Quadriplegia (tetraplegia) results from a severe spinal cord injury (SCI) in the cervical vertebrae (C1-C8). This damage interrupts communication between the brain and body, causing a loss of motor and sensory function in all four limbs and the torso. Individuals with high-level SCI face significantly higher mortality rates compared to the general population. This increased risk stems from secondary complications, as the nervous system struggles to regulate vital physiological processes.
Respiratory System Failure
Respiratory complications are the leading cause of death for individuals with quadriplegia, remaining a significant threat throughout the lifespan. This vulnerability arises because the cervical spinal cord controls the nerves necessary for breathing muscles. A high-level SCI, especially above the C5 vertebra, damages the pathways to the intercostal and abdominal muscles, which are responsible for forced exhalation and an effective cough.
The phrenic nerve, which controls the diaphragm, can also be impaired or paralyzed in very high cervical injuries, sometimes necessitating mechanical ventilation. The paralysis of accessory muscles means the individual cannot generate the necessary force for a strong cough. This inability to clear secretions from the lungs leads to mucus plugging and the collapse of lung tissue, known as atelectasis.
Atelectasis promotes bacterial growth, leading directly to pneumonia, the most frequently cited cause of death. Respiratory disorders account for approximately 28% of deaths in the first year after injury and 22% of long-term mortality. Furthermore, the risk of pulmonary embolism, a blockage in the lung’s artery often caused by blood clots from the legs, is elevated due to immobility.
Cardiovascular Instability and Autonomic Dysfunction
The second major category of life-threatening complications involves the cardiovascular system, destabilized by the disruption of the Autonomic Nervous System (ANS). The ANS regulates involuntary functions like heart rate, blood pressure, and body temperature. When a high-level SCI severs the connection between the brain and the sympathetic nervous system, the heart and blood vessels lose their ability to respond normally.
In the acute phase, this disruption can lead to neurogenic shock, characterized by bradycardia (low heart rate) and hypotension (low blood pressure). Over time, individuals often suffer from orthostatic hypotension, a sudden drop in blood pressure when moving upright. This occurs because the blood vessels cannot constrict quickly enough to compensate for gravity, leading to inadequate blood flow to the brain.
A severe threat is Autonomic Dysreflexia (AD), a syndrome unique to those with SCI above the T6 level. AD is an uncontrolled sympathetic nervous system discharge triggered by a stimulus below the injury, such as a full bladder or a pressure sore. This surge causes a rapid spike in systolic blood pressure. Unmanaged AD can lead directly to a stroke, cerebral hemorrhage, or myocardial infarction, making it a medical emergency that requires swift identification and removal of the triggering stimulus.
Chronic Infections and Systemic Breakdown
Chronic infections and their systemic consequences contribute significantly to long-term mortality. The constant need for bladder management, often involving catheters, predisposes individuals to frequent Urinary Tract Infections (UTIs). A neurogenic bladder, which cannot fully empty, compounds this risk, making UTIs a persistent health concern.
Chronic UTIs can lead to antibiotic resistance, making subsequent infections difficult to treat effectively. If a UTI is left untreated or resistant, the infection can progress into the bloodstream, resulting in sepsis. Sepsis is a systemic inflammatory response that can lead to organ failure and death.
Another common source of sepsis is pressure injuries (bedsores), which develop due to prolonged, unrelieved pressure on the skin. Because quadriplegia involves a loss of sensation, individuals may not feel the early signs of tissue damage, allowing the injury to progress to a deep wound. If these open sores become infected, bacteria can penetrate the deeper tissues and enter the bloodstream, triggering systemic breakdown. The cycle of chronic infection, antibiotic resistance, and progression to sepsis or eventual renal failure represents an ongoing risk to survival.