Epilepsy

Diagnosis

The epileptic syndromes are classified according to seizure types, symptoms, clinical findings and the causes of epilepsy. The seizures are classified according to symptoms and findings during the attack and this depends on which brain region is involved.

Classification of seizures and their associated symptoms

Types of epilepsy are characterised to seizure type. These are split into two broad groups, each with several subgroups:

1) Partial seizures

These arise from localised cortical regions and may spread to other cortical areas and to the opposite hemisphere involving the whole of the brain. The symptoms will depend on which part of the brain is affected and what physical or mental activity that part of the brain controls. There are three types of partial seizures:

• Simple partial seizures
  Simple partial seizures are those attacks which show evidence of a localised onset, during which consciousness (responsiveness) is preserved. The discharge is usually confined to a single hemisphere and the symptoms are specific to the affected brain region. Depending upon which region of the cortex is affected the symptoms may be motor, sensory, autonomic (sweating, gastric discomfort, vomiting), or psychic (anxiety, deja vu).
  
  
• Complex partial seizures
  Complex partial seizures are those attacks which show evidence of a localised onset, but during which consciousness (responsiveness) is altered. The seizure is often associated with automatism, eg repetitive hand movements, smacking, chewing etc. There is often a postseizure confusion period. This seizure type is often confused with the absence seizure type (see below).
  
  
• Secondary generalised partial seizures
  These seizures are those attacks in which a partial seizure spreads to both hemispheres. The patient is unconscious and presents motor involvement with cramps.

2) Generalised seizures

These attacks are evoked from deeper brain regions, eg the thalamus  and spread simultaneously to both hemispheres. There are several types of generalised seizures and the symptoms of each type are described below:

• Tonic-clonic seizures
  The attack shows evidence of an involvement of both hemispheres and starts with the tonic phase, in which the patient's muscles stiffen, and after several seconds, progresses to the clonic phase during which the patient experiences repetitive generalised convulsions. The total duration is typically 20-30 seconds with a postseizure confusion phase with respiratory problems. There may also be urine and faecal incontinence during the seizure.
  
  
• Absence seizure
  This type of seizure is nonconvulsive and lasts between 5 and 30 seconds. A person may be unaware of their surroundings and may stare into space, appearing 'frozen'. Discrete eye movements (myoclonic jerks) may appear. There is either a very short, or no, postseizure period associated with this seizure type.
  
  
• Myoclonic seizure
  These are various types of seizure where short bursts of muscular (myoclonic) jerks are experienced. The jerks may appear in all body parts, but mostly the arms are affected.
  
  
• Tonic and clonic seizures
  Tonic and clonic seizures may appear alone without progression.
  
  
• Atonic seizures
  This is a relatively seldom type of seizures with sudden loss of muscle tone which can cause the individual to fall and suffer severe lesions to the body and head.

Status epilepticus is a medical emergency which occurs if the epileptic attack is prolonged, or if several seizures follow each another within a short time period. Status epilepticus with tonic-clonic seizures is a severely dangerous condition, carrying a significantly increased health risk and requiring immediate treatment and often intensive care. Other epileptic seizures can present as status epilepticus, eg complex partial status, which are also associated with a significant health risk.

An epileptic syndrome is a terminology used for classification of different epilepsies and is the combined information of seizure types, clinical findings such as age of onset, severity of the epilepsy, heredity, presence of other neurological disorders and clinical findings. There are several epileptic syndromes which include:

• Neonatal
  febrile convulsions and benign myoclonic epilepsy in infancy

• Epilepsies affecting people of a younger age
  benign epilepsies with centrotemporal spikes and absence epilepsy

• Epilepsies affecting the adult (elderly) population
  partial epilepsy associated with former stroke or tumours

• Epilepsies affecting both the young and adult population
  temporal lobe epilepsy and juvenile myoclonic epilepsy