A rare case of facet joint synovial cyst connected to the intrathecal space: a case report.

Unexpected injection of local anesthetics into the intrathecal space can cause adverse effects, such as hypotension, shortness of breath, bradycardia, numbness or weakness, nausea and vomiting and serious complications, such as respiratory arrest, loss of consciousness and cardiac arrest. In this study, we report a case of a 68-year-old woman with a facet joint synovial cyst connected to the intrathecal space. The patient's clinical symptoms and radiological findings were consistent with those of a facet joint synovial cyst; however, during facet joint synovial cyst aspiration, it was found that the cyst was connected to the intrathecal space. Our experience shows that during the procedure of facet joint injection and facet joint synovial cyst aspiration, local anesthetics may be inadvertently injected intrathecally. Although this is highly uncommon, it can lead to serious side effects, such as total spinal anesthesia. Therefore, we present this case, along with a brief literature review.