Purpose or Case Report: Chiari Type I deformity (C1) is associated with bony deformity of the skull base and herniation of cerebellar tonsils. MRI is used for diagnosis and surgery is advised for symptomatic children. We present a case series using MR imaging including CSF flow, in a variety of children with C1 to demonstrate a variety of outcomes both surgical and non-surgical: spontaneous resolution, spontaneous worsening, post-surgical improvement.

Case 1: A 6-year-old (y) girl referred for imaging with short stature and growth hormone deficiency demonstrated incidental findings of C1 without syringomyelia. No surgery (Sx) was performed, and follow-up (F/U) MRI at age 7 y demonstrated spontaneous resolution of the tonsillar ectopia and expansion of the CSF spaces at craniocervical junction (CCJ).

Case 2: A 7 y boy with headaches and staring spells underwent an MRI demonstrating 6 mm protrusion of pointed cerebellar tonsils and CSF space reduction at CCJ. No Sx was performed, and F/U imaging at age 9 y demonstrated spontaneous improvement in cerebellar tonsillar position and increased bidirectional CSF flow at CCJ.

Case 3: A 2-week-old girl underwent brain MRI demonstrating an ectopic neurohypophysis, under opercularization suggesting brain immaturity and a normal CCJ. F/U MRI at 6 y of age showed interval spontaneous development of C1 with decreased CSF spaces at CCJ.

Case 4: A 17-month-old boy underwent brain MRI for unsteady gait and poor vestibular response, which showed C1 and narrow CSF spaces at the foramen magnum and with reduced CSF flow. At age 3 y, after posterior fossa decompression, F/U MRI showed post-surgical improvement of the position of the cerebellar tonsils and increased CSF space at CCJ.

Case 5: A 8 y girl with headaches and intermittent dizziness underwent MRI demonstrating 15 mm protrusion of the pointed cerebellar tonsils and marked decrease in the CSF at CCJ. After suboccipital craniotomy, MRI at age 8 y demonstrated a post-surgically improved CSF space and improved bidirectional CSF flow, at CCJ.
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Conclusions: It is important to be aware of a variety of different outcomes with Chiari Type I deformity, including spontaneous resolution, spontaneous worsening, improvement with surgery and even deterioration after surgery. More research is required to determine objective criteria for predicting outcome which include both anatomic measures and physiologic measures of CSF flow, so that better surgical decisions can be made and for evaluating patients who have undergone surgery.