37 Coma Flashcards
Abulia:
eyes open but demonstrates no spontaneous interaction with the environment
may answer questions with vigorous stimulation
Causes of abulia?
severe bifrontal lobe damage (lobotomy at its worst)
Akinetic mutism:
no evidence of mental activity can be elicited with vigorous stimulation; “vegetative”
Sleep promoting area?
Destruction causes…
ventrolateral preoptic nucleus
insomnia
Location of arousal center?
midbrain (RAS)
MC site of lesion generating coma?
paramedian tegmental area just ventral to the aqueduct of Sylvius from the midbrain to the rostral pons
Lesions confined to _____ can cause coma in the absence of midbrain and thalamic injury
upper pons
Location of RAS?
intralaminar nuclei of thalamus, tegmentum of midbrain, tegmentum of upper 1/3 pons
Role of monoaminergic systems?
improve the signal to noise ratio for messages from the thalamus (= prevent any misperception of incoming sensory stimuli)
Function of VLPO?
inhibit the many centers that promote wakefulness in the ascending arousal system
Ascending Arousal System receives feedback from:
thalamus, the limbic system, the frontal and association cortex
Why is it important for Ascending Arousal System to receive feedback?
Loss causes:
pathways mediate emotional memories, permit concentrated attention to 1 sensory modality when necessary
Loss = apathy and indifference to sensory stimuli
Transtentorial herniation of the medial temporal lobe or the uncus of the temporal lobe causes:
- CN3 entrapment, likely starting with pupillary contr nerves
- PCA entrapment (causing ipsalat ischemia and stroke in the occipital lobe)
(then, pressure on the midbrain and diencephalon produce ischemia and cause increasing lethargy, stupor and coma)
Falcine herniation sometimes traps and compresses:
What does this cause?
one or both anterior cerebral arteries against the falx
ischemic stroke in the parasagittal cortex on one or both sides
Progression of central herniation?
rostral to caudal
- reticular grey in both thalami
- hypothalamus
- midbrain
- Decorticate or flexor posturing (late)
- decerebrate or extensor posturing (late)
Effects of thalami compression in central herniation?
increasing lethargy due to early pressure on the reticular grey in both thalami
Effects of hypothalamic compression in central herniation?
central sympathetic tracts originating in hypothalamus compromised –> small but still reactive pupils
**small due to the unopposed cholinergic activity mediated by the Edinger-Westphal nucle
Effects of midbrain compression in central herniation?
Edinger-Westphal nuclei fail = Constrictive pupillary tone is lost + pupils become fixed in mid-position
Early warning of central herniation?
Cheyne-Stokes respirations (apneic spells interspersed with hyperventilation periods)
Intrinsic brainstem lesions causing infratentorial compression?
top of basilar artery ischemic stroke
pontine hemorrhage
Extrinsic brainstem lesions causing infratentorial compression?
cerebellar hemorrhage
cerebellar infarction
cerebellar brain tumor
1’ brainstem lesions cause:
- segmental CN deficits
- asc spinothalamic tract dysf
- desc corticospinal tract dysf
- early cerebellar signs
Pontine hemorrhage: Clinical syndrome?
- abrupt coma
- pinpt pupils
- decerebrate rigidity or flaccid quadriplegia
- horiz gaze paresis
- ocular
How does one recognize metabolic encephalopathy at the bedside?
neurological deficits are diffuse and global
CT in metabolic encephalopathy?
nml
Symptoms in metabolic encephalopathy?
- pupils stay reactive to light
- asterixes
- multifocal myoclonus
- tremor
Account for about 90% of delirium in the elderly:
dehydration, drug intoxication and infection
In non-traumatic coma, absence of ____ carries a poor prognosis.
pupillary light reflex at 3 days
In hypoxic coma, absence of ____ carries a poor prognosis.
purposeful motor movement in 3 days
