Oct4 A1-Loss of Consciousness Flashcards
what is LOC
loss of arousal, awareness and responsiveness. inferred from behavior and response to stimuli (absent)
2 things that have to happen for LOC to happen
either damage to
- both cerebral hemispheres
- reticular activating system in the brainstem (where consciousness arises from). projects to thalamus which projects to cortex
pyramid of cognition
- awake
- alert
- appropriate
- attention
LOC = none of those are present.
note: in general, when some of these lacking, just describe it
what is alteration of consciousness
not completely normal consciousness but also not a complete loss of consciousness (eyes open, standing up but not responding to voice)
diff ways seizures can affect consciousness
- LOC
- alteration of consciousness
- no effect on consciousness
ddx of SUDDEN TRANSIENT ISOLATED COMPLETE LOC
- syncope
- cardiac (aortic stenosis or arrhythmias)
- neurological (seizure)
syncope def
transient, self-limited LOC caused by global cerebral hypo-perfusion (insufficient blood flow)
- is NOT a diagnosis but a sx
- usually ORTHOSTATIC or NEURALLY-MEDIATED (one subtype of that is vasovagal syncope). note: could also separate syncope in groups of syncopes linked to diff precipitating factors (situational syncope), like micturition syncope (a vasovagal syncope triggered by urination), orthostatic syncope (triggered by standing up, etc.
causes of orthostatic syncope
- benign
- hypovolemia (volume depleted, dehydrated)
- medication-related (like antihypertensives that interfere with contraction of blood vessels)
- specific diseases (like ANS failure where compensatory mechanisms to keep the BP don’t work)
- the taller, the more likely
- counteracted by intermittent contraction of legs and abdomen*
causes of vasovagal syncope subtype of neurally-mediated syncope
syncope precipitated by vagal stimuli
- emotion
- pain
- direct stimulation
why aortic stenosis and arrhythmias cause STIC LOC
they cause cerebral hypoperfusion like the causes of syncope
how do you make a diagnosis of the cause of a STIC LOC (how to know which of the 3 causes it is)
based on history only
questions to ask on STIC LOC
- witnesses
- when, where, what
- state of the patient
- prodrome (sx preceding LOC)
- what happened (fall, injury, convulsion)
- where they stressed, happy, fatigued, didn’t eat or drink all day, etc.
- after (recovery, confusion, recall. how quickly woke up, how long did the episode last)
typical hx for syncope as cause of STIC LOC
- situation (prolonged standing or sudden standing, heat, dehydration, skipping meals, micturition, having blood drawn + other circumstances likely to cause syncope)
- prodromal sx (feeling faint or dizzy, change in vision (blurring, yellow or black, seeing starts), sweating, nausea, looking pale), felt like they would lose consciousness
- RAPID RECOVERY of consciousness and alertness (may wonder what happened but know who they are, where they are, can answer Qs, are not somnolent, confused)
typical hx for seizure as cause of STIC LOC
- to mimic syncope, a seizure must cause LOC and a fall to the ground so this usually means generalized tonic-clonic seizure which has the following typical pres of these things happening in order*
- vocalization (starts with loud cry)
- tonic stiffening of limbs
- clonic movements (jerking of limbs)
- tonic-clonic sx for 1-2 min
- prolongd post-ictal period (unconscious for 5-10 min)
- confused for >10 min when regain consciousness
- possible urine incontinence and tongue biting
why detailed hx is imp in seizures for cause of STIC LOC
- bc other seizure types than generalized tonic-clonic seizures exist that can cause ALTERED consciousness (with eyes open and maintained postural tone/no fall)
- have to know if just jerky mvmt (clonic) or other things too
