Spontaneous Resolution of Aberrant Cerebellar Tonsil Movement in a Patient with Improving Chiari I Malformation.

Chiari malformation Type 1 (CMI) is traditionally characterized as a descent of the cerebellar tonsils more than 5mm below the foramen magnum. In some patients with CMI, there is aberrant pulsatile movement of the tonsils downward during cardiac systole which can affect cerebrospinal fluid (CSF) flow at the foramen magnum. Here, we present an 18-year-old female patient with CMI who presented with worsening symptoms of her CMI. Magnetic resonance imaging (MRI) at this time indicated an increase in cerebellar tonsil movement and decreased CSF flow at the foramen magnum. At her follow-up appointment, she had complete resolution of the aberrant motion of her tonsils and CSF flow returned to baseline without surgical intervention. Her symptoms also improved during this time, and she is now able to be followed by her primary care physician. The increased pulsatile movement of cerebellar tonsils in patients with CMI has been linked to diminished CSF flow at the foramen magnum and symptom severity. Spontaneous resolution of CMI is rare and has only ever been documented as ascension of the cerebellar tonsils. This case describes restoration of normal tonsil movement and baseline CSF flow corresponding with a resolution of symptoms where a complete resolution in tonsillar ectopia was not present.