A seizure represents a temporary disruption of normal brain activity, resulting from uncontrolled electrical discharges within the brain. This neurological event can manifest in various ways, from subtle changes in awareness to dramatic convulsions. The body responds to a seizure with a cascade of physiological adjustments, which can sometimes be detected through changes in blood test results. Understanding these laboratory alterations provides insight into the body’s immediate and delayed reactions to a seizure. These changes can offer supportive evidence for a seizure occurrence and help differentiate it from other medical events.
Immediate Biochemical Changes
Following a seizure, certain biochemical markers show rapid and transient elevations. Serum prolactin (PRL), a hormone released by the pituitary gland, frequently rises significantly within minutes after a generalized tonic-clonic seizure or a complex partial seizure. Prolactin levels typically peak around 10 to 30 minutes after the event and usually return to their baseline within 60 to 100 minutes. This elevation can be a useful diagnostic tool, particularly for distinguishing epileptic seizures from non-epileptic events, with robust increases seen in approximately 80% of generalized tonic-clonic seizures and 43-46% of complex partial seizures. An elevation to at least twice the baseline value or above the upper limit of normal is typically considered significant.
Lactic acid, or lactate, also increases in the blood immediately after a seizure. This occurs due to intense muscle activity and altered cellular metabolism during the seizure, which forces cells to shift to anaerobic respiration in the absence of sufficient oxygen. Lactate levels usually peak within 15 to 60 minutes following the seizure and typically normalize within one to two hours. This elevation indicates the metabolic stress the body experiences during a seizure.
Muscle and Metabolic Indicators
Beyond immediate markers, other laboratory values reflect the physical and metabolic strain placed on the body during a seizure, often with a slightly more prolonged elevation. Creatine kinase (CK), particularly the CK-MM type found predominantly in skeletal muscle, elevates due to muscle breakdown and exertion during tonic-clonic seizures. CK levels typically begin to rise within hours, peaking several hours to two days after the seizure, and can remain elevated for several days.
Blood glucose levels can also show a transient increase following a seizure. This elevation results from the body’s stress response, which involves the release of hormones like adrenaline and cortisol. This glucose rise is usually mild and temporary, reflecting the body’s mobilization of energy reserves during the physiological stress of the event. Transient changes in electrolytes such as sodium, potassium, calcium, and magnesium can sometimes occur. These shifts may be influenced by factors like dehydration, vomiting, or certain medications.
Inflammatory and Stress Responses
A seizure also triggers a generalized stress and inflammatory response within the body, which can be seen in changes to the white blood cell count. A temporary increase in the total white blood cell (WBC) count, particularly neutrophils, commonly occurs after a seizure. This phenomenon, known as reactive leukocytosis, is a physiological response to the stress of the seizure and does not typically indicate an infection. The WBC count usually resolves within 24 to 48 hours as the body recovers from the acute event.
Interpreting Lab Findings
Laboratory testing after a suspected seizure primarily serves to support a diagnosis, especially when the event was not witnessed or presented atypically. These tests also help in ruling out other medical conditions that might mimic seizure symptoms. The timing of sample collection is crucial for accurate interpretation of these results. For instance, prolactin levels should ideally be measured within 10 to 30 minutes of the event, while CK levels are more indicative when drawn within 24 to 48 hours.
It is important to understand that no single laboratory marker is definitive for diagnosing a seizure. While some markers, like prolactin, offer higher specificity for certain seizure types, their elevations can also occur due to other conditions or strenuous physical activity. For example, intense exercise can elevate both CK and lactate, and physiological stress can increase white blood cell count and glucose levels. Therefore, laboratory findings must always be considered alongside a comprehensive clinical history and other diagnostic tools, such as an electroencephalogram (EEG). It is also important to note that not all types of seizures, nor every individual, will show these characteristic laboratory elevations, particularly with focal seizures or absence seizures, and the prolactin response can diminish with closely spaced seizures.