Overview of Epilepsy
Epilepsy is a clinical syndrome of highly synchronized abnormal discharges of neurons in the brain due to multiple causes. It is clinically characterized by convulsions of the limbs and/or loss of consciousness, in addition to sensory, psycho-behavioral, and autonomic disorders, and is episodic, transient, stereotyped, and recurrent in nature. The clinical process of each seizure is called epileptic seizure. In epilepsy, a specific epileptic phenomenon with a specific etiology and consisting of specific signs and symptoms is called epileptic syndrome.
Etiology
The causes of epilepsy are extremely complex and can be categorized into three main groups according to their causes. Those with known causes are called symptomatic or secondary epilepsies; those with unknown causes that may be genetically related are called idiopathic epilepsies; and those with clinical manifestations suggestive of symptomatic epilepsies but whose causes are not yet clear are called cryptogenic epilepsies.
1. Idiopathic epilepsy
Idiopathic epilepsy is characterized by suspected genetic predisposition, no other obvious causes, onset at a particular age, characteristic clinical and electroencephalographic manifestations, and clear diagnostic criteria.
2. Causes of symptomatic epilepsy
There are clear central nervous system lesions affecting structure or function, such as traumatic brain injury, cerebrovascular disease, tumor, infection, parasites, congenital and genetic metabolic disorders, cortical developmental disorders, neurodegenerative disorders and certain systemic diseases.
3. Cryptogenic epilepsy
Epilepsy is more common clinical manifestations suggestive of symptomatic epilepsy, but no clear etiology has been found. It can start at a particular age without specific clinical and EEG manifestations.
Symptoms
The symptoms of epilepsy are varied according to the epilepsy. Most patients have no symptoms or signs at all in the interictal period; epilepsies of specific etiology may have signs and symptoms of the primary cause. Characteristic symptoms of different types of seizures are common:
1. Partial seizures
It is the most common type of epileptic seizure and starts on one side of the brain structure. If the seizure is not accompanied by impaired consciousness, it is called simple partial seizure; if it is accompanied by impaired consciousness and cannot be recalled after the seizure, it is called complex partial seizure.
(1) Simple partial seizures can be divided into four subtypes, partial motor seizures, somatosensory seizures or special sensory seizures, autonomic seizures and psychogenic seizures. Most of them manifest as convulsions of localized limbs, numbness and pins and needles sensation of limbs, excessive sweating, vomiting, forgetfulness and other symptoms.
(2) Complex partial seizures are mainly characterized by consciousness disorders, delusions, hallucinations and other psychiatric symptoms, and motor disorders such as automatisms.
2. Generalized seizure
(1) Tonic-clonic seizures, also known as grand mal seizures in primary epilepsy, are characterized by generalized convulsions and impaired consciousness. Typical seizures can be divided into four clinical phases: tonic phase, clonic phase and postictal phase. Typical EEG in the seizure phase: the tonic phase starts with an enhanced 10 times/second spike-like rhythm, followed by decreasing frequency and increasing amplitude; the clonic phase is characterized by diffuse slow waves with intermittent spikes; and the late spasm phase is characterized by obvious EEG suppression, which is more pronounced the longer the seizure lasts.
(2) Tonic seizure: generalized tonic muscle spasm, straightening of limbs, head and eyes tilted to one side, often accompanied by obvious autonomic symptoms such as pallor and palpitation.
(3) Clonic seizures Almost always occur in infants, characterized by repetitive clonic jerks with loss of consciousness. Generalized repetitive clonic seizures. Obvious autonomic symptoms such as pallor and flushing.
(4) Aphasic seizures are divided into typical aphasic seizures and atypical aphasic seizures, and there is a big difference between the two in terms of clinical symptoms, EEG background activity and changes in the period of activity, and prognosis.
(5) Myoclonic seizure is a sudden, rapid and short-lived muscle contraction that involves the whole body and may be limited to the face, trunk or limbs. They are mostly seen in patients with idiopathic epilepsy who have a better prognosis.
(6) Atonic seizures are caused by postural tension and last for a few seconds to 1 minute. If the duration is short, the disturbance of consciousness may not be obvious and the patient will wake up immediately after the seizure.
(3) Persistent status epilepticus
Each convulsive seizure lasts more than 5 minutes, or more than 2 seizures, and consciousness is not fully recovered in the interictal period.
Examination
1. Three major routine tests and sugar and electrolyte tests
Blood, urine, biochemistry, stool routine examination and blood sugar, electrolyte (calcium and phosphorus) measurement.
2. Cerebrospinal fluid examination
Central nervous system infections, such as viral encephalitis, increased pressure, increased white blood cell count, increased protein, bacterial infections, and sugar and chloride decreased. Eosinophilia can be found in brain parasitic diseases. In central nervous system syphilis, syphilis spirochete antibody test is positive. Intracranial tumors can have increased intracranial pressure and increased protein.
3. Serum or cerebrospinal fluid amino acid analysis
Possible abnormalities of amino acid metabolism can be detected.
4. Neurophysiologic examination
The traditional method of EEG recording, although it can identify epileptic foci and epileptic regions, often fails to correctly correlate EEG seizures with clinical seizure symptoms. Therefore, the use of closed-circuit television or television images recorded simultaneously with EEG for long-range surveillance can often record multiple habitual seizures, differentiate between pseudo-epilepsies and determine the relationship between seizure onset and clinical symptoms.
5. Neuroimaging
CT and MRI (magnetic resonance imaging) have greatly improved the diagnosis of structural abnormalities in epileptic lesions. Functional brain tests currently in clinical use include cation diffraction tomography (PET), single photon diffraction tomography (SPECT), and MRI spectroscopy (MRS).PET measures cerebral glucose and oxygen metabolism, cerebral blood flow, and neurotransmitter function.SPECT also measures cerebral blood flow, metabolism, and neurotransmitter function, but is not as accurate as PET at quantifying these changes. MRS can measure changes in certain chemicals, such as acetylaspartate, choline-containing substances, creatine, and lactate, in the epileptic region.
6. Neurobiochemical tests
Ion specific electrodes and microdialysis probes have been used that can be placed in the epileptic regions of the brain to measure certain biochemical changes between, during and after seizures.
7. Neuropathologic examination
It is a pathological examination of surgically removed epileptic foci to determine whether the cause of epilepsy is due to brain tumor scarring, vascular malformations, scleritis inflammatory developmental abnormalities or other abnormalities.
Diagnosis
Diagnosis is based on seizure history and reliable detailed description of the seizure by witnesses, supplemented by evidence of epileptic discharges on EEG.
Treatment
The treatment of epilepsy can be divided into five areas: seizure control, etiologic treatment, surgical treatment, general hygiene and prevention. The most important of these is seizure control, which is currently treated with medication. There are no therapies or medications to correct the underlying pathological abnormalities of epilepsy, so there is no short-term cure. Seizure control can only be achieved through various means.
1. Principles of drug therapy
The drug treatment of any disease should follow certain principles in order to improve the therapeutic effect. This is especially important in the treatment of epilepsy. Currently effective antiepileptic drugs can make most of the epileptic patients seizure control. Clinical application of antiepileptic drugs should master the following principles:
(1) Timing of medication Clear diagnosis of epilepsy is the prerequisite for medication. If there are 2 or more seizures in 1 year, the drug should be used. Higher recurrence rate is seen in patients with progressive or organic encephalopathy, definite paroxysmal spikes and slow waves or frequent focal spikes on EEG, and also in partial seizures, neurological signs, mental retardation or psychiatric disorders. If these conditions are not present in the first attack, the risk of recurrence is low and medication may be delayed. If there are clear factors contributing to the seizure, such as drugs, alcohol, fatigue, stress, photosensitivity, etc., the patient should first remove these factors, and then use the medication according to the situation after observation.
(2) Use of medication according to the type of seizure 1) Carbamazepine, valproate, lamotrigine, topiramate, phenobarbital, levetiracetam, zonisamide, gabapentin, oxcarbazepine can be used as monotherapy for partial seizures. Phenytoin sodium has been gradually withdrawn from the first-line drugs for the treatment of partial-onset seizures due to its non-linear pharmacokinetic characteristics, its tendency to cause toxic side-effects, the number of drug-drug interactions, and the obvious side-effects of long-term use.2) Sodium valproate, topiramate, lamotrigine, and levetiracetam can be used for the monotherapy of various types of generalized seizures. Carbamazepine, phenobarbital, phenytoin sodium, and oxcarbazepine can be used as monotherapy for generalized tonic-clonic seizures.3) Sodium valproate, lamotrigine, topiramate, and levetiracetam are broad-spectrum AEDs that are effective for both partial and generalized seizures and can be used as an option in cases where seizure classification is uncertain.
(3) Long-term medication Once a medication and dosage have been found that provides complete seizure control, it should be used without interruption. Generally, the drug should be continued for another 3 to 5 years after the seizure is fully controlled if there is no adverse reaction before stopping the drug can be considered. Different treatments should be given depending on the cause, type of seizure, and frequency of seizures. If there is a history of encephalitis or birth injury, symptomatic epilepsy should be treated for a longer period of time, and complex partial seizures should be treated with caution. Those with frequent seizures and abnormal EEG should also be treated with long-term medication.
(4) Single-drug therapy as far as possible Because the combined use of two or more antiepileptic drugs can easily lead to chronic poisoning, and after poisoning, it is easy to increase the frequency of seizures, so at present, we advocate the use of a single drug. Monotherapy should start with a small dose and slowly increase to the lowest effective dose.
(5) Reasonable combination of drugs, such as excluding the selection of drugs, insufficient dosage, medication irregularity and other factors to confirm the failure of monotherapy, before adding the second drug. If the seizure or myoclonic seizure cannot be controlled by single drug, ethosuximide and sodium valproate can be used in combination, or one of them can be effective with benzodiazepines. However, drugs with the same chemical structure, such as phenobarbital and pramipexole (paracetamol), clonazepam and diazepam should not be used in combination. Combined use of more than two drugs is even more contraindicated. For mixed epilepsy, drugs can be combined according to the type of seizure, but no more than three kinds of drugs are appropriate.
(6) Adjustment of drug dosage principle Generally, it is advisable to start with a small dose, and then gradually increase the dosage to the smallest effective dose that can control the seizure and not produce toxic reactions. Due to individual differences, the principle of individualization should be adopted. Children need to calculate the dosage according to their body weight, infants and young children due to the body’s faster metabolism of drugs, the dosage is relatively larger than that of older children. Those who have frequent and difficult to control seizures should not be forced to completely control the seizures and increase the dosage too much, so as to produce adverse reactions.
(7) Principle of drug replacement The principle of adding new drugs and decreasing old drugs should be adopted for drug replacement. After the addition of a new drug, until the seizure is controlled or the maximum tolerable dose is reached, the original drug should be gradually reduced and converted to a single drug. It is not advisable to stop using the old drugs abruptly after adding new drugs, as this may cause aggravation of seizures or induce epileptic status epilepticus.
(8) Principles of drug reduction and discontinuation At present, it is mostly advocated that after epilepsy is completely free of seizures, the drug should be continued and then gradually discontinued according to the type of seizures, frequency of seizures, and the magnitude of toxicity of the drug. The principle of withdrawing antiepileptic drugs is: the principle of slow and gradual reduction. Generally speaking, after 4 to 5 years of complete control of generalized tonic-clonic seizures, tonic seizures and clonic seizures, and six months after the cessation of catatonic seizures, drug withdrawal can be considered.
2. Commonly used antiepileptic drugs
(1) Barbiturates The most commonly used is phenobarbital. The most commonly used is phenobarbital. It is effective for generalized and partial seizures, but not for catatonic seizures. Very few patients develop allergic rash. It is rarely used because it significantly affects cognitive function in children as well as adults.
(2) Acetylenic urea The most commonly used is phenytoin (phenytoin sodium). It is effective for generalized and partial seizures, and can also be used for complex partial seizures and autonomic seizures. Ineffective for cataplexy, occasionally induces cataplexy. Because of its obvious impact on cognitive function, it is now used sparingly.
(3) Succinimides The most commonly used is ethosuximide. The most commonly used is ethosuximide, which is effective for typical and atypical catatonic seizures, and can also be used for myoclonic seizures, but is ineffective for other types of seizures. A few adults have delirium, fuzzy state or schizophrenia-like symptoms.
(4) Benzodiazepines Nitrazepam: It is suitable for myoclonic seizures, atonic seizures and catatonic seizures, and is also effective for complex partial seizures. The indications and adverse effects are the same as those of nitrazepam, but the sedative effect is small. The antiepileptic effect is greater than that of nitrazepam.
(5) Iminostilbene The most commonly used ones are amidostilbene, nocodazole, nociceptin and carbamazepine, which are effective for complex partial seizures, can reduce behavioral abnormalities and mental dullness, and are also effective for generalized tonic-clonic seizures and simple partial seizures.
(6) Valproic acid Sodium valproate, effective for all types of seizures, is more effective for generalized seizures (including generalized tonic-clonic seizures, apoplectic seizures, and myoclonic seizures) than partial seizures, and is more effective for seizures for which other drugs are ineffective.
(7) A new generation of antiepileptic drugs Lamotrigine, with a therapeutic spectrum similar to that of phenytoin (phenytoin sodium), is effective in partial seizures and secondary generalized seizures. Refractory epilepsy additive or single use to make most of the patients to reduce the number of seizures; Gabapentin, refractory generalized seizures, simple partial seizures as an additive treatment is effective, the effect on cataplexy seizures is not certain; Oxcarbazepine, has an antiepileptic effect. The indications are the same as carbamazepine.
At present, although the drug treatment of epilepsy has made great progress, there are still a small number of patients who have difficulty controlling seizures, and surgical treatment can be used. Surgical treatment of epilepsy is an intervention for people with refractory epilepsy that uses surgical procedures to improve or control seizures.