Time: 0 second
Question No. 2
Q: What are the essential preconditions for brainstem death testing? (2 marks)
Answer No. 2
- The patient is comatose and mechanically ventilated for apnoea 1
- There should be no doubt that the patient's condition is due to irreversible brain damage of known aetiology 1
2
Question No. 3
Q: What is the legal time of death following brainstem death testing? (1 marks)
Answer No. 3
- Legal time of death is retrospectively noted as the time that the first set of tests confirms brainstem death 1, though death is not declared until after the 2nd test
1
Question No. 4
Q: How is the corneal reflex performed and what response would be expected in the case of brainstem death? (2 marks)
Answer No. 4
Test
Procedure
Confirmatory Response in Brainstem Death
Corneal Reflex
Cornea is brushed lightly with a swab with care taken to avoid damage to the cornea 1
No blinking elicited by stimulation 1
2
Question No. 5
Q: Which cranial nerves and brainstem level is involved in the corneal reflex? (3 marks)
Answer No. 5
Test
Sensory Nerve
(Afferent Pathway)
Motor Nerve
(Efferent Pathway)
Brainstem Level
Corneal Reflex
Ophthalmic branch of trigeminal nerve (V) 1
Facial nerve (VII) 1
Pons 1, trigeminal and facial nuclei
3
Question No. 6
Q: How is the caloric reflex performed and what response would be expected in the case of brainstem death? (3 marks)
Answer No. 6
Test
Procedure
Confirmatory Response in Brainstem Death
Caloric (Oculo-vestibular) Reflex
At least 50ml of ice cold water 0.5 is instilled into the external auditory meatus over one minute 0.5. Head should be at 30 degrees to the horizontal plane. Clear access to the tympanic membrane must be confirmed by direct visualisation with and otoscope before testing 1
No eye movement during or following injection 1
3
Question No. 7
Q: Which cranial nerves and brainstem level is involved in the caloric reflex? (3 marks)
Answer No. 7
Test
Sensory Nerve
(Afferent Pathway)
Motor Nerve
(Efferent Pathway)
Brainstem Level
Caloric (Oculo-vestibular) Reflex
Vestibulocochlear nerve (VIII) 1
Oculomotor nerve (III) 0.5 & abducens nerve (VI) 0.5
Pons, nucleus vestibularus, nucleus abducens 1
3
Question No. 8
Q: How could brainstem death be confirmed in a patient with severe maxillofacial trauma? (1 marks)
Answer No. 8
- Where brain death cannot be confirmed according to clinical testing alone use of an ancillary test may be required 1
1
Question No. 9
Q: Which other situations may ancillary testing be required for diagnosis of brainstem death? (2 marks)
Answer No. 9
- Inability to exclude the influence of residual sedative drugs 1
- High cervical cord injury 1
2
Question No. 10
Q: Give 3 ancillary tests that may be useful in confirming brainstem death? (3 marks)
Answer No. 10
Measures of brain Electrical Activity
Measures of brain Electrical Activity
EEG 1
- Most popular and validated test worldwide, though there has been a recent move away
- Isoelectric EEG may be mimicked by conditions such as hypothermia, barbiturates, or other central nervous system (CNS) depressants - hence it is of little value when these are suspected
Somatosensory or Auditory Evoked Potential (SSEP) 1
- A peripheral stimulus given (i.e. median nerve} and a response is measured at the contralateral primary sensory cortex
- Absence of transmission measured 20 ms (N20 response) after stimulation suggests brainstem dysfunction
- May be useful where coma of toxic aetiology is suspected - short-latency responses that are absent in brain death but preserved in toxic and metabolic disorders
Measures of Blood Flow
Measures of Blood Flow
Cerebral Angiography
(4 vessel) 1
(4 vessel) 1
- Contrast medium is injected in the aortic arch under high pressure to reach both anterior and posterior circulations
- Confirmatory testing demonstrates absence of intracerebral filling beyond the carotid or vertebral arteries' entry to the skull
Transcranial Doppler 1
- Useful only if a reliable waveform is found
- Complete absence of flow may not be reliable if inadequate windows exist
- Confirmatory testing should demonstrate either reverberating flow or small systolic peaks in early systole
Cerebral Scintigraphy 1
- Non-invasive and safe measure of cerebral blood flow
- No patient transport required if a portable gamma camera is available
- Technetium 99 m is given by intravenous bolus with images obtained by a gamma camera every 3 seconds for a total of 60 seconds
- External carotid flow is either digitally subtracted or excluded by forehead tourniquet
- Confirmatory testing demonstrates no radionuclide localization in the middle cerebral artery, anterior cerebral artery, or basilar artery territories of the cerebral hemispheres
Spiral CT or MRI angiography 1
- Increasingly available and investigated as ancillary tests
- Confirmatory testing demonstrates absence of intracerebral filling beyond the carotid or vertebral arteries' entry to the skull
3