Epilepsy
Contents
• Epilepsy
• Classification
• Status
epilepticus
• Pathophysiology
Objectives
At the end of PDF Notes, student will be able to
•
Define
epilepsy
•
Define
status epilepticus
•
Classify
epilepsy
•
Describe the
pathogenesis of epilepsy
Epilepsy
• Chronic
brain disease of diverse etiology
• Characterized
by recurrent paroxysmal episodes of uncontrolled excitation of brain neurons
• Manifesting as brief episodes (seizures) of
loss of consciousness, with or without characteristic body movements
(convulsions)
Status epilepticus (SE)
Continuous
convulsion lasting longer than 30 minutes OR Occurrence of serial convulsions
between which there is no return of consciousness
Pathophysiology of
• Normally,
a balance between excitatory and inhibitory factors - proper functioning of a
healthy human brain
• Reduction of inhibitory synaptic
activity or enhancement of excitatory synaptic activity -trigger a seizure
• NTs mediating the bulk of synaptic
transmission in the mammalian brain are amino acids
• GABA - principal inhibitory
• Glutamate - excitatory
neurotransmitters
• Repeated
epileptic discharge can cause neuronal death (excitotoxicity).
• A relative deficiency of inhibitory
neurotransmitters such as GABA
• An increase in excitatory neurotransmitters
such as glutamate would promote abnormal neuronal activity
Clinical
manifestations
• Depend on the location of the focus
and the pathways involved in its spread
• ‘Generalised’ - initial activation
of both hemispheres of the brain
• ‘Partial’ or ‘Focal’ - discharge starts in a localised area of the
brain
Grandmal seizure
• Generalized
convulsion, also called the grand-mal seizure.
• Patient
loses consciousness and usually collapses.
• Followed
by generalized body stiffening (called the "tonic" phase of the
seizure) for 30 to 60 seconds,
• violent
jerking (the "clonic" phase) for 30 to 60 seconds,
• patient
goes into a deep sleep.
• During
grand-mal seizures, injuries and accidents may occur,
• Tongue
biting and urinary incontinence
Absence seizures
• Short
loss of consciousness (just a few seconds) with few or no symptoms
• Patient,
most often a child
• Seizures
begin and end abruptly
• Patients
are usually not aware that they are having a seizure, except that they may be
aware of "losing time."
Myoclonic seizures
• Consist
of sporadic jerks
• Usually
on both sides of the body
• Patients
sometimes describe the jerks as brief electrical shocks
• When violent, these seizures may result in
dropping or involuntarily throwing objects
Clonic seizures
·
Repetitive
·
Rhythmic jerks
·
Involve both sides of the body at the same time
Tonic seizures
Tonic seizures are characterized by stiffening of the
muscles.
Atonic seizures
• Sudden
and general loss of muscle tone
• Particularly
in the arms and legs
• Often
results in a fall
Simple partial seizures
• Key feature is preservation of
consciousness
• A sudden depolarization within a group of
neurons called Paroxysmal depolarizing shift (pds)
• Lasts for 200 ms occurs in case of
patients with partial seizures.
• This
results in generation of an abnormally rapid train of action potentials
Complex partial seizure
• Impaired consciousness lasting 30
seconds to 2 minutes
• Often associated with purposeless
movements such as lip smacking or hand wringing
• Associated
with amnesia
Secondarily generalized seizure
Ø Partial
seizures may get generalized
Ø spreading
along diffuse connections to involve both cerebral hemispheres
Ø This seizure spread occurs through several
pathways
ü U FIBRES connect various regions of the
cortex.
ü CORPUS CALLOSUM allows for spread between
hemispheres.
ü THALAMOCORTICAL PROJECTIONS provide a pathway
for diffused synchronized spread throughout the brain
Summary
• Epilepsy
is characterized by recurrent paroxysmal episodes of uncontrolled excitation of
brain neurons
• Manifesting as brief episodes (seizures) of
loss of consciousness, with or without characteristic body movements
(convulsions)
• Continuous convulsion lasting longer than 30 minutes is status epilepticus
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