Case 2: A 6-Year-Old Boy Who "Can't Sit Still"
Colten is 6-year-old boy who is referred to a neurologist by his pediatrician for further evaluation and treatment of possible attention-deficit/hyperactivity disorder (ADHD).

Colten was diagnosed with ADHD by his pediatrician, who prescribed the stimulant, methylphenidate; this improved the boy's daytime alertness and concentration. However, Colten also became more "jittery," anxious, and irritable, and methylphenidate was discontinued. At this time, Colten was referred to a neurologist.

Colten arrives at his appointment with his mother and both provide the history. Colten's mom states that her son has always been a restless child. As far back as she can remember, he has been unable to sit still for more than a few minutes. Sometimes Colten walks away in the middle of a house chore, and worse, he sometimes walks away in the middle of a conversation. This has been a particular problem at school, where his teachers have also noted his restlessness and inability to stay focused on a task for an extended period of time. This has resulted in Colten learning more slowly than other students, and he is falling behind in his class. Teachers at his school are now debating whether Colten should repeat the first grade.

Colten's mom adds that he seems anxious and is irritable toward her and his brother. He does not sleep well at night and often thrashes in bed. She often has walked into his room in the morning to find his pillows and sheets disheveled.

Colten himself says very little. He says that he tries the best that he can, but he is unable to explain why he is restless and unable to pay attention. He awakens tired and remains so throughout the day. He states that his legs ache after playing at recess. He becomes sad when he is reminded that he may not be able to move to the next grade along with his friends.

Allergies: No known drug allergies.
Past medical history: None.
Past surgical history: None.
Current medications: None.
Review of systems: "Growing pains."
Social history: Colten has an older brother, who is healthy. They live with their parents in a 2-story, single-family home. There is no tobacco, alcohol, or illicit drug use in the family.
Family history: Colten's mother has been diagnosed with restless legs syndrome (RLS).
Physical examination: Physical exam, including a detailed neurologic assessment, is normal.
Laboratory tests: Complete blood cell count and chemistry panels (including creatinine level, folate level, and iron studies) are normal.

Colten is a 6-year-old boy with a history of hyperactivity, inattention, nonrestorative sleep, and anxiety.

The differential diagnosis includes ADHD, epilepsy, learning disorder, RLS, periodic limb movements in sleep, and sleep-disordered breathing.

An electroencephalogram does not detect any epileptiform abnormalities. Neuropsychological testing does not reveal any evidence of developmental delay or learning disorders.

A polysomnogram demonstrates hundreds of periodic limb movements, many of which are associated with arousals. No sleep-disordered breathing is identified.

Laboratory tests reveal normal iron and ferritin levels.

The neurologist diagnoses RLS and periodic limb movements in sleep. The diagnosis of RLS is based on clinical symptoms and can be difficult to make in a child who is unable to provide a detailed history. A positive family history coupled with complaints of growing pains, hyperactivity, anxiety, mood changes, and achiness after exercise raise the suspicion for the diagnosis. Exercise is known to exacerbate the symptoms of RLS.

The polysomnogram demonstrated the presence of hundreds of periodic limb movements, many of which were associated with arousals. This can explain the restless and nonrestorative sleep that Colten is experiencing, as well as his daytime fatigue.

The neurologist prescribes a low dose of a dopamine agonist to treat Colten's RLS and periodic limb movement disorder. Almost immediately, Colten's restlessness resolves and his ability to pay attention significantly improves. According to his mother, Colten is in brighter spirits, and his performance in school has improved such that he is catching up to his classmates.

Inattention and hyperactivity among general pediatric patients can be associated with symptoms of periodic limb movements and RLS. Some children diagnosed with growing pains meet the diagnostic criteria for RLS. A family history of RLS is common in these children. Periodic limb movements in sleep may directly lead to symptoms of ADHD through the mechanism of sleep disruption. Thus, when a child presents with symptoms of hyperactivity, inattention, irritability, and growing pains, the differential diagnosis and workup should include RLS in addition to ADHD.

Supported by an independent educational grant from GlaxoSmithKline.