Purpose: This clinical trial aims to evaluate the indications, therapeutic effects and side effects of betaine in refractory syringomyelia.

Primary outcome measure: The primary endpoint is the change of ASIA at week 12. The clinical efficacy is defined as ASIA increase ≥ 1 at week 12, as compared with that before betaine usage.

The pathogenesis of syringomyelia is poorly understood and duraplasty or shunting is not always effective. Although it is generally thought that syringomyelia is simply an accumulation of CSF from the subarachnoid space, the pathogenesis is likely to be more complex and may involve cellular and molecular processes.

The investigators supposed that betaine might play a key role in the pathogenesis of syringomyelia, especially post-traumatic syringomyelia(PTS), and that betaine, as an Osmotic homeostasis-related drug, would protect Osmotic homeostasis in syringomyelia.

Primary objectives: This clinical trial aims to evaluate the indications, therapeutic effects and safety of betaine in refractory syringomyelia.

Inclusion Criteria:

• Contraindication to duraplasty and shunting treatment due to history or high risk of severe adverse effects,
• non-effective response to duraplasty and shunting treatment in 12 months prior to study entry.
• Estimated life expectancy must be greater than 12 months.
• Ability to understand and willingness to sign a written informed consent document, or constant caregivers who well understand and willingness to sign a written informed consent document.
• Must be able to swallow tablets

Exclusion Criteria:

• Participants have a cardiometabolic disease for which they take prescribed medications
• Evidence of tumor metastasis, recurrence, or invasion;
• History of psychiatric diseases ;
• History of seizures;
• History of arteriosclerotic cardiovascular diseases (ASCVD), e.g. stroke, myocardial infaction, unstable angina, within 6 months;
• New York Heart Association Grade II or greater congestive heart failure;
• Serious and inadequately controlled cardiac arrhythmia;
• Significant vascular disease, e.g. moderate or severe carotid stenosis, aortic aneurysm, -history of aortic dissection;
• Severe infection;
• History of allergy to relevant drugs;
• Pregnancy, lactation, or fertility program in the following 12 months;
• History or current diagnosis of peripheral nerve disease;
• Abnormal in liver and renal function;
• Active tuberculosis;
• Transplanted organs;
• Human immunodeficiency virus;
• Participation in other experimental studies.