Central Nervous System Flashcards
(28 cards)
What is the definition of epilepsy?
chronic disorder characterized by seizures that usually recur unpredictably and in the absence of any consistent provoking factors
What percentage of the population suffers from epilepsy?
1%
What percentage of epilepsy patients have one seizure type and what percentage have mixed seizure types?
70% one type
30% mixed types
What are the two types of causes of epilepsy?
PRIMARY cause: most are idiopathic (no known cause)
SECONDARY cause: neoplasms (tumor), cerebral infections, fever, trauma, metabolic disorders (hypoglycemia, hypocalcemia), withdrawal
What are the two categories of seizures?
Partial: most common. 70-80% of seizure disorders
-short alterations in consciousness and body movements
Genralized:
- most often seen in children
- temporary lapses in consciousness lasting a few seconds
- staring off into space, may experience movements of eyes, head, or hands but do NOT CONVULSE
What are the two subcategories of partial seizures?
SIMPLE partial seizures: 20-60s
-no impaired consciousness
COMPLEX partial seizures: 45-90s
- impaired consciousness, lack of responsiveness
- memory impairment
- often have prelude symptoms
What are the sub categories of generalized seizures?
absence (staring into space)
myoclonic (twitchy muscles)
tonic-clonic (thrashing)
tonic (lose consciousness, muscles initially stiffen)
atonic (lose muscle tone)
What percent of pts will achieve complete control with drug therapy?
50%
What percent of pts will have reduced freq. of seizures with drug therapy?
25%
How often must a seizure occur before drug therapy can be initiated for epilepsy? What must happen before they discontinue therapy?
2 or more unprovoked seizures within 6-12 months
seizure free for at least 2 yrs
What are the 8 drugs used for epileptic drug therapy?
Phenytoin
Carbamazepine
Valproic acid / Divalproex
Benzodiazepines
Gabapentin
Topiramate
Phenobarbital
Lamotrigine
What is the biological cause of a seizure? (what happens at a cellular level)
an imbalance within excitatory and inhibitory circuits in the brain
What are the two ways that antiepileptic drugs try to prevent seizures?
altering electrical transmission by affecting ion channels in the cell membrane
altering chemical transmission between neurons by affecting neurotransmitters in the synapses
What is phenytoin’s mechanism of action?
stabilizes neurons against hyper excitability through Na channels
What types of seizures might phenytoin be used for?
generalized
- tonic-clonic
- not effective for absence seizures
Partial (complex and simple)
What can be said of the dosage for phenytoin?
need a blood test to determine dosage; target is 40-80 umol/L
doses over 400 BID (too hard on stomachs)
What are the routes of phenytoin?
injectable and oral
-IM or SC route not recommended due to extravasation at site (eats into tissue)
What are the adverse effects of phenytoin?
CNS:
- drowsiness, confusion
- signs of toxicity: ataxia, nystagmus
Dermatological:
- skin rash
- gingival hyperplasia (thick gums)
- extravasation
Others:
-HIRSUTISM (body hair growth)
What is ataxia?
wobbling/staggering drunk like state
What is nystagmus?
wobbly eyes
What are the precautions that must be taken with phenytoin? (5)
monitor for reactions
reinforce importance of good dental hygiene
do not abruptly stop this med
do not use with alcohol
separate from enteral feeding (tube feeding) 1-2 hrs as it will prevent absorption in the stomach
What is carbamazepine’s mechanism of action?
affects Na channels and inhibits rapid firing of brain cells
What types of seizures is carbamazepine used for?
generalized: tonic clonic
Partial: simple and complex
What are some other uses for carbamazepine?
trigeminal neuralgia (pain disorder in the face)
bipolar disorder
