Ch. 21 - Epilepsy Flashcards
Definition of epilepsy
Tendency to have recurrent seizures; transient derangement of nervous system 2/2 sudden, excessive, and disorderly discharge of cerebral neurons
What are the 3 major seizure types?
Generalized
Partial
Unclassifiable
Describe the electrical discharges in generalized seizures
Bilateral, synchronous and symmetrical, involving BOTH cerebral hemispheres
Describe a tonic-clonic (grand mal) seizure
Tonic phase 10-15 sec (LOC, body stiffens, clench teeth, bite tongue, apnea, urinary incontinence)
Clonic phase 1-2 min (rhythmic muscle contractions)
Postictal phase (confusion and drowsiness)
What are the common types of generalized seizures?
Tonic-clonic (grand mal), absence (petit mal), myoclonic, tonic, atonic
What are the types of partial (focal) seizures?
Simple partial, complex partial
Describe an absence (petit mal) seizure
Brief LOC 5-10 sec with starring or blinking but only minimal motor involvement; consciousness regained with amnesia of event
EEG appearance of absence seizure
Bilateral synchronous 3-Hz spike and wave activity
What can provoke an absence seizure or its EEG abnormality?
Hyperventilation
Describe a myoclonic seizure
Brief, usually single, jerking of trunk +/- limbs
EEG appearance of myoclonic seizure
Bilateral synchronized spike and wave activity
What differentiates partial from generalized seizures?
Electrical activity of partial seizures starts in defined focus
Define simple partial vs. complex partial seizures
Simple partial - w/o impairment of consciousness
Complex partial - with impairment of consciousness
Where do most complex partial seizures arise from?
Temporal lobe (often begin with an aura - taste, smell, deja vu, fear)
What are automatisms?
Lip smacking, chewing movements, repetitive swallowing, upper limb movements
What happens when electrical discharge of a partial seizure generalizes?
Can have secondarily generalized tonic-clonic seizure
What are the 3 types of post-traumatic seizures?
Immediate, early, and late epilepsy
Describe immediate post-traumatic epilepsy
Occurs at the time of, or within minutes, of head injury; usually does not recur; good prognosis; does not predispose to late post-traumatic epilepsy
Describe early post-traumatic epilepsy
Occurs within 1 week of head injury; complicates injuries (e.g. intracranial hemorrhage, prolonged amnesia); predisposes to late post-traumatic seizures
Describe late post-traumatic epilepsy
Occurs after 1 week following head trauma (can be years later)
Factors predisposing to late post-traumatic epilepsy
Post-traumatic amnesia >24 hrs, intracranial hemorrhage, early seizures, depressed skull fracture
Tx of post-traumatic epilepsy
Phenytoin or carbamazepine
What is the incidence of seizures following craniotomy?
18%
What is the drug of choice for postoperative seizure prophylaxis?
Phenytoin for 6 months
What is the relationship between the grade of malignancy of a glioma and the seizure risk?
Inverse! Lower grade a/w higher risk of seizure
DDx for seizures
Syncope (emotional, cardiac, postural, vasovagal), migraine (aura vs. partial seizure), pseudoseizures, movement disorders (Tourette’s vs. myoclonic seizure)
What hormone is often elevated after seizures?
Prolactin
What is the chance of recurrence in a patient with first seizure?
78% in 3 years
Should you start an antiepileptic after 1st seizure?
Controversial; randomized studies say yes (esp. if structural lesion and early life onset)
AED after head injuries?
Decreases risk of early seizures (first 7 days) but not thereafter
Use phenytoin or carbamazepine
AED after craniotomy?
Not shown to make a difference but we use them anyway
AED ppx after febrile seizure?
Not shown to make a difference
AED in patients with glioma?
Use valproate (1st line); levetiracetam if not controlled
AEDs in pregnancy?
Increase risk of fetal abnormalities to 4-8% (vs. 2-3%); risk fo child and mother is greater if mother has uncontrolled seizures
AVOID valproate (neural tube defects)
What drugs are used for emergent initial therapy in status epilepticus?
Lorazepam IV; can also use midazolam IM or rectal diazepam
What therapy is used to maintain control in status epilepticus?
IV phenytoin, valproate, or levetiracetam
What should you do if seizure don’t stop in status epilepticus?
Intubate, continuous EEG monitoring, general anesthesia (often with propofol to burst suppression)
Phenytoin
For partial and generalized motor seizures
Tox: Steven-Johnson syndrome
Metabolized in liver
Half-life 24 hrs + saturation pharmokinetics (“S” shaped)
CHEAP
Carbamazepine
2 or 3x daily dosage
Tox: bonw marrow, rash, lower WBC, hyponatremia
Liver metabolism
Topiramate
2x daily dosing
Tox: major cognitive slowing (esp. speech)
Renal clearance
Lamotrigine
2x daily dosing
Tox: rash, major drug intercation with valproate (doubles VPA levels)
Liver metabolism
Valproate
For partial and generalized seizures
Rapid turnover in brain
Tox: weight gain, hair loss, liver, NEURAL TUBE DEFECTS
Liver metabolism
2-3x daily dosing
EXPENSIVE
Levetiracetam
For partial and generalized seizures
Well-tolerated with few drug interactions (useful in ELDERLY)
Tox: behavioral (hostility, paranoia)
2x daily dosing
Kidney clearance
Indications for surgery in epilepsy
Seizures persist despite AED therapy
Seizure onset in FOCAL area of brain (and area can be removed with low risk of functional deficit)
Outcome after temporal lobe resection for epilepsy
75-80% become seizure-free
Complications after temporal lobe resection for epilepsy
Often unrecognized ‘pie in the sky’ visual defect
Verbal memory deficit after dominant hemisphere resection (‘subtle naming changes’)
Other surgical therapies available for epilepsy
Vagal nerve stimulator, deep brain stimulation (anterior thalamic nuclei), gamma knife radiosurgery
What is medical tx of choice for absence seizures?
Ethosuximide
