Chiari malformation type 1: are we doing less with more? Illustrative case

Abstract

Background: Classic treatment of Chiari malformation type 1 consists of foramen magnum decompression. Selected patients may require occipitocervical fixation, transoral odontoidectomy, tonsillectomy, and so forth. Treatment standardization does not yet exist, and some patients risk being overtreated.

Observations: A 20-year-old man with headache and Chiari malformation type 1 underwent extradural bone decompression. One year later, he was managed with the extradural section of his filum terminale. Eighteen months later, the patient underwent monitoring of intracranial pressure, occipitocervical stabilization, transoral odontoidectomy, minimally invasive subpial tonsillectomy, and occipital cranioplasty. His headache never changed, and he progressively developed hemiparesis and swallowing and respiratory disturbances. Two years later, a new magnetic resonance imaging scan showed extended syringomyelia with scarce peritonsillar subarachnoid space. The umpteenth operation consisted of the removal of a constricting epidural scar, arachnoid dissection, total tonsillectomy, creation of a wide subarachnoid space, and dural sac augmentation. The patient's initial postoperative course was smooth, and his headache improved. However, 8 days after surgery, the patient acutely presented with vegetative disturbances and died because of malignant brainstem edema of unknown origin.

Lessons: The story of this patient is not so uncommon. He underwent all the possible surgical treatments rather than a timely adequate osteodural decompression. Probably, he received less with more.

Keywords: CM1 = Chiari malformation type 1; CSF = cerebrospinal fluid; CT = computed tomography; Chiari malformation; FMD = foramen magnum decompression; ICP = intracranial pressure; MRI = magnetic resonance imaging; foramen magnum decompression; occipitocervical stabilization; syringomyelia; transoral odontoidectomy.

FIG. 1.

Left: MRI (sagittal view) performed 30 months after extradural bone decompression. A small syrinx was evident. There were scarce subarachnoid spaces. The cerebral ventricles were normal, and there was no evidence of pannus at the odontoid level. Right: CT scan (sagittal reconstruction) showing a normal clivoaxial angle (142°). The Grabb-Oakes and Harris measurements were also normal.

FIG. 2.

CT scans. Axial view (left) and coronal reconstruction (right) 2 years after craniocervical fixation. The screws (arrows) were embedded in abundant artificial bone substitute (asterisks), which was also used for cranioplasty. Any attempt at surgical modification of the head position was deemed impossible.

FIG. 3.

MRI scans (sagittal view). Left: Image obtained 2 years after craniocervical fixation, odontoid removal, and minimally invasive subpial tonsillectomy. The syringobulbia was grossly unchanged, but extended syringomyelia had developed. The posterior subarachnoid space was virtually absent, whereas a thin ventral film was visible. Right: Image obtained 3 days after tonsillectomy, arachnoid dissection, and dural augmentation. The syringobulbia had decreased, whereas the syringomyelia was unchanged. A wide subarachnoid space was freely communicating with the 4th ventricle.