Week 4: Basis of Consciousness and Seizures Flashcards
What are the different types of brain herniations? (and their alternate names)
- Subfalcine (AKA cingulate): compresses the ACA
- Transtentorial (AKA uncal): compresses III, cerebral peduncle, reticular formation
- Foramen magnum (AKA tonsillar)
Mesencephalic reticular formation projects where? Loss of this would result in ….
To the intralaminar nuclei
Loss of either the mesencephalic reticular formation OR the intralaminar nuclei would result in loss of consciousness
What are teh three types of thalamic nuclei and what is an example of a “non-specific” thalamic nucleus?
- Relay: have well defined input and output (e.g. VPL/VPM relay body sensations to cortex)
- Association: project to association areas
- Non-specific: project broadly, involved in more general functions, like awareness
The centromedian nucleus
What is the equation for cerebral perfusion pressure? What is normal intracranial pressure for an adult?
CPP= mean arterial pressure- intracranial pressure (normal is 5-15 mmHg)
barbituates and benzos act on what type of channel?
GABA a
Loss of which nuclei would produce the following symptoms?
- difficulty in phonation and swallowing
- nystagmus
- dysarthria, trouble moving tongue
- pain and temperature loss on the face
- nystagmus: vestibular nuclei (in caudal pons/rostral medulla)
- difficulty swallowing and phonating: nucleus ambiguus (SVE for IX, X) (found in medulla)
- dysarthria, trouble moving tongue: hypoglossal nucleus
- spinal nucleus of trigeminal nerve (ipsilateral face…vs. temp/pain for body is via spinothalamic and is CL)
What do the pupils do in metabolic coma vs. supratentorial mass-causing-coma? Are opoid OD pupils reactive?
Remain reactive in metabolic coma… not so with the mass
Opioid pinpoint pupils are reactive
What is the Cushing response?
Systolic hypertension, bradycardia and erratic respiration seen in response to increased ICP, especially in children
Why do we hyperventilate someone with increased ICP?
To offload CO2. In the brain, vessels dilate when PCO2 goes up in the area (resistance goes down) so that waste can be cleared. Therefore, lowering PCO2 is one way to get blood volume out of the head…the Monroe-Kelly doctrine…
What is a generalized vs. a partial seizure? Categories of each?
Generalized involves both cerebral hemispherse, partial is a focal seizure.
Generalized
- Tonic: sustained contraction
- Tonic-clonic
- myoclonic (single brief jerk )(**no post-ictal state)
- Atonic (sudden loss of muscle tone)
- Clonic
- Absence (the blank stare) (**no post-ictal state
Partial
- In simple partial the pt does not lose awareness
- In *complex *partial the pt has impaired consciousness (e.g. automatisms like lip smacking)
Secondary generalized (a generalized seizure following a partial seizure)
“aura” is AKA….
simple partial seizure
What are the components of consciousness?
- Level of consciousness
- Reticular formation esp. neurotransmitter systems (NE, 5-HT, dopa, histamine, cholinergic
- State of consciousness (how responsive you are to the environement)
- thalamic reticular nucleus important (GABAnergic), fires at 40Hz and the frequency of the firing seems to be important
- Content
- Prefrontal cortex and parietal cortex (is the same as the association areas?)
How many seizures do you have to have to have epilepsy?
2 or more, and they must be unprovoked (e.g. not metabolic or known sructural)
epilepsy= tendency towards recurrent seizures
What are the most important seizure mimics?
TIA
Migraine
Aura
Syncope
Psychogenic
What is the definition of status epilepticus? What is the mortality associated with this?
>5 min of continuous seizure or >2 discrete seizures without complete recovery of consciousness between them.
20% mortality for adults in first episode
What is the concentration of anesthetic required to inhibit autonomic reflexes vs. that required to simply inhibit pain?
Need a higher concentration. You have to inhibit the gag reflex so the pt can be intubated
What determines to time to induction of a inhaled anesthetic?
What determines/is a measure of an inhaled anesthetic’s potency?
Time to induction depends on solubility in blood (partition coefficient). More soluble, longer time to induction.
Mean Alveolar concentration : the dose required to prevent movement in 50% of patients. inversely proportion to lipid solubility (so, something that is very lipid soluble will have a low MAC). increases with age, temperature.
What is the definition of MAC?
=mean alveolar concentration. It is the alveolar that prevents movement in 50% of patients
depends on age, body temp, pregnancy…
Why don’t you give inhaled anesthetics during c-sections?
because is relaxes the uterus….inhaled anesthetics depress excitable tissues
You can have primary and secondary brain injury. The primary injury is usually due to what? The secondary brain injury is usually due to what?
Primary: diffuse axonal injury from impact
Secondary: hypoxia, infxn, hypotension, seizure, ICP
Thiopental, propofol, ketamine and etomidate are what kind of anesthetics?
IV
What are severe, moderate and mild GCS scores?
Severe 3-7
Moderate 8-12
Mild 13-15
What can a chronic subdrual hematoma be confused with?
Dementia, stroke…always keep on the DDx
What are the most common causes of epilepsy in infancy, childhood, adolescence and adulthood?
Infancy (things that show up at the beginning of life):
- metabolism, birth injury, malformations
Childhood (slower to present genetic things, kids get into accidents, kids have immature immune systems):
- genetic, CNS infxn, trauma
Adolescent (teens get into accidents, they also experiement with drugs and alcohol):
- trauma, intoxication, withdrawal
Adult:
- stroke/TIA, tumor, metabolic disturbance, neurodegenerative
What is the gist of the Canadian CT Head Rule?
CT is only required for patients with minor head injuries AND:
- High risk for neurologic intervention
- GCS < 15 after 2 hours
- Suspected skull fracture
- Any sign of basal skull fracture (Battle’s, racoon eyes, ottorhea…)
- Vomiting >2 times
- Age >65
- Medium risk
- retrograde amnesia
- dangerous mechanism
minor head injury=witnessed loss of consciousness, definite amnesia, witnessed disorientation
What are some possible/common seizure precipitants?
EtOH withdrawal
hormonal variations (?menstruation)
fever
sleep deprivation
What ions currents (and direction) promote excitation and inhibition in the brain?
Excitation: Na and Ca in
Inhibition: K out, Cl in
What receptor do benzos and barbituates act on and what ion current does that promote?
GABA a: Cl- inward
What are the side effects of dilantin (phenytoin) and valproic acid?
N.B: all AEDs are teratogenic, but to different degrees
Phenytoin:
- gingival hypertrophy
- hirsutism
- coarsening of facial features
Valproic acid:
- weight gain
- menstrual irregularities
- transient hair loss
What are the most commonly used drugs for treating epilepsy and what are their MOAs?
- Sodium channel blocking
- Phenytoin
- Carbamazepine
- Lamotrigine
- Barbituates: prolong GABA a opening (more Cl- in, more K+ out)
- Benzodiazepines: increase frequency of GABAnergic firing
- Levetiracetam: somehow neuromodulates calcium channels
- Gabapentin….
Which drug has more side effects: phenytoin or carbamazepine?
Carbamazepine has fewer side effects than dilantin
What drugs are efficacous for primary generalized epilepsy? What drugs do partial seizures?
Primary generalized
- valproic acid
- lamotrigine
- levitiracetam
- dilantin
Partial seizures: so many more possibilties, including gabapentin and topiramate
Which AEDs do you need serum concentrations for?
Carbamazepine
Phenytoin
Phenobarbital
Primidone
Valproic acid
(**all the older ones. The newer ones don’t need levels)
How to abort status epilepticus?
Lorazepam followed by phenytoin
What are the TIPS causes of unconsciousness?
Trauma/Tumour/Temperature/Toxin
Infection
Psychogenic
Seizure/subdural hematoma/subarachnoid hemorrhage/stroke
What are the AEIOU causes of metabolic unconsciousness?
Alcohol
Electrolyte imbalance
Infxn/Insulin
Oxygen/Opiates/Other drugs
Uremia
Morning headaches or headache on valsalva indicate what?
increased ICP
