CASE REPORT
Chiari Type I malformation and upper airway obstruction in adolescents

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Abstract

Chiari Type I malformation is characterized by cerebellar tonsil herniation through the foramen magnum. Manifestations may include new-onset upper airway obstruction. We describe two patients who had bilateral vocal cord paralysis and Chiari Type I malformation. These cases highlight the importance of suspecting a neurologic abnormality such as Chiari malformation in new-onset upper airway obstruction and/or bilateral vocal cord paralysis in adolescents in the absence of an obstructive lesion, though the development of cranial neuropathies or radiographic evidence may be delayed. Establishing a proper diagnosis is critical as Chiari I malformation can be treated with neurosurgical decompression, with possible improvement.

Introduction

The Chiari malformations, a group of congenital hindbrain and spinal cord abnormalities defined by caudal herniation of the posterior fossa contents through the foramen magnum, are summarized in Table 1 [1], [2], [3], [4], [5]. Type I is the mildest of the group in severity. It is characterized by herniation of the cerebellar tonsils through the foramen magnum.

Presentation of Chiari I malformation often occurs late in adolescence or during early adulthood [2], [3], [4], [5], [6]. Several studies show a slight female preponderance in symptomatic patients [5], [7], [8], [9]. The signs and symptoms of Chiari I malformation are variable and often subtle; the presentation is sometimes mistaken for that of multiple sclerosis The many possible otolaryngologic manifestations are listed in Table 2 [5], [10], [11], [12].

The most common presenting complaints are occipital headaches, cervical pain, weakness, and dizziness [5], [6]. Lower cranial nerve disturbances are also well-documented. The symptoms may be induced or exacerbated by a Valsalva maneuver. Hyperreflexia and nystagmus are the most common findings on physical examination [6]. Syringomyelia is present in 20–75% of Chiari I malformations [2].

While children with Chiari Type II malformations tend to have a significantly higher incidence of airway abnormalities compared to patients with Type I malformation, new-onset upper airway obstruction due to upper airway hypotonicity or vocal cord paralysis may also occur in Chiari Type I malformation in older patients [13]. Vocal cord paralysis has been found in approximately 7% of patients with Chiari Type I malformation, compared 12.6–16.7% of patients with Chiari II malformation [13], [14]. Most cases of vocal cord paralysis in Chiari I malformation involve abductor vocal fold paralysis, but a rare case of adductor vocal fold palsy in Chiari malformation has been described [15].

Section snippets

Patient 1

An 18 year-old male was referred for evaluation of new-onset snoring, gasping, and daytime somnolence. Examination revealed mildly enlarged tonsils, moderately enlarged adenoids, and a normal larynx. He developed severe stridor over the next 5 days, requiring intubation. Flexible laryngoscopy revealed bilateral vocal cord paralysis. MRI of the brain revealed herniation of the cerebellar tonsils consistent with Chiari Type I malformation. Neurosurgical decompression was performed and resolution

Discussion

A MRI demonstrating the cerebellar tonsil tips 5 mm below the foramen magnum is the standard for diagnosis of Chiari Type I malformation. However, 14–30% of patients who meet radiologic criteria on MRI for Chiari I malformation are asymptomatic [7], [9]. The asymptomatic patients are described as having tonsillar ectopia. Treatment is not recommended for asymptomatic patients.

The pathogenesis of the congenital Chiari malformation is not well understood. Though there are several hypotheses,

Conclusion

Neurological weakness due to Chiari Type I malformation should be considered in the differential diagnosis of new-onset upper airway obstruction in previously healthy children and adolescents in the absence of an obstructive lesion. Close clinical and radiologic follow-up is recommended as development of radiographic evidence or cranial neuropathies such as vocal cord paralysis may be delayed in Chiari I malformation.

Establishing a proper diagnosis is important as symptomatic Chiari

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Presented at the scientific poster session of the American Academy of Otolaryngology-Head and Neck Surgery Annual Meeting in San Diego, CA, on September 23–24, 2002.

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