A.9 - Unconsciousness due to metabolic origin

Question 1

what is Unconsciousness due to metabolic origin?

Answer 1

• 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

Question 2

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

Answer 2

• 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.

Question 3

what can cause Unconsciousness due to metabolic origin?

Answer 3

● 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)

Question 4

what can cause prolonged hypoglycemia?

Answer 4

insulin overdose

fasting

alcohol intoxication

insulinomas (rarely)

Question 5

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

Answer 5

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

Question 6

does hypoglycemia cause focal necrosis?

Answer 6

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

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

Question 7

how severe hypoglycemia might injure the brain?

Answer 7

● 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

Question 8

what blood glucose level can cause coma?

Answer 8

levels <0,6 mmol/l can cause coma

Question 9

what is Hyperosmolar hyperglycemia?

Answer 9

Results from the hyperosmolar effect of severe hyperglycemia

Question 10

what are the neurological signs of hyperosmolar diabetic coma?

Answer 10

epileptic siezures

focal signs

Question 11

how do you diagnosehyperosmolar diabetic coma?

Answer 11

blood glucose > 16mmol/L

high serum osmolarity

Question 12

what can Hyperosmolar hyperglycemia cause?

Answer 12

Can cause involuntary movements, seizures and hemiparesis

Question 13

is vascular thrombosis involved in Hyperosmolar hyperglycemia?

Answer 13

Vascular thrombosis is not uncommon

Question 14

is ketoacidosis involved in Hyperosmolar hyperglycemia?

Answer 14

Ketoacidosis is mild or does not occur

Question 15

when does diabetic ketoacidosis cause neurological problems?

Answer 15

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

Question 16

How diabetic ketoacidosis cause neurological problems?

Answer 16

Develop progressive neurological impairment with lethargy, and ultimately coma

Question 17

what are the symps of diabetic ketoacidosis ?

Answer 17

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

Question 18

what are the causes of hypoxia?

Answer 18

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

Question 18

what are the neurological signs of Transient global ischemia?

Answer 18

• Flexion-extension spasticity
• bilateral pyramidal signs
  (vegetative state

Question 19

how does lung disease or PE affect the CNS?

Answer 19

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

Question 19

how does anemia or blood loss affect the CNS?

Answer 19

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

Question 20

how does reduced cardiac output affect the CNS?

Answer 20

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

Question 21

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

Answer 21

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

Question 22

how does high altitude affect the CNS?

Answer 22

low O2 tension of the atmosphere –> hypoxia

Question 23

when consciousness is lost during hypoxia?

Answer 23

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

Question 24

for how long hypoxia can be tolerated?

Answer 24

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

Question 25

what can CO intoxication lead to?

Answer 25

CO intoxication leads to bilateral necrosis of globus pallidus

Question 26

Vulnerability to hypoxia (most to least)

Answer 26

* grey matter is more vulnerable than white* ○ Frontal cortex ○ Hippocampus, parietal/occipital cortex ○ Basal ganglia/cerebellum ○ Brain stem

Question 27

what are the symptoms of hypoxia affectinng the brain?

Answer 27

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

Question 28

what are the symptoms of hypercapnia?

Answer 28

- headache - confusion - disorientation - involuntary movements - papilledema - depressed limb reflexes - extensor plantar response

Question 29

when does CO2 narcosis occurs?

Answer 29

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

Question 30

how does hypothermia affect the CNS?

Answer 30

symptoms of metabolic encephalopathy are observed (headache, tremor, myoclonus) Common in alcoholics with Wernicke encephalopathy (deficiency of B1)

Question 31

How does uremia causes disorders of consciousness?

Answer 31

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

Question 32

what are the Neurological signs of uremia?

Answer 32

- epileptic siezures - myoclonus - coma in end stage

Question 33

how do you diagnose disorder of consciousness due to uremia?

Answer 33

- Slow waves are found on the EEG - elevated serum: 1. creatinine 2. potassium 3. urea

Question 34

how can you treat disorder of consciousness due to uremia?

Answer 34

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

Question 35

what are the main neurological signs of Hepatic encephalopathy?

Answer 35

- tremor - asterixis - confusion - delirium - vegetative state

Question 36

Hepatic encephalopathy onset?

Answer 36

acute or chronic onset

Question 37

how do you diagnose hepatic encephalopathy?

Answer 37

elevated serum ammonia

Question 38

what are the causes of Hepatic encephalopathy?

Answer 38

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

Question 39

what are the most severe stages of Hepatic encephalopathy?

Answer 39

At earlier phases the patient is in an agitated confusional state Unconsciousness and coma are the most severe stages

Question 40

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

Answer 40

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

Question 41

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

Answer 41

Hypernatremia Hyponatremia Hypercalcemia, hypocalcemia, hypomagnesemia, hypokalemia hyperkalemia

Question 42

how Hypernatremia can cause disorders of consciousness?

Answer 42

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

Question 43

what are the neurological signs of hypernatremia?

Answer 43

delirium muscle weakness disturbance of consciousness