Syringomyelia denotes the formation of a cavity in the spinal cord. The spinal cord is the downward continuation of the brain. All communication between the brain, the trunk and the limbs occurs through it. The formation of an expanding cavity within the spinal cord can play havoc with this communication system and result in weakness of the trunk, limbs and damage to them consequent to loss of sensations.
Chiari malformation consists of a downward migration of a part of the hindbrain into the upper part of the spinal canal with consequent compression of the junction of the brain and spinal cord.
Your doctors may have found evidence of damage to the spinal cord and compression of the junction of the brain and spinal cord not yet evident to you. The principal reason why surgery may have been advocated by them is to prevent such damage from worsening.
Please discuss the pros and cons of such surgery with your doctors for they are best equipped to inform you. If the damage is likely to worsen, waiting for a year may lead to unwelcome consequences for you. I suggest you delay marriage till this issue is resolved. When you do decide to marry, keep your future bride informed of your illness and the steps you have taken towards its treatment.