Learning Objectives
- The examination of brain death is different from the standard neurological exam
- Ancillary testing may be crucial to the determination
- Significant ethical issues are raised by severe brain injury and brain death
History
A 56 year old man collapses on the street while jogging one morning before work. A neighbor finds him within 2 minutes, calls 911 and starts CPR. The ambulance arrives within 2 minutes. At that time, he has no pulse or respirations. He is treated with CPR and defibrillation, he develops a rhythm, and he is brought to the emergency room. At the emergency room he requires ventilation and hemodynamic support. He is transferred to intensive care. He does not regain consciousness. You are asked to evaluate the possibility of brain injury and his chances for recovery.
At the time of his syncope, he was taking aspirin, metoprolol, and simvastatin.
He has a past medical history of coronary artery disease with stent to the LAD and left main arteries two years ago.
He has a family history of coronary artery disease (father), Diabetes mellitus and stroke in his mother, and leukemia in his sister (who died at age 39).
He smoked cigarettes for 35 years and quit 2 years ago. He has six to eight drinks per week.
Review of systems: He was unable to respond to any questions.
Examination
His temperature is 97.3 F, his blood pressure is 89/54, and his pulse is 115. He is unconscious, lying in bed, with an endotracheal tube, central line to the right IJ, and radial line to the left radial. His eyes are closed. Pupils are moderately large and they do not react to light on either side, direct or indirect. He does not respond to pain or nasal tickle. There is no blink to threat or to corneal stimulation. Doll’s eyes movements are absent. The cold water caloric response is absent on both sides. There is no gag response on either side. There are no spontaneous movements. Deep tendon reflexes are diffusely suppressed and muscle tone is absent. The toes do not respond to plantar stimulation.
Localization and Neuroanatomy
This is a 56 year old man who lost consciousness. He did not wake after cardiac and pulmonary resuscitation. His examination indicates a global cerebral injury, as there is no response to stimuli, no spontaneous movement, reflexes are suppressed, and there are no brainstem reflexes. Note that the examination of brainstem reflexes is different in this setting than usual. Corneal response, cold water caloric response and gag response are not often indicated for a patient who is conscious. Although corticospinal tract injuries tend to result in increased muscle tone, increased deep tendon reflexes, and upgoing toes, the findings vary in the earliest part of the clinical course.
Diagnosis
A patient without brainstem reflexes is presumed to have brain death. Different hospitals have policies for this determination depending on patient age and their staff. Often, the determination must be made by two examiners over a defined period of time. The examiners must be trained to perform this examination. The patient’s temperature must be close to normal. There must be a period of time without sedative medication. For patients who are candidates for organ donation, additional criteria may be significant.
In the setting of brain death evaluation, traditional MRI and CT scans tend not to help as much as desired. Although they may show evidence of a large stroke or cortical edema, both of which can be ominous clinical findings, neither of these tests can confirm brain death. At times, both of these studies may appear normal.
Patients with brain death have no respiratory drive. A ten minute apnea test can help confirm clinical brain death. In this test, a patient is treated with 100% oxygen, but no ventilation. After ten minutes, if their PaCO2 has risen without any evidence of respiration, one can conclude that respiratory drive has been compromised.
A cerebral perfusion study can be helpful in the setting of a brain death evaluation. In principle this test is cerebral angiography. It may be done as a nuclear medicine scan, a traditional cerebral angiogram, or sometimes, an angiogram monitored by CT or MRI. In any case, a metabolically inactive brain will have no blood flow.
A specially-administered EEG can also be used to confirm clinical brain death. A metabolically-inactive brain will generate no cortical discharges, and the EEG should show evidence of electrocerebral silence in this setting.
Treatment
There is no treatment for clinical brain death. This diagnosis is considered equivalent to cardiac or respiratory death in a medico-legal sense. The difference is that cardiac and pulmonary function can be supported when the brain is dead, leading to some differences of opinion about life, medical duty, spirituality and personal rights. Patients with a severe brain injury have unique ethical issues. Next of kin and medical wishes may not be clear. In the setting of brain death, the hospital may wish to discontinue life support, sometimes against the wishes of the patient or their family. These topics are well-addressed by other authors.
Patients with an examination showing some signs of brain stem function may recover, although recovery tends to be limited. Patients who show spontaneous eye opening and pupillary response have been shown to have a small chance of limited cognitive and functional recovery within 3-6 months. Patients with incomplete caloric or gag responses may require prolonged support with locomotion or feeding. The exam tends to be worst at clinical onset, although no recovery should be expected if brain death is determined.
Review Questions
- Which of these examination findings is not consistent with clinical brain death?
a. absent pupillary light response
b. intact cold water caloric response on the left side
c. absent response to corneal stimulation
d. no response to plantar stimulation
e. downgoing response to plantar stimulation - The following exam finding is critical to making a brain death determination
a. absent brainstem reflexes on both sides
b. increased deep tendon reflexes on both sides
c. impaired cerebellar movements
d. positive Babinksi / downgoing plantar response
e. abnormal gait evaluation - Which of these tests suggests clinical brain death?
a. an MRI of the brain that shows bilateral brain stem stroke
b. a cerebral perfusion study that shows flow through the vertebral arteries only
c. a 10 minute apnea test that shows 12 agonal breaths
d. an EEG that shows a low amplitude 2-4 Hz frequency over the parieto-occipital regions
e. none of the above