An 8-year-old boy is brought to the physician by his mother for several episodes of unusual
“daydreaming” over the past three weeks in which he will suddenly stop all activity and stare into
space with a blank look. Sometimes it appears as though his eyelids flutter. These episodes
generally last less than ten seconds. His teacher has also reported observing similar episodes. One
year ago, he was treated for a tonic-clonic seizure. Which of the following best describes the most
appropriate pharmacologic therapy for this patient?
- A) Inhibition of thalamic T-type calcium channels
- B) Inhibition of sodium channels
- C) Inhibition of sodium channels + increase GABA
- E) Inhibition of GABA reuptake
0 voters
The answer is C.
This is a favorite USMLE “trick” question.
The “daydreaming” episodes are classic for absence (petit mal) seizures, which usually manifest as
a vacant stare lasting about 10 seconds. There is usually no confusion, headache, or drowsiness
afterward. Signs and symptoms of absence seizures include:1
• Sudden stop in motion without falling
• Lip smacking
• Eyelid flutters
• Chewing motions
• Finger rubbing
• Small movements of both hands
The optimal monotherapy for children and adolescents with absence seizures is ethosuximide2
,
which blocks thalamic T-type calcium channels.3
However, if absence and generalized tonic-clonic seizures coexist, valproic acid is
preferred.2, 4 Ethosuximide is considered to be less efficacious for tonic-clonic seizures.2
Valproic acid blocks sodium channels and increases GABA.5
Phenytoin, carbamazepine, and lamotrigine block neuronal voltage-gated Na+ channels.6
Tiagabine is a selective GABA reuptake inhibitor