17.1 Brain Death Prerequisites and Clinical Exam (02.I)

Why this evaluation is an examination topic

Quick Answer: Brain death/death by neurologic criteria (BD/DNC) is permanent loss of function of the brain as a whole, including the brainstem: coma, brainstem areflexia, and apnea after an adequate carbon dioxide stimulus. The 2023 American Academy of Neurology (AAN), American Academy of Pediatrics (AAP), Child Neurology Society (CNS), and Society of Critical Care Medicine (SCCM) consensus guideline, published in Neurology, is the current U.S. professional document. Start only when the cause is known and catastrophic, then exclude drugs, hypothermia, shock, and severe metabolic confounders. Neuromuscular blockade must be off, confirmed with a train-of-four (TOF). Adults need a minimum of one complete examination; children need two independent examinations separated by 12 hours at every pediatric age.

Independent OpenExamPrep teaching in this section covers determination of death by neurologic criteria listed under Diagnostic studies and procedural skills in the ABPN Content Specifications. This is not an AAN, AAP, CNS, SCCM, ABIM, or ABPN product. Hospital policy and state law still govern how a given unit writes the note; the examination tests whether you know when not to start, what the bedside brainstem examination must show, and how adult and pediatric processes differ.

The 2023 document replaced the 2010 AAN adult update and the 2011 AAP/CNS/SCCM pediatric guideline with one age-spanning process. It uses BD/DNC rather than “brain death” alone, and it prefers permanent (will not resume spontaneously, and restorative interventions will not be used) over a looser everyday use of irreversible. That language change does not create a shortcut. You still need a mechanism that is known to destroy brain function, enough time that recovery is not still in play, and an examination that is not being faked by a drug, a cold core, or a MAP that is in the dirt.

Known cause first, then confounders

Before anyone opens eyelids, the record must show a catastrophic brain injury whose mechanism is known to lead to BD/DNC: massive traumatic injury, catastrophic intracranial hemorrhage, malignant infarction with herniation, or a documented anoxic-ischemic insult after cardiac arrest are the usual stories. An unexplained coma with a normal head computed tomography (CT) is not a BD/DNC workup. Imaging does not replace the examination, but it must make the cause intelligible.

Then exclude conditions that can mimic brainstem areflexia or apnea:

• Sedatives, anesthetics, and illicit CNS depressants — wait several half-lives, check levels when they exist (for example phenobarbital, some benzodiazepines), and remember hypothermia and organ failure prolong clearance. If the drug effect cannot be excluded, you do not have a valid examination.
• Neuromuscular blockade — a silent motor examination is worthless if the patient is still paralyzed. Confirm with TOF peripheral nerve stimulation (typically ulnar nerve, four equal twitches) after the infusion has been off. Residual rocuronium after hepatic failure is a classic false-positive trap.
• Hypothermia — cold brain is a quiet brain. The 2023 process requires normothermia. Teaching summaries of the guideline treat core temperature above 36°C as the operational floor. The 2010 adult AAN update used ≥36°C; 2023 does not relax that physiologic expectation.
• Shock and hypovolemia — the 2010 adult update used systolic blood pressure (SBP) ≥100 mm Hg as the usual floor. The 2023 document requires hemodynamic stability with both an adequate SBP and an adequate mean arterial pressure (MAP), not a single casual cuff reading. Bedside summaries of 2023 treat MAP below 75 mm Hg as a hypotensive confounder. Euvolemia and pressors used to meet those floors are allowed; untreated shock is not.
• Severe metabolic, acid-base, and electrolyte derangements — profound hypoglycemia, extreme hyperosmolar states, severe acidosis or alkalosis, and catastrophic sodium or liver-failure encephalopathy can depress responsiveness. Correct what can be corrected. If a metabolic mess cannot be fully repaired but the rest of the examination and apnea test later look consistent with BD/DNC, that is an ancillary-testing problem (next section), not a reason to shrug and proceed.

Temperature and blood pressure: teach the 2023 floors without inventing a looser rule

Targeted temperature management after cardiac arrest is the usual reason a neuro ICU waits a full day after the last cold hour. Rewarm, hold the examination, and do not order a nuclear flow study at hour 6 of rewarming to “get it over with.”

Neuroendocrine activity does not decide the question. Diabetes insipidus is common after severe herniation; its presence or absence neither proves nor excludes BD/DNC. Pregnancy is not a contraindication to evaluation. There is no obligation to obtain consent to initiate a BD/DNC evaluation, though families should be informed, offered the chance to observe, and treated as partners in communication — ethics of disagreement belong in a later chapter.

The clinical examination: coma plus absent brainstem reflexes

The patient must be comatose: no awareness, no purposeful response to visual, auditory, or tactile stimulation, and no cranial-nerve-distribution grimace to noxious stimulus at the supraorbital ridge, temporomandibular joint, or nail bed. Any movement that remains must be attributable to spinal reflexes (Lazarus sign, triple flexion, undulating toe). Those spinal movements do not exclude BD/DNC; a facial grimace or a localizing arm does.

Work the brainstem from midbrain to medulla. Both sides must be unresponsive.

Pupils and cornea

Pupillary light reflexes are absent bilaterally. Pupils are typically midposition to dilated (often about 4–9 mm). Pinpoint pupils push you back toward opioids, pontine tegmental injury that is not yet a complete BD/DNC picture, or a drug confounder. Use a bright light in a dark room; do not call a sluggish 2 mm pupil “absent” with a phone flashlight at noon. Corneal reflexes are absent bilaterally (cotton wisp or a drop of saline on the cornea, watching for lid movement). Avoid grinding the cornea into an abrasion in a potential donor; the finding is absence of response, not theatrical force.

Oculocephalic and vestibulo-ocular (cold calorics)

The oculocephalic reflex (doll’s eyes) is tested only when the cervical spine is stable. Rapid horizontal (and, if appropriate, vertical) head rotation should produce no eye movement within the orbit — the eyes stay fixed with the head. If cervical or skull-base integrity is in doubt, skip oculocephalic testing. The 2023 process allows BD/DNC without that one maneuver when bilateral oculovestibular (cold caloric) testing is absent and every other criterion is met — you do not automatically owe an ancillary test solely because a collar stayed on, provided calorics can be done.

Vestibulo-ocular / oculovestibular testing: confirm the canal is free of cerumen and the tympanic membrane is intact, elevate the head about 30 degrees, and irrigate with ice water (a typical adult volume is about 50 mL). Observe for at least one minute. Any tonic deviation toward the irrigated ear, or nystagmus, is a brainstem response and stops the BD/DNC examination. Wait several minutes before testing the other ear. Facial trauma that destroys both canals is a reason the calorics cannot be completed — that is an ancillary indication, not a pass.

Gag, cough, and infant oral reflexes

Gag (pharyngeal) and cough (tracheal) reflexes must both be absent. Gag is stimulated at the posterior pharynx. Cough requires deep tracheal suctioning, not a polite tickle at the endotracheal-tube hub. In infants, sucking and rooting are additional brainstem-mediated responses that must be absent when they can be assessed.

How many examinations, and who performs them

Adults: clinicians must perform a minimum of one complete BD/DNC examination. A second clinician may perform a separate independent examination because two looks can reduce a false-positive from a missed twitch or a sloppy caloric. The 2010 adult AAN update also treated a single examination as sufficient; 2023 keeps that minimum while explicitly allowing a second look. Local hospital policy may still require two adult examinations — follow the policy, but do not tell the examination that U.S. professional consensus demands two adult exams.

Children (term neonate ≥37 weeks through 17 years): two clinicians must each perform a separate independent examination, including apnea testing with each examination. The interval is 12 hours for all children, independent of age. That is a 2023 change from the 2011 pediatric intervals (24 hours for term newborns through 30 days, 12 hours from 31 days to 18 years). Unlike 2011, 2023 does not recommend ancillary testing to shorten the inter-examination wait.

Examiners are attending-level clinicians privileged by the hospital; 2023 also addresses when trained advanced practice providers may participate under institutional rules. The point for the examination is not the credentialing flowchart. It is: one complete adult examination is the minimum; children get two examinations 12 hours apart; do not use a scan to skip the pediatric clock.

Worked bedside scenarios

A 54-year-old with a gunshot wound through both hemispheres is 36.4°C, MAP 82 mm Hg on norepinephrine, TOF 4/4, and toxicology negative. One complete examination plus a valid apnea test can complete adult BD/DNC if every reflex is absent. Ordering electroencephalography “just in case” is not required.

A 6-year-old after asphyxia was cooled to 33°C, rewarmed to 36.5°C six hours ago, and looks unresponsive. Do not start BD/DNC. Wait at least 24 hours after rewarming. A nuclear study today does not buy you the missing hours.

A 28-day-old term neonate with massive ICH: two examinations, 12 hours apart (not the old 24-hour neonatal gap), each with apnea testing, after confounders are gone.

Exam traps

Calling BD/DNC during hypothermia or while a cisatracurium infusion is still running. Treating spinal triple flexion as “the patient moved.” Skipping cold calorics because doll’s eyes were awkward, then declaring death anyway without an ancillary test when calorics truly cannot be done. Using the 2011 neonatal 24-hour gap as if 2023 had not set 12 hours for every child. Claiming adults always need two examinations. Starting the examination because “the CT looks unsurvivable” without a known mechanism and a confounder checklist.