Brain death and neurologist

neurologist will be often called in to declare brain death.It is often a tricky situation especially when patient is in a ventilator.The heart and lung will be often functioning normally in these cases.
So how brain death is declared.
Unresponsiveness
The patient is completely unresponsive to external visual, auditory, and tactile stimuli and is incapable of communication in any manner.
Absence of cerebral and brain stem function
Pupillary responses are absent, and eye movements cannot be elicited by the vestibulo-ocular reflex or by irrigating the ears with cold water.
The corneal and gag reflex are absent, and there is no facial or tongue movement.
The limbs are flaccid, and there is no movement, although primitive withdrawal movements in response to local painful stimuli, mediated at a spinal cord level, can occur.
APNOEA TEST: An apnea test should be performed to ascertain that no respirations occur at a PCO2 level of at least 60 mmHg. The patient oxygenation should be maintained with giving 100% oxygen by a cannula inserted into endotracheal tube as the PCO2 rises. The inability to develop respiration is consistent with medullary failure.
Nature of coma must be know
Known structural disease or irreversible systemic metabolic cause that can explain the clinical picture.
Some causes must be ruled out
Body temperature must be above 32 C to rule out hypothermia
No chance of drug intoxication or neuromuscular blockade
Patient is not in shock
EEG and Brain blood flow studies are not mandatory but often helpful in doubtful cases.