Cerebellar and hindbrain motion in Chiari malformation with and without syringomyelia

Abstract

<jats:sec> <jats:title>OBJECTIVE</jats:title> <jats:p>The pathogenesis of syringomyelia associated with Chiari malformation type I (CM-I) is unclear. Theories of pathogenesis suggest the cerebellar tonsils may obstruct CSF flow or alter pressure gradients, or their motion might act as a piston to increase CSF pressure in the spinal subarachnoid space. This study was performed to measure cerebellar tonsillar and hindbrain motion in CM-I and assess the potential contributions to syrinx formation.</jats:p></jats:sec> <jats:sec> <jats:title>METHODS</jats:title> <jats:p>Sixty-four CM-I patients and 25 controls were retrospectively selected from a clinical database, and all subjects had undergone cardiac-gated cine balanced fast-field echo MRI. There were a total of 36 preoperative CM-I scans, which consisted of 15 patients with and 21 patients without syringomyelia. Nineteen patients underwent paired pre- and postoperative imaging. Anteroposterior (AP) and superoinferior (SI) movements of the tip of the cerebellar tonsils, obex, fastigium of the fourth ventricle, pontomedullary junction, and cervicomedullary junction were measured. The distance between the fastigium and tip of the tonsils was used to calculate tonsillar tissue strain (Δ<jats:italic>i</jats:italic>/<jats:italic>i</jats:italic><jats:sub>0</jats:sub>).</jats:p></jats:sec> <jats:sec> <jats:title>RESULTS</jats:title> <jats:p>CM-I patients had significantly greater cerebellar tonsillar motion in both the AP and SI directions than controls (AP +0.34 mm [+136%], p &lt; 0.001; SI +0.49 mm [+163%], p &lt; 0.001). This motion decreased after posterior fossa decompression (AP −0.20 mm [−33%], p = 0.001; SI −0.29 mm [−36%]; p &lt; 0.001), but remained elevated above control levels (AP +56%, p = 0.021; SI +67%, p = 0.015). Similar trends were seen for all other tracked landmarks. There were no significant differences in the magnitude or timing of motion throughout the hindbrain between CM-I patients with and without syringomyelia. Increased tonsillar tissue strain correlated with Valsalva headaches (p = 0.03).</jats:p></jats:sec> <jats:sec> <jats:title>CONCLUSIONS</jats:title> <jats:p>Cerebellar tonsillar motion may be a potential marker of CM-I and may have use in tailoring surgical procedures. The lack of association with syringomyelia suggests that tonsillar motion alone is not the driver of syrinx formation. Tonsillar tissue strain may play a part in the pathophysiology of Valsalva headaches.</jats:p></jats:sec>

Syringomyelia presenting with unilateral optic neuropathy: a case report

“…Although these two cases of syringomyelia were idiopathic, Chiari type-1 malformation has been reported as one of the etiologic factors in syringomyelia 6. It has been postulated that idiopathic syringomyelia is similar to that seen in Chiari type-1 malformation in terms of its pathogenesis 7.…”

“…It has been postulated that idiopathic syringomyelia is similar to that seen in Chiari type-1 malformation in terms of its pathogenesis 7. This malformation, also known as hindbrain hernia, is a structural abnormality in the region of craniovertebral junction, causing cerebellar tonsils to go below the foramen magnum and obstruct cerebrospinal fluid circulation 6. The rise in spinal subarachnoid pressure subsequently causes fluid to move upward inside the syrinx and into the brainstem, leading to a condition known as syringobulbia 8.…”

“Stealth cranioplasty:” A novel endeavor for symptomatic adult Chiari I patients with syringomyelia: Technical note, appraisal, and philosophical considerations

“…This sequence of happenings is very much in concordance with the Monro–Kellie doctrine of constant total intracranial volume. [ 7 10 11 12 13 ] We feel that the basic pathology of CM is the anomalous shallow posterior fossa, and our surgical strategy is to try to render the posterior fossa capacious for reversal of the symptoms. Herniated and impacted neural tissues consequently block the natural CSF passage and change the CSF dynamics in the CVJ, mostly around the foramen magnum, giving rise to SM in many cases.…”

“Stealth Cranioplasty” for Adult Chiari Malformation Type 1: A Philosophical Journey of Innovation, Adaptation, and Evolution

“…Interestingly, in cases of acquired Chiari malformation (ACM), surgical management of only the primary lesion has shown to improve ACM which also supports the discrepancy between the volume of the posterior fossa and its contents [39]. From different studies, it is now proposed that development of Chiari results from multifactorial etiologies, where small PF remains to be the most crucial one [40][41][42][43][44][45][46][47][48][49][50][51][52]. The theory of small PF is further strengthened by demonstration of CM by creating smaller basichondrocrania and posterior cranial fossa than controls by producing a state of hypervitaminosis A in experimental models of rodents [53].…”

“…Many techniques have been described in the literature like partial cranioplasty with methyl methacrylate (MMA) [115,116], with autologous bone [117][118][119][120][121][122], and cranioplasty with different varieties of titanium prosthesis [48,[123][124][125][126]. Tacking of duraplasty with or without cranioplasty has also been described by some authors with intention to keep the cistern patent and to prevent adhesion [48,120,122,123,127]. We have tried to blend the procedures in an effective and least invasive way to give the utmost benefit to the patients.…”