Coma Lecture Flashcards
Coma Pathophysiology
- Bilateral __ __ impairment
- Damage to or distortion of the __ __ ___ system in the brainstem
Coma Pathophysiology
Can be due to diffuse or metabolic dysfunction
Bilateral cerebral hemisphere impairment:
- Direct structural lesion of both hemispheres
- Indirect (lesion of one hemisphere but affecting both)
Damage to or distortion of the ascending reticular activating system in the brainstem
- Direct (stroke)
- Secondary (brain herniation)
the __ ___ ___ system is involved with the general activation of the brain to produce a crude consciousness.
Components:
- upperr brain stem: brainstem reticular formation, raphe nuclei
- diencephalic region: thalamus, hypothalamus, basal forebrain.
the reticular formation projects to the __, __, and __ ___
the thalamus contains a ___ ___ ___ which relays info to all other nuclei
The ascending reticular activating system is involved with the general activation of the brain to produce a crude consciousness.
Components:
- upperr brain stem: brainstem reticular formation, raphe nuclei
- diencephalic region: thalamus, hypothalamus, basal forebrain.
the reticular formation projects to the thalamus, basal forebrain, and hypothalmaus
the thalamus contains a diffuse projection nuclei which relays info to all other nuclei
identify diffuse, and focal causes of coma
Diffuse (bilateral) cerebral hemisphere impairment
- metabolic/toxic
- Anoxia
- Traumatic brain injury
- Increased ICP
- Seizure
Focal (bilateral, direct or indirect) cerebral hemisphere impairment
- Large mass lesions
Damage to, or distortion of the ascending reticular activating system
- Direct (stroke)
- Secondary (brain herniation)
*
Note: Comas of unknown origin
Metabolic and diffuse:: exogenous overdose, endogenous metabolic, anoxia or ischemia, infection (meningitis), subarachnoid hemorrhage, concussion or postictal
Supratentorial lesions: intracerebral hematoma, subdural hematoma, brain tumor, cerebral infarct, abscess, epidural hematoma
Subtentorial lesions: brainstem infarct, brainstem hemorrhage, cerebellar hemorrhage, cerebellar tumor, cerebellar infarct, cerebellar abscesses
Psychiatric
determine the differences between Uncal and central herniation
Brain Herniation: process whereby part of the brain is squeezed across structures within the skull
Uncal Herniation: unilateral dilated pupil, contralateral extensor plantar response.
Late→ ipsilateral hemiparesis (false lateralizing sign = kernohans phenomenon)Kernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect,
Central Herniation: increasing obtundation, pupils small, equal, extensor plantar responses, decorticate posturing
Late → mid-position fixed pupils.
Top GCS you can get:
Motor is x/__
Verbal is x/___
Eye opening is x/__
Top score is 15
Motor is x/6
Verbal is x/5
Eye opening is x/4
Coma cocktail
thiamine, followed by lgucose. Naloxone (for opioid OD) and flumazenil (for benzo OD)
hat to do if you suspect increased ICP or herniation
raise head of bed, hyperventilate, restrict fluids, mannitol.
consider steroids and neurosurgical consultation after CT scan/
Cortical posturing
Decerebrate posturing
Cortical posturing→ in response to painful stimuli, patient will have flexion of both elbows, and plantar flexion of both feet.
In Decerebrate posturing→ extension of elbows, flexion of feet
Cortical posturing→ in response to painful stimuli, patient will have __ of both elbows, and __ flexion of both feet.
In Decerebrate posturing→ __ of elbows, __ of feet
Cortical posturing→ in response to painful stimuli, patient will have flexion of both elbows, and plantar flexion of both feet.
In Decerebrate posturing→ extension of elbows, flexion of feet
unequal pupils = CN___ problem
CNIII
Pupils in Coma
Parasympathetic lesions: Lesions of the Edinger-Westphal nucleus, CN III, or parasympathetic result in a ___ and ___ (___) pupil.
Sympathetic Lesions: Lesions along the sympathetic pathway result in a __, ___ pupil.
Pupils in Coma
Parasympathetic lesions: Lesions of the Edinger-Westphal nucleus, CN III, or parasympathetic result in a dilated and nonreactive (fixed) pupil.
Sympathetic Lesions: Lesions along the sympathetic pathway result in a small, reactive pupil.
-you get small pupils (pin point pupils) in opioid overdose because you have inhibited the sympathetic system
pupillary light reflex is mediated by ___ system. Light enters left eye and strikes __, exciting retinal ganglion cell (red), which projects to the ipsilateral ___ ___ nucleus of the midbrain. This neuron projects bilateral and __ the __ where it projects to the __-__ nucleus. Axons from the EWN (green) project to ciliary ganglia (parasympathetic), and the motor neuron effector connects to the pupillary constrictor muscle in the iris of both eyes.
pupillary light reflex is mediated by parasympathetic system. Light enters left eye and strikes retina, exciting retinal ganglion cell (red), which projects to the ipsilateral olivary pretectal nucleus of the midbrain. This neuron projects bilateral and crosses the midline where it projects to the Edinger-Westphal nucleus. Axons from the EWN (green) project to ciliary ganglia (parasympathetic), and the motor neuron effector connects to the pupillary constrictor muscle in the iris of both eyes.
Outline how the sympathetic system dilates the eyes
first order neuron in hypothalamus has axons that project through brainstem down into spinal cord. This first order neuron forms synaptic connections with the second order neuron in the anterolateral column of the spinal cord. Second order neurons (green) have axons that travel back up and down the sympathetic cervical chain ganglia, and form synaptic connections with the third neuron in the superior cervical sympathetic ganglion in the carotid region, which projects to the pupillary dilator muscles of the iris. Sympathetic system thus dilates the eyes.
Frontal Eye field; region in ___, ___ to the motor cortex. Important for moving eyes to the ___ side.
- FEF machination results in moving eyes to contralateral side.
- ex/ Activation of the right FEF will drive eyes to the __.
Axons from the right FEF will cross down into the spinal cord, cross the midline at level of __, and project to the left __ (parapontine reticular formation, that helps control gaze).
First, the neuron forms the first synaptic connections with the second order neurons in the PPRF of the contralateral side.
The second order neurons in the PPRF connect to the __ nucleus (__) on the same side as the PPRF, either on the lateral or medial aspect.
- Neurons in __ aspect of the abducens nucleus project to __ __ muscle of __ eye to move __ eye leftward
- Neurons on the medial aspect of abducens nucleus cross the midline and project anteriorly to __ __ __ __ (__), where the third order neuron and the ocular motor nucleus project to the __ rectus muscle of the right eye, pulling the right eye to the left.
Frontal Eye field; region in cortex anterior to the motor cortex. Important for moving eyes to the contralateral side.
- FEF machination results in moving eyes to contralateral side.
- ex/ Activation of the right FEF will drive eyes to the left.
Axons from the right FEF will cross down into the spinal cord, cross the midline at level of midbrain, and project to the left PPRF (parapontine reticular formation, that helps control gaze).
First, the neuron forms the first synaptic connections with the second order neurons in the PPRF of the contralateral side.
The second order neurons in the PPRF connect to the abducens nucleus (MLF) on the same side as the PPRF, either on the lateral or medial aspect.
- Neurons in lateral aspect of the abducens nucleus project to lateral rectus muscle of left eye to move left eye leftward
- Neurons on the medial aspect of abducens nucleus cross the midline and project anteriorly to cranial nerve III nucleus (Adduction), where the third order neuron and the ocular motor nucleus project to the medial rectus muscle of the right eye, pulling the right eye to the left.
In the case of an FEF lesion right side;
- Lesions of FEF will result in paresis of __ gaze.
- Can’t drive eyes to the __, and eyes will drift to the __. Left limb paralysis
- Eyes are looking __ from the paralyzed side.
Lesions of the left pontine reticular formation/left ____ tract will result in;
Paresis of __ eye movement (paresis of ipsilateral gaze), eyes will drift to the __, __ LIMB paralysis
Looking __ from the lesioned side.
Eyes are deviated to the __ side.
In the case of an FEF lesion right side;
- Lesions of FEF will result in paresis of contralateral gaze.
- Can’t drive eyes to the left, and eyes will drift to the right. Left limb paralysis
- Eyes are looking away from the paralyzed side.
Lesions of the left pontine reticular formation/left corticospinal tract will result in;
Paresis of leftward eye movement (paresis of ipsilateral gaze), eyes will drift to the right, RIGHT LIMB paralysis
Looking away from the lesioned side.
Eyes are deviated to the paralyzed side.
the ___ ___ are required to understand the oculocephoalic reflex.
this system involves semicircular canals and the ___.
Vestibular labyrinth, cochlea.
Turning head up and down makes the fluid in the semicircular canals flow around.
The red arrows point towards the ampulla, which contains the cristae; contains hair cells that can sense the semicircular canal fluid movement. When lymphatic fluid travels in the direction of the arrow, there is an increase in the firing rate of the hair cells in the ampulla.
If the fluid travels in the opposite direction of the arrow, there is a decrease in the during rate of the hair cells in the ampulla.
The endolymph can bend and bow the cupula which is near the receptor hair cells, which provides vestibular directionality.
Ampulla is located anterior to the main part of the semicircular canal. Both fists represent ampulla and the arms represent the horizontal semicircular canals.
Head turning left cause an increase firing of left CN VIII (adduction, left eyes adduct in (ie stay right) afferent fibers, Decreased firing of right CN VIII afferent fibers (right eye abducts more to stay in the fixed position)
Outline the oculocephalic reflex and what it should be in a comatose patient
Head is turned rapidly to one side (left)
Eye deviation to the right
Normal response is that the doll’s eyes are present.
Your eyes move the opposite direction that your head is turning in order to maintain the forward gaze
Turning head to left → increase in firing in the left semicircular canal → increase firing rate of afferent eye fibers.
Axons of neurons that are on hair cells project to vestibular nuclei → neurons project to either ipsilateral oculomotor nucleus, which projects to left medial rectus, which will pull the left eye to the right, which is the opposite direction that you are turning your head (left)
Summary: turn head to left, then see an increase in left hair cells, then increase in firing rate of cranial nerve 8 (oculomotor nucleus), which projects to the vestibular nuclei on same side, then there are two groups of neurons; one that projects to the ipsilateral oculomotor nucleus, and the other that projects to the left medial rectus, pulling the left eye to the right. Another group in the medial vestibular nucleus projects to the abducens nucleus on the other side (right side), which projects to the right lateral rectus, which then pulls the right eye to the right.
In a comatose patient, if you move them to the left, their eyes will move to the opposite direction if the OCF is intact so that their eyes maintain looking up at the ceiling.
A lestion in the __ __ ___ causes locked in syndrome:
Patient is awake
Complete paralysis of the lower cranial nerve and limb muscles→ usually only vertical eye movements seen
Lesion in basis bilateral pontis
T/f sleep wake cycles are messed up in people in a persistent vegetative state
false. they still have intact diencepahlic and brain stem function, therefore the suprachiasmatic nucleus (hypothalamus) and dorsal raphe nuclei are intact to create an adequate sleep-wake cycle.
they do not have evidence of awareness of self or surroundings
Prerequisites for Brain Death
The irreversible loss of:
- Capacity for consciousness
- All brainstem functions (including breathing)
- Must be greater than 12-24 hours duration (in adults)
Prerequisites:
- Clinical or neuroimaging supportive of a catastrophic neurologic event
- Exclusion of reversible causes (drugs, toxins, etc)
- Core temperature >32
T/F in someone braindead, there is still brainstem reflexes (ex/ pupiillary reaction_
false
Physical Exam Criteria:
- Coma
- Apnea
- No brainstem function
- No pupillary reaction to light
- No spontaneous eye movements
- No oculocephalic reflex
- No corneal or gag reflex
- No voluntary movements (spinal cord reflexes including reflex withdrawal may be present)
Confirmatory Tests of Brain Deat
EEG: no electrical activity in 30 minute period
Cerebral angiogram: no intracerebral flow
Somatosensory evoked potentials: no response
Radionuclide scanning: no radnuclide uptake.
