A 9-year-old boy is brought to the emergency department by his babysitter after "passing out" at home. The babysitter says, "He was playing video games and I noticed his eyes started blinking a lot. He did not respond when I called his name and then he slumped to the floor. He has been very sleepy since waking up." The boy had been well, with no fevers, upper respiratory symptoms, or vomiting. He takes carbamazepine for epilepsy and has not had a seizure in years. He also takes loratadine as needed for allergic rhinitis. The patient has no known drug allergies and his immunizations are up to date. It has been a stressful time for him as his parents are going through a divorce and he has been splitting time between 2 homes. The boy also just returned from a week-long stay at his grandparents' house. Vital signs are normal. On physical examination, the patient is drowsy but able to answer questions and follow directions. Pupils are 4 mm bilaterally and equally reactive to light. Cardiopulmonary examination is normal. The abdomen is soft and nontender without hepatosplenomegaly. Muscle tone and strength are normal in all extremities. Plantar reflexes are downgoing. There are no skin rashes or lesions. Which of the following is the best next step in evaluation of this patient?

Question

A 9-year-old boy is brought to the emergency department by his babysitter after "passing out" at home.  The babysitter says, "He was playing video games and I noticed his eyes started blinking a lot.  He did not respond when I called his name and then he slumped to the floor.  He has been very sleepy since waking up."  The boy had been well, with no fevers, upper respiratory symptoms, or vomiting.  He takes carbamazepine for epilepsy and has not had a seizure in years.  He also takes loratadine as needed for allergic rhinitis.  The patient has no known drug allergies and his immunizations are up to date.  It has been a stressful time for him as his parents are going through a divorce and he has been splitting time between 2 homes.  The boy also just returned from a week-long stay at his grandparents' house.  Vital signs are normal.  On physical examination, the patient is drowsy but able to answer questions and follow directions.  Pupils are 4 mm bilaterally and equally reactive to light.  Cardiopulmonary examination is normal.  The abdomen is soft and nontender without hepatosplenomegaly.  Muscle tone and strength are normal in all extremities.  Plantar reflexes are downgoing.  There are no skin rashes or lesions.  Which of the following is the best next step in evaluation of this patient?

Quizplus · Accepted Answer

Explanation: This patient has had a breakthrough seizure, a seizure that occurred despite previously successful antiepileptic therapy. Subtherapeutic drug levels are a common cause of breakthrough seizures in children with known epilepsy. Common causes for subtherapeutic drug levels include altered drug metabolism (eg, phenytoin), increasing patient weight, and nonadherence to the therapeutic regimen. In this case, the most likely cause is medication nonadherence, which often occurs in patients with psychosocial stressors (eg, divorce, multiple third-party caregivers). Therefore, measuring a serum carbamazepine level would be the best next step in evaluation of this patient. If levels are subtherapeutic, adherence improves when providers discuss problem solving and sources of stress or fears and provide additional education regarding epilepsy. Risk factors for nonadherence include family communication issues, complex medical regimens, and depressed socioeconomic status (eg, inability to afford medications, unreliable transportation). If the serum carbamazepine levels are therapeutic, additional workup such as follow-up electroencephalography and serum electrolyte evaluation would be indicated. (Choice A) Carbamazepine can cause fulminant hepatic failure with resulting hyperammonemia, hepatic encephalopathy, and seizure. This patient's normal behavior prior to the seizure and lack of vomiting or asterixis make hepatic failure unlikely; therefore, serum ammonia level and liver function tests are not indicated. (Choice B) Inborn errors of metabolism often present with seizure but typically at a younger age (eg, infancy). When metabolic disorders present with seizures, the seizures typically are not controlled until the metabolic error is corrected. (Choice D) CT scan is indicated if the patient exhibits pre-seizure altered mental status or an abnormal neurologic examination. This patient, however, exhibits equal and reactive pupils, normal reflexes, and normal behavior prior to the seizure; therefore, an intracerebral process (eg, tumor, hematoma) is unlikely. (Choice E) An ECG would be appropriate evaluation for syncope but would yield little information toward a diagnosis of partial seizure with secondary generalization. This patient exhibits post-event somnolence, suggesting a seizure rather than a syncopal event. Educational objective: Nonadherence to medications is a major cause of breakthrough seizures in patients with epilepsy. Prompt measurement of serum antiepileptic drug concentrations is an important part of the initial workup for these patients. References: Behavioral predictors of medication adherence trajectories among youth with newly diagnosed epilepsy. (http://www.ncbi.nlm.nih.gov/pubmed/26209946) Patterns of nonadherence to antiepileptic drug therapy in children with newly diagnosed epilepsy. (http://www.ncbi.nlm.nih.gov/pubmed/21521848)

A 9-Year-Old Boy Is Brought to the Emergency Department by His