Seizures after surgery stem from a surprisingly wide range of causes, from shifts in blood chemistry and reactions to medications to the physical trauma of the operation itself. They can happen after almost any type of procedure, though rates vary dramatically depending on the surgery. After cardiac operations, for instance, roughly 1 in 100 patients experiences a postoperative seizure. After brain surgery, rates climb higher. Understanding the causes and risk factors matters because some triggers are preventable, and because not every episode of shaking or altered consciousness in a recovery room is actually an epileptic seizure.
How Common Are Postoperative Seizures
The frequency depends heavily on what kind of surgery was performed. In a study of more than 7,200 consecutive cardiac surgery patients, about 0.8% had a postoperative seizure, and more than half of those patients went on to have at least one recurrence.1Journal of Cardiothoracic and Vascular Anesthesia. Recurrent Seizures Following Cardiac Surgery: Risk Factors and Outcomes in a Historical Cohort Study That number sounds small, but it adds up quickly when you consider how many cardiac operations are performed each year. For neurosurgical procedures involving the brain itself, rates are substantially higher. After burr-hole drainage for chronic subdural hematoma, early seizures occurred in about 5% of patients in one series, with the rate climbing to nearly 14% in patients whose brain imaging showed mixed-density lesions.2Churchill Livingstone / ScienceDirect. Early post-operative seizures after burr-hole drainage for chronic subdural hematoma: correlation with brain CT findings
Children undergoing heart surgery face a particularly high burden. Among nearly 3,850 pediatric cardiac surgery patients screened at one center, about 4.2% developed neurological complications in the first ten days. Seizures were the single most common complication, affecting more than 40% of the children who had any neurological event.3PubMed Central. Neurological complications after pediatric cardiac surgery The mortality rate among children who developed neurological complications was about a third, underscoring how seriously these events are taken in pediatric intensive care.
Metabolic and Electrolyte Shifts
One of the most common and most preventable causes of postoperative seizures has nothing to do with the brain directly. When blood sodium levels drop sharply after surgery, the resulting condition can trigger seizures, brain swelling, and in severe cases, permanent damage. This risk is especially relevant in surgeries that involve large volumes of intravenous fluid or irrigating solutions. During hysteroscopic procedures, for example, absorption of hypotonic irrigation fluid can dilute the blood dramatically. In one reported case, a patient’s sodium fell to 84 mmol/L during a uterine procedure, leading to seizures and confirmed brain edema despite treatment with concentrated saline.4PubMed Central. Severe hyponatremia with seizures and confirmed mild brain edema by hysteroscopic myomectomy: a case report
The phenomenon is not limited to gynecological procedures. A landmark study documented 15 previously healthy women who developed severe low sodium after various elective surgeries. All 15 recovered normally from anesthesia, but roughly two days later, when their average sodium had drifted down to about 108 mmol/L, they developed grand mal seizures followed by respiratory arrest. Every one of them either died or suffered permanent brain damage.5PubMed. Hyponatremia, convulsions, respiratory arrest, and permanent brain damage after elective surgery in healthy women The delay between surgery and seizure onset is what makes this so dangerous. By the time symptoms appear, the brain has been soaking in dangerously diluted fluid for hours. Modern monitoring of fluid balance and electrolytes during and after surgery is designed to catch these shifts before they become catastrophic, though vigilance varies between institutions.
Anesthetic Agents
The drugs used to keep you unconscious during surgery can themselves provoke seizure-like brain activity. Several common anesthetic agents, including sevoflurane, enflurane, etomidate, and to a lesser extent propofol, have been shown to induce abnormal electrical patterns in the brain. These episodes most commonly occur during induction (going under) or emergence (waking up), when drug concentrations in the brain are transitioning through intermediate levels rather than sitting at the full surgical dose.6PubMed. The howling cortex: seizures and general anesthetic drugs Full-blown generalized seizures from anesthetics alone are rare, but the abnormal electrical activity can look alarming and sometimes complicates the picture when medical teams are trying to figure out why a patient is not waking up normally.
Medications That Lower the Seizure Threshold
Beyond anesthetics, several categories of drugs commonly given in the perioperative period can push the brain toward seizure activity. The antibiotic cefepime, a powerful drug often administered after surgery to prevent or treat infections, is a well-documented offender. Even when dosed appropriately for a patient’s kidney function, cefepime can cause neurotoxicity that manifests as confusion, inability to eat, and a form of ongoing seizure activity that may not produce visible convulsions.7PubMed Central. Cefepime-Induced Neurotoxicity Patients with reduced kidney function are at highest risk because the drug accumulates, but cases have been reported even at standard renal doses.
Tranexamic acid, a clot-promoting drug used heavily in cardiac and orthopedic surgery to reduce bleeding, has also been identified as a contributing factor to postoperative seizures, particularly after cardiopulmonary bypass.8PubMed Central. Seizures Following Cardiopulmonary Bypass The drug crosses into the brain and can act as an excitatory agent at high enough concentrations. Dose-dependent seizure risk with tranexamic acid has become a practical concern for surgical teams, prompting some to lower their standard doses.
Transplant recipients face a distinct pharmacological threat. Tacrolimus, one of the most widely used anti-rejection drugs, can trigger a condition called posterior reversible encephalopathy syndrome, which often presents with seizures alongside headache, visual disturbances, and high blood pressure. This complication affects somewhere between 0.5% and 5% of solid organ transplant recipients.9PubMed Central. Tacrolimus-induced posterior reversible encephalopathy syndrome following liver transplantation It has been reported after kidney, liver, and bone marrow transplants alike.10PubMed Central. Tacrolimus associated posterior reversible encephalopathy syndrome – a case series and review In most cases, the syndrome resolves when the drug is stopped or the dose is reduced. One pair of case reports described patients who developed seizures 15 days and two months after transplant, respectively, and both recovered after their tacrolimus was switched to a different immunosuppressant.11PubMed Central. Calcineurin Inhibitors Associated Posterior Reversible Encephalopathy Syndrome in Solid Organ Transplantation: Report of 2 Cases and Literature Review
Cardiac Surgery and Cardiopulmonary Bypass
Heart surgery carries seizure risks beyond those shared with other operations. The use of a bypass machine reroutes blood away from the heart and through an artificial circuit, which can shower tiny particles of plaque from the aorta into the brain’s blood vessels. Other identified factors include low blood pressure reaching the brain during bypass, the type of procedure (open-chamber operations carry more risk), and the medications used to control bleeding.8PubMed Central. Seizures Following Cardiopulmonary Bypass The combination of these insults means that cardiac surgery patients may experience seizure activity from microstrokes, metabolic derangement, or drug toxicity simultaneously, making it harder to pin down a single cause.
A concerning subset of these patients develops seizure activity that produces no visible shaking at all. In one study of cardiac surgery patients who failed to wake up as expected, continuous brain monitoring revealed that two out of five were in an ongoing seizure state without any outward clinical signs.12Journal of Critical Care. Evaluating the obtunded patient after cardiac surgery: The role of continuous electroencephalography These nonconvulsive seizures can cause progressive brain injury if they go unrecognized, which is why neurologists increasingly advocate for continuous brain wave monitoring in cardiac ICUs.
Inflammation, Infection, and the Blood-Brain Barrier
Surgery triggers an inflammatory response throughout the body, and when that response becomes severe, as in sepsis, the brain’s protective barrier starts to break down. Under normal conditions, a tightly sealed layer of cells prevents most blood-borne substances from entering brain tissue. During severe infection or overwhelming inflammation, inflammatory molecules damage this barrier, allowing toxic mediators to flood into the brain and activate immune cells that would normally remain quiet.13PubMed Central. Targeting the Blood-Brain Barrier to Prevent Sepsis-Associated Cognitive Impairment The resulting cascade includes microclot formation, localized loss of blood supply, and brain swelling.14PubMed. Sepsis and Cerebral Dysfunction: BBB Damage, Neuroinflammation, Oxidative Stress, Apoptosis and Autophagy as Key Mediators and the Potential Therapeutic Approaches
Animal research has shown that this inflammatory state directly increases how easily the brain produces seizures. When researchers mimicked sepsis-like conditions in rats, they found elevated levels of several key inflammatory molecules in both the blood and the brain, along with measurably increased barrier permeability and heightened susceptibility to seizures. Reducing the inflammatory state appeared to reverse the increased seizure risk.15Epilepsy Research. Increase in seizure susceptibility in sepsis like condition explained by spiking cytokines and altered adhesion molecules level with impaired blood brain barrier integrity in experimental model of rats treated with lipopolysaccharides For surgical patients, this means that postoperative infections, even those originating far from the brain, can create the conditions for seizures by triggering body-wide inflammation that eventually breaches the brain’s defenses.
Alcohol and Substance Withdrawal
Any patient with heavy alcohol use who undergoes surgery faces the risk of withdrawal seizures, typically appearing one to three days after their last drink. The underlying problem is that chronic alcohol exposure causes the brain to adapt by dialing down its own calming signaling pathways. When alcohol is abruptly removed during a hospital stay, the brain is left in a state of overexcitability. This is especially common after trauma surgery and operations on the upper digestive tract, where rates of alcohol dependence among patients tend to be higher.16PubMed Central. Perioperative Management of Alcohol Withdrawal Syndrome The same principle applies to benzodiazepine dependence and, to some extent, other sedative drugs. Surgical teams increasingly screen for alcohol use before elective procedures so that preventive protocols can be started early.
The Problem of Nonconvulsive Seizures
One of the most underappreciated aspects of postoperative seizures is that many of them are invisible to the naked eye. Nonconvulsive status epilepticus is a state of continuous or near-continuous seizure activity in the brain that produces no obvious shaking or jerking. It may look like a patient who simply is not waking up, or who seems confused and sluggish. Without continuous brain wave monitoring, these episodes are easily missed or mistaken for lingering effects of anesthesia or sedation.
After surgery for ruptured brain aneurysms, continuous monitoring detected nonconvulsive seizure activity in about 15% of patients. Every one of those cases occurred in patients who had undergone open surgery rather than a less invasive approach.17Clinical Neurology and Neurosurgery. Nonconvulsive status epilepticus after surgery for ruptured intracranial aneurysms: Incidence, associated factors, and impact on the outcome The detection challenge is real even in well-equipped hospitals. Continuous brain wave monitoring is expensive, not universally available, requires skilled interpretation, and its sensitivity drops when fewer electrodes are used or when recordings are reviewed without accompanying video of the patient.18PubMed Central. The Impact of Nonconvulsive Status Epilepticus after Cardiac Surgery on Outcome This means nonconvulsive seizures are almost certainly underdiagnosed in many surgical ICUs, and patients with unexplained failure to recover consciousness after surgery may be seizing without anyone realizing it.
Seizure Prevention After Brain Surgery
For patients undergoing craniotomy, especially for tumors, preventive anti-seizure medication is standard practice, though the choice of drug has shifted over the years. Phenytoin was the traditional go-to for decades, but levetiracetam has increasingly taken its place. Multiple systematic reviews and meta-analyses now show that levetiracetam is at least as effective as phenytoin for preventing early postoperative seizures, with a more favorable side-effect profile.19PubMed Central. Postoperative seizure prophylaxis after craniotomy: a current evidence and ongoing controversy
A meta-analysis focused specifically on brain tumor patients found that levetiracetam cut the odds of postoperative seizures roughly in half compared to control treatments, with the benefit being strongest for early seizures in the days immediately following surgery. Levetiracetam also outperformed both phenytoin and sodium valproate in head-to-head comparisons, and it caused fewer adverse drug reactions.20Frontiers in Neurology. Efficacy and safety of levetiracetam in preventing postoperative seizures in adult patients with brain tumors: a meta-analysis How long to continue prophylaxis remains debated. Many institutions use a short course of one to two weeks after surgery, though the optimal duration likely depends on the type of surgery and individual risk factors.
Pre-existing Epilepsy and Medication Changes
Patients who already have epilepsy face a distinct set of concerns around surgery. Beyond the general postoperative risks, any disruption to their regular anti-seizure medication schedule can trigger breakthrough seizures. This is relevant not just for epilepsy surgery but for any operation requiring fasting, altered gut absorption, or changes to the drug regimen. For patients who have previously had successful epilepsy surgery, the question of whether to continue anti-seizure drugs afterward is a live one. Data from one long-term follow-up showed that among patients who completely stopped their medications after epilepsy surgery, about 14% had a seizure recurrence within two years and 36% within five years. By contrast, patients who stayed on their medications had recurrence rates of only 3% and 7% over the same periods.21PubMed. Discontinuation of antiepileptic drugs after successful epilepsy surgery The gap is large enough that stopping medication is approached cautiously even when surgery has been successful.
When It Looks Like a Seizure but Is Not One
Not every episode of shaking or unresponsiveness in the recovery room is a true epileptic seizure. Psychogenic nonepileptic seizures are events that look very much like seizures from the outside but are not driven by abnormal electrical activity in the brain. They can occur in the postoperative setting, particularly in patients with a history of anxiety, trauma, or conversion disorders. The stress of surgery and the disorientation of waking from anesthesia can be powerful triggers.
Recognizing these events matters enormously because the treatment is completely different. Giving anti-seizure medications to someone having a psychogenic episode does nothing to help and can cause serious harm, including respiratory depression from intravenous benzodiazepines and the risks of unnecessary intubation.22Brazilian Journal of Anesthesiology (English Edition). Psychogenic non-epileptic seizures in the post-anesthesia recovery unit Certain clinical clues help distinguish the two: psychogenic events often involve side-to-side head movements, eyes squeezed shut (epileptic seizures typically produce open eyes), and waxing-and-waning intensity over longer durations than most epileptic seizures. Video-EEG monitoring, when available, can confirm the diagnosis definitively.
What Early Seizures Mean for Long-Term Prognosis
For patients undergoing epilepsy surgery, whether a seizure occurs in the first month after the operation carries real prognostic weight. In a study of 112 pediatric epilepsy surgery patients, 44% had at least one seizure within 30 days of their procedure. Among those who seized early, only about a quarter went on to have good long-term seizure control, compared to 76% of patients who made it through the first month seizure-free.23Seizure. Acute postoperative seizures and long-term outcome following pediatric epilepsy surgery This does not mean early seizures guarantee a poor outcome, but they shift the odds substantially and often prompt surgical teams to reassess whether the intended brain tissue was fully removed or disconnected.
Outside of epilepsy surgery, early postoperative seizures after cardiac or other major operations also raise longer-term concerns. In the cardiac surgery cohort mentioned earlier, more than half of patients who had one postoperative seizure went on to have recurrences.1Journal of Cardiothoracic and Vascular Anesthesia. Recurrent Seizures Following Cardiac Surgery: Risk Factors and Outcomes in a Historical Cohort Study Whether these patients need long-term anti-seizure medication is a case-by-case decision that weighs the suspected cause against the likelihood of recurrence. A seizure clearly triggered by a transient metabolic problem that has been corrected carries a very different prognosis than one caused by a perioperative stroke.