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Diagnosis of Epilepsy: Definitions and Workup
Essentials
- To investigate any ictal symptoms, the patient should be asked to provide the most accurate possible description of the seizure. The physician should establish and record the course of the seizure, including pre-ictal as well as post-ictal signs and symptoms.
- Eyewitness accounts of the event are of utmost importance and should be obtained immediately after the seizure. This may be crucial for diagnosis and should be obtained in person, such as by telephone.
- The patient should be referred for further neurological investigations in specialized care. The purpose of such investigations is to confirm the type of seizure, to examine its aetiology and to assess the risk of recurrence of epileptic seizures.
- Brain imaging is used to find out whether there is a structural problem in the brain that predisposes the patient to epilepsy. Imaging should be arranged quickly, but not necessarily as an emergency. In adult-onset epilepsy, a brain tumour should be considered as a possible cause.
- Electroencephalography (EEG) is used to examine electrical activity in the brain. A normal inter-ictal EEG does not rule out the possibility of epilepsy but an epileptiform EEG increases the risk of recurrent seizures and supports the diagnosis of epilepsy.
- The diagnostic approach after a first seizure associated with alcohol withdrawal should be the same as after an epileptic seizure, and a single brain scan is warranted.
- If an episode of unconsciousness is not clearly epileptic in nature, an adult patient will often primarily need cardiac investigations.
- A driving ban should be imposed in the emergency department already on any patient who has had an epileptic seizure.
Epidemiology and definitions
- It has been estimated that 8-10% of the population will experience at least one epileptic seizure during their lifetime, and 4-5% will develop epilepsy.
- Less than 1% have epilepsy needing continuous pharmacological treatment http://www.who.int/news-room/fact-sheets/detail/epilepsy.
- An epileptic seizure is a transient disturbance in brain function that is due to abnormal, excessive or synchronized electrical neuronal activity in anatomic areas of the brain of varying size.
- Epilepsy is a brain disease in which the brain has a chronic tendency to spontaneously produce epileptic seizures and patients may additionally have problems in neurological, cognitive, mental or social performance in consequence of the disease.
- If the seizure is associated with some immediate, exceptional provoking factor (significant intoxicant abuse or withdrawal, extreme stress, such as sleep deprivation or fasting, a systemic disorder, such as a significant electrolyte disturbance or high fever), it should not be treated as epilepsy if the provoking factor can be otherwise eliminated or treated.
- To diagnose epilepsy, the patient must have a tendency to have recurrent (no less than two) seizures in the absence of any significant predisposing factor. If a chronic factor predisposing to seizures has been found, epilepsy can be diagnosed after the first seizure.
- It is important to examine the aetiology of the epilepsy to know what kind of epileptic disease the patient has and to be able to target the treatment appropriately.
- Aetiological classification of epilepsies
- Structural (e.g. cerebral infarction, brain tumour, aberrant cerebral cortical development)
- Genetic (e.g. single gene mutation, chromosomal abnormality)
- Infectious (e.g. herpes, HIV)
- Metabolic (e.g. mitochondrial disorder, porphyria)
- Immune-mediated (e.g. autoimmune encephalitis)
- Unknown cause
- Despite investigations, the cause of the epilepsy may remain unknown. However, there may be a currently unidentified structural or genetic cause, for example. Therefore in these cases, the aetiology should be regularly reassessed.
Clinical examination
- In some cases, the first examination is as an emergency case in association with the patient's first convulsive tonic-clonic seizure. However, it is also possible to see a patient with ictal symptoms first at a normal scheduled visit.
Description of the seizure
- The patient and an eyewitness should be asked for a description of the seizure as soon as possible after it. Such a description plays a central role in assessing whether the seizure was an epileptic one or a symptom of some other differential diagnostic condition (such as cardiogenic or psychogenic). It should be noted that some patients may have partial or complete amnesia covering the events.
- The patient should be asked about the following:
- What was the patient doing at the onset of the seizure?
- Were there any symptoms or sensations occurring before or at the onset of the seizure?
- Does the patient remember anything about the events or any sensations during the seizure?
- Does the patient have any memories from after the seizure; at what point did he/she feel normal again?
- Did the patient have any post-ictal symptoms?
- An eyewitness should be asked about the following:
- During the seizure: duration of the seizure, symmetry and type of symptoms, associated symptoms, skin colour, incontinence and tongue biting
- After the seizure: occurrence and duration of sleep and confusion, any aggressiveness or anxiety, resuming speech and any paralysis.
Seizure types
- Knowing the different types of epileptic seizures helps to assess whether any ictal symptom described by the patient could be epileptic.
- Epileptic seizures are divided into focal onset and generalized seizures.
- In a focal onset seizure, the electrical disturbance has a focal onset but may spread more extensively within the brain; the first symptoms suggest a focal disturbance.
- Types of focal onset seizure
- Focal onset seizure with no loss of awareness but other symptoms (seizures with limited symptoms)
- Motor symptoms: twitching, contractions of the limbs, deviation of the gaze or the posture of the head or body, vocalisations
- Non-motor symptoms
- Sensory symptoms: visual, auditory, olfactory, gustatory, vertiginous
- Autonomic symptoms: palpitations, abdominal sensations, sweating, flushing, pallor, salivation, pupil dilatation, sexual reactions
- Emotional and cognitive symptoms: disturbances of speech production and understanding, déjà-vu phenomena, memory distortion, fear, anxiety, hallucinations
- Behaviour arrest symptoms
- Focal onset impaired awareness seizure
- First symptom as in seizures with limited symptoms but proceeds to impaired awareness. The process may be so quick that the patient does not notice the initial symptom.
- There may be automatisms, at least partially coordinated, elaborate, nonpurposeful movements and behaviours of which the patient is not aware, such as lip smacking, swallowing, bustling around or aimless walking, picking at clothes or objects or undressing.
- Focal onset convulsive tonic-clonic seizure
- First symptom as in seizures with limited symptoms but proceeds to convulsive tonic-clonic seizure. The process may be so quick that the patient does not notice the initial symptom.
- In a generalized seizure, there is a sudden disturbance in the electrical activity of the brain that occurs simultaneously in both cerebral hemispheres.
- Types of generalized seizure
- Generalized convulsive tonic-clonic seizure without prodromal symptoms
- Absence seizure
- Myoclonic seizure (i.e. muscle twitching)
- Episodes starting in adulthood that the patient describes as absence seizures usually represent impaired awareness of focal origin.
Patient history
- Underlying diseases
- History of brain disease, head injuries, developmental anomalies, febrile convulsions
- Intoxicant abuse
- Psychiatric diseases
- Cardiovascular diseases
- Any history of ictal symptoms for which the patient has not sought medical assistance
- Predisposing factors (sleep-deprivation, fasting, alcohol ingestion or withdrawal, medications, flickering light)
Physical examination
- If the physician is able to examine the patient during the seizure or immediately thereafter, it is important to note and to record
- orientation, possible confusion, memory of the seizure
- the presence of injuries, signs of whether the patient has bitten his/her tongue
- any neurological abnormality: asymmetry (Todd's paresis?), abnormal (positive) Babinski sign, asymmetric pupils
- suggestive evidence of excessive use of alcohol or other intoxicants prior to the seizure
- blood pressure, pulse, heart auscultation
- If the physician does not see the patient until several days after the seizure, there are usually no longer any significant clinical findings. However, it is advisable to look for unilateral neurological symptoms and signs of increased intracranial pressure.
Laboratory tests
- Basic blood count with platelet count, fasting plasma glucose, Na, K, creatinine, ionised calcium, CK, ALT, CRP, TSH
- ECG (conduction times must be measured)
- If intoxicant abuse is suspected, GT, CDT/PEth and urine drug screen, as considered necessary
Imaging
- Brain imaging is necessary after the first epileptic seizure. The aim is to recognize any structural abnormality predisposing the patient to epilepsy and to facilitate immediate exclusion of any causes requiring immediate treatment, such as brain tumours or fresh cerebral events.
- Plain brain CT is sufficient in most emergency cases. Emergency MRI of the brain is necessary if the patient is pregnant, if CT is contraindicated and, after due consideration, in young people (below 25 years).
- MRI of the brain should be arranged urgently on an outpatient basis if not done in the emergency department.
Investigations in a neurology unit
- Further investigations and diagnosis of epilepsy after an epileptic seizure are done in a neurology unit in specialized care. Optimal management is based on exact diagnosis, i.e. the type of seizures as well the type of epilepsy or epilepsy syndrome should be identified.
- The central aims of the investigations and the diagnosis of epilepsy are:
- to confirm the nature of the seizure (whether epileptic or of another type)
- to investigate the aetiology of the seizure (e.g. identifying any structural aetiology by imaging)
- to assess the risk of recurrence of epileptic seizures and to diagnose epilepsy if the risk is increased.
- Workup
- EEG
- Done to examine electrical activity in the brain; an awake EEG is recorded first, followed by a sleep EEG if needed.
- Epileptiform EEG findings (sharp waves, spikes, spike-slow wave complexes and bursts) are strongly suggestive of epilepsy.
- A normal inter-ictal EEG does not rule out the possibility of epilepsy.
- An MRI scan of the brain is the most recommended imaging study in epilepsy.
- An MRI is indicated whenever the aetiology of the seizure has not been confirmed by a CT scan obtained in the acute situation or by other investigations.
- MRI scanning is used to reveal structural aetiological factors not detectable by CT scanning of the brain, such as aberrant cerebral cortical development.
- Cardiological investigations
- Should be considered for the purpose of differential diagnosis in cases where the seizures are not clearly epileptic in nature and where neurological investigations fail to show a clear epileptic aetiology.
- Recommended investigations include a cardiological consultation, echocardiography, continuous ambulatory ECG monitoring or tilt testing.
- Special investigations in problematic cases
- For the workup of atypical seizures, treatment-resistant epilepsy or unclear aetiology, continuous ambulatory EEG monitoring, EEG video-telemetry, a CSF test or genetic investigations may be necessary.
References
- Scheffer IE, Berkovic S, Capovilla G et al. ILAE classification of the epilepsies: Position paper of the ILAE Commission for Classification and Terminology. Epilepsia 2017;58(4):512-521. [PubMed]
- Thijs RD, Surges R, O'Brien TJ et al. Epilepsy in adults. Lancet 2019;393(10172):689-701. [PubMed]
- Beghi E, Giussani G, Sander JW. The natural history and prognosis of epilepsy. Epileptic Disord 2015;17(3):243-53. [PubMed]
- Peter C, Camfield C. Modes of onset of epilepsy and differential diagnosis. Handb Clin Neurol 2013;111():447-53. [PubMed]