Epilepsy

seizure is a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.

Epilepsy is a condition where there is an enduring predisposition to generate epileptic seizures.  A diagnosis is defined by the International League Against Epilepsy as:

  • At least 2 unprovoked seizures occurring >24 hours apart OR
  • One unprovoked seizure and a clinical probability of further seizures (similar to that if the patient had 2 seizures i.e. >=60%) OR
  • Diagnosis of an epileptic syndrome

Background and Epidemiology

  • About 10% of the general population will have (what sounds like) an epileptic seizure in their lifetime.
    • The prevalence of epilepsy is about 0.5%.
    • => Of those presenting with a seizure- 19/20 will NOT have a diagnosis of epilepsy.  This is important (Do not diagnose epilepsy without careful consideration, as treatment and implications for the patient’s life could be detrimental)
  • Epilepsy is usually diagnosed EITHER in childhood/adolescence (usually generalised epilepsies due to genetic/congenital factors) OR in the >60s (usually focal epilepsies due to degenerative/pathological changes)
  • Around 70% respond to the first three antiepileptic drugs that are tried.  Around 20-30% will have refractory epilepsy which is non-responsive to conventional treatment.

Classifying Epilepsies by Aetiology

  • There are 6 ‘classes’ of epilepsy aetiology:
    • Genetic- Genetic Generalised Epilepsies (previously known as Idiopathic generalised epilepsies)
      • Thought to account for about 30% of all epilepsies
      • Multiple different variants of epilepsy e.g. Dravet’s syndrome (SCN1A mutations); GEFS+ etc – with different modes of inheritance
      • Can be inherited/familial, but de novo mutations are not uncommon
    • Structural
      • Presence of a distinct structural lesion that could significantly increase the risk of seizures e.g. trauma, hypoxic-ischaemic injury (e.g. stroke), tumour, congenital dysplasia
    • Metabolic
      • Causes include porphyria, uraemia, amino-acidopathies, pyridoxine (vitamin B6) dependent seizures
      • NB can be mixed metabolic-genetic
    • Immune
      • Autoimmune encephalopathy e.g. Anti-NMDA receptor encephalitis and anti-LGI1 encephalitis
    • Infectious
      • Most common cause worldwide.
    • Unknown

Presentation

History and witness history is crucial.

  • Ask about the presenting complaint.  What happened?
    • During- was the patient conscious?  Was the patient moving/jerking? (Were these across the whole body or one area?) Did they go stiff?  Were there any other symptoms (see below)?
      • Also ask about the following- any tongue-biting? any incontinence? (these can be used to distinguish epileptic from non-epileptic attacks- they are signs of loss of consciousness)
    • How long did it last? How did symptoms/signs progress during the seizure?  Could the patient interact with the environment?
    • Did anything bring the seizure on?  Were there any warning signs (either noticed by the patient e.g. smells, sights, tingling, dizziness, palpitations; or by a witness e.g. going blank, eye rolling, lip smacking)
    • Does anything make the seizure go away?  What happens after the seizure?  (Are they tired/zoned out?  Are they themselves? Do they remember what happened/what is happening? Are there any residual symptoms e.g. headache, aches, focal neurological signs?)
  • How many seizures/attacks have they had?  Are they all the same?  (this second Q is particularly important because epilepsy (particularly focal-type) should cause similar symptoms every time- if they are different, then consider excluding epilepsy as a diagnosis).

Examination is rarely helpful in diagnosing epilepsy (NB be aware of the differential diagnosis for fits, faints and funny turns) except in diagnosing epilepsy syndromes.

Classifying Epileptic Seizures and Epilepsy

It is important to try and classify a patient’s symptoms as either focal or generalised.

focal epileptic seizure is one caused by abnormal electrical activity occurring in a particular brain area (unilaterally).  Note that these can progress to a generalised epileptic seizure, which is caused by spread of the electrical activity to more than one brain area (usually to the other hemisphere- resulting in bilateral symptoms and a loss of consciousness).

Focal Epilepsy is epilepsy secondary to a focal abnormal region of the brain (can cause both focal and generalised seizures).

Generalised Epilepsy is epilepsy secondary to a brain which has a tendency to be abnormally hyperresponsive/hyperactive.  It only causes generalised seizures.

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Symptoms of localised focal seizures (most commonly frontal and temporal)

Specific types of seizures

  • Generalised
    • Tonic-clonic (any combination)
      • Tonic phase

        • Loss of consciousness and collapse.  All the muscles contract, causing stiffness.  There may also be a ‘cry’ as air is expelled from the lungs.  The patient may bite their tongue and they may go blue.
      • Clonic Phase

        • Repetitive contraction and relaxation of the muscles causes jerking movements.  There may be loss of bowel/bladder control.
    • Absence
      • Typical
        • ‘Blank spell’ (unresponsive, staring ‘into space’) which typically lasts <10 secs.
        • Occasionally seizures can last longer (still <20 secs) and also cause stereotypical behaviours e.g. blinking, chewing, hand gestures
        • Can sometimes be brought on by hyperventilation
      • Atypical
        • Often more pronounced motor symptoms
        • onset and cessation can be less obvious e.g. patient may be slightly responsive for several minutes before becoming non-responsive
      • Absence with special features
        • Myoclonic absence
          • Myoclonia is a predominant feature, often preceding the absence seizure (usually a diagnosis of Juvenile myoclonic epilepsy)
        • Eyelid Myoclonia
          • EM with absences (EMA) is a rare diagnosis- features include absences with eye twitching, rolling, jerking etc
            • A quick upward jerk of the eyelid is characteristic but often missed
    • Myoclonic
      • Myoclonic
        • Characterised by brief jerks caused by rapid contraction/relaxation of the muscles (usually in the upper limbs; usually bilateral)
        • Patient is usually conscious (cf other ‘generalised’ seizures- classed as generalised because of bilateral effects and a tendency to go onto to develop other generalised seizures)
      • Myoclonic atonic
        • Myoclonic attack immediately followed by an atonic (lack of muscle tone, often causing collapse) attack (drop seizure)
        • Doose syndrome is the most common cause
      • Myoclonic tonic
        • Initial myoclonic phase immediately preceeds a tonic or clonic-tonic seizure
    • Clonic (much rarer than tonic-clonic but can occur)
    • Tonic
      • Isolated tonic seizures can sometimes occur e.g. in Lennox-Gastaut syndrome
      • Consciousness is often preserved, although they frequently occur during sleep
    • Atonic
      • ‘Drop attacks’- often accompanied by a loss of consciousness- characterised by a complete loss of muscle tone
  • Focal
  • Unknown
    • Epileptic spasms
    • consider non-epileptic attacks

Investigations

  • A note on EEG
    • EEG is abnormal in 10-15% of the general population and can be normal in patients with epilepsy.  It is NOT a good diagnostic test.  In patients >35, it is unlikely that an EEG will help at all with the diagnosis.
      • It can be used to try and help distinguish focal and generalised seizure disorders (as a student/junior doctor, this is the main reason why you should/would request an EEG- other uses are more specialised)
        • Other uses include identifying brain areas suitable for resective surgery; checking presence of, and response to treatment in, status epilepticus
  • Video telemetry is the gold-standard (although this might be because seizures can be witnessed in a hospital setting, rather than the EEG results)
  • Imaging (MRI)
    • Used if there is a suspicion over a structural aetiology
  • Blood tests may also find an underlying cause
  • ECG should be performed (particularly in the acute setting) to rule out arrhythmial syncope  

Management

  • For seizure type
    • Focal
      • Carbemazepine is first line.  Lamotrigine is second line.
        • Sodium valproate, topiramate and levetiracetam can be considered as third line treatments
    • Generalised
      • Sodium valproate is recommended first line treatment.
        • In males, this may be suitable.  In females, the side effect may not be acceptable
      • Lamotrigine is second line.  Topiramate can also be used
      • Levetiracetam is often used if side effects are not acceptable or if a quick effect is require
    • Absence
      • Ethosuximide is often a first line drug used in absence seizures
  • Stopping medications
    • stopping medications can be considered after 2 years if the patient has been seizure free.  Medications should be stopped over 2-3 months

Management of an acute seizure

ABCDE!

Give a benzodiazepine (lorazepam or diazepam IV or rectal diazepam/buccal midazolam).  NB must be extremely careful not to over sedate as this can mimic another seizure (creating a vicious circle).

Before administering emergency antiepileptic treatment it is important to establish a cause (a seizure could be due to hypoglycaemia (50ml 50% dextrose is treatment) or alcohol abuse (IV thiamine).

Phenytoin is the antiepileptic drug of choice in acute status epilepticus and seizures because rapid loading is possible..  Keppra and valproate may also be used.  Is seizing continues, propofol and midazolam infusions may be required in an intensive care setting.

Lifestyle advice

  • Driving
    • Patients generally need to be fit-free for a year before the DVLA say they can drive.
Epilepsy in older people
Note that epilepsy has peak presentations in young people and again in older people (>60).  In this group, presentation is often less dramatic (focal seizures without generalisation) and may mimic other diagnoses such as TIA/stroke, orthostatic hypotension/vasovagal syncope and arrhythmias.  Epilepsy may also be secondary to cerebrovascular disease and can be common in vascular dementia.  Management should focus on least side effects and drug-drug interactions: Lamotrigine and gabapentin are generally best tolerated.
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