What is epilepsy?
Epilepsy is a disorder of the brain characterized by repeated seizures.
A seizure is usually defined as a sudden alteration of behaviour due to a temporary change in the electrical functioning of the brain. Normally, the brain continuously generates tiny electrical impulses in an orderly pattern. These impulses travel along the network of nerve cells in the brain and throughout the whole body via chemical messengers called neurotransmitters.
In patients with seizures, the normal electrical pattern is disrupted by sudden and synchronized bursts of electrical energy that may briefly affect their consciousness, movements or sensations.
Types of Seizures:
Typically, seizures belong in one of two basic categories: generalized seizures and partial seizures. The difference between these types is in how they begin. Generalized seizures begin with a widespread electrical discharge that involves both sides of the brain at once. Partial seizures begin with an electrical discharge in one limited area of the brain.
Partial seizures can affect any part of body depending upon the area of origin in brain, for eg: it can affect right hand only, right leg only, left face only.
To further classify partial seizures is whether consciousness (the ability to respond and remember) is impaired or preserved.
What are the causes of seizures?
The causes of seizures and epilepsy are numerous and vary according to both the setting of the seizure (i.e., acute symptomatic versus unprovoked) and the type of seizure (i.e., focal versus generalized onset).
In around 70% of patients with epilepsy, a cause cannot be ascertained.
Compared with children and young adults, older adults with a first seizure are more likely to have a cause of seizure identified by an initial evaluation and neuroimaging.
Acute symptomatic seizures —Virtually any acute insult to the brain can cause a seizure. In adults, common causes include: Acute symptomatic seizures — Virtually any acute insult to the brain can cause a seizure. In adults, common causes include:
1) Acute stroke: ischemic or haemorrhagic
2) Subdural hematoma (SDH)
3) Subarachnoid haemorrhage (SAH)
4) Cerebral venous thrombosis (CVT)
5) CNS infections: Meningitis or encephalitis, brain abscess
6) Traumatic brain injury
7) Eclampsia
8) Hypoxic-ischemic injury
9) Metabolic abnormalities: Hypoglycaemia, hyponatremia, hypocalcaemia
10) Drug overdose
11) Withdrawal of alcohol, benzodiazepines, opioid
Underlying epilepsy- Commonly identified etiologies of focal epilepsy in adults include the following:
1) Mesial temporal lobe epilepsy (>80 percent of patients have seizure onset in adolescence, but presentation may be delayed into young adulthood)
2) Cerebrovascular disease
3) Primary or metastatic brain tumours
4) Vascular malformations
5) Prior central nervous system infection, such as neurocysticercosis
6) Head injury
7) Neurodegenerative dementia, including Alzheimer disease
How to evaluate and diagnose epilepsy?
Description of the event — An accurate description of the seizure is important but may be difficult to obtain from the patient. So, ask the description from witnesses.
Patients with focal seizures without impairment of consciousness can typically provide a complete description of the event, whereas patients with focal seizures with impairment of consciousness or generalized seizures typically cannot, or can only remember the early stages of the seizure.
The majority of seizures end spontaneously within two to three minutes.
The timing of the seizure in relation to sleep is also important to determine.
Laboratories — Blood glucose should be checked in all patients with a first seizure. Other laboratory evaluations that are appropriate for the evaluation of seizure include
i. Electrolytes (sodium and potassium)
ii. Calcium, Magnesium
iii. Complete Blood Count
iv. Renal function tests
v. Liver function tests
vi. Urinalysis, and
vii. Toxicology screens
Electroencephalography (EEG) — The EEG is an essential study in the diagnostic evaluation of epileptic seizures. If abnormal, the routine, interictal EEG may aid in supporting the diagnosis of epileptic seizures and may also suggest whether a patient has generalized or focal seizures
Although, routine EEG demonstrates epileptiform abnormalities in approximately 25 percent of patients.
Use of sleep deprivation and provocative measures during the test, such as hyperventilation and intermittent photic stimulation, increases the yield.
However, a normal EEG does not rule out epilepsy.
Neuroimaging — A neuroimaging study should be performed in all adults with a first seizure to evaluate for a culprit structural brain abnormality.
Magnetic resonance imaging (MRI) is preferred over computed tomography (CT) because it has superior sensitivity for detecting a variety of acute and remote causes of seizure and epilepsy, including infarcts, tumours, mesial temporal sclerosis, and cortical dysplasia.
What is the treatment of epilepsy?
Early post-seizure management — Most seizures remit spontaneously within two minutes and rapid administration of a benzodiazepine or antiseizure medication is not required.
Seizures that last longer than 5 to 10 minutes or serial clinical seizures without an interictal return to baseline consciousness meet the definition of status epilepticus, such patients need immediate hospitalisation and treatment with intravenous benzodiazepines and anti-seizure medications.
When to start antiseizure medication therapy — The decision whether to start antiseizure medication therapy immediately after a first seizure depends on multiple factors, including the probability that the event represented a seizure, the suspected or confirmed cause of the seizure based on the initial evaluation, the stability of the patient, and the estimated risk of recurrent seizure.
Approximately one-third of patients will have a recurrent seizure within five years, and the risk is increased 2- to 2.5-fold in association with any of the following factors:
1) Epileptiform abnormalities on EEG
2) Symptomatic cause, as identified by clinical history or neuroimaging (e.g., brain tumor, brain malformation, prior central nervous system infection)
3) Abnormal neurologic examination, including focal findings and intellectual disability
4) A first seizure that occurs during sleep
Indications for hospitalization — Hospitalization may be required for patients who
1) Have a first seizure associated with a prolonged postictal state
2) Status epilepticus
3) The presence of a neurologic or systemic illness or insult requiring additional evaluation and treatment
4) Incomplete recovery, or
5) Serious seizure-related injury
Driving — Most if not all require at least some period of abstinence from driving after a seizure or other event associated with loss or alteration of consciousness.