Primarily talk to us about it before choosing a treatment for your CTS. Try to find out as much as possible about the injection to which you reacted. These injections contain different steroids, varying or no local anaesthetic and other chemicals such as stabilisers and preservatives. For example, the commercial preparation 'Kenalog' used in this area contains not only the steroid (Triamcinolone acetate), but also sodium chloride, benzyl alcohol, carboxymethylcellulose sodium, polysorbate 80 and either sodium hydroxide or hydrochloric acid used to balance the pH (acidity). You may have had an allergic reaction to one of the other components of the injection or you may have reacted to one of the synthetic steroids which are not native to the human body. It does not necessarily follow that you would also react to a different preparation so knowing exactly which preparation you have had a reaction to is a vital piece of information.
As you already know chiari occurs when the lower portion of the cerebellum herniates or protrudes downwards in to the spinal canal. A spinal procedure like LP (Lumbar Puncture, also called as spinal tap) is a relatively contra indicated in patients with chiari condition, because when CSF (cerebrospinal fluid) is taken out then the decreased fluid pressure in the spinal canal sometimes can trigger further downward displacement of the lower portions of the cerebellum (means it may exacerbate the chiari malformation). It is really a rare possibility but a potential possibility.