What is the best course of action for a 16-year-old patient with Attention Deficit Hyperactivity Disorder (ADHD) on methylphenidate (Ritalin) who has been experiencing a tremor of the right hand for 5 months, with a family history of tremors and Parkinson's disease, and recently treated for neuroborreliosis (Lyme disease)?

Approach to Right Hand Tremor in an Adolescent on Methylphenidate with Recent Neuroborreliosis

Discontinue methylphenidate immediately and observe for tremor resolution over 2-4 weeks, as stimulant-induced tremor is the most likely diagnosis in this clinical context. 1

Initial Management: Address Medication-Induced Tremor

• Methylphenidate commonly causes tremor as a dose-dependent adverse effect through its dopaminergic and noradrenergic mechanisms, and this should be the primary consideration in any ADHD patient on stimulants presenting with new-onset tremor 1

• Stop the methylphenidate for a trial period of 2-4 weeks to determine if the tremor resolves, which would confirm medication-induced etiology 1

• If ADHD symptoms become unmanageable during this washout period, consider switching to a non-stimulant alternative such as atomoxetine or guanfacine rather than restarting methylphenidate 1

Rule Out Post-Infectious Sequelae

• Neuroborreliosis can cause persistent neurologic symptoms including tremor, though this is uncommon after appropriate treatment 1

• The patient was treated for neuroborreliosis 2 months ago, but the tremor predates this treatment by 3 months, making post-Lyme tremor less likely as the primary etiology 1

• If tremor persists after methylphenidate discontinuation, consider repeat neurologic evaluation to assess for incomplete resolution of neuroborreliosis, though most patients show improvement within weeks to months after appropriate antibiotic therapy 1

• Persistent neurologic symptoms after standard Lyme treatment typically manifest as subtle distal paresthesias or memory impairment rather than isolated tremor 1

Evaluate for Essential Tremor Given Family History

• The strong family history (great-grandmother and grandfather with tremor) raises suspicion for essential tremor, which can manifest in adolescence 2, 3

• Essential tremor typically presents as bilateral postural and kinetic tremor, though it can begin unilaterally 2, 3, 4

• If tremor persists after medication discontinuation, perform detailed tremor characterization: assess whether it occurs at rest, with posture, or with action; evaluate for head or voice involvement; and test for improvement with alcohol (classic feature of essential tremor) 2, 3, 4

Consider Functional/Conversion Disorder

• Functional tremor should be considered in adolescents, particularly if the tremor shows variable frequency, amplitude, or direction 2, 5

• Key diagnostic features include: tremor that worsens with attention and improves with distraction; entrainability (tremor frequency changes when the patient performs rhythmic movements with the unaffected hand); and sudden onset in the context of stress or illness 2, 5

• The recent treatment for neuroborreliosis could serve as a precipitating stressor for functional neurologic symptoms 5

Parkinson's Disease: Unlikely but Consider Given Family History

• Juvenile-onset Parkinson's disease is extremely rare but should be considered given the family history 6, 7

• Parkinsonian tremor is typically a rest tremor (4-6 Hz, "pill-rolling"), not an action tremor, and is usually accompanied by rigidity and bradykinesia 6, 7, 8

• Beta-blockers like propranolol are NOT indicated for parkinsonian tremor and should only be used for essential tremor or enhanced physiologic tremor 2, 6

Diagnostic Algorithm

1. Immediately discontinue methylphenidate and observe for 2-4 weeks 1

2. If tremor resolves: Diagnosis is medication-induced tremor; consider non-stimulant ADHD alternatives if needed 1

3. If tremor persists: Perform detailed neurologic examination focusing on:

   • Tremor characteristics (rest vs. action, frequency, amplitude) 2, 3, 4
   • Signs of parkinsonism (rigidity, bradykinesia, postural instability) 6, 7, 8
   • Features suggesting functional tremor (variability, entrainability) 2, 5
   • Other neurologic signs suggesting incomplete Lyme treatment 1

4. If essential tremor is confirmed (bilateral action tremor, positive family history, no other neurologic signs): Consider propranolol 80-240 mg/day or primidone as first-line treatment 2

5. If functional tremor is suspected: Provide empathetic explanation of diagnosis and refer for physical therapy with rhythm modification techniques and cognitive behavioral therapy 5

Critical Pitfalls to Avoid

• Do not start tremor-specific medications (propranolol, primidone) before discontinuing methylphenidate, as this treats the symptom without addressing the likely cause 1, 2

• Do not assume the tremor is related to neuroborreliosis simply because of temporal proximity; the tremor preceded treatment by 3 months 1

• Do not use propranolol if parkinsonian features are present, as beta-blockers are ineffective for parkinsonian tremor and indicated only for essential tremor 2, 6

• Avoid dismissing functional tremor as "psychogenic" or "not real"; these symptoms are involuntary and require specific therapeutic approaches 5