Jerking movements are a recognized, often unsettling, phenomenon in advanced illness and the active dying phase. These involuntary muscle movements are not a direct sign of the moment of death but rather a symptom of the body’s declining physiological function. The medical term for this type of movement is myoclonus, and understanding its cause can bring clarity during a confusing time.
Understanding Myoclonus
Myoclonus is the term for a sudden, brief, shock-like, involuntary twitching or jerking of a muscle or group of muscles. It is a symptom resulting from abnormal electrical activity within the central nervous system, not a specific disease. Movements can be minor, like isolated twitches, or generalized, affecting the entire body. Healthy individuals often experience myoclonus, such as the “sleep start” that occurs when falling asleep.
Myoclonus is classified as positive when it results from an active muscle contraction. Negative myoclonus, conversely, is a sudden loss of muscle tone causing a brief lapse in posture. While observing end-of-life myoclonus is often distressing for family members, the movements are typically not painful to the dying person. Since they are not a sign of suffering, the primary focus of care is managing the symptom to ensure comfort.
Physiological Reasons for Movement Before Death
The onset of myoclonus near the end of life signals a shift in the body’s internal environment, often due to failing organ systems. A common cause is an alteration in the chemical balance of the blood, known as metabolic encephalopathy. As the kidneys or liver fail, waste products and toxins build up, irritating the nervous system and leading to involuntary movements. For instance, uremia from kidney failure or hepatic encephalopathy from liver failure can both manifest as twitching.
A lack of sufficient oxygen reaching the brain, known as hypoxia, is another trigger for myoclonus in the terminal phase. Declining respiratory function causes a buildup of carbon dioxide in the blood (hypercarbia), which acts as a neurotoxin that excites the central nervous system. This irritation can lead to generalized twitching or muscle spasms. These movements are a physical manifestation of the severe internal stress on the brain and spinal cord.
Medications used for pain management, particularly opioids, can also contribute to myoclonus through opioid-induced neurotoxicity. Certain opioid metabolites, such as those from morphine, can accumulate and become neuro-excitatory, especially if the patient has impaired kidney function. This chemical irritation can cause brief muscle jerks or even generalized seizures. Adjusting the type or dose of pain medication is often necessary to alleviate this drug-related twitching and improve patient comfort.
Reflexive Movement After Clinical Death
A different, though startling, type of movement can occur after clinical death (cessation of heartbeat and breathing). These movements are purely reflexive and do not indicate a return to consciousness or life. They result from the temporary “release” of the spinal cord from the brain’s control. The spinal cord contains localized nerve circuits (reflex arcs) that can function briefly without input from the inactive brain.
These post-mortem reflexes can manifest as simple finger or toe jerks, or more complex actions like the “Lazarus sign.” The Lazarus sign is an involuntary reflex where a person’s arms may briefly rise and then drop crossed over the chest. This movement is mediated entirely by the spinal cord and is a known, rare occurrence, even in patients declared brain dead. While witnessing such movement can be disturbing, it is a residual physiological response of the nervous system, not a sign that the deceased person is aware or suffering.
Determining When to Seek Immediate Medical Attention
If a person is receiving palliative or hospice care, mild, intermittent myoclonus is an expected part of the dying process. This should be reported to the care team rather than prompting an emergency call. The care team is prepared for these movements and can often manage them effectively with simple adjustments to comfort medications. They may prescribe a short-acting benzodiazepine, such as lorazepam, which calms the nervous system and reduces involuntary twitching.
Immediate medical attention is necessary if the movements are sudden, severe, and generalized, suggesting an acute seizure rather than simple myoclonus. A full-blown seizure, especially in a relatively stable patient, may require prompt intervention to prevent injury or distress. If the person is not under active palliative care, or if the movements are causing acute pain or injury, seeking urgent medical assessment is appropriate. The distinction rests on whether the movement is an anticipated, manageable symptom of terminal decline, or a sudden, severe neurological event.