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Coma/Herniation Syndromes
Neuro Assessment 8
87
Anatomy
Graduate
10/24/2011

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Term
Lethargy
Definition
Sleepy but easily aroused
Term
Hypersomnia
Definition
excessively sleepy but normal cognition when awakened
Term
obtundation
Definition
mental blunting, decreased alertness
Term
Stupor
Definition
eyes open only briefly after vigorous stimulation before returning to deep sleep. Cognition impaired
Term
Coma
Definition
Eyes Remain Closed after vigorous stimulation
Term
Delirium
Definition
disoriented, misperception of sensory stimuli, hallucinations. Vacillates between quiet, sleepy periods and hyper-vigilance/agitation
Term
Abulia
Definition
Awake but apathetic, no spontaneity.
Cognitive function my be normal with virorous stimulation
Term
What usually occurs in a patient with severe bifrontal lobe damage (lobotomy)?
Definition
Abulia
Term
Akinetic mutism
Definition
silent, alert-appearing immobility.
No mental activity with vigorous stimulation
Term
If akinetic mutism lasts more the 30 days what is the patient said to be in?
Definition
Persistent Vegitative state
Term
What usually occurs in a patient wi disease of frontal lobes and hypothalamus?
Definition
Akinetic mutism
Term
If a patients appears to be in a vegetative state but has fragments of awareness and meaningful interaction what are they said to be in?
Definition
Minimally Conscious State, MCS
Term
What are the 2 components of consciousness?
Definition
Arousal and Content
Term
What does the the content of consciousness refer to?
Definition
Awareness of:
One self
Environment
Term
How is wakefulness achieved?
Definition
neural circuits the mediate sleep-wake cycles
Term
What is the ascending arousal system?
Definition
Rostral Brainstem area responsible for sleep-wake cycles achieved by neural circuits
Term
What does disruption of the Ascending arousal system cause?
Definition
Stupor and coma
Term
What is caused by disease affecting the content of consciousness?
Definition
Dementia
Term
Where were lesions found in patients with encephalitis lethargica, (1916)?
Definition
rostral periaquductal grey matter and posterior 3rd ventricle
Term
Where lesions found that cause insomnia?
Definition
rostral hypothalamus
Term
Where is the sleep promoting area?
Definition
ventrolateral preoptic nucleus
Term
What does a brainstem transection at the level of the cervical medulla cause?
Definition
quadriplegia and respiratory arrest
Term
At what point does a lesion of the brainstem affect wakefulness defined by the EEG pattern?
Definition
upper pontine and midbrain level
Term
What type of brain wave pattern on EEG is characterixtic for the awake state?
Definition
"desynchronized"
Term
What type of brain wave pattern on EEG is seen in sleep and in some patients with coma?
Definition
"synchronized", high voltage slow waves
Term
Where are the 4 Primary lesions that cause coma?
Definition
1. Extensive, acute bihemispheric disease
2. Lesions of the diencephalon (thalamus & hypothalamus)
3. Lesions of midbrain peri-aquiductal grey
4. Involvement of upper one third of pontine tegmentum.
Term
What do all the primary lesion areas have in common except for bihemispheric lesions?
Definition
include the reticular grey formation
Term
Where is the paramedian tegmental area?
Definition
ventral to the aqueduct of Sylvius from midbrain to the rostral pons
Term
What do Lesions below the rostral pons disrupt? What does it cause?
Definition
corticospinal and corticobulbar tracts bilaterally
Leave patient quadriplegic with paralyzed lower face - unable to speak, swallow, or breath on own, but conscious, aware, can see and hear, and usually retain eye movement control
Term
T/F Lesions confined to the upper pons can cause coma even in the absence of midbrain & thalamic injury.
Definition
True
Term
What is the reticular activating system?
Definition
areas of the reticular formation that could when damaged result in coma
Term
Where does the RAS lie?
Definition
intralaminar nuclei of the thalamus, the tegmentum of midbrain, and tegmentum of upper 1/3rd pons
Term
Where do the LDT and PPT project to and what does it cause?
Definition
Project to thalamic relay nuclei and inhibit it from firing
Increases wakefulness and thalamus in "transmission" mode
Term
What does increased bursting by thalamic relay neurons promote?
Definition
synchronization of cortical activity and induces sleep
Term
What directly activates the cortex?
Definition
monoaminergic inputs
Term
What causes delirium?
Definition
misperception of incoming stimuli
Term
How do monoaminergic inputs avoid misperception?
Definition
improve the signal to noise ratio
Term
Where is the sleep promoting center in the brain?
Definition
Ventro-Lateral Preoptic nucleus, VLPO
Term
What inhibitory neurotransmitter does the VLPO depoly?
Definition
GABA
Term
What parts of the brain sends feedback to the AAS?
Definition
Thalamus
Limbic System
Frontal and association cortex
Term
What pathways mediate emotional memories?
Definition
Feedback pathways to the AAS
Term
What does loss of feedback to the AAS cause?
Definition
apathy and indifference to sensory stimuli
Term
What are the 2 broad categories coma is divided into?
Definition
Structural and Metabolic
Term
what are structural causes of coma?
Definition
Supratentorial mass lesions
Acute obstructive hydrocephalus
Infratentorial mass lesions
Term
What are Metabolic causes of coma?
Definition
Reversible injury - sedative overdose
Irreversible injury - hypoxia in cardiac arrest
Term
What type of coma will show focal deficits on exam and an abnormal CT or MRI?
Definition
Structural
Term
In a patient with a blow to the side of the head who has early loss of pupil reactivity to light, what should be done immediately?
Definition
surgery
Term
What nerve is entraped by a transtentorial herniation of the uncus?
Definition
Oculomoter, CN3
Term
What symptoms will develop after pupillary abnormality cause by an uncal herniation?
Definition
ptosis and weakness of ocular movement
increased lethargy and contralateral hemiparesis
Contralateral Babinski sign
Term
What artery can become trapped in an uncal herniation? What can this cause?
Definition
posterior cerebral artery
ipsilateral ischemia and stroke
Term
What are small hemorrhages in the brainstem called?
Definition
Duret's hemorrhages
Term
What gets caught between the herniating temporal lobe and the upper brainstem?
Definition
Oculomoter nerve
Term
What does a falcine herniation cause?
Definition
trap and compress anterior cerebral arteries against the falx to cause ischemic stroke in the parasagittal cortex
Term
What can produce diffuse and symmetrical pressure on the brain medial and downward to cause central herniation?
Definition
metabolic insults - hypoxia or cerebral edema that accompanies fulminant liver failure
Term
What is a late sign of central herniation?
Definition
Decorticate or flexor posturing followed by decerebrate or extensor posturing
Term
What is an early warning sign of central herniation?
Definition
Cheyne-Stokes respirations
Term
What are Cheyne-Stokes respirations?
Definition
characterized by apneic spells interspersed with hyperventilation periods
Term
What are the symptoms of central herniation?
Definition
Lethargy -> small reactive pupils -> Constrictive pupillary tone is lost, pupils become fixed in midposition
Term
How does a Central Herniation proceed through the brain stem?
Definition
Rostral -> Caudal deterioration
Thalamus(Reticular grey area) -> Hypothalamus(Central Sympathetic Tracts)-> Midbrain (Edinger-Westphal nuclei)
Term
Where are infratentorial lesion found?
Definition
below the cerebellar tentorium in the posterior fossa.
Term
What are examples of Intrinsic Infratentorial lesions?
Definition
Directly damage the brainstem
-Top of the basilar arter ischemic stroke
-Pontine hemorrhage
Term
What are examples of Extrinsic Inratentorial Lesions?
Definition
Compress and Distort the brainstem
-Cerebellar hemorrhage, Infarction, Brain Tumor
Term
What do Primary Brainstem Lesions cause?
Definition
Segmental Cranial Nerve Deficits
Ascending tract dysfunction
- Pain and Temperature (Spinothalamic)
- Fine touch, vibration and proprioceptive (medial lemniscus)
Descending (Corticospinal, central sympathetic) tract dysfunction - motor pathways
Early cerebellar signs
Term
What is the clinical syndrome of a Pontine hemorrhage?
Definition
Coma is abrupt
Pupils are pinpoint
Decerebrate rigidity or Flaccid Quadriplegia
Horizontal gaze paresis
Ocular bobbing
Term
What is the largest category of coma etiologies?
Definition
Metabolic Encephalopathy
Term
What are some examples of Metabolic Encephalopathy?
Definition
hyponatremia
hypoglycemia/hyperglycemia
hypothermia
uremia
hepatic failure
thiamine deficiency
hypoxia
drug intoxications
Term
How is a metabolic encephalopathy recognized?
Definition
Neuro-exam - "non-focal"
Head CT - Negative
Pupils stay reactive to light!!
Asterixes, multifocal myoclonus and tremor
Term
What are the most common etiologies for Asterixes, multifocal myoclonus and tremor?
Definition
Uremia, Liver failure, Hypoxia
Term
What metobolic conditions can pupils become dilated and fixed?
Definition
atropine poisoning
botulism and glutethimide intoxication
Term
What account for about 90% of cases in the elderly?
Definition
Dehydration
Drug Intoxication
Infection
Term
What can mimic metabolic encephalopathy?
Definition
post-ictal state
Term
How can a new metabolic encephalopathy be mistaken for an acute structural lesion?
Definition
unmask an old lesion, like a stroke, and create focal weakness
Term
What is the immediate management of coma?
Definition
ABC's
-Secure Airway
-Cardiac monitor
-IV access & Blood drawing
Stabilize Neck
History
Exam
Empirical D50, Thiamine, Naloxone
(All preformed simultaneously)
Term
If you find normal vital signs in someone who is not responding to voice or nailbed pinch, what should be considered?
Definition
Psychogenic coma
Term
What is the most helpful in making a diagnosis when assessing a comatose patient?
Definition
History
Term
What does the presence of retinal venous pulsations mean?
Definition
No increased intracranial pressure
Term
What is Central neurogenic hyperventilation attributed to?
Definition
Midbrain lesions
neurogenic pulmonary edema
Term
What is Cluster and ataxic breathing associated with?
Definition
caudal pontine or medullary lesions
Term
What types of noxious stimuli can be used to arouse patients who do not respond to voice command?
Definition

supraorbital pressure nailbed pinch Sternal rub

(do NOT use titty twisters)

Term
What is the flexor response (decorticate posturing) to pain due to?
Definition
loss of coritcal control of brainstem motor centers
Term
What is the Extensor response (decerebrate posturing) due to?
Definition
loss of red nucleus and rubrospinal tract in the midbrain
Term
what is the hierarchy of motor responses following brain injury?
Definition
Obeys
Localizes
Withdraws
Abnormal flexion (decorticate posturing)
Extensor response (decerebrate posturing)
No Response
Term
What is the Glasgow coma score based on?
Definition
Eye opening, Motor response, verbal response
Term
What is the prognosis of a patient with a score 8 or below?
Definition
Poor
Nursing home care
Term
What is the prognosis for a Glasgow coma score of 3?
Definition
Very Poor
Usually Death
Term
At day 3 abscence of what reflexes caries a poor prognosis for non-traumatic coma?
Definition
absence of pupillary light and corneal reflex
Term
Absence of what at 3 days carries a poor prognosis in hypoxic coma?
Definition
purposful motor movements
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