Epilepsy/Coma Flashcards
What is epilepsy?
What is epilepsy syndrome?
When a person has recurrent seizures due to an underlying process
Group of clinical and pathological characteristics that suggest underlying etiology but direct cause is unknown
What is a seizure?
What determines the presentation?
A paroxysmal (comes and goes) event which abnormal hype synchronous discharge from CNS neurons.
The presentation is determined by what area of the CNS the hyper synchronized discharge comes from.
Motor cortex- flailing
Hippocampus- feeling of doom
What is the prevalence of epilepsy in America?
1% have recurrent seizures (2.7million people)
NOT A RARE DISORDER
What are certain risk factors that put people at risk for developing epilepsy?
Mental retardation
Cerebral palsy
Alzheimer’s
Strokes
What are the three most common neurological disorders in the US?
Stroke
Alzheimer’s
Epilepsy
Why is the risk of death from epilepsy and epilepsy related causes so high?
People can seize when showering and drown, or when driving and crash, etc.
The treatment only stops seizures in 60-70% of people
When taking a history of a patient with epilepsy, who do you need to take accounts from?
The patient and a witness because often they lose consciousness during the seizure
Does negative testing rule out seizures as a diagnosis?
No, but if the tests are positive, the person definitely has seizures and there is a good chance of epilepsy
How is cerebral electrical activity recorded?
What are 3 major shortcomings with this technique?
Electroencephalogram (EEG) which places electrodes on the persons scalp to record electrical activity .
- The potential difference is 0.01mV and sums local electrical response for 1 cm so it is difficult to localize
- It is difficult to record seizures or irregular activity in th more medial aspects of the brain because the electrodes need to go through too many layers
- Time resolution is compromised so you can’t see events that are happening faster than 1000hz
What can the MRI show for a person with neurological damage?
Hemmohage, stroke, tumors and other structural lesions that put a person at risk for epilepsy
What are the key features to look for on the EEG?
Amplitude, frequency, L/R symmetry and oscillation in the waveform
In adults, what rhythm is interrupted due to the activation of the visual cortex?
The alpha rhythm (10hz)
On the EEG, what do even numbers represent?
What do odd numbers represent?
Even- right side
Odd- left side
What will a seizure do to the amplitude of a spike on the EEG?
It will increase the amplitude because there is a hypersynchronization of neuronal firing
What is the time period between seizures called? What would it look like on an EEG?
What is the time period when the person is having a seizure?
Interictal period would be characterized by isolated spike and wave or normal appearance
Ictal period is characterized by a prolonged run of spike and discharge waves
Why does the failure to detect epileptic discharges not rule out epilepsy?
The reading could have been done during an interictal period
How long is the standard EEG recording temporally?
20 minutes
What is a tonic/clonic stroke disorder?
Involuntary contractions with sustained posture (tonic) followed by rhythmic large amplitude shaking (clonic)
What are absence seizures?
Sudden loss of responsiveness (staring, unable to speak)
What are myoclonic seizures?
Brief shock-like jerks of arms or legs
What are atonic seizures?
Sudden loss of muscle tone and postural control
Seizures can be divided into two main categories. What are they and what are the characteristics of each?
Partial-unilateral EEG abnormalities, unilateral symptoms, focal sensory, motor, aura
Generalized- bilateral EEG abnormalities, nonfocal symptoms, loss of consciousness
What are focal signs for a seizure?
The feeling that you know a seizure is coming.
Partial seizures tend to be focal, while generalized seizures tend to be non-focal
Partial seizure can be broken down into two categories. What are they and what are the characteristics of each?
- Simple partial seizure- consciousness is preserved
2. Complex partial seizure- temporal lobe, altered consciousness
What are the four major types of generalized seizures?
- Tonic/clonic
- Absence
- Atonic
- Myoclonic
What is low b6 a sign of?
What is it associated with?
GABA insufficiency
Metabolic disorders that predispose infants to seizures
What is the most common cause of seizures in infants?
The elderly?.
Infants- congenital malformations
Elderly- strokes
What do recurrent seizures cause?
How can this lead to the Progression of the seizure disorder?
- Secondary loss of neurons
- Scarring of medial temporal lobe
- Loss of hippocampus volume
Leads to progression by:
- Scarring causing development of a new seizure
- Change in the quality or duration of spells
What is the major determinant of whether a seizure is going to decrease hippocampal volume?
The duration of the seizure (over 30 min is bad)
The number of seizures is not that correlated
What are major “lifestyle” risks for seizures?
- Alcohol- withdraw from alcohol
- Lack of sleep
- drug abuse
- Flashing lights
What 3 major types of drugs are used for seizures?
What are the side affects?
Na channel use dependent blockers
GABAaR enhancers
GABA analogs
All three are aimed at stopping the transmission of electrical signal
Fatigue, poor concentration and coordination
If the drugs fail (as they do in 30-40% of cases) what is the last resort for severe seizures?
Electrical stimulation (vagus deep brain stimulation) It can determine whether surgery is an option for lesion resection, disconnection of the corpus callosum or hemispherectomy
How do doctors do fine mapping of the seizure focus?
They place a grid on the pia matter of the brain to map where the lesion is.
What is consciousness?
What are the two major components?
Consciousness is an awareness of self and surroundings
- Content- cognitive and affective (emotional) function- cortex
- Arousal- state of wakefulness - brainstem (ARAS)
Stimuli to what organ promotes sleep?
Stimulus to what area promotes wakefulness?
Thalamus- sleep
Ascending reticular activating system in the rostral brainstem- wakefulness
What area of the brainstem contains the ascending reticular activating system?
What two neurotransmitters do the neurons of the ARAS send to the thalamus?
rostral brainstem- pon and midbrain
Norepinephrine (adrenergic)
Acetylcholine (Cholinergic projections)
If you ablate the ARAS what would you see?
Persistent sleep-like state
What does the rostral pontine reticular formation do?
What does the caudal pontine and medullary reticular formation control?
Rostral reticular formation modulates forebrain activity like sleep/wake.
Caudal reticular formation modulate premotor coordination of lower somatic and visceral motor neuron pools (gamma neurons)
What are the terms used to describe levels of sensorium and arousal?
Alert Inattentive Drowsy Lethargic Stuporous Coma
What happens in the ARAS is perpetually stimulated?
The person will have insomnia
What is coma?
What can cause it?
A state of reduced consciousness where the person is unresponsive to all external stimuli.
They have no cerebral sleep-wake cycles on the EEG.
It can be caused by loss of function of the ARAS or loss of function of BOTH cerebral hemispheres.
Is loss of function of one cerebral hemisphere sufficient to cause coma?
No
What level of consciousness if regulated by the cerebral cortex?
What level of consciuosness is regulated by the brainstem?
- Content -cognition and affect
2. Arousal
What is the major scale used in the ER for level of consciousness?
What three factors does it measure?
Why is the name a misnomer?
Glasgow coma scale
- Best eye response
- Best verbal response
- Best motor response
It is a misnomer because It actually measures depressed function on the way to coma, not levels of coma.
What are the Glasgow coma scale ranges for severe, moderate and minor function?
How many levels are there to assess for eyes, verbal, motor?
Below 8 is severe
9-12 is moderate
13 and up is mild.
4, 5, 6
What are the three main causes for coma?
- Metabolic brain dysfunction (drug intoxication)
- Localized to hemispheres (hemmohage)
- Localized to brainstem (infarct)
What signs would help us localize the cause of the coma to the brainstem?
Messed up cranial nerves so:
Abnormal pupil reflex to light
Abnormal eye movements
What is the classic cause for a brainstem caused coma?
Intracranial mass lesion increases pressure and there is uncul herniation over the edge of the Tentorium cerebelli which presses into the lateral brainstem which will dilate the pupil, cause ptosis, down and out palsy
What causes of coma have the best outcome? Worst?
Drug intoxication-excellent prognosis with increased bloodflow and o2 delivery
Metabolic lesions- better than structural
Worst prognosis for longer duration coma and older people
What physical sign and for what duration is the worst prognosis for coming out of a coma?
Loss of pupil reflex for over 12 hours
What is chronic vegetative state?
Persistent unresponsive state but brainstem function is returned.
- Eye opening on command
- Sleep wake cycles return
- Spontaneous respirations
