Epilepsy

Question 1

What are the current diagnostic methods in epilepsy?

Answer 1

Diagnosis requires 2 or more seizures that cannot be explained by clinical problems originating outside of the brain.

Patients are given an electroencephalogram (EEG), but the chances that a seizure will occur during the test are very low, but interictal spikes and brief epileptiform.

MRI scans are used to exclude structural underlying causes of epilepsy, such as tumours.

Blood tests for prolactin are used, as it is raised for short levels after seizures, particularly tonic/clonic seizures. Measurement of this hormone is useful to distinguish between epilepsy and pseudoseizures.

Question 2

How do electroencephalograms work?

Answer 2

Many neurones within the cortex have roughly parallel dendrites. Many of the dendrites are doing the same thing at the same time, so produce a voltage that can be detected through the scalp, skull and meninges.

During an epileptic seizure, the neurones become excessively synchronised, which can be detected by the EEG.

Question 3

What is a generalised seizure, and what are the subtypes?

Answer 3

A generalised seizure is one that results in a loss of consciousness.

Tonic clonic (Grand mal)
Absence epilepsy (Petit mal)
Tonic seizures
Atonic seizures
Myoclonic seizures

Question 4

What is a tonic clonic seizure?

Answer 4

The patient becomes rigid and may fall during the tonic phase, which is followed by the clonic phase where muscles rhythmically relax and contract. Following there is usually a period of tiredness and confusion.

Question 5

What is absence epilepsy?

Answer 5

Patient looses consciousness for just a few seconds. The seizures are not associated with changes in muscular activity (apart for some small rhythmic movement of the eyelids or facial muscles). These are common in children and are often mistaken for day dreaming.

Question 6

What is a tonic seizure?

Answer 6

Widespread muscular contraction, usually leading to falling. There is a rapid recovery, but there is risk of injury from seizures.

Question 7

What is an atonic seizure?

Answer 7

Sudden loss of muscle tone. There is risk of injury when falling.

Question 8

What is a myoclonic seizure?

Answer 8

Brief sudden movement (jerking) of one or more limbs; or the trunk.

Question 9

What is a focal seizure, and what are the subtypes?

Answer 9

Seizures that begin in a specific region, patient is usually aware of what is occurring.

Focal sensory seizures
Focal motor seizures
Temporal lobe epilepsy

Question 10

What is a focal sensory seizure?

Answer 10

Patient expresses sensory symptoms which alter dependant on location

Question 11

What is a focal motor seizure?

Answer 11

Patient expresses tonic OR clonic contractions on the contralateral side. More bizarre movements occur when spike occurs in the frontal lobe.

Question 12

What is temporal lobe epilepsy?

Answer 12

Excessive synchronisation int he temporal lobe, which is the association region of the cortex and is closely related to the limbic system, so the seizure gives a mix of sensory, motor and emotional symptoms. Patients describe an aura at onset of seizure which may consist of taste, odour or abdominal sensations, feeling of deja vu or irrational fears.

Question 13

What is a secondary generalisation seizure?

Answer 13

Those that begin in a primary location, but the abnormal activity spreads

A Jacksonian march is when seizures spread though contiguous parts of the cortex producing seizures in closely associated regions. (One example is hand - forearm - upper arm - shoulder)

Question 14

What is reflex epilepsy?

Answer 14

When seizures are triggered by sensory stimuli, most commonly flickering or stroboscopic light

Question 15

What is status elipticus?

Answer 15

When seizures fail to stop spontaneously. It is a serious medical emergency, which is felt untreated can quickly lead to death.

Question 16

What is the difference between symptomatic and idiopathic epilepsy?

Answer 16

Symptomatic epilepsy are usually secondary to neuronal migration disorders, head injury, tumours, neuronal loss and gliosis.

Idiopathic epilepsies are rarely associated with harmful side effects, and usually respond well to treatment. They are usually genetic.

Question 17

What are neuronal migration disorders?

Answer 17

These occur by mutations that interfere with the complex process of organising the brains electrical activity. These include a 2nd layer of grey matter within the white matter (double cortex), a very smooth cortex lacking normal gyri and sulci (lissencephaly) and loss of small gyri in place of normal ones (polymicrogyri).

Question 18

How can head injuries lead to epilepsy?

Answer 18

When blood is drawn, the breakdown product: ferric and ferrous ions are produced, which is an irritant which can lead to seizures.

Question 19

How can tumours lead to epilepsy?

Answer 19

Tumours can cause the release of glutamate into the ECF, increasing the activity of neurones.

Question 20

What gene mutations can cause idiopathic epilepsy?

Answer 20

Monogenic mutations follow Mendelian inherence, polygenic mutations do not.

Monogenic:
alpha-1A322D can cause autosomal dominant juvenile myoclonic epilepsy
KCNQ2/3 codes for K+ channels, and can cause bengign familial neonatal epilepsy

Polygenic:
CACNA1H code for low threshold transient Ca2+ channels, which can lead to childhood absence epilepsy

Question 21

What is genetic concordance and how is it calculated?

Answer 21

Concordance is the presence of the same trait in both identical twins.

Concordance = (2 x concordant pairs) / (2 x concordant pairs + discordant pairs)

Generalised epilepsies tend to have a higher concordance than focal epilepsy