14b. Epilepsy

 

- Prevealence: 1%

- High <20yo, >50yo

- Most common location: temporal lobe (followed by frontal, occipital, parietal)

 

Epileptic seizures

          clinical manifestations of excessive and/or hypersynchronous abnormal neuronal activity

          almost always arise in cerebral cortex

 

Epilepsy: requirement for diagnosis

          a chronic disorder characterized by recurrent (>1) unprovoked seizures

          cannot be secondary to metabolic disorder (e.g. hyponatremia)

 

Seizure Classification (Patients may have more than one seizure type)

1.         Partial (focal, local) seizures

- begins in part of ONE hemisphere (determined by clinical or EEG evidence)

a.         Simple or Complex partial seizure

- Simple: do not affect consciousness

- Complex: Impairment of consciousness (either at or not at onset); duration: >30s, with or without aura

b.         Evolving or Non-Evolving to generalized tonic-clonic convulsions (GTC)

2.         Generalized Seizures (convulsive or non-convulsive)

- begins both hemispheres without evidence of focal onset

a.         Absence (impairment of awareness/responsiveness; may be associated with minor motor manifestations: blinking, etc.; no aura; duration: <15s)

b.         Myoclonic (brief sudden contractions; may be generalized or confined to a single muscle; consciousness usually preserved)

c.         Clonic (repetitive jerks)

d.         Tonic (sustained muscular contractions)

e.         Tonic-clonic (loss of consciousness sudden tonic muscular contractions generalized clonic; rhythmic vocalizations may be involved)

f.         Atonic (sudden decrease in muscle tone head drop, sudden fall to the ground)

3.         Unclassified

 

Etiology classification

1.         Idiopathic (most homogeneous group)

2.         Symptomatic (known insult: head trauma, tumors, infarcts, etc.)

3.         Cryptogenic (probably symptomatic, but insult not known)

 

Differential diagnosis (non-epileptic)

1.         syncope (if cardiac, commonly a long prodrome, usually associated with motor activity, associated with motor activity (brief multifocal clonus) not associated with abnormal EEG activity)

2.         hyperventilation

3.         hypoglycemia

4.         migraine (aura is gradual and of longer duration)

5.         transient cerebral ischemia (usually associated with negative signs: weakness, etc., whereas seizures produces positive signs: hallucinations, involuntary movement, etc.)

6.         transient global amnesia

7.         movement disorders

8.         sleep disorders

9.         psychogenic seizures (= pseudoseizures) (purely emotional in nature; out-of-phase movements; conversion syndrome)

 

Treatment

All respond to: valproate, clonazepam, felbamate

Status epilepticus (medical emergency): benzodiazepine and fosphenytoin, generalized anesthesia