Epilepsy
PKGhatak, MD
Epilepsy is abnormal electrical activity of the brain producing alteration of muscle tone or convulsions, and changes in behavior and consciousness of an individual. Any one of these symptoms or various combinations of symptoms are the features of epilepsy. Convulsions are commonly known as seizures. Seizures and epilepsy are often used one for the other but strictly speaking when two or more seizures occur at least 24 hours apart then it is called epilepsy.
Previously seizures were classified by various names and at one time 30 to 40 different names were used. At present, there are two main groups of seizures
1. Primary generalized seizures. 2. Partial or limited seizures.
1. Primary generalized seizures. Previously this was called Grand Mal seizures. In primary generalized seizures, abnormal electrical activities originate from both sides of the brain.
2. Partial limited seizures originate from one limited area of the brain and remain localized to one half of the brain.
Commonly used terms for seizures are:
Simple focal. 2. Complex focal. 3. Absence of seizures. 4. Atonic seizures. 5. Tonic-Clonic seizures. 6. Myoclonic seizures.
This classification is not hard and fast because one type of seizure may change to another, for example, a simple focal seizure may turn into a complex focal, or a tonic seizure turns into a tonic-clonic seizure.
A list of medical conditions that may cause seizures.
Alcohol withdrawal.
Hypoglycemia (very low blood sugar)
Cerebral anoxia
Strokes
Certain medications
Encephalitis and meningitis
Sleep deprivation
Sustained exposure to flashing bright light
High fever and teething in children
Drug abuse- usually cocaine and amphetamine.
A-V malformation of the brain
Eclampsia of pregnancy
Hypothyroidism
Electrolyte imbalance.
Brain tumors.
Common causes of seizures according to the age of patients.
In young children. Brain injury during birth, Congenital abnormalities of the brain, Fever.
Young adults. Traumatic brain injury. Surgical scar of the brain, Drug abuse.
Adults. Brain injury and tumors.
Elderly. Strokes, Alzheimer's disease, Hypoglycemia, electrolyte imbalance.
CNS infection is an additional cause for all groups.
Clinical Presentation.
Absence or Petit Mal seizure.
It is commonly seen in children between 4 to 14 years of age. Sudden onset of a blank look in the middle of a conversation, smacking of lips and chewing motion. The seizures generally last only 10 to 15 seconds. The cortico-thalamic tract propagates abnormal impulses. Inheritance of GABRG2, GABRG3 and CACN gene mutations produce malfunction of energy dependent T calcium channels produce hyperexcitable brain cells and initiate seizures. This condition generally resolves at puberty.
Atonic seizure or Drop Attack. Sudden loss of muscle tone or strength causes the patient to fall on the ground, attacks lasting 15 to 30 seconds. The patients retain consciousness during the attack. The cause of the origin of this seizure is unknown.
Simple Local and Complex Seizures.
In simple local seizure is also called Aura. The seizures are either movement abnormality or sensory or autonomic or psychological abnormal experiences. Muscle tightening, rolling eyeballs head movements are some of the common movement abnormalities. Numbness or crawling of insects under the skin is often mentioned by the patients. Hallucination involving hearing or vision is common. The patients may experience unfounded fear or anxiety. The patients are fully cognizant of abnormal muscle movements or sensory experiences and can fully recall incidents.
Complex seizures are like Simple Local seizures but the patients are not aware of the seizures during the attack or do not remember anything after the seizures stop. This seizure is also known as Temporal lobe epilepsy.
4.Tonic-Clonic seizures.
Violent muscle contractions and fall on the ground and complete loss of consciousness, often a shrill cry is heard due to laryngeal muscle contractions, air entry to trachea may be prevented producing cyanosis, foaming of the mouth, chattering of teeth or forceful mouth closure, involuntary urination, arching backward due to back muscle contractions are some of the features of grand mal seizures. This seizure, the general public understands to be epilepsy. The seizures last several minutes and when exceeding 5 minutes this becomes an emergency known as Status Epilepticus.
5.Myoclonic seizure.
The muscle contractions are tonic-clonic but limited to a small number of muscles. Convulsions last only 2 to 3 seconds and the patient remains conscious.
Diagnosis of seizures.
An eyewitness account of a tonic-clonic attack is as good as a diagnosis that can be made on clinical grounds only to be confirmed by an Electroencephalogram (EEG; see footnote) and MRI. In many cases, photic stimulation is used for additional EEG recording. Other provocation tests may be required for localizing.
EEG in a normal person shows wave patterns classified on the frequency of waves per second. Normal waves are Alpha - 8 to 13 waves per second, Beta -13 per second, Theta - 4 to 7 per second, Delta -up to 4 per second, Gamma - 25 to 100 per second. The waves are not synchronized.
EEG in epilepsy shows synchronized spikes waves, each wave lasting 1/12 second followed by delta waves.
MRI in epilepsy. MRI shows structural abnormalities of the brain. In epilepsy, the MRI should be normal unless the epilepsy is due to other medical conditions deforming the brain. Other forms of MRI, like functional MRI, are useful for research purposes.
In suspected CNS infection spinal fluid examination and proper cultures and immunological studies are needed.
Treatment.
Status Epilepticus is an emergency. After securing the patient on a stable surface the airway is protected and supplemental oxygen is administered.
IV Lorazepam 2 mg is given slowly, repeated after 1 minute in steps till the seizure stops or the maximum dose of 0.1 mg/Kg is given. If after 30 minutes the seizure continues, then Levetiracetam 20 mg IV is given. Alternatively, Valproic acid 40 mg IV may be used. If seizures continue then the Anesthesiology team is called and general anesthesia is induced to control convulsions.
Oral medication.
There are several effective oral medications available. The choice depends on the type of seizure, age and sex of the patients. In pregnancy and breastfeeding special attention is required.
Commonly used oral drugs are Levetiracetam, Phenytoin, Valproic acid, Lamotrigine, Topiramate, Phenobarbital, Zonisamide, Carbamazepine and Gabapentin.
In most cases one drug is not enough to control seizures, two or more drugs are required. Levetiracetam is well tolerated and has few side effects. It works differently from other anticonvulsant drugs. Levetiracetam combines with SV2 protein and prevents the release of neurotransmitter that is responsible for the epileptic electric discharge.
Duration of therapy.
Oral medications are continuously used for months and unless patients have no seizures for consecutive two years drugs are not stopped. In most patients, drugs are required for life. Therapeutic blood levels of many drugs are available and should be utilized to adjust the dosage. Phenytoin therapeutic level is 10 to 20 mcg/ml. Care should be taken in adding an additional dose of phenytoin at the higher range of therapeutic level because a small addition may push blood levels well past the normal range.
Surgery.
Removal of a single scar of the brain provides the best surgical outcome in uncontrollable seizures. The use of Laser ablation has increased safety. In recent years increasing numbers of drug resistant patients are opting for surgery. Many additional images, provocation tests and on the operating table brain mapping provide a more detailed location of the origin of the seizure and spare the functional areas of the brain.
Footnote:
Brain cells generate tiny electrical charges from various metabolic processes. These electrical activities can be recorded by placing electrodes on the head attached to a recording machine, unlike an EKG machine. Up to 64 electrodes and several hours of recording may be necessary to detect epileptic spikes. Each electrode records the activities of the cells directly underneath it and graphs are inscribed on a moving paper and all the leads record at the same time and each lead is identified by its position on the head.
In normal conditions, the brain cells are at different levels of activity and their activities are not synchronized. EEG of an epileptic discharge stands out as large waves and many adjoining leads record the same waveform synchronously.
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