Brain death explained: What happens when doctors say you're dead but your heart still beats?

Boniface Kariuki was a young mask vendor going about his daily business in Nairobi's City Centre when his life changed forever on June 17, 2025. During protests calling for justice for Albert Ojwang’—a teacher and blogger killed in police custody—a police officer shot Boniface in the head at point-blank range.

After two surgeries at Kenyatta National Hospital, doctors declared "His brain stem is completely dead." Yet, Boniface's heart continued to beat.

This raises profound questions: When exactly did Boniface die? Was it when doctors declared that his brainstem was completely dead, or was it when his heart finally stops beating?

His case, linked to police brutality, illustrates the complex medical and philosophical questions about what exactly classifies death — especially one linked to brain injury.

Our reporter Hellen Shikanda spoke to Dr Beverly Cheserem, an Assistant Professor and Consultant Neurosurgeon at the Aga Khan University Hospital, who answers the questions you may have regarding brain death, also known as brainstem death.

We start with the basics... what does our brain look like?

There are three main sections to your brain. The top portion of your brain, called the cerebral hemisphere (or cerebrum), is the biggest part. It deals with movement, sight, and executive thinking. It is what gives you memory, the ability to plan, and your sense of self.

At the back of the head, we have another part called the cerebellum. It deals with balance of the body. We are now learning more about how it can also perform some emotional assessments.

We then have the middle portion, which is the brainstem, which has three segments. There is the midbrain, the pons, and the medulla. They work as a superhighway, connecting your body to the outside world and to each other. They are also in charge of the Reticular Activating System that gives you consciousness, alertness, and awareness. When you wake up in the morning, it turns on and makes you awake. It also deals with controlling all the cranial nerves—your eyes, your hearing, and even your facial movement. They are also part of the regulation of your blood pressure and breathing.

When you have any acquired brain injury, it depends on which segment has been damaged and whether it is temporary or permanent.

So what is brain death?

There is an international classification for brain death. It looks at this central portion of your brainstem to see whether you have partial or total loss of function. Brain death is the total loss of function. In other words, if a doctor gives your brain an ideal environment, will it sustain basic functions of life?

So you assess the cranial nerves. A person can breathe to check if they are well oxygenated and there are no other reasons why it could be suppressed. This could be through medications, through low sugar levels, or abnormal electrolytes. If the person cannot breathe off the machine and they are not able to initiate breathing, this is termed brainstem death.

How long has this classification of brainstem death been in the medical field?

It has been around for about 100 years. Prior to that, there were no ventilator machines. In those days, when your brain could not sustain your ability to breathe or maintain your blood pressure, it was rapidly followed by cardiorespiratory death—the inability to breathe and for your heart to function.

Most people completely understand that when you don't have a pulse and you are not breathing, then you are dead. When ventilators were invented, doctors were able to supplement the functions that the brain's nervous system was doing by putting you on the machine. The machines were meant to be for supportive care. When people are ventilated, medical experts are trying to give a body time to recover by taking over some of its functions for a temporary period of time. The problem it created, though, was knowing if somebody was not going to survive without the machine. That is why the International Criteria for Brain Stem Testing was established.

How is this done in Kenya?

It follows the international criteria. Usually, the people who treat the patient are not the ones who perform the official brainstem testing. This is to remove the idea of conflict of interest. The tests for brainstem function are routine parts of medical examinations that all doctors know how to do. If a doctor has a suspicion that their patient is brainstem dead, they have an obligation to invite a member who is not directly involved in their care to corroborate what they think. The law says that two independent individuals at two separate times perform the test. In Kenya, it only allows them to put the patient on minimum support. This is because it has been established that escalation of care is futile. We don't have a clear law that allows someone to take someone off the ventilator.

Why do doctors conduct this test?

There are three main reasons: one is to allow patients and family to be guided regarding the prognosis, to allow for palliative and end-of-life care support, and in some countries, to discuss organ donation.

What then is the time of death?

Internationally, the time of death is really the first time you declare brainstem death. So, the second one is just a confirmatory test. Around the world, once a doctor confirms brainstem death, it allows them to take the patient off the ventilator. Death is often a process, rather than an event.

What is the difference between brainstem death and a coma?

When doctors do a scale of consciousness, they mostly use the Glasgow Coma Scale. A conscious person has some connection with the outside world in a meaningful and predictable way. When one is in a coma, their ability to connect with the outside world is sufficiently impaired. In the Glasgow Coma Scale, a conscious person is scored at 15. A person who is in a coma, on the other hand, gets a score of below 8. It is an extrapolation of which parts of the brain are working.

A coma can be temporary and could sometimes be reversed, but brainstem death is irreversible. Someone who has brainstem death cannot have any form of bodily response; it is mostly their heart that is beating. Someone who is brain dead cannot breathe off the machine. The heart keeps beating because it has its own pacemaker. There are bundles of nerves in the heart that are able to stimulate electrical activity in the heart for a period of time.

What causes brainstem death?

It is the end stage of failure of the nervous system. This process can be progressive or a sudden event. It could be part of a wider health problem that has affected one's nervous system, or it could be sudden, from significant trauma like being hit on one's head.

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