DISTURBANCES OF CONSCIOUSNESS Flashcards
What are the two parts of the brain that control the normal conscious state?
Cerebral hemispheres
Brainstem reticular activating system
What are the two most common causes of transient loss of consciousness?
Syncope
Seizures
Other than syncope and seizures, what are the other causes of transient loss of consciousness?
Hypoglycaemia Narcolepsy/cataplexy Hyperventilation Vertebrobasilar ischaemia Vertebrobasilar migraine Psychogenic or 'non-epileptic' attacks
What is the definition of syncope?
Transient loss of consciousness and posture that results from a global reduction in blood flow to the brain.
What is vasovagal syncope?
Syncope as a result of a sudden drop in blood pressure resulting from peripheral vasodilation. There is a subsequent paradoxical bradycardia (explained by the Bezold-Jarisch reflex) mediated by the vagus nerve, which leads to further drop in blood pressure and the result is syncope.
What are the common precipitates of vasovagal syncope?
Prolonged standing (especially in a hot or crowded place)
Strong emotion
Intense pain
What would indicate cerebral hypoxia in someone suffering vasovagal syncope?
Their eyes would roll upwards
Brief clonic movements
What is micturition syncope?
Vasodilatation during emptying of bladder, which occurs alongside postural hypotension on standing and bradycardia. Most common in men who get up to go to the loo in the middle of the night. Sudden loss of consciousness followed by rapid recovery.
What are some of the features of vasovagal syncope?
Patient is usually upright Light headedness Gradual dimming of vision Ringing in the ear Salivation Sweating Nausea Vomiting Pallor (which lasts even after recovery of consciousness) Clammy Low volume slow pulse
What is cough syncope?
Sustained coughing elevates the intrathoracic pressure sufficiently to impair venous return to the heart.
What is postural hypotension?
Upright posture is accompanied by an uncompensated fall in blood pressure and therefore also cerebral blood flow..
Who is most likely to suffer from postural hypotension?
Adolescents
People who have been in bed a long time due to illness
Autonomic neuropathy (eg diabetes, Guillain-Barre)
Hypovolaemia (eg blood loss, diuretic therapy, Addison’s disease)
Neurodegenerative diseases (Parkinson’s, multisystem atrophy)
Drug (antihypertensives)
What is syncope due to primary cardiac dysfunction?
Syncope of direct cardiac origin caused by a cardiac arrhythmia, aortic stenosis, HOCM, pulmonary stenosis, pulmonary hypertension, PE, ventricular failure (eg MI, dilated cardiomyopathy). Syncope is usually abrupt without warning. There is marked pallor followed by rapid return of colour. Brief tonic or clonic movements may be present.
What is syncope due to carotid sinus disease?
If a patient with hypersensitive carotid sinus (eg atheromatous disease) turns their head quickly when wearing a tight collar, or if carotid sinuses are massaged, patient can become hypotensive and lose consciousness.
What are some of the key differences between syncope and a seizure that can help you differentiate which was responsible for the loss of consciousness?
Syncope often standing whereas seizure any position.
Onset of seizure is sudden with little warning. Syncope often has prodrome.
Tone is reduced or normal in syncope, whereas seizures often involves prolonged increase in tone.
Urinary incontinence is common in seizure, less common with syncope.
Patient may bite their tongue during generalized seizure, less common with syncope.
Following a seizure, patient is confusedm drowsy with headache and aching muscles - postictal state. Following syncope, patient recovers quickly with slight malaise.
Injury is more common with seizures.
What are the prodromal symptoms (warning signs) of hypoglycaemia?
Feeling tremulous (shaky)
Sweaty
Palpitations
Disorientation
What are the causes of hypoglycaemia?
Overtreatment of diabetes Liver failure Hypopituitarism Addison's disease Insulinomas
Does hypoglycaemia occur in healthy subjects who have not eaten?
No.
What is narcolepsy?
A disorder associated with excessive sleepiness and sleep attacks at inappropriate times. Associated with cataplexy as well as hypnogogic and hypnopompic hallucinations. There is a strong genetic component.
What is cataplexy?
Attacks of sudden reduction in muscle tone, lasting several seconds to minutes, usually precipitated by excitement or emotion.
What does hypnogogic mean?
The transitional state of going to sleep.
What does hypnopompic mean?
The transitional state of waking up.
What are the characteristic features of hyperventilation?
Breathlessness Light-headedness Perioral and digital paraesthesia Carpopedal spasm Submammary or axillary chest pain Anxiety or fatigue
What is vertebrobasilar ischaemia?
Compromised verterbrobasilar arterial system leads to hypoxia of the brainstem reticular formation and hence loss of consciousness. Other symptoms include diplopia (double vision) and vertigo.
In a patient who has suffered syncope, what investigations would need to be carried out?
ECG (perhaps Holter monitor - 24 hour)
Echocardiogram
Tilt-table test
Having suffered a loss of consciousness, what are the laws surrounding driving for that patient?
Patients are required to notify the DVLA after a single episode of loss of consciousness, unless the event is a simple vasovagal faint with provoking factors.
If the cause is identified as cardiovascular and is treated, patients are not allowed to drive for 4 weeks.
If the cause is likely to be cardiovascular but is not identified and hence not treated, patients are not allowed to drive for 6 months.
If the cause is identified as being a seizure or is unidentified, patients are not allowed to drive for 6 months.
What are the three components of the Glasgow Coma Scale?
Eye opening
Verbal response
Motor response
What is the maximum score in the Glasgow Coma Scale?
15
What is the minimum score in the Glasgaw Coma Scale?
3
How many points are attributed to the motor response component of the GCS?
6
How many points are attributed to the verbal response component of the GCS?
5
How many points are attributed to the eye opening component of the GCS?
4
What are the 6 different levels of motor response as defined by the GCS?
- No response
- Extensor response to pain (Decerebrate)
- Flexor response to pain (Decorticate)
- Flexion/withdrawal to pain
- Purposeful movement towards site of painful stimulus (hand crosses midline to clavicle when supraorbital pressure applied)
- Obeys command
What are the 5 different levels of verbal response as defined by the GCS?
- None
- Incomprehensible sounds (Moaning)
- Inappropriate words (Random or exclamatory articulated speech)
- Disorientated speech (confusion)
- Orientated speech
What are the 4 different levels of eye opening as defined by the GCS?
- None
- In response to pain
- In response to speech
- Spontaneous
Can you name any conditions that may resemble coma but are not true coma?
Non-convulsive status epilepticus
Akinetic mutism
Locked-in syndrome
Catatonia
What is akinetic mutism?
Damage to the profrontal or premotor areas responsible for initiating movements. Patients have preserved awareness, and can follow with their eyes but are unable to intiate movements or obey commands.
What is locked in syndrome?
Extensive lesion of the ventral pons which interrupts the corticobulbar and corticospinal pathways, with sparing of the reticular pathways and therefore sparing of consciousness. Patients are alert but unable to speak or move their face or limbs.
What is catatonia?
Most often seen in catatonic depressive states and schizophrenia. Patient is silent and there is no volitional motor or emotional response to external stimuli.
What are the features to examine in the comatose patient?
Sign of head injury Neck stiffness (if no evidence of cervical spine injury) Respiratory pattern Pupil response Resting position of eyes Ocular movements Fundoscopic abnormalities Corneal reflexes Limb posture and spontaneous movements Reflexes and plantar responses GCS
When might neck stiffness be seen in a comatose patient?
Meningitis
Sub-arachnoid haemorrhage
What respiratory patterns might be seen in a comatose patient?
Cheyne-Stokes respiration: alternate hyper- and hypoventilation. Associated with opiate overdose, impaired cardiac output, and brainstem or medullary dysfunction.
Central neurogenic hyperventilation: lesions of lower midbrain and upper pons
Apneustic respiration: pauses of 2-3 seconds occur after inspiration - pontine lesions
When might pin point pupils be seen in a comatose patient?
Pontine lesions
Opiates
Parasympathomimetics
When might you see pupils that are fixed in a mid-position (neither constricted nor dilated) in a comatose patient?
Midbrain lesions
Severe sedative drug overdose
Hypothermia
When might you see pupils that are fixed in a dilated position in a comatose patient?
Significant brainstem damage
Overdose of anticholinergics or sympathomimetic
When might you see a unilateral fixed dilated pupil in a comatose patient?
Associated with ipsilateral third nerve palsy:
Supratentorial mass with uncal herniation
Posterior communication artery aneurysm
Primary brainstem lesion
What might conjugate lateral deviation of the eyes tell you about a comatose patient?
Large cerebral lesions produce eye deviation towards a lesion (contralateral to limb paralysis)
Seizures produce eye deviation away from the lesion
What might lateral and downward deviation of an eye tell you about a comatose patient?
Usually due to an ipsilateral third cranial nerve palsy
What would inward deviation of an eye tell you about a comatose patient?
Usually due to an ipsilateral sixth cranial nerve lesion
What conjugate depression of the eyes tell you about a comatose patient?
Midbrain lesion or compression
What is the oculocephalic reflex (doll’s eye reflex) and when is it used?
This is used to test whether the brainstem is intact in comatose patients. On rotating the head to the left and right, the eyes will maintain their position by conjugate movements in the opposite direction.
What is the oculovestibular reflex and when is it used?
This is used to test whether the brainstem and midbrain are intact in a comatose patient. Cold water is poured into one ear. This should cause deviation of the eyes towards the irrigated side.
When might the corneal reflex be suppressed in a comatose patient?
Large contralateral acute cerebral lesions.
What is the decerebrate posture and what is it associated with?
Extension at the elbows
Pronation and flexion of the wrist
Extension at the knee
Plantar flexion of the feet
Lesions in the upper brainstem but can occur in association with massive hemispheric lesions, or in setting of metabolic coma
What is the decorticate posture and what is it associated with?
Flexion at the elbows
Flexion of the wrists
Extension at the knee
Plantar flexion of the feet
Lesions at or above the diencephalon (thalamus and hypothalamus)
What are the immediate investigations for someone in a comatose state?
Temperature - hypothermia Blood glucose U&Es and creatinine FBC and INR ABG Blood culture ECG X-ray Head CT/MRI LP for CSF EEG Cerebral angiography
What are the specific features that indicate brainstem death in the comatose patient?
Mid-position/fully dilated, fixed and non-reactive pupil
Absent corneal reflexes
Absent oculocephalic and oculovestibular reflexes
Absent gag reflex
No grimace in response to facial pain
Absent ventilatory reflexes
