Seizures: Basic concepts and clinical approach- Dr. YK Amdekar
M3 India Newsdesk Jul 20, 2020
Dr. YK Amdekar explains basic concepts of seizures and how to effectively make a clinical diagnosis of seizures in children which in most cases is possible through meticulous history-taking of the event and understanding of the preceding medical causes.
Before you begin, take the quiz below to test your knowledge on the subject.
What is a seizure?
The brain is like an electrical network in which neurons (nerve cells) communicate with each other through electrical signals to generate multiple functions. Disturbance in this electrical circuit leads to a sudden abnormal event that is referred to as a seizure. The site of abnormality is mainly the cerebral cortex though the subcortical area may also be involved that results in subtle brain dysfunction.
What goes wrong in the electrical circuit?
Biochemically, it is the ionic imbalance that leads to either too much of excitatory transmission response or too little of inhibitory response and results in a seizure. Most often, the ionic balance is restored by nature itself and so the seizure stops by itself within 1 to 2 minutes. Nature rarely fails, but if it does happen, then the seizure continues for a longer time and it would need a drug to stop it.
What is the difference between seizure and convulsion?
Convulsion is a type of seizure which manifests as jerking movements or stiffness of some parts of the body. However, a seizure may present without such movements or stiffness because manifestations depend upon which part of the brain is responsible for sudden electrical discharge.
Convulsion results when part of the brain that controls body movements (motor system) is involved. Involvement of other parts of the cerebral cortex do not manifest with convulsion but presents as a sudden attack of emotional disturbances if the temporal lobe is the site of abnormal electrical discharge or when the parietal lobe is involved; the result is sensory manifestations. Thus, the seizure may not present with convulsions, though convulsion is the most common type of seizure and many times, both terms are used interchangeably.
Types of seizures
They are classified into two major groups:
- Generalised seizures: They always present with loss of consciousness even for a brief period while localized seizure may or may not lose consciousness.
- Localised (focal) seizure: It depends on the extent of involvement: At times, localised seizure may spread to other parts and become generalised. Hence, it is the onset of seizure that decides focal or generalised, and not further progress.
Each group is further divided into motor (presents as movements - convulsion) and non-motor (without movements). At times it is difficult to classify seizure type as it may be mixed and also may change.
Presentation & seizure types
- Generalised motor seizure may present as stiffness (tonic), jerky movements (clonic) or both (tonic-clonic), atonic (sudden loss of muscle strength) and myoclonic (muscle spasm). In tonic seizure, spasm of respiratory muscles leads to apnoea and cyanosis. In-built neural mechanism breaks this phase, breathing starts and clonic phase begins.
- Generalised non-motor seizure (absence seizure) presents with very transient lapse of awareness when the person stops momentarily and in the next seconds resumes what he/she was doing.
- Localised (focal) motor seizure presents as abnormal movements of a part of the body with or without loss of consciousness. Focal non-motor presents as emotional change without loss of consciousness.
What is epilepsy?
Unprovoked recurrent seizures are referred to as epilepsy. Unprovoked means the seizure occurs without any apparent trigger factor. It may be idiopathic (cause not known), often genetic or at times secondary to previous brain damage.
Aetiology of seizure
It is classified into acute symptomatic (due to present existing disease), remote symptomatic (due to brain damage resulting from previous disease) or idiopathic (cause not known).
Acute symptomatic seizure
- Simple febrile seizure: The most common cause is simple febrile seizure which occurs due to sudden rise in body temperature in a genetically susceptible child. Around 5% of normal children suffer from simple febrile seizures. The first episode usually presents between the ages of 6 months and 2 years though such a seizure may recur even up to the age of 6 years. The seizure typically occurs during the first 24 hours of onset of fever, lasts for a minute or less, is self-limiting and the child becomes normal without any sequelae. There is no need for treatment though recurrence can be prevented by use of clonazepam only during the first 24 to 36 hours of onset of fever along with an antipyretic. (2.5 mg twice a day for 3 doses orally).
- Intracranial infection: This may occur at any age and is accompanied by persistent fever, vomiting and change in sensorium. Such a child needs hospitalisation.
- Hypocalcemia: It is another cause that may present in an infant or young toddler having active vitamin D deficiency- rickets. This is a seizure that does not end with post-ictal (at the end of seizure) drowsiness. Neonates born with low birth weight may also suffer from hypocalcemia.
Remote symptomatic seizure
It is a result of brain damage caused by previous illness that may have resolved completely though leaving behind disturbed brain function. Obviously, one clue to such remote symptomatic seizure is a child with developmental delay. Birth injury, significant serious head injury, severe brain infections and congenital brain malformations are common causes of remote symptomatic seizure. Treatment consists of using anti-epileptic drugs.
It occurs in the normal brain and may be triggered by subtle events such as minor illness. Often such a seizure may not recur. If it recurs, it is termed as idiopathic epilepsy. Modern science may find a specific cause for idiopathic seizure or epilepsy in the form of genetic or biochemical defect.
There are several conditions that mimic a seizure and it is important to differentiate them. Such conditions include movement disorders (dystonia) or benign sleep myoclonus, sudden fall (syncope, vertigo), breath-holding spasm. Each of these conditions have typical presentation that is different from a seizure. Most of them retain consciousness.
Detailed history of the event is most important. It should be obtained from the one who has actually observed the event. Ideally, it could be captured on video; that helps a lot. This is because, onset of seizure is vital to understand the nature of seizure. If onset is missed, vital information is lacking. Besides onset, duration, progress and accompanying symptoms offer a clue to probable diagnosis.
- Seizure preceding by fever may be simple febrile seizure or fever triggered hypocalcemic seizure (both of them recover quickly) or meningitis (that is accompanied with vomiting and change in sensorium)
- Seizure without fever may be remote symptomatic (abnormal brain function) or idiopathic (cause unkown)
Physical examination can detect abnormal neurological findings if any and whether these findings denote active disease or old disease. Normal neurological status suggests either simple febrile convulsion or hypocalcemia that leaves no sequelae. A child with active meningitis is sick besides neck rigidity and drowsiness whereas those with remote symptomatic seizures also have abnormal neurological findings but the child is not sick and has delayed development.
Probable diagnosis decides whether tests are required or not. Simple febrile seizure does not need any test; it is a clinical diagnosis based on characteristic presentation and exclusion of other causes. Meningitis is proved by CSF examination, hyppcalcemia due to vitamin D deficiency by serum calcium, phosphorus and alkaline phosphatase and bone X-ray. Brain damage due to previous disease may need neuro-imaging. EEG is required only in case of epilepsy.
Most often, a seizure stops on its own before any intervention. Only when the patient presents during active seizure, one may use diazepam or midazolam to control the event. Nasal puff of midazolam is easy to administer even by parents that aborts the attack quickly.
Long term anti-convulsant drugs are not necessary except in case of epilepsy or when active symptomatic seizure has a risk of recurrence. Simple febrile seizure needs no treatment but recurrence can be prevented by clobazam given at the onset of fever along with an antipyretic drug. Three doses at 12-hour intervals suffice as chance of seizure is only in the first 24 hours of onset of fever.
In summary, occurrence of seizure is frightening to parents and a challenge to a doctor. However, the only decision the doctor has to make is about the need of immediate hospitalisation (meningitis, severe head injury or uncontrolled seizure) and subsequent need for investigations (in case of recurrent seizures). Rarely during active seizure, diazepam or midazolam may be required.
Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.
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