A seizure is a transient occurrence of signs and symptoms caused by abnormal excessive or synchronous neuronal activity within the brain. This electrical activity can disrupt the autonomic nervous system, which controls involuntary processes like breathing and heart rate. Due to this interference, breathing can be severely affected or temporarily stop during a seizure. This respiratory compromise is a serious risk, ranging from brief pauses in respiration to significant oxygen deprivation, depending on the seizure type and duration.
Physiological Causes of Breathing Interference During Seizures
Seizures disrupt breathing through two primary mechanisms: central nervous system failure and mechanical obstruction. Central apnea occurs when seizure activity directly involves the brainstem, which houses the respiratory control centers. This causes the brain to stop sending signals to the diaphragm and chest muscles, leading to a temporary cessation of breathing efforts.
Mechanical interference is the second cause of breathing disruption. During the tonic phase of a convulsive seizure, the muscles of the chest wall and the larynx become rigid. This stiffness, sometimes called laryngospasm, physically prevents air from moving in and out of the lungs.
The airway can also be obstructed by the tongue relaxing into the back of the throat, or by the accumulation of saliva or vomit. Following the active seizure, the post-ictal state often occurs, characterized by hypoventilation. Breathing is typically shallow or slow during this time, and the person may experience periods of apnea, which can lead to low oxygen levels.
Seizure Types Associated with Respiratory Risks
The risk of breathing compromise is highest in seizures involving large-scale muscle contractions and loss of consciousness. Generalized tonic-clonic seizures pose the highest respiratory risk. The tonic phase involves widespread, sustained muscle contraction of the breathing muscles, causing a temporary cessation of breath.
Focal seizures that spread (focal to bilateral tonic-clonic seizures) also carry a high risk once they generalize. Certain focal seizures involving autonomic nervous system regions, such as the amygdala, can cause ictal central apnea, where the person stops breathing without convulsions.
Seizure duration and frequency are significant risk factors. Prolonged seizures (status epilepticus) severely increase the risk of oxygen deprivation and subsequent injury. Underlying health conditions, such as obstructive sleep apnea, can also exacerbate breathing difficulties during and after a seizure.
Bystander First Aid for Seizure-Related Breathing Issues
The immediate priority for a bystander is to keep the person safe during the seizure.
During the Seizure
- Gently ease the person to the floor.
- Clear the surrounding area of any hard or sharp objects.
- Place a soft, flat item, such as a folded jacket, under the person’s head for cushioning.
- Never attempt to restrict the person’s movements.
- Never put anything into their mouth, as this can cause severe injury.
After the Seizure
Once convulsive movements have stopped, the person should be gently turned onto their side into the recovery position. This position keeps the airway clear by allowing saliva or fluid to drain from the mouth, preventing aspiration. Any tight clothing around the neck should be loosened.
The seizure should be timed from start to finish. Emergency medical services should be called immediately if the seizure lasts longer than five minutes, if breathing does not immediately resume, or if the person turns blue.
Understanding Sudden Unexpected Death in Epilepsy (SUDEP)
Sudden Unexpected Death in Epilepsy (SUDEP) is the most serious outcome associated with seizure-related respiratory and cardiac risks. SUDEP is defined as the non-traumatic, non-drowning death of a person with epilepsy where no other cause is found upon post-mortem examination. It is the leading cause of epilepsy-related death, affecting approximately one in every 1,000 adults with epilepsy annually.
The primary theory suggests that SUDEP results from a cascade of events, often involving severe respiratory failure followed by cardiac arrest. Seizure-induced apnea (temporary cessation of breathing) leads to severe oxygen deprivation, which triggers a dangerous slowing of the heart rate.
The biggest modifiable risk factor for SUDEP is uncontrolled generalized tonic-clonic seizures. Consistent adherence to prescribed antiseizure medication is the most effective way to reduce the risk. Other preventative measures include discussing SUDEP risk with a healthcare provider and utilizing nocturnal monitoring devices for those who experience seizures during sleep.