causing depolarization in the neurons. Hyperexcitability is usually prevented by several inhibitory mechanisms, involving negative ions like chloride ions and inhibitory neurotransmitters. Alteration in voltage-gated ion channels is causing increased excitatory and decreased inhibitory transmission cases hyperexcitability. Glutamate is the primary excitatory neurotransmitter in brain and GABA, the inhibitory. Excitation of neurons along with too little inhibition causes hyperexcitability. Epileptic focus along with hyperexcitability and hyper-synchronization of neurons causes seizure.
As with any other type of seizure, it is most important to make sure that the episode is, indeed, a seizure. Detailed history from the patient and family members is important.
Diagnosing a simple partial seizure can be difficult, especially when sensory, autonomic, or psychic symptoms are predominant. Suspicion of simple partial seizure is based on typical history and reproducible patterns with known simple partial seizure types. A neurological examination may or may not show subtle focality. Some patients may have postepileptic paresis (Todd paralysis). Examination during a seizure is helpful to assess consciousness. The patient should be able to follow simple commands and remember the events postictally to make a diagnosis of simple partial seizure. Simple commands like moving extremity on both sides, repeating a two syllable command will help assess responsiveness. Some patients with motor manifestations may not be able to perform a motor task but remember the instructions postictally; this should be interpreted as intact responsiveness.
Symptoms depend on the area involved.
Clinical data alone is often not enough to precisely diagnose and localize focal seizures. Scalp and intracranial EEG may be needed to diagnose accurately. EEG done after the suspected seizure episode may be normal or nonspecific. MRI head is required to identify the underlying etiology
Seizure characteristics that favor an epileptic diagnosis include younger age at onset, stereotyped patterns of movements, shorter duration of seizures, nocturnal occurrence and presence of MRI, and EEG abnormalities.
In general, patients suffering from partial seizures of unknown etiology or of structural origin should be treated with antiepileptic drugs.
Focal seizures caused by non–neurological pathologies like infections and electrolyte imbalance are managed by treating the underlying etiology. It is important to know if the seizure fits into a particular type of epilepsy or epilepsy syndrome in order to decide treatment and determine prognosis.
Appropriate seizure medication is chosen based on the type of seizure, side effect profile of the medication, the age of the patient, use of other medications and co-morbid medical conditions. Carbamazepine and lamotrigine are the first-line antiepileptic drugs (AED) for simple partial seizures. Alternative first-line drugs include valproate, oxcarbazepine, and levetiracetam. One of these medications should be considered if the other two are not tolerated or can not be used. If the first AED is ineffective or not tolerated, then another AED of these five drugs should be considered. If the second AED is also not effective, then adjunctive therapy is added. Adjunctive therapy for focal seizures includes carbamazepine, lamotrigine, levetiracetam, oxcarbazepine, sodium valproate, gabapentin, topiramate, and clobazam. If adjunctive therapy is also not effective or not tolerated, then referral to a tertiary epilepsy center should be considered, where other AED may be tried.
AEDs can control seizures in about two-thirds of epilepsy patients. The ketogenic diet can help control seizures in some children. It is a specialized high fat, low carb and controlled protein diet, that should be considered in children with intractable seizures when at least two AEDs have been ineffective.
Vagus nerve stimulation
Vagus nerve stimulation (VNS) involves an electric stimulator inside the body that connects to the left vagus nerve in the neck. It helps to calm down the irregular electrical activity in the brain. It can reduce the frequency, severity, and length of seizures. VNS therapy should be considered in patients whose seizures are not controlled with AEDs and are not candidates for surgery. Antiepileptic effects of VNS therapy may take up to two years, and AED should always be used along with it. If VNS therapy is effective, it may be possible to reduce the medications slowly.
Surgery should be considered for refractory seizures where a specific area of the brain is responsible for causing seizures. Surgery involves removing or separating the specific area of the brain causing seizures.
Some conditions that initially can present like simple partial seizures include the following:
Absence seizures, hemifacial spasm, benign childhood epilepsy, Migraine variants, transient ischemic attack, hypoglycemia, cervical disc problems, myoclonus, panic attacks, and psychosis.
Patients with partial seizures have a higher risk of seizure recurrence than those with generalized seizures. However, recurrence rates of simple and complex partial seizures appear to be the same. Risk of seizure-related complications like aspiration, and overall morbidity and mortality are lower in simple partial seizures than in those where consciousness is impaired.
Simple partial seizures can result in falls and trauma. Uncontrolled or poorly controlled seizures can cause chronic neurological and cognitive impairment. Prognosis of simple partial seizure is believed to be similar to that of complex partial seizure and is dependent on the underlying etiology of seizures.
Some special focal epileptic syndromes include the following:
Benign Epilepsy with Centrotemporal Spikes
Benign Epilepsy with Centrotemporal Spikes (BECTS) is a benign form of focal motor epilepsy in children, featuring centrotemporal spikes. It accounts for 6% to 10% of all childhood epilepsies. The age of onset is 3 to 13 years with a peak at 7 to 8 years. It is more common in boys. Some reports suggest autosomal inheritance. Centrotemporal spikes are characteristic of BECTS but not pathognomic, as they can be seen in more complex epilepsy syndromes as well. Seizures typically occur during sleep, either shortly after falling asleep or just before awakening. Classically, the unilateral lower face is involved with facial twitching, paresthesia, and dysarthria. Hemi convulsions may occur, especially in young children. They can rarely become generalized. The seizures are brief, occurring in clusters, followed by prolonged seizure-free intervals. Typical EEG findings are high amplitude diphasic spike or sharp waves with prominent aftercoming slow waves in the contralateral centrotemporal area. BECTS have an excellent prognosis, and most children achieve remission by puberty regardless of antiepileptic drug therapy. Pharmacotherapy is usually not needed in the majority of cases. Anti-seizure drugs like valproate may be used in severe cases or with frequent symptoms.
Early-Onset Benign Occipital Epilepsy
Also known as panayiotopoulos syndrome, early-onset benign occipital epilepsy accounts for 1% to 2% of children with focal epilepsy. The age of onset is 3 to 8 years with a peak at 5 years. It is more common in girls. Seizures are almost always nocturnal and present with autonomic symptoms, most commonly nausea and vomiting. The seizure frequently lasts longer than 30 minutes, and about one-third of patients may develop focal status epilepticus. Early-onset benign occipital epilepsy may evolve into generalized seizures, and consciousness may be impaired. Ictal EEG shows rhythmic theta or delta activity with intermixed spikes that start posteriorly. Most children have occasional seizures and do not require pharmacological treatment.
Late-Onset Benign Occipital Epilepsy
Late-onset benign occipital epilepsy is also known as Gastaut type epilepsy. It presents in mid to late childhood with a peak age of eight years. It manifests as frequent, often more than 15, brief visual seizures mostly visual hallucinations or blindness. Typically, there is no impairment in consciousness unless there is a secondary generalization.
Epilepsia Partialis Continua
Epilepsia partialis continua is also known as partial continuous epilepsy and represents a type of focal motor status epilepticus. It is characterized by continuous rhythmic or semi rhythmic clonic movements of one muscle group that remain localized and continue for hours, days, weeks, or months without spreading to other parts of the body. Any muscle group can be affected, but distal musculature is more commonly affected. They may develop at any age. Several acute or chronic cerebral lesions may cause these partial seizures. These seizures are often mistaken for slow tremors or movement disorders. They are particularly common in Rasmussen syndrome. This type of seizure activity responds poorly to AEDs, and all patients should be evaluated for an underlying lesion that may be amenable to surgical treatment.
Supplementary Sensorimotor Seizures
These seizures originate from the supplementary sensorimotor area (SSMA) and are characterized by rapid onset, asymmetrical posturing involving one or more extremities. Typically, both sides of the body are affected. These seizures are usually brief, lasting 10 to 40 seconds, but may be frequent, occurring in clusters. SSMA seizures tend to occur during sleep. Speech arrest and vocalization can happen during these episodes. Consciousness is typically preserved. Only a few patients who experience SSMA seizures actually have SSMA epilepsy. These seizures can get misdiagnosed as nonepileptic or psychogenic seizures because the involvement of all extremities with preserved consciousness can be misleading.