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Difficulty: MediumPediatric Neurologic Disorders

A 14-year-old boy is evaluated in the pediatric neurology clinic due to a 1-year history of progressive difficulty walking. He reports feeling unsteady and frequently trips over his own feet, especially in the dark. His parents note that his handwriting has become increasingly messy over the past few months. His early motor and language milestones were achieved at the appropriate ages. Vital signs are within normal limits. Neurological examination reveals a wide-based gait. When asked to stand with his feet together and eyes closed, he sways significantly and requires assistance to maintain his balance. Muscle strength is 5/5 in all extremities, but deep tendon reflexes are absent at the knees and ankles. Sensation to vibration and joint position is markedly diminished in the toes. Musculoskeletal examination is notable for bilateral high plantar arches and a lateral curvature of the thoracic spine. Which of the following is the most important next step in evaluation to screen for the most common cause of mortality in this condition?

  1. A
    Hemoglobin A1c measurement
  2. EchocardiographyAnswer
  3. C
    Pulmonary function testing
  4. D
    Standardized developmental assessment
  5. E
    Noncontrast computed tomography of the head

Answer

Echocardiography
The correct answer is echocardiography. This patient's clinical presentation of progressive ataxia, absent lower extremity reflexes, loss of proprioception, a positive Romberg sign, pes cavus, and kyphoscoliosis is classic for Friedreich ataxia. Friedreich ataxia is an autosomal recessive neurodegenerative disorder caused by a GAA trinucleotide repeat expansion in the frataxin gene. The most common cause of mortality in these patients is cardiac dysfunction, specifically hypertrophic cardiomyopathy. Therefore, echocardiography is the most important screening test to evaluate for concentric left ventricular hypertrophy and cardiac contractility, allowing for early cardiologic intervention.

Step-by-Step Solution

1
Analyze the patient's neurological symptoms and physical examination findings.
The patient exhibits progressive ataxia, loss of proprioception and vibration sense (posterior column involvement), absent lower extremity reflexes (peripheral neuropathy), pes cavus, and kyphoscoliosis.
Identifying the classic constellation of signs is required to establish the underlying diagnosis.
2
Synthesize the findings to determine the most likely diagnosis.
The combination of these specific neurological deficits and musculoskeletal deformities in an adolescent is highly characteristic of Friedreich ataxia.
Friedreich ataxia is an autosomal recessive trinucleotide repeat disorder that classically presents in early adolescence with this exact phenotype.
3
Identify the most significant life-threatening complication associated with this diagnosis.
The most common cause of death in Friedreich ataxia is cardiac dysfunction, typically hypertrophic cardiomyopathy.
Understanding the natural history and mortality risks of the disease dictates the necessary screening and management steps.
4
Select the appropriate screening test to evaluate for this specific complication.
Echocardiography is the indicated test to screen for hypertrophic cardiomyopathy.
Echocardiography allows for direct visualization of ventricular wall thickness and cardiac function, preventing sudden cardiac death or severe heart failure complications.

Key Concept

Identification of Friedreich ataxia and its association with hypertrophic cardiomyopathy as the leading cause of mortality.
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Topics

Pediatric Neurologic Disorders

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