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Neuro > A.9 - Unconsciousness due to metabolic origin > Flashcards

A.9 - Unconsciousness due to metabolic origin Flashcards

1
Q

what is Unconsciousness due to metabolic origin?

A
  • Unconsciousness due to metabolic origin is usually a disorder of awareness.
  • It can also manifest as persistent vegetative state (PVS), also called unresponsive wakefulness syndrome
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2
Q

what are the general symptoms of Unconsciousness due to metabolic origin?

A
  • pupils are normal in size and reactive to light
  • eye movements are usually full and conjugate
  • depressed mental state
  • confusion with impairment of consciousness
  • depressed respiratory
    rate
  • limb movements are symmetrically reduced and associated with hypotonicity.
  • Hemiparesis can
    occur in:
    –> non-ketotic hyperosmolar coma
    –> hepatic, hyperglycemic and uremic encephalopathy.
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3
Q

what can cause Unconsciousness due to metabolic origin?

A

● Deficiency of essential substrates (glucose, oxygen, vitamin B12)

● Exogenous toxins (eg. drugs, heavy metals, solvents)

● Endogenous toxins/systemic metabolic diseases (eg. uremia, hepatic encephalopathy, electrolyte imbalances, thyroid storm)

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4
Q

what can cause prolonged hypoglycemia?

A

insulin overdose

fasting

alcohol intoxication

insulinomas (rarely)

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5
Q

how can you differentiate between comatose state due to hypoglycemia and a structural cause?

A

In hypoglycemia, pupillary light reactions may be intact, while in structural damage they are usually absent

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6
Q

does hypoglycemia cause focal necrosis?

A

Hypoglycemia does NOT cause focal necrosis in brain, brainstem or spinal cord.

the CNS structures remain intact even in long-standing, severe hypoglycemia

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7
Q

how severe hypoglycemia might injure the brain?

A

● The superficial layers of the cortex are damaged, particularly the dendrites, but laminar necrosis (as in global ischemia) is not seen

● Necrosis also develops in the hippocampus, caudate nucleus and granular cells of dentate gyrus

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8
Q

what blood glucose level can cause coma?

A

levels <0,6 mmol/l can cause coma

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9
Q

what is Hyperosmolar hyperglycemia?

A

Results from the hyperosmolar effect of severe hyperglycemia

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10
Q

what are the neurological signs of hyperosmolar diabetic coma?

A

epileptic siezures

focal signs

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11
Q

how do you diagnosehyperosmolar diabetic coma?

A

blood glucose > 16mmol/L

high serum osmolarity

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12
Q

what can Hyperosmolar hyperglycemia cause?

A

Can cause involuntary movements, seizures and hemiparesis

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13
Q

is vascular thrombosis involved in Hyperosmolar hyperglycemia?

A

Vascular thrombosis is not uncommon

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14
Q

is ketoacidosis involved in Hyperosmolar hyperglycemia?

A

Ketoacidosis is mild or does not occur

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15
Q

when does diabetic ketoacidosis cause neurological problems?

A

In patients with known diabetes, but can also be the first manifestation

Often precipitated by infection or poor medical compliance

occurs due to accumulation of acetone and ketone bodies

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16
Q

How diabetic ketoacidosis cause neurological problems?

A

Develop progressive neurological impairment with lethargy, and ultimately coma

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17
Q

what are the symps of diabetic ketoacidosis ?

A
  • confusion
  • coma (rarely)
  • Dehydration (due to osmotic diuresis)
  • Fatigue, Weakness
  • Headache, Abdominal pain
  • Kussmal breathing
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18
Q

what are the causes of hypoxia?

A
  • Reduced arterial oxygen pressure
  • Reduced hemoglobin to carry oxygen
  • Reduced flow of blood containing O2
  • high altitudes
  • Biochemical block of cerebral utilization of O2
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18
Q

what are the neurological signs of Transient global ischemia?

A
  • Flexion-extension spasticity
  • bilateral pyramidal signs
    (vegetative state
19
Q

how does lung disease or PE affect the CNS?

A

Reduced arterial oxygen pressure –> Hypoxia due to PE causes confusion and lethargy before loss of consciousness

19
Q

how does anemia or blood loss affect the CNS?

A

Reduced hemoglobin to carry oxygen –> pO2 does not drop, but substrate availability is decreased or O2 fails to bind to hemoglobin –> hypoxia

20
Q

how does reduced cardiac output affect the CNS?

A

reduced cerebral blood flow –> Reduced flow of blood containing O2 –> schemic hypoxia

21
Q

what is histotoxic hypoxia and how does it influence the CNS?

A

cyanide poisoning –> Biochemical block of cerebral utilization of O2 –> hypoxia

22
Q

how does high altitude affect the CNS?

A

low O2 tension of the atmosphere –> hypoxia

23
Q

when consciousness is lost during hypoxia?

A

Consciousness is lost in some seconds, if pO2 drops under 40 mmHg

24
Q

for how long hypoxia can be tolerated?

A

Hypoxic hypoxia (without ischemia) can be tolerated for 10-40 minutes without permanent damage to the brain, even if pO2 is below 20 mmHg

25
Q

what can CO intoxication lead to?

A

CO intoxication leads to bilateral necrosis of globus pallidus

26
Q

Vulnerability to hypoxia (most to least)

A
  • grey matter is more vulnerable than white*

○ Frontal cortex
○ Hippocampus, parietal/occipital cortex
○ Basal ganglia/cerebellum
○ Brain stem

27
Q

what are the symptoms of hypoxia affectinng the brain?

A

○ Pupils: large-reactive
○ Eye movements: no movement – conjugate (if severe)

28
Q

what are the symptoms of hypercapnia?

A
  • headache
  • confusion
  • disorientation
  • involuntary movements
  • papilledema
  • depressed limb reflexes
  • extensor plantar response
29
Q

when does CO2 narcosis occurs?

A

in COPD or obesity-ventilation syndrome, if pCO2 is > 50 mmHg

30
Q

how does hypothermia affect the CNS?

A

symptoms of metabolic encephalopathy are observed (headache, tremor, myoclonus)

Common in alcoholics with Wernicke encephalopathy (deficiency of B1)

31
Q

How does uremia causes disorders of consciousness?

A

it is called Renal/uremic encephalopathy

A sign of acute renal failure

Brain amino acid metabolism is also impaired, and causes an imbalance between excitatory and inhibitory neurotransmitters or accumulation of false neurotransmitters

32
Q

what are the Neurological signs of uremia?

A
  • epileptic siezures
  • myoclonus
  • coma in end stage
33
Q

how do you diagnose disorder of consciousness due to uremia?

A
  • Slow waves are found on the EEG
  • elevated serum:
    1. creatinine
    2. potassium
    3. urea
34
Q

how can you treat disorder of consciousness due to uremia?

A

The condition is reversed with dialysis, but may take 1-2 days before it is totally reversed

35
Q

what are the main neurological signs of Hepatic encephalopathy?

A
  • tremor
  • asterixis
  • confusion
  • delirium
  • vegetative state
36
Q

Hepatic encephalopathy onset?

A

acute or chronic onset

37
Q

how do you diagnose hepatic encephalopathy?

A

elevated serum ammonia

38
Q

what are the causes of Hepatic encephalopathy?

A
  • increased ammonia
  • false neurotransmitters
  • endogenous benzodiazepine-like structures
  • abnormal fatty acid metabolism
  • free radical damage
  • cerebral edema
39
Q

what are the most severe stages of Hepatic encephalopathy?

A

At earlier phases the patient is in an agitated confusional state

Unconsciousness and coma are the most severe stages

40
Q

what are the neurological signs in comatose patients due to hepatic encephalopathy?

A
  • hemiparesis
  • ocular bobbing
  • dysconjugate eye
    movements
  • tonic downward deviation of the eyes
  • In deep coma: decerebrate posture and agonal respiration can be present
41
Q

what are the Electrolyte disturbances that can cause disorders of unconsciousness?

A

Hypernatremia

Hyponatremia

Hypercalcemia, hypocalcemia,

hypomagnesemia,

hypokalemia
hyperkalemia

42
Q

how Hypernatremia can cause disorders of consciousness?

A

○ Hyperosmolar diabetic hypernatremia: mostly in elderly diabetic patients
○ Leads to osmotic dehydration of the brain

43
Q

what are the neurological signs of hypernatremia?

A

delirium

muscle weakness

disturbance of consciousness

44
Q
A

Neuro (12 decks)

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