20.01.1 Introduction to Epilepsy

Epilepsy is a disruption of the normal electrical activity of the brain resulting in seizures. Epilepsy affects 1-2% of Australians. Thus, about 400,000 Australians have epilepsy.

There are 40 different types of seizures, but they can be grouped together into about 6 main groups. Seizures are associated with changes in sensation, awareness, and behaviour. Only some times are seizures associated with convulsions, muscle spasms or loss of consciousness.

15% of people with epilepsy have a learning disability.

About 50% of cases of epilepsy have no known cause. For the other 50%, the causes of epilepsy include head injury, stroke or brain hemorrhage, lack of oxygen to brain for prolonged period (birth trauma, cardiac arrest), brain infections, brain tumours, chronic alcohol abuse. Epilepsy is not necessarily lifelong, many children or adults outgrow epilepsy or have long term remission from epilepsy.

The pharmacological treatment of epilepsy is quite successful. Up to 70% of people with epilepsy gain full seizure control with treatment.

Epilepsy can be divided into partial and generalised seizures. The partial seizures all originate from the cerebral cortex. The cerebral cortex controls a variety of things include attention and consciousness. The partial seizures can be divided into two types; simple, and complex (Table 20.1). Both simple and complex partial seizures can lead to secondary generalized tonic-clonic seizures.

Table 20.1 Partial seizures (Copyright QUT, Sheila Doggrell)

Partial seizures begin focally in the cerebral cortex, and with simple partial seizures, the manifestations can be diverse depending on the region of the cortex activated. For instance, if the focal point is in the motor cortex representing the left thumb, the epilepsy maybe clonic (jerking) of the left thumb. There is no loss of consciousness with simple partial seizures.

In contrast, complex partial seizures are associated with a loss of consciousness, and this loss of consciousness lasts for 30 seconds to 2 minutes. Complex partial seizures are also associated with purposeful behaviour such as lip smacking or hand wringing.

Both simple and complex partial seizures can lead to secondary generalised tonic-clonic seizures. These are associated with a loss of consciousness. In the tonic phase the body becomes stiff due to the sustained contraction of muscles, and this is followed by the clonic phase when there is jerking of the muscles throughout the body. These secondary generalised tonic-clonic seizures last about 1-2 minutes.

Generalised seizures involve both hemispheres of the brain from the start (Table 20.2). In absent seizures (petit mal), there is an abrupt onset of impaired consciousness, and this is associated with staring and cessation of ongoing activities (rather like a day dream). Absent seizures last 1-2 minutes.

Myoclonic seizures are brief shock-like contractions of muscle. Often myoclonic seizures are restricted to one extremity (e.g. one leg) but may be more generalised.

Table 20.2 Generalised seizures (Copyright QUT, Sheila Doggrell)

Finally, there are generalised tonic-clonic seizures (grand mal), which have the same characteristics as those that can develop from partial seizures, but are not preceded by partial seizures.

The worst type of epilepsy is status epilepticus. Most partial and generalised seizures terminate spontaneously. When this does not happen, the ongoing tonic-clonic seizures are known as status epilepticus. The definition of what constitutes status epilepticus is 30 minutes of continuous seizure activity or a series of seizures without return to full consciousness between seizures

Status epilepticus is a very serious condition. Overall the mortality is about 20% in status epileptics, although death is often related to underlying brain injury. In neonates (newborns) status epilepticus may be related to perinatal (period just before and after birth), hypoxia insults or metabolic insults. In the elderly, status epilepticus is usually secondary to ischemic insults