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Difficulty: Very hardPediatric Neurologic Disorders

An 18-month-old toddler is transferred to a tertiary care center for progressive unsteadiness, refusal to walk, and unusual eye movements that began two weeks ago. The patient had previously achieved independent ambulation at 13 months. Her parents note she has become exceptionally cranky and exhibits sudden jerky body movements. They also mention they are worried because she speaks about 15 individual words but has not yet started combining them into two-word phrases. She is afebrile, and her vital signs are age-appropriate. Neurologic evaluation reveals chaotic, multi-directional, rapid conjugate ocular movements occurring without a distinct slow phase. She also demonstrates brief, involuntary, shock-like muscle spasms in her proximal limbs and trunk. When seated, she has marked truncal titubation. She was started on intravenous vancomycin and ceftriaxone two days ago; however, blood and cerebrospinal fluid cultures drawn at that time remain sterile, and she has no signs of infection. The medical team plans to initiate high-dose intravenous corticosteroids and rituximab later today.

Which of the following diagnostic or management steps are indicated for this patient? (Select exactly 2 options)

  1. Assessment of urinary homovanillic acid and vanillylmandelic acid levelsAnswer
  2. Cross-sectional imaging of the thorax, abdomen, and pelvisAnswer
  3. C
    Speech therapy referral for developmental language delay
  4. D
    Continuation of empiric broad-spectrum antimicrobial therapy
  5. E
    Provision of her scheduled measles, mumps, and rubella vaccination today

Answer

The correct steps are the assessment of urinary homovanillic acid and vanillylmandelic acid levels, and cross-sectional imaging of the thorax, abdomen, and pelvis.
The correct steps address the required diagnostic workup for a toddler presenting with opsoclonus-myoclonus-ataxia syndrome (OMAS), commonly referred to as 'dancing eyes, dancing feet' syndrome. The clinical presentation is defined by rapid, conjugate, multidirectional eye movements without a slow phase, accompanied by diffuse myoclonus and truncal ataxia. In this age group, up to 50% of OMAS cases represent a paraneoplastic syndrome secondary to an occult neuroblastoma. Therefore, it is critical to aggressively screen for this malignancy. The evaluation includes testing urine for elevated catecholamine metabolites (homovanillic acid and vanillylmandelic acid) and performing cross-sectional imaging (such as magnetic resonance imaging or computed tomography) of the thorax, abdomen, and pelvis to locate a primary tumor along the sympathetic chain or in the adrenal glands.

Step-by-Step Solution

1
Identify the patient's clinical syndrome based on the physical examination findings.
The combination of chaotic, multidirectional eye movements (opsoclonus), sudden muscle jerks (myoclonus), and severe unsteadiness (ataxia) establishes the diagnosis of opsoclonus-myoclonus-ataxia syndrome (OMAS).
Recognizing this classic triad is essential to guide the subsequent etiological workup.
2
Determine the most common underlying etiology for this syndrome in a pediatric patient.
In toddlers, OMAS is most frequently a paraneoplastic manifestation of an occult neuroblastoma.
Paraneoplastic immune dysregulation triggered by the tumor causes the central nervous system findings.
3
Select the appropriate diagnostic tests to identify the underlying tumor.
The workup must include measurement of urinary catecholamine metabolites (homovanillic acid and vanillylmandelic acid) and comprehensive cross-sectional imaging (chest, abdomen, and pelvis).
Neuroblastomas typically arise from the sympathetic ganglion chain or adrenal medulla and secrete catecholamines, making these tests highly sensitive for detection.
4
Evaluate the distractors based on pediatric milestones, infectious disease principles, and immunization guidelines.
A 15-word vocabulary is normal at 18 months, ruling out a language delay. Negative cultures at 48 hours in an afebrile patient indicate antibiotics should be stopped. Planned immunosuppression contraindicates live vaccines.
Integrating knowledge from multiple pediatric domains prevents inappropriate management steps.

Key Concept

Opsoclonus-myoclonus-ataxia syndrome in toddlers is a paraneoplastic neurologic disorder that mandates an immediate diagnostic evaluation for an underlying neuroblastoma.
Estimated Time:1m 30s
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Topics

Pediatric Neurologic Disorders

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