Anatomical Basis of Syringomyelia Occurring with Hindbrain Lesions

Abstract

Hindbrain lesions that distort or compress the cervicomedullary junction are commonly associated with syringomyelia. As a basis for discussing pathogenetic mechanisms, the upper end of the central canal of the spinal cord was examined histologically in six aborted fetuses and 14 adults dying of natural causes; the results were correlated with magnetic resonance images in 40 normal subjects. The central canal of the medulla, which extends from the cervicomedullary junction to the fourth ventricle, was found to migrate dorsally, elongate in dorsoventral diameter, and dilate beneath the tip of the obex to form a large, everted aperture. This opening communicates directly with the subarachnoid space through the foramen of Magendie and is indirectly continuous with the main body of the fourth ventricle. In adults, the aperture of the central canal is located approximately 1.0 cm below the tela choroidea inferior and 3.5 cm below the midpoint of the fourth ventricle. Analysis of magnetic resonance imaging scans in 45 patients with syringomyelia and simple hindbrain lesions revealed two patterns of cavity formation: 1) lesions that obstructed the upper end of the central canal or its continuity with the subarachnoid space produced a noncommunicating type of syringomyelia; and 2) lesions that obstructed the basilar cisterns or the foraminal outlets of the fourth ventricle produced a communicating type of syringomyelia (hydromyelia) in association with hydrocephalus. Evidence is presented that syrinxes occurring with hindbrain lesions are not caused by a caudal flow of cerebrospinal fluid from the fourth ventricle into the central canal of the spinal cord.

A Feline Case of Isolated Fourth Ventricle with Syringomyelia Suspected to be Related with Feline Infectious Peritonitis

“…Furthermore, these were cases of deformation or hydrocephalus with blockage of the outlet of the fourth ventricle. It has been reported that syringomyelia following blockage of the outlet of the fourth ventricle was due to central canal enlargement (hydromyelia) that was caused by inflow from the ventricles [13,18]. Hence, we suspected that the syringomyerlia of this cat was due to a hydromyelia because hydrocephalus, enlargement of the fourth ventricle, and an ependymal lining the inner wall of the syrinx were detected.…”

Interstitial spinal-cord oedema in syringomyelia associated with Chiari type 1 malformations

“…Ball and Dayan1 argued that CSF enters the syrinx through the perivascular spaces when the spinal subarachnoid pressure is increased during coughing or straining. Several authors3 4 6 16 17 supported the theory of entrance of CSF from the subarachnoid space via the perivascular spaces. Milhorat et al 3 proposed that the central canal would function as a sink that is capable of clearing substances from the parenchymal tissue of the spinal cord to the fourth ventricle.…”

Syringomyelia Fluid Dynamics and Cord Motion Revealed by Serendipitous Null Point Artifacts during Cine MRI

“…Subsequent authors have highlighted the lack of communication between the syrinx and fourth ventricle and postulated that the fluid entered the syrinx from the spinal subarachnoid space. 6,9,10 With the advent of dynamic MR imaging and intraoperative sonography, Oldfield et al 6 proposed that the downward movement of the tonsils seen during systole caused a "pistonlike" effect, resulting in a CSF pressure wave that contracted the cord and forced fluid into it. Researchers argued, however, that if fluid pressure caused the cord to contract, it would be unlikely that any fluid could enter the cord.…”