An 8-year-old boy comes into the office with his mother due to her concern that he has not been paying attention in class or at home for the past 2 months. She states that he will often stare into space for a few seconds, even while being spoken to. Vital signs are normal, and the physical examination is unremarkable. An electroencephalogram (EEG) shows a 3-Hz spike and wave pattern. Ethosuxamide is prescribed.
Which of the following is the mechanism of action of this medication?
- A) Inhibition of calcium channels in the subthalamic nucleus
- B) Inhibition of GABA reuptake
- C) Inhibition of thalamic T-type calcium channels
- D) Inhibition of voltage gated potassium channels
- E) Inhibition of voltage gated sodium channels
C) Inhibition of thalamic T-type calcium channels
Absence seizures are episodes of unconsciousness in which the patient appears to stare into space for a few seconds. Typically, a child will appear to not be paying attention in school or at home. There is no postictal state. EEG shows 3-Hz spike and wave complexes. Ethosuximide prevents the 3-Hz spike and wave pattern by inhibiting T-type calcium channels in the thalamus. This reduces thalamic neuron burst firing, which prevents seizures from occurring.
Key Learning Point
Absence seizures are treated with ethosuximide. Ethosuximide inhibits T-type calcium channels in the thalamus.