A 47-year-old man is brought in after a motor vehicle accident. He was driving under the influence of alcohol when he sustained a crash against a pole. His medical history is significant for hypertension but he does not take any medications. His temperature is 98.6°F (37.0°C), blood pressure is 110/80 mmHg, pulse is 60/min, and respirations are 12/min on a ventilator. His Glasgow coma score (GCS) on presentation is 6. Initial urine toxicology is negative. The patient is admitted to the intensive care unit and appropriate care is initiated. One week later, the patient’s GCS score is now 3. Laboratory studies do not show significant electrolyte, acid-base, or endocrine disturbances. Sedative and paralytic agents are withdrawn. Which of the following findings on physical exam would be compatible with brain death?
Conjugate eye movement to the left with rotation of the head to the right
Grimacing after noxious stimulus to the arm
Flexion of the thigh, leg, and foot upon noxious stimulation of the foot
Spontaneous respiration 1 minute after disconnection from a ventilator
Flexion of the thigh, leg, and foot upon noxious stimulation of the foot
This patient with a Glasgow coma score (GCS) of 3 and a known mechanism of injury due to motor vehicle accident trauma is normothermic, normotensive, not on sedatives, and without laboratory abnormalities so they are appropriate for examination of brain death. Cortical and brain stem function must be absent in brain death; however, spinal cord reflexes such as triple flexion (flexion of the thigh, leg, and foot upon noxious stimulation of the foot) may remain intact in patients with brain death.

The clinical brain death exam may be performed in patients with evidence of irreversible central nervous system catastrophe after a known mechanism of trauma or medical injury. The patient must not have other causes for obtundation, and should be euthermic, not on sedative or paralytic agents, not be intoxicated due to drugs or poisoning, and not have other severe electrolyte, acid-base, or endocrine disturbances. In brain death, there must be no cerebral motor response such as moaning or grimacing to pain in all extremities and the face. Brain stem reflexes such as the pupillary light reflex, corneal reflex, oculocephalic reflex, vestibulo-ocular reflex, gag reflex, and apnea test should also be absent in brain death. Spinal cord and deep tendon reflexes may still be present in brain death. Complex movements mediated by the spinal cord such as triple flexion and the Lazarus sign (raising the arms and dropping them crossed on the chest after noxious stimulus) do not preclude a diagnosis of brain death.

Greer et al. review neurologic criteria for the determination of brain death. They discuss how to clinically differentiate spinal motor responses from brain-mediated motor responses. They recommend understanding these distinctions in order to properly examine patients with brain death.

Incorrect Answers:
Answer A: Blinking after saline is applied to the cornea indicates a positive corneal reflex. In the corneal reflex, the ophthalmic branch of the trigeminal (V1) nerve senses stimulus to the cornea, and bilateral temporal branches of the facial nerve (VII) activate the orbicularis oculi muscles to blink. Brainstem reflexes must be absent in brain death, so the presence of a corneal reflex is not compatible with a diagnosis of brain death.

Answer B: Conjugate eye movement to the left with rotation of the head to the right describes the oculocephalic reflex. In this reflex, movement of the head stimulates endolymph in the horizontal semicircular canal to rotate, causing the firing of the ipsilateral vestibulocochlear (VIII) nerve. This leads to activation or inhibition of the contralateral abducens (VI) and oculomotor (III) nerves. Brainstem reflexes must be absent in brain death, so the presence of an oculocephalic reflex is not compatible with a diagnosis of brain death.

Answer D: Grimacing after the noxious stimulus of the arm indicates some residual cortical function. Grimacing is not a spinal cord reflex and requires some cortical processing of sensory information. All cortical function must be absent in brain death, so grimacing to pain would not be compatible with brain death.

Answer E: Spontaneous respiration 1 minute after disconnection from a ventilator in a patient without diabetes insipidus and with normal blood gas values and systolic blood pressure above 90 mmHg indicates a negative apnea test. The apnea test assesses respiratory control system reflexes in the brainstem. Apnea testing is an important component of the brain death exam, and a negative apnea test is incompatible with brain death.

Bullet Summary:
Although brain death criteria universally include the absence of cortical and brainstem function, spinal cord and deep tendon reflexes may be preserved in patients with brain death.