Monthly Case

A 57-year-old male patient had a first tonic clonic generalized epileptic seizure out of wakefulness without hints for focal onset. The patient was otherwise healthy. Diagnostic tests in another hospital including routine EEG and brain MRI were normal. During an outpatient visit, we attributed the spell to an isolated unprovoked seizure. Due to low seizure recurrence risk, we did not recommend an antiepileptic drug. Following the driving guidelines, the patient was not allowed to drive a car on his own for 6 months after the seizure.

Some days later, the general practitioner made thorough laboratory tests and detected markedly decreased serum magnesium levels (0.29 mmol/l; normal values for adults: 0.7-1.0 mmol/l). In patients without prior epilepsy, magnesium deficiency may be the acute cause of an epileptic seizure, this constellation is termed acute symptomatic seizure. Following the definition of the International League against Epilepsy, serum magnesium levels have to be lower than 0.3 mmol/l to cause and explain an acute symptomatic seizure.

Magnesium blocks the excitatory NMDA receptor in the brain. Is magnesium lacking, this receptor is disinhibited, neuronal excitation is increased. In the extreme, this may result in clinical manifestation of an epileptic seizure.

Thus in the current patient, the seizure was not isolated unprovoked but acute symptomatic. This change in allocation did not result in a different recommendation regarding not administering an antiepileptic drug but regarding driving restrictions. After an acute symptomatic seizure, the patient is not allowed to drive a car on his own for a total of 3 months, if the cause of the seizure is rectified. Even though in the current patient the cause for magnesium deficiency could not be identified, with daily substitution and frequent lab controls the patient now has regular serum concentrations.

This case indicates that there may be very rare acute causes for epileptic seizures. These may impact the risk for seizure recurrence and thus for driving restrictions.

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