Abstract
Object. Alteration of cerebrospinal fluid (CSF) flow has been proposed as an important mechanism leading to the development of syringomyelia. We hypothesize that a "presyrinx" condition due to potentially reversible alteration in normal CSF flow exists and that its appearance may be due to variations in the competence of the central canal of the spinal cord.
Methods. Five patients with clinical evidence of myelopathy, no history of spinal cord trauma, enlargement of the cervical spinal cord with T1 and T2 prolongation but no cavitation, evidence for altered or obstructed CSF flow, and no evidence of intramedullary tumor or a spinal vascular event underwent MR imaging before and after intervention that alleviated obstruction to CSF flow.
Results. Preoperatively, all patients demonstrated enlarged spinal cords and parenchymal T1 and T2 prolongation without cavitation. Results of magnetic resonance (MR) imaging examinations following intervention in all patients showed resolution of cord enlargement and normalization or improvement of cord signal abnormalities. In one patient with severe arachnoid adhesions who initially improved following decompression, late evolution into syringomyelia occurred in association with continued CSF obstruction.
Conclusion. Nontraumatic obstruction of the CSF pathways in the spine may result in spinal cord parenchymal T2 prolongation that is reversible following restoration of patency of CSF pathways. We refer to this MR appearance as the "presyrinx" state and stress the importance of timely intervention to limit progression to syringomyelia.
Introduction
Syringomyelia occurs in a number of clinical settings, most commonly following trauma or in association with a Chiari malformation. Other causes include infectious or inflammatory arachnoiditis, tumors of the spine and spinal cord, posterior fossa tumors, and cervical spondylosis. Syringes typically appear as well-defined discrete cavities containing fluid that is iso-intense to CSF on all sequences. The pathophysiology of syringomyelia is controversial, but experimental models and clinical studies have implicated alterations in CSF flow as a significant factor in the development and progression of certain types of syringomyelia. The hypothesis that CSF normally flows along perivascular spaces within the parenchyma of the spinal cord to the central canal is supported by experimental studies. Variations in patency of the central canal of the spinal cord have been associated with the development of different types of syringomyelia and likely play a role in determining the location of a syrinx remote from a focus of CSF obstruction as is commonly seen in the Chiari I malformation. The reversibility of syringomyelia following restoration of CSF pathways has been well documented in patients undergoing posterior fossa decompression for Chiari malformation, removal of extradural masses, and lysis of adhesions.
We identified five myelopathic patients with no history of spine trauma who had underlying conditions associated with alterations of CSF flow. These patients had enlargement and T2 prolongation of the spinal cord, without frank cavitation, on MR imaging studies which improved or reversed following restoration of CSF flow pathways. We hypothesized on the basis of historical, imaging, and operative findings that obstruction to normal CSF flow pathways resulted in the cord enlargement and MR signal abnormalities that reversed following restoration of normal CSF pathways. We also hypothesized that variation in patency of the central canal of the spinal cord plays a role in the genesis of this "presyrinx" state.