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 à sudden tonic muscular contractions à generalized clonic; rhythmic vocalizations may be
involved)
f.
Atonic (sudden
decrease in muscle tone à 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