Overview
Generalised seizures involve both brain hemispheres at onset, leading to an immediate loss of consciousness. They can also occur secondary to the spreading of a focal seizure.
They can be divided into:
- Motor generalised seizures – with physical movement
- Non-motor generalised seizures – without physical movement
An overview of seizures, epilepsy, classification, epidemiology, risk factors, general management, and implications in pregnancy can be found in Seizures and Epilepsy: An Overview.
Presentation
Motor Generalised Seizures
Motor generalised seizures include physical movement and may be:
- Tonic-clonic (grand mal) – this is what people stereotypically see seizures as:
- Increased tone – stiffening followed by
- Clonus – regular (rhythmic) muscle jerking
- Tonic:
- Increased tone – stiffening
- Clonic:
- Clonus – regular (rhythmic) muscle jerking
- Myoclonic:
- Myoclonus – irregular (non-rhythmic) muscle jerking
- Myoclonic–tonic–clonic:
- Myoclonus – irregular (non-rhythmic) muscle jerking followed by
- Increased tone (stiffening) followed by
- Clonus – regular (rhythmic) muscle jerking
- Atonic:
- Atonic – sudden loss of muscle tone and strength, patients may suddenly go limp
- Myoclonic–atonic:
- Myoclonus – irregular (non-rhythmic) muscle jerking followed by
- Atonicity – sudden loss of muscle tone and strength, patients may suddenly go limp
- Epileptic spasms:
- Sudden, involuntary tightening of a muscle
Non-Motor Generalised Seizures
Physical movements do not predominate in non-motor generalised seizures. These are also known as absence seizures. They may be:
- Typical absence:
- Person suddenly stops all activity and looks like they are staring into space/has a blank look
- The eyelids may flutter or the eyes may turn upwards
- Usually lasts for <10 seconds
- Atypical absence:
- The person stops all activity but this occurs more slowly and lasts longer
- There may be eyelid fluttering or automatisms (e.g. lip-smacking, chewing, or hand motions such as rubbing the fingers together)
- Lasts ≥20 seconds
- Myoclonic absence:
- The person suddenly stops all activity and looks like they are staring into space/has a blank look and
- There is myoclonus – irregular (non-rhythmic) jerking of the limbs
- Eyelid myoclonia:
- The person suddenly stops all activity and
- There is eyelid myoclonia – irregular (non-rhythmic jerks) of the eyelid
- The eyes may roll upwards
Investigations
- Blood glucose:
- Hypoglycaemia can cause provoked seizures
- Full blood count:
- Leukocytosis may suggest a central nervous system (CNS) infection
- Urea and electrolytes (U&Es):
- Hyponatraemia, hypernatraemia, and uraemia can cause seizures
- ECG:
- To identify cardiac-related conditions that can mimic seizures
- Toxicology screen:
- Considered if illicit substances are suspected
- Examples are cocaine, amfetamines, and opioids
- Serum prolactin:
- Consider if there is doubt that an actual seizure occurred
- Prolactin is elevated within 10-20 minutes
- Neuroimaging – ideally an MRI brain:
- To identify structural abnormalities, intracranial masses etc.
- A CT may be performed if an MRI is contraindicated
- Electroencephalogram (EEG):
- May show epileptiform activity that corresponds with a specific epilepsy syndrome
- A normal EEG does not rule out epilepsy:
- Sleep-deprived EEGs or manoeuvres provoking a seizure (e.g. hyperventilation or photic stimulation) may be performed
- Ambulatory EEG monitoring for up to 48 hours may be considered
Management
Overview
- Generalised tonic-clonic seizure:
- 1st-line: sodium valproate
- 2nd-line: lamotrigine or carbamazepine
- Carbamazepine may worsen myoclonic or absence seizures
- Absence seizures:
- 1st-line: sodium valproate or ethosuximide
- 2nd-line: lamotrigine
- Do not offer carbamazepine or phenytoin
- Myoclonic seizures:
- 1st-line: sodium valproate or levetiracetam or topiramate
- Tonic or atonic seizures:
- 1st-line: sodium valproate or lamotrigine
