Objective: the clinical course of syringomyelia associated with craniocervical junction abnormalities is variable. About half of the unoperated patients have benign course. This is difficult to explain on the basis of the present pathogenetic theories. Therefore, to understand the mechanism of syrinx progression better, we studied the value of syrinx size, syrinx morphology, and the syrinx/spinal cord size ratio in predicting the rate of progression and the severity of myelopathy in these patients.
Methods: 103 adult patients with syringomyelia associated with Chiari 1 malformation and/or radiographic signs of underdeveloped posterior cranial fossa were clinically and MRI examined. Patients were subdivided according to the type of disease progression. Severity of neurological deficits, and MRI features (the extent of cerebellar tonsillar displacement, anteroposterior diameter of cavities, the spinal cord and cyst/cord ratio and the shape of cavities) were measured.
Results: a significant relationship was found between the mid-sagittal diameter of the syrinxes and the type of disease course; patients with short duration and rapid progression had the largest diameters of cavities, whereas patients with longer duration as well as with slow rate of progression had smaller diameters (chi(2)=28.90, P<0.05; chi(2)=29.89, P<0.01; r=-0.24, P<0.05). In addition, a correlation was found between the anteroposterior diameter of the spinal cord and cyst/cord ratio and the disease duration (r=0.52, P<0.05 and r=0.48, P<0.05, respectively).
Conclusions: the initial years for the development of symptomatic syringomyelia associated with CCJ malformations are characterized by relatively rapid clinical progression accompanied with distended cavities. In the later periods of unoperated syringomyelia, some patients show delay in the progress of syrinxes accompanied with collapse of cavities, probably either due to a spontaneous formation of drainage between the syrinx and the subarachnoidal space, or due to the restoration of abnormal CSF dynamics at the CCJ level.