Seizures occur in roughly 1 to 29 percent of patients after brain surgery, depending on the type of tumor, its location, and whether the patient had seizures before the operation. That wide range reflects how many variables influence the risk: a person undergoing removal of a small frontal-lobe glioma faces a very different likelihood than someone having a posterior fossa meningioma resected. What makes postoperative seizures particularly tricky is that some produce no visible symptoms at all and can only be caught on continuous brainwave monitoring.
How Common Are Postoperative Seizures
The reported rates of seizures after craniotomy for brain tumors span a broad range. Studies using different mixes of tumor types and patient populations report post-craniotomy seizure rates anywhere from about 1 percent to 29 percent.1PubMed Central. A New Predictor Score for Postoperative Seizures in Brain Tumor Patients Without a Seizure History (BRAINNN Score) One single-center study of nearly 200 patients found that about 14 percent developed post-craniotomy seizures.2PubMed Central. Incidence, risk factors and outcomes of seizures occurring after craniotomy for primary brain tumor resection The spread has a lot to do with how the tumors in a given study behave biologically. Tumors that grow within the brain tissue itself, like gliomas, tend to carry a different seizure profile than tumors that grow on the brain’s surface, like meningiomas. Lumping them together in one study muddies the numbers considerably.
Even within a single tumor type, reported seizure rates vary. For brain tumor surgery specifically, one study of early postoperative seizures found they occurred in about 5 percent of patients overall, though the rate climbed among subgroups with specific risk features.3Scientific Reports. Early postoperative seizures (EPS) in patients undergoing brain tumour surgery The bottom line for patients and families is that the risk is real but not overwhelming for most people, and knowing the individual risk factors helps put these numbers in context.
Early Versus Late Seizures
Clinicians split postoperative seizures into two buckets based on timing. Early seizures happen within seven days of the operation. Late seizures appear after that initial week.4PubMed. Predictors of early and late postoperative seizures in meningioma patients: a systematic review and meta-analysis Some research groups draw even finer lines, defining delayed postoperative seizures as those arriving between seven and sixty days after surgery.5PubMed Central. The Occurrence and Relationship of Postoperative Seizure and de novo Epilepsy after Craniotomy Surgery: A Retrospective Single-Center Cohort Study
The distinction matters because the causes and implications differ. Early seizures are often provoked by the acute effects of surgery itself: swelling, bleeding, metabolic shifts, or the temporary disruption of the barrier between the bloodstream and the brain. Research in both humans and animal models has shown that when that barrier breaks open, the leakage alone can trigger seizures even without any other brain damage.6PubMed Central. Seizure-Promoting Effect of Blood–Brain Barrier Disruption Late seizures, by contrast, tend to reflect more structural changes: scar tissue forming in the brain, ongoing inflammation, or the development of a lasting seizure-prone zone around the surgical site.7PubMed Central. Intractable seizures after cranioplasty, a dreadful post-operative complication managed efficiently from Nepal: A case series Early seizures do not always mean a person will develop epilepsy, but late seizures carry a stronger signal that the brain’s wiring has been altered in a lasting way.
Why Brain Surgery Can Trigger Seizures
The brain’s electrical activity is a balance between excitatory and inhibitory signals. Surgery disrupts that balance through several overlapping mechanisms. The most immediate is physical trauma to brain tissue. Cutting through cortex, retracting tissue to reach a deep tumor, and removing the tumor itself all cause local injury. Swelling follows, and with it comes increased pressure on surrounding neurons.
Disruption of the blood-brain barrier is another major contributor. This barrier normally keeps blood proteins and immune cells out of direct contact with neurons. When surgery breaks it open, substances that do not belong in the brain’s extracellular space flood in. That alone is enough to provoke seizures, as demonstrated in studies that measured the extent of barrier disruption and found it correlated with seizure risk.6PubMed Central. Seizure-Promoting Effect of Blood–Brain Barrier Disruption
For late seizures, a different set of processes takes over. As the surgical site heals, scar tissue can form in the brain. In the case of cranioplasty procedures (where a piece of skull is replaced), the healing of post-traumatic contusions and the scarring of the exposed temporalis muscle may produce abnormal electrical discharges. Oxidative stress also plays a role: the generation of free radicals can damage cortical cells, creating a focus of abnormal electrical activity that persists long after the wound has healed on the outside.7PubMed Central. Intractable seizures after cranioplasty, a dreadful post-operative complication managed efficiently from Nepal: A case series
Who Faces the Highest Risk
Two risk factors come up repeatedly across studies: having seizures before surgery and the location of the tumor. Patients who experienced preoperative seizures are roughly two and a half times more likely to have post-craniotomy seizures compared to those who were seizure-free going into the operation.2PubMed Central. Incidence, risk factors and outcomes of seizures occurring after craniotomy for primary brain tumor resection The risk also rises with the number of preoperative seizures: patients with two or more had a meaningfully higher rate of early postoperative seizures than those with zero or one.3Scientific Reports. Early postoperative seizures (EPS) in patients undergoing brain tumour surgery
Tumor location matters a great deal. Tumors involving or pressing on the frontal, central, temporal, or insular regions of the brain are associated with significantly more early postoperative seizures compared to tumors in other areas.3Scientific Reports. Early postoperative seizures (EPS) in patients undergoing brain tumour surgery These regions sit close to the brain’s motor and sensory control areas, and they are inherently more excitable.
Tumor type and grade also play a role. Histology was an independent predictor of early postoperative seizures in at least one large series.3Scientific Reports. Early postoperative seizures (EPS) in patients undergoing brain tumour surgery Low-grade gliomas, somewhat counterintuitively, were more strongly linked to postoperative seizures and worse epilepsy outcomes at six and twelve months than high-grade gliomas in a tertiary hospital study from Vietnam.8Scientific Reports. Tumor-related epilepsy and post-surgical outcomes: tertiary hospital experience in Vietnam The likely explanation is that slow-growing tumors spend more time infiltrating and reorganizing nearby brain tissue, creating a larger zone of abnormal electrical activity.
An unexpected finding in some research is that smaller tumors (under about 4 centimeters) may actually carry a higher risk of postoperative seizures than larger ones.2PubMed Central. Incidence, risk factors and outcomes of seizures occurring after craniotomy for primary brain tumor resection This could be because smaller tumors in eloquent cortex receive more aggressive resection relative to their size, or because larger tumors may have already destroyed the surrounding tissue that would otherwise generate seizures.
Anti-Seizure Medication Before and After Surgery
Whether to give anti-seizure drugs to patients who have never had a seizure before their brain surgery is one of the more debated questions in neurosurgery. Across randomized trials and combined analyses, routine preventive use of these medications in seizure-free patients has not consistently reduced postoperative seizure rates, and older drugs in particular carry real risks of side effects and drug interactions.9PubMed. Postoperative Seizure Prophylaxis in Intracranial Tumors: Evaluating the Role of Anti-Seizure Medication in Seizure-Naïve Patients Some evidence points to a modest benefit within the first postoperative week, but that protection does not hold up over longer follow-up periods. Current guidelines do not support blanket preventive treatment for every patient; instead, a targeted approach based on individual risk factors is preferred.
When preventive medication is used, the choice of drug has shifted substantially. Phenytoin was the standard for decades because it was cheap and familiar, but it comes with a narrow effective dose range, requires blood-level monitoring, and can cause liver problems, skin reactions, and heart rhythm changes. Levetiracetam has largely replaced it at many hospitals because it does not need blood-level monitoring and has a cleaner side-effect profile.10PubMed Central. Postoperative seizure prophylaxis after craniotomy: a current evidence and ongoing controversy Head-to-head comparisons have favored levetiracetam: one prospective study found a seizure rate of about 1.4 percent with levetiracetam versus roughly 15 percent with phenytoin, and phenytoin had to be withdrawn in several patients due to liver dysfunction, skin eruptions, and heart rhythm problems.11PubMed. Levetiracetam versus phenytoin for seizure prophylaxis during and early after craniotomy for brain tumours: a phase II prospective, randomised study
Beyond seizure prevention, levetiracetam may offer secondary benefits. A preliminary study found that patients who received it before surgery showed faster recovery of consciousness and neurological function compared to a control group. Their awareness and functional recovery scores improved significantly earlier, starting around the third postoperative day versus the fourteenth day in the control group.12Interdisciplinary Neurosurgery. Prophylactic administration of levetiracetam accelerates consciousness level and neurological recovery after neurosurgical operation with supratentorial craniotomy – Preliminary report These findings are preliminary and come from a single study, but they have added to the momentum behind levetiracetam as the go-to option when prevention is warranted.
Seizures During Awake Brain Surgery
Awake craniotomy, where patients remain conscious during portions of surgery so the surgeon can test brain functions in real time, carries its own seizure risk. The brain is being directly stimulated with electrical probes to map critical areas for language and movement, and that stimulation can tip neurons into a seizure. In one study of glioma patients undergoing awake surgery with levetiracetam alone, intraoperative seizures occurred in about 36 percent of cases.13PubMed. Intraoperative seizure outcome of levetiracetam combined with perampanel therapy in patients with glioma undergoing awake brain surgery That is a strikingly high rate, which reflects the provocative nature of cortical stimulation mapping rather than a failure of treatment.
When seizures do occur during awake surgery, the first-line response is physical: flushing the exposed brain surface with ice-cold saline solution to cool the tissue and interrupt the electrical storm. If that does not work, the anesthesia team gives incremental doses of a sedative like midazolam, followed if necessary by a loading dose of an additional anti-seizure drug.14PubMed Central. Intraoperative Seizures During Awake Craniotomy for Brain Tumor Resection Adding a second anti-seizure drug (perampanel) to levetiracetam before surgery dropped the intraoperative seizure rate to about 7 percent and eliminated intractable seizures entirely in one study. Tumors involving motor-related brain regions and a history of preoperative seizures were the strongest predictors of an intraoperative seizure regardless of the drug regimen.13PubMed. Intraoperative seizure outcome of levetiracetam combined with perampanel therapy in patients with glioma undergoing awake brain surgery
The Hidden Problem of Non-Convulsive Seizures
Not all postoperative seizures look like what most people picture: shaking, loss of consciousness, and dramatic muscle contractions. A substantial fraction are non-convulsive, meaning the brain is in a sustained seizure state but the patient shows no visible signs or perhaps only subtle confusion. In one study using continuous brainwave monitoring after brain tumor surgery, non-convulsive seizure activity was detected in 5 percent of patients, and that silent seizure activity accounted for roughly three-quarters of total seizure time.15PubMed Central. Continuous EEG monitoring after brain tumor surgery In one patient, a non-convulsive seizure ran for 42 minutes before anyone realized it was happening.
Catching these events matters because delays in recognizing and treating non-convulsive seizures can worsen outcomes.16Journal of neurosurgery. Seizure incidence in the acute postneurosurgical period diagnosed using continuous electroencephalography A standard 30-minute brainwave recording might miss intermittent seizures entirely, while continuous monitoring greatly increases the chance of catching them. The challenge is resource allocation: continuous monitoring is labor-intensive and requires skilled technicians and neurologists to interpret the data around the clock. A prospective study looking specifically at neurosurgical patients with suspected non-convulsive seizures found seizure activity in only 4 percent of monitored patients, raising questions about how to select the right patients for this resource-heavy tool.17Clinical Neurophysiology Practice. The diagnostic value of continuous EEG for the detection of non-convulsive status epilepticus in neurosurgical patients – A prospective cohort study Hospitals are actively working on better ways to identify who should get continuous monitoring and who can safely be observed clinically.
How Anesthesia Itself Can Contribute
The drugs used to put patients to sleep and keep them under during brain surgery have their own complex relationship with seizures. Propofol, one of the most commonly used intravenous anesthetics, has a paradoxical profile: at low doses or during the transition in and out of anesthesia, it can actually promote seizure-like electrical activity in the brain and occasionally trigger visible seizures. At higher, sustained doses, it flips and becomes anticonvulsant. The explanation involves how rapidly the drug’s concentration changes in the brain during induction and emergence, combined with its effects on different receptor systems.18Austin J Anesthesia and Analgesia. Anesthesia-Related Perioperative Seizures: Pathophysiology, Predisposing Factors and Practical Recommendations
For patients and families, this means that a seizure occurring during the transition out of anesthesia is not necessarily a sign that the surgery went wrong or that the brain was damaged. It may be a pharmacological effect that resolves on its own. Anesthesiologists are well aware of this risk and often have anti-seizure medications ready during emergence. Still, any seizure in the postoperative period warrants evaluation to rule out surgical complications like bleeding or swelling.
Children Face a Different Profile
Pediatric brain surgery carries its own set of considerations. In a series of 165 children who underwent brain surgery, postoperative seizures occurred in about 9 percent. Focal seizures, which start in one area and may or may not spread, made up slightly more than half of the cases, with generalized seizures accounting for the rest. Early seizures (within the first week) were the most common pattern, occurring in nearly half of the children who seized, while immediate and late seizures each made up about a quarter.19PubMed Central. Postoperative Epileptic Seizures in Children
Of particular concern is the subset who go on to develop epilepsy. In the same series, about 3 percent of all children developed epilepsy, diagnosed at an average of roughly three and a half months after surgery. The types included focal seizures that evolved into full-body convulsions, primary generalized seizures, and absence seizures. Follow-up in these children ranged up to about ten years, underscoring the need for long-term monitoring even when the immediate postoperative period goes smoothly.19PubMed Central. Postoperative Epileptic Seizures in Children The developing brain responds differently to surgical injury than the adult brain, and families should expect that pediatric neurosurgeons will want to follow children closely for months to years after an operation.
Do Postoperative Seizures Mean Worse Overall Outcomes
A natural fear is that having a seizure after brain surgery signals that something has gone seriously wrong and the long-term outlook is bleak. The evidence on this point is somewhat reassuring, at least for tumor patients. In one study, post-craniotomy seizures were not associated with increased rates of complications or death.2PubMed Central. Incidence, risk factors and outcomes of seizures occurring after craniotomy for primary brain tumor resection That said, seizures are not benign events. Each seizure stresses the brain, and prolonged or repeated seizures can contribute to further injury. Early identification and prompt treatment remain important, even if the seizure itself does not change the surgical prognosis.
The longer-term question is whether postoperative seizures predict the development of chronic epilepsy. The answer depends heavily on context. An early seizure within the first day or two, especially one connected to metabolic shifts or medication effects, is less worrisome than a seizure that appears weeks later and suggests the brain has developed a lasting seizure focus. Patients who have late seizures are more likely to need ongoing anti-seizure medication and may face driving restrictions, employment limitations, and quality-of-life impacts that extend well beyond the surgical recovery period.
Emerging Tools for Predicting Seizure Risk
Researchers are working on tools to better predict which patients will develop seizures after brain surgery, with the goal of targeting preventive treatment to those who need it most. One approach involves brain imaging. A recent study tested whether structural brain imaging features, combined with clinical information, could predict seizure recurrence after a first unprovoked seizure. The best-performing model achieved modest accuracy, doing better than chance but still far from a reliable crystal ball.20PubMed. Structural brain imaging biomarkers for predicting seizure recurrence after a first unprovoked seizure Clinical factors alone performed even worse, barely separating future seizure patients from those who remained seizure-free.
Other teams are developing composite risk scores that weigh factors like tumor location, surgical approach, preoperative seizure history, and tumor histology to generate a personalized risk estimate before surgery even happens.1PubMed Central. A New Predictor Score for Postoperative Seizures in Brain Tumor Patients Without a Seizure History (BRAINNN Score) These scoring systems are still being validated, but they represent a shift toward more individualized decision-making about who gets anti-seizure medication and how aggressively they are monitored. For patients, this means the conversation with their surgeon before an operation is likely to become more specific and data-driven in the coming years, moving away from one-size-fits-all protocols toward plans tailored to the particular anatomy and biology of their case.