From the Guidelines
During a seizure, it is crucial to order calcium, phosphate, and magnesium levels because abnormalities in these electrolytes can either cause seizures or occur as a result of seizure activity, and correcting these imbalances is essential for proper seizure management and prevention of recurrence. Low calcium (hypocalcemia) is a well-known trigger for seizures, as calcium plays a crucial role in neuronal excitability and muscle contraction, as seen in patients with 22q11.2 deletion syndrome where hypocalcemia can trigger seizures at any age 1. Similarly, low magnesium (hypomagnesemia) can lower the seizure threshold by increasing neuronal excitability through its effect on NMDA receptors and calcium channels. Phosphate levels are often checked alongside calcium since they have an inverse relationship in the body, and abnormal phosphate levels can indirectly affect neurological function.
Some studies suggest that routine laboratory testing, including serum calcium, magnesium, or phosphate levels, may not be necessary in otherwise healthy patients with new-onset seizures 1. However, in certain cases, such as patients with underlying medical disorders or those taking diuretics, these tests may be indicated. For example, a study by Turnbull et al found that 11 out of 136 patients with new-onset seizures had correctable laboratory abnormalities, including hypocalcemia and hypomagnesemia 1.
Identifying and correcting electrolyte abnormalities is essential for proper seizure management, as treating the underlying electrolyte disorder may be more effective than simply administering anti-seizure medications. Additionally, certain anti-seizure medications can affect these electrolyte levels, and prolonged seizures themselves can cause electrolyte disturbances through increased muscle activity and metabolic demands. Therefore, ordering calcium, phosphate, and magnesium levels is a critical step in the evaluation and management of patients with seizures, particularly in those with underlying medical conditions or those who are at risk of electrolyte imbalances.
From the FDA Drug Label
Magnesium is an important cofactor for enzymatic reactions and plays an important role in neurochemical transmission and muscular excitability. Predominant deficiency effects are neurological, e.g., muscle irritability, clonic twitching and tremors. Hypocalcemia and hypokalemia often follow low serum levels of magnesium. Magnesium prevents or controls convulsions by blocking neuromuscular transmission and decreasing the amount of acetylcholine liberated at the end-plate by the motor nerve impulse.
The reason to order calcium, phosphate, and magnesium in the context of seizures is that magnesium plays a crucial role in neurochemical transmission and muscular excitability. Hypocalcemia often follows low serum levels of magnesium, and magnesium deficiency can cause neurological effects such as muscle irritability, clonic twitching, and tremors.
- Magnesium helps prevent or control convulsions by blocking neuromuscular transmission.
- Calcium and phosphate levels are also important to monitor, as hypocalcemia can occur with magnesium deficiency.
- Monitoring these electrolytes can help identify and manage potential deficiencies or imbalances that may contribute to seizure activity 2.
From the Research
Electrolyte Imbalance and Seizures
- Electrolyte imbalance, particularly hypomagnesaemia and hypocalcaemia, has been associated with seizures in adults and children 3, 4.
- Studies have shown that serum magnesium and calcium levels are lower in patients with epilepsy compared to controls 3, 4.
- Hypophosphatemia has also been linked to convulsive seizures, with one study finding that it was associated with generalized tonic-clonic seizures 5.
Role of Calcium, Phosphate, and Magnesium
- Calcium and magnesium play crucial roles in neurotransmitter release and muscle contraction, and their imbalance can lead to seizures 6.
- Phosphate levels have also been found to be affected in patients with epilepsy, with hypophosphatemia being a potential marker for diagnosing convulsive seizures 5.
- Vitamin D supplementation has been shown to affect calcium metabolism in patients with epilepsy, but its impact on seizure control is still unclear 7.
Clinical Implications
- Ordering calcium, phosphate, and magnesium levels can help identify electrolyte imbalances that may be contributing to seizures 3, 4, 5.
- Correcting these imbalances may help in managing seizures and improving patient outcomes 3, 4, 5.
- Further studies are needed to fully understand the relationship between electrolyte levels and seizures, as well as the effects of vitamin D supplementation on seizure control 7.