Attention-Deficit Hyperactivity Disorder (ADHD)

01Pathophysiology

Hyperkinetic disorder arises from a neurodevelopmental imbalance in catecholamine signaling, primarily involving dopamine and norepinephrine, within the prefrontal cortex and its connections to the striatum and cerebellum. The prefrontal cortex is responsible for executive functions: sustained attention, impulse inhibition, working memory, and behavioral regulation. When dopaminergic tone in this circuit is insufficient, the child's brain cannot adequately filter irrelevant stimuli or suppress inappropriate motor responses.

This is why the child switches from one task to another. The uploaded PPDGJ III text describes this precisely: the child prematurely terminates tasks and leaves activities unfinished, not because of sensory or perceptual disturbance, but because attention is pulled toward novelty. Laboratory studies generally do not reveal abnormal sensory processing, reinforcing that this is a disorder of attentional regulation, not sensory input.

The hyperactivity component reflects a failure of the motor inhibition circuits. The basal ganglia, which gate voluntary movement, receive inadequate modulatory input. The result is excessive motor output that is contextually inappropriate. As stated in the PPDGJ III guidelines, the hallmark is restlessness "in situations demanding relative calm." A child running during recess is normal; a child who cannot remain seated during a structured classroom task, and whose activity level is excessive compared to same-age and same-IQ peers, meets the threshold.

The impulsivity dimension, described in the PPDGJ III as an associated (penyerta) feature, reflects the same prefrontal deficit. The child cannot inhibit a prepotent response: answering before questions are completed, cutting into conversations, acting recklessly without anticipating consequences. This connects directly to weak response inhibition, a core executive function deficit.

An important point from the PPDGJ III text that is highly testable: learning difficulties and motor clumsiness frequently co-occur but must be coded as separate diagnoses. They are not part of the hyperkinetic disorder diagnosis itself. This distinction matters because test questions may present a child with both hyperkinetic symptoms and a reading difficulty, and the student must recognize these as two separate conditions.

02Classification and Clinical Manifestation

By Domain

Critical PPDGJ III requirement: Both inattention and hyperactivity must be present and demonstrable in more than one setting (e.g., home, school, clinic). A child who is inattentive only at school but perfectly focused at home does not meet criteria. This "pervasiveness" rule is a frequent testing point.

03Diagnostic Workup

The diagnosis of hyperkinetic disorder under PPDGJ III is entirely clinical. There is no blood test, imaging study, or single psychometric instrument that confirms the diagnosis. This is a point where students frequently err: they select an EEG or brain MRI as the "confirmatory test," which is incorrect.

The workup begins with a comprehensive clinical interview with the parent or caregiver, focusing on developmental history, age of symptom onset (must be before age 7), symptom duration (must exceed 6 months), and the pervasiveness of symptoms across settings. A separate interview or questionnaire from the child's teacher is essential because the PPDGJ III mandates that symptoms are present in more than one environment.

Behavioral rating scales such as the Conners Parent/Teacher Rating Scale or the SNAP-IV are valuable adjuncts. They standardize the observation and allow comparison to normative data for the child's age and sex. However, they are screening instruments, not diagnostic tools on their own.

Direct observation of the child during the clinical encounter can be informative but is not sufficient alone. Some children with hyperkinetic disorder may transiently suppress symptoms in a novel one-on-one setting, leading to a false sense of normalcy.

The PPDGJ III text in your uploaded image makes an important point about the benchmark for diagnosis: inattention and hyperactivity must be excessive relative to children of the same age and IQ. A cognitively gifted child who is bored in a below-level classroom may appear inattentive but does not have a hyperkinetic disorder. Conversely, a child with intellectual disability may appear inattentive, but the inattention may be proportional to their cognitive level and therefore not meet criteria.

When to consider additional testing:

• Thyroid function tests if there are signs of hyper- or hypothyroidism

• Lead level if environmental exposure is suspected

• EEG only if clinical features suggest absence seizures (brief staring spells that are stereotyped and abrupt, unlike the variable distractibility of hyperkinetic disorder)

• Audiometry and vision screening to rule out sensory deficits mimicking inattention

04Management and Treatment

Step 1: Psychoeducation. Before any medication is discussed, the family must understand the nature of the condition. It is a neurodevelopmental disorder, not a result of poor parenting or willful misbehavior. This framing reduces stigma and improves treatment adherence.

Step 2: Behavioral interventions. For children under 6 years old, behavioral parent training is the recommended first-line treatment. Pharmacotherapy is generally reserved for cases that do not respond adequately. For school-age children (6 years and older), the evidence supports combined treatment (medication plus behavioral intervention) as superior to either alone.

Step 3: Pharmacotherapy with methylphenidate. This is the most tested pharmacological fact. Methylphenidate is a dopamine and norepinephrine reuptake inhibitor that increases catecholamine availability in the prefrontal cortex, directly addressing the pathophysiological deficit. Dosing begins at 5 mg once or twice daily and is titrated upward in 5-10 mg increments at weekly intervals until optimal symptom control is achieved with tolerable side effects. The typical effective dose range is 0.3 to 1 mg/kg/day.

Common side effects to know for the exam: decreased appetite, insomnia, headache, abdominal pain, and mild increases in heart rate and blood pressure. Growth suppression may occur with long-term use (hence the need for growth monitoring). Drug holidays during school vacations are sometimes used to mitigate growth effects and reassess the need for continued therapy.

Contraindications and cautions for methylphenidate:

• Known cardiovascular disease or structural heart abnormalities (screen with a focused cardiac history; routine ECG is debated but recommended if risk factors are present)

• Uncontrolled hypertension

• Concurrent use of MAO inhibitors

• Active psychosis or severe anxiety (stimulants may worsen these)

• History of substance abuse in the adolescent (consider atomoxetine or extended-release formulations with lower abuse potential)

Step 4: Second-line agents. Atomoxetine is a non-stimulant option with a slower onset of action (full effect may take 4-6 weeks). It is preferred when stimulants are poorly tolerated, when there is comorbid anxiety, or when substance abuse risk is a concern. Other options include alpha-2 agonists (clonidine, guanfacine), used either as monotherapy in milder cases or as adjuncts.

Step 5: Long-term management. Hyperkinetic disorder is a chronic condition. Treatment is ongoing, with periodic reassessment. There is no fixed "end date" for therapy. Medication should be continued as long as it remains beneficial, with annual reassessment of need.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The single most common way students get questions about hyperkinetic disorder wrong on the exam is by applying DSM criteria to a PPDGJ III question. PPDGJ III, which follows the ICD-10 framework, requires both inattention and hyperactivity to be present. There is no "predominantly inattentive type" in this system. A vignette describing a quiet, dreamy child who is inattentive but not hyperactive does not meet PPDGJ III criteria for hyperkinetic disorder, even though it would qualify as ADHD Predominantly Inattentive Type under DSM-5. If you see this pattern on the exam, do not select hyperkinetic disorder.

The second major trap involves comorbid conditions. The PPDGJ III text in the uploaded image explicitly states that learning difficulties and motor clumsiness are "very common" but "must be coded separately." A student who sees a vignette with a hyperactive, inattentive child who also has reading difficulty may be tempted to lump everything under one diagnosis. The correct approach is to identify two conditions: a hyperkinetic disorder and a separate learning disorder.

The third trap is the pervasiveness requirement. A child whose symptoms appear only in one setting (e.g., only at school, where the teacher is strict, but not at home) does not meet PPDGJ III criteria. The vignette must describe symptoms across at least two settings. When a vignette carefully states that the child behaves normally at home, that is a deliberate signal from the test writer that the diagnosis is not hyperkinetic disorder.

Finally, remember the age and duration thresholds: onset must be before age 7, and duration must exceed 6 months. A vignette describing a child whose behavioral problems started at age 9 following a family stressor is pointing you toward an adjustment disorder or anxiety, not hyperkinetic disorder. The test writer places these details in the stem intentionally; read them carefully.

The core competency being tested is the ability to apply a structured diagnostic framework (PPDGJ III) accurately, distinguish clinical mimics using discriminating details in the vignette, and recognize that hyperkinetic disorder is a clinical diagnosis that does not require neuroimaging or laboratory confirmation.