A.9 - Unconsciousness due to metabolic origin Flashcards
what is Unconsciousness due to metabolic origin?
- 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
what are the general symptoms of Unconsciousness due to metabolic origin?
- 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.
what can cause Unconsciousness due to metabolic origin?
● 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)
what can cause prolonged hypoglycemia?
insulin overdose
fasting
alcohol intoxication
insulinomas (rarely)
how can you differentiate between comatose state due to hypoglycemia and a structural cause?
In hypoglycemia, pupillary light reactions may be intact, while in structural damage they are usually absent
does hypoglycemia cause focal necrosis?
Hypoglycemia does NOT cause focal necrosis in brain, brainstem or spinal cord.
the CNS structures remain intact even in long-standing, severe hypoglycemia
how severe hypoglycemia might injure the brain?
● 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
what blood glucose level can cause coma?
levels <0,6 mmol/l can cause coma
what is Hyperosmolar hyperglycemia?
Results from the hyperosmolar effect of severe hyperglycemia
what are the neurological signs of hyperosmolar diabetic coma?
epileptic siezures
focal signs
how do you diagnosehyperosmolar diabetic coma?
blood glucose > 16mmol/L
high serum osmolarity
what can Hyperosmolar hyperglycemia cause?
Can cause involuntary movements, seizures and hemiparesis
is vascular thrombosis involved in Hyperosmolar hyperglycemia?
Vascular thrombosis is not uncommon
is ketoacidosis involved in Hyperosmolar hyperglycemia?
Ketoacidosis is mild or does not occur
when does diabetic ketoacidosis cause neurological problems?
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
How diabetic ketoacidosis cause neurological problems?
Develop progressive neurological impairment with lethargy, and ultimately coma
what are the symps of diabetic ketoacidosis ?
- confusion
- coma (rarely)
- Dehydration (due to osmotic diuresis)
- Fatigue, Weakness
- Headache, Abdominal pain
- Kussmal breathing
what are the causes of hypoxia?
- Reduced arterial oxygen pressure
- Reduced hemoglobin to carry oxygen
- Reduced flow of blood containing O2
- high altitudes
- Biochemical block of cerebral utilization of O2
what are the neurological signs of Transient global ischemia?
- Flexion-extension spasticity
- bilateral pyramidal signs
(vegetative state
how does lung disease or PE affect the CNS?
Reduced arterial oxygen pressure –> Hypoxia due to PE causes confusion and lethargy before loss of consciousness
how does anemia or blood loss affect the CNS?
Reduced hemoglobin to carry oxygen –> pO2 does not drop, but substrate availability is decreased or O2 fails to bind to hemoglobin –> hypoxia
how does reduced cardiac output affect the CNS?
reduced cerebral blood flow –> Reduced flow of blood containing O2 –> schemic hypoxia
what is histotoxic hypoxia and how does it influence the CNS?
cyanide poisoning –> Biochemical block of cerebral utilization of O2 –> hypoxia
how does high altitude affect the CNS?
low O2 tension of the atmosphere –> hypoxia
when consciousness is lost during hypoxia?
Consciousness is lost in some seconds, if pO2 drops under 40 mmHg
for how long hypoxia can be tolerated?
Hypoxic hypoxia (without ischemia) can be tolerated for 10-40 minutes without permanent damage to the brain, even if pO2 is below 20 mmHg
what can CO intoxication lead to?
CO intoxication leads to bilateral necrosis of globus pallidus
Vulnerability to hypoxia (most to least)
- grey matter is more vulnerable than white*
○ Frontal cortex
○ Hippocampus, parietal/occipital cortex
○ Basal ganglia/cerebellum
○ Brain stem
what are the symptoms of hypoxia affectinng the brain?
○ Pupils: large-reactive
○ Eye movements: no movement – conjugate (if severe)
what are the symptoms of hypercapnia?
- headache
- confusion
- disorientation
- involuntary movements
- papilledema
- depressed limb reflexes
- extensor plantar response
when does CO2 narcosis occurs?
in COPD or obesity-ventilation syndrome, if pCO2 is > 50 mmHg
how does hypothermia affect the CNS?
symptoms of metabolic encephalopathy are observed (headache, tremor, myoclonus)
Common in alcoholics with Wernicke encephalopathy (deficiency of B1)
How does uremia causes disorders of consciousness?
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
what are the Neurological signs of uremia?
- epileptic siezures
- myoclonus
- coma in end stage
how do you diagnose disorder of consciousness due to uremia?
- Slow waves are found on the EEG
- elevated serum:
1. creatinine
2. potassium
3. urea
how can you treat disorder of consciousness due to uremia?
The condition is reversed with dialysis, but may take 1-2 days before it is totally reversed
what are the main neurological signs of Hepatic encephalopathy?
- tremor
- asterixis
- confusion
- delirium
- vegetative state
Hepatic encephalopathy onset?
acute or chronic onset
how do you diagnose hepatic encephalopathy?
elevated serum ammonia
what are the causes of Hepatic encephalopathy?
- increased ammonia
- false neurotransmitters
- endogenous benzodiazepine-like structures
- abnormal fatty acid metabolism
- free radical damage
- cerebral edema
what are the most severe stages of Hepatic encephalopathy?
At earlier phases the patient is in an agitated confusional state
Unconsciousness and coma are the most severe stages
what are the neurological signs in comatose patients due to hepatic encephalopathy?
- hemiparesis
- ocular bobbing
- dysconjugate eye
movements - tonic downward deviation of the eyes
- In deep coma: decerebrate posture and agonal respiration can be present
what are the Electrolyte disturbances that can cause disorders of unconsciousness?
Hypernatremia
Hyponatremia
Hypercalcemia, hypocalcemia,
hypomagnesemia,
hypokalemia
hyperkalemia
how Hypernatremia can cause disorders of consciousness?
○ Hyperosmolar diabetic hypernatremia: mostly in elderly diabetic patients
○ Leads to osmotic dehydration of the brain
what are the neurological signs of hypernatremia?
delirium
muscle weakness
disturbance of consciousness
