Seizure types

Dravet syndrome is initially characterised by prolonged recurrent seizures. Seizures usually start in the first year of life; over time other seizure types can occur.

Initial Seizures

Recognising febrile seizures is important in the diagnosis of Dravet syndrome. Febrile seizures are caused by a high or rapidly rising temperature, often due to illness or vaccination. These are usually tonic clonic or hemiclonic seizures.

  • Tonic clonic seizures involve a stiffening of the arms and legs (tonic phase), followed by jerking of the arms, legs, and head (clonic phase).
  • Hemiclonic seizures are similar, though only one side of the body convulses.
  • Febrile seizures are very common in childhood and usually are not associated with a form of epilepsy.

The first suggestion of Dravet syndrome may be when the first febrile seizure happens in early infancy and is prolonged, lasting more than ten minutes and sometimes over half an hour (status epilepticus). These very long seizures may cause the child to be admitted to intensive care and have emergency treatment in A&E.

Other Seizures

These seizure types may occur between ages one to four:

Myoclonic seizures: These can be described as ‘jumps’. They are caused by rapid contraction and relaxation of the muscles. Small jerks in sleep are perfectly normal and can occur in people without epilepsy. In someone with epilepsy, myoclonic seizures cause abnormal movements on both sides of the body at the same time resulting in a jerk of the shoulders and arms or a drop of the head. Sometimes a rapid myoclonic seizure will cause a fall.

Focal seizure with impairment of awareness: With this type of seizure the person may appear unresponsive and confused as their consciousness is impaired. Automatic movements such as smacking of the lips, wandering, or fumbling movements of the hand may be present.

Atypical absence seizures: Absence seizures are usually brief (usually less than 20 seconds), and have a sudden start and finish. They have two essential components:

  • Clinically, the impairment of consciousness (absence) – they can be associated with head nodding and a fall may occur.
  • Electroencephalography (EEG) shows generalised spike-and-slow wave discharges.

Atonic seizures: Also called drop seizures, akinetic seizures or drop attacks, atonic seizures are a type of seizure that comprises a brief lapse in muscle tone caused by temporary alterations in brain function. The seizures are brief – usually less than 15 seconds. The seizure itself causes no damage, but the loss of muscle control can result in indirect damage from falling. In some cases, a person may become temporarily paralysed in part of his or her body. This usually does not last longer than three minutes.

Non-convulsive status: Refers to less-than-full mental capacity in a patient, typically as a result of continuous seizure activity.

Changes to Seizure Patterns

Increase in seizure frequency, decrease in status episodes: Generally as the child gets older, typically around four years of age, status seizures begin to settle. However, patients with Dravet syndrome will remain prone to status seizures, particularly when experiencing illness and infection. Seizure frequency may increase around the time when the status seizures begin to settle, therefore patients may have more seizures but they may be shorter in duration and not always require emergency medication.

Development of focal seizures with impairment of awareness: Sometimes a person may get warning of a seizure called an aura and the patient may walk up to their parents/carers in this phase. Once consciousness is impaired, the person may display automatic behaviour such as lip smacking, chewing or swallowing. There may also be loss of memory (amnesia). The person may still be able to perform routine tasks such as walking, although such movements are not purposeful or planned.

You may not recognise that anything is wrong. It can be very difficult to know if a patient is experiencing a complex partial seizure, particularly if they are non-verbal or have a severe developmental delay or learning disability.

Development of myoclonic seizures: These seizures may appear, generally between the ages of one and four, often building up to a generalised tonic clonic seizure.

Development of nocturnal (night-time) seizures: As children get older they may begin to experience their seizures at night, particularly as they transition through sleep phases. For some families this feels like a positive change as their child will not sustain any injuries from falling, but for others it may cause additional anxieties and fears.

Nocturnal (Night-time) Seizures

Night-time can be the most stressful time for parents due to the worry about missed seizures and the risk of SUDEP (sudden unexpected death in epilepsy).

There are a number of options to reduce worry and incidence, notably:

  • Obtaining a specialist bed/cot for your child. These beds can have high sides to ensure the patient cannot fall out and injure themselves. Some cots have sides that are high enough to ensure the patient cannot climb out.
  • Sleeping in a double bed with your child.
  • Pulse oximeter machines that monitor a person’s heart rate and oxygen levels. Typically when someone has a seizure their heart rate increases and their oxygen levels drop. If they are being monitored on a pulse oximeter machine during a seizure the monitor may sound an alarm, so that parents/carers can administer emergency treatment if necessary. The pulse oximeter is attached to the patient by a sticky probe, generally on the toe. These machines are not routinely available on the NHS, as so far there is no proof that they reduce the chance of SUDEP, however they can provide reassurance for many families. It is important for families to remember that machines can develop faults. This type of monitoring should never be a replacement for the observation of clinical signs.
  • Epilepsy mattress monitors which alert to tonic clonic seizures and can also be set up to sound an ‘out of bed’ alarm to alert if the patient has got up.
  • Good quality video camera (baby monitor) or CCTV.
  • Having a single bed in the patient’s bedroom for a parent or carer to use when the patient is unwell.
  • Exploring respite options, for example the patient staying somewhere where there is waking night staff or accessing waking nights in your own home.