Authors: Han Soo Chang Tsukasa Tsuchiya Naoaki Fujisawa Soichi Oya Toru Matsui
Publish Date: 2011/11/04
Volume: 154, Issue: 1, Pages: 141-145
Abstract
Despite a number of various hypotheses in the literature the pathophysiology of syringomyelia is still not well understood In this article we report two cases of cervical syringomyelia not associated with Chiari I malformation Both cases had a septumlike structure in the subarachnoid space on the dorsal side of the cord at the craniovertebral junction Cardiacgated phasecontrast cinemode magnetic resonance imaging MRI demonstrated decreased cerebrospinal fluid CSF flow on the dorsal side of the spinal cord Surgical excision of this septum restoring the CSF flow resulted in a prompt reduction of the syrinx size in both cases Findings in these cases contradict the currently prevailing hypothesis of syrinx formation that postulate that the pistonlike movement of the cerebellar tonsils enhance the pulsatile CSF flow in the spinal subarachnoid space driving the CSF into the syrinx through the perivascular space of Virchow and Robin The authors propose that a mechanism based on the decreased pulsatile CSF flow in the spinal subarachnoid space will be more suitable as a hypothesis in studying the pathophyisiology of syringomyelia These cases also provide an important lesson in managing the patients with syringomyelia not associated with Chiari I malformationThe authors present two cases of syringomyelia not associated with Chiari I malformation At surgery a septum was found in the subarachnoid space attached to the dorsal surface of the spinal cord Excision of the septum led to clinical improvement and reduction in the syrinx in both casesThe cases are noteworthy in that they serve as a reminder of the potential pitfalls in ascribing a diagnosis of “idiopathic syringomyelia” too readiliy A syrinx shunt with its unpredictable effect and durability might have been considered in each of these cases Where there is perhaps greater contention in this paper is in the pathophysiological explanation The authors suggest that these cases are incompatible with the current theories of syrinx formation CSF ingress along the perivascualar spaces and suggest a mechanism more reminiscent of the Gardner hypothesis based on a pressure gradient in the opposite direction from the central canal outward The findings of reduced flow distal to the septum demonstrated on cine MRI were used in support of this argument however it seems that there is a potential pitfall here in assuming that reduced flow may equate with reduced pressureThis entity of syrinx formation due to “occult” CSF obstruction at the craniovertebral junction has been described by Chern et al 1 in the paediatric population In their experience scar tissue or a tissue veil similar to the septum described here is a frequent finding in these “Chiari malformation type 0” casesWhilst the precise mechanism of syrinx formation in these cases may remain open to debate it seems that some functional obstruction to CSF circulation at the cranioverteral junction is the likely initiating event and this needs to be seriously considered lest one ends up treating the effect rather than the cause
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