2.1.1 There are several types of spinal cyst, all of which are rare. Tarlov or perineural cysts affect nerve roots, most commonly in the sacral region of the spine. The majority are asymptomatic, but they may occasionally cause symptoms such as radicular pain or urinary dysfunction. Arachnoid cysts develop as a result of defects of the dura, usually in the thoracic region of the spine. They can cause radicular pain or loss of sensory or motor function. Spinal echinococcal cysts are a rare feature of hydatid disease, and may also cause radicular pain or loss of neurological function.
2.1.2 Painful spinal cysts are often managed conservatively with analgesics. Open surgery to drain or remove cysts may be indicated if pain is refractory to medical therapy, or if there is a threat of permanent neurological impairment.
2.2.1 A small-gauge needle is inserted into the cyst under computed tomography (CT) or magnetic resonance imaging (MRI) guidance. Cyst contents are aspirated, and the decrease in cyst volume is documented by imaging. Where cysts are present at more than one spinal level, several aspiration procedures may be needed.
2.3.1 The evidence available is from one case series and three case reports. In a case series of three patients with sacral perineural cysts, two experienced pain relief for up to 3 weeks and one for several weeks (number not stated). Case reports of two patients, one with an arachnoid cyst and one with spinal hydatid cysts, reported that image-guided aspiration rendered each patient asymptomatic during follow-up of 1 year. A case report of a patient with a Tarlov cyst reported that aspiration produced immediate pain relief; however, pain recurred after 5 days and the patient underwent open decompression.
2.3.2 Follow-up imaging of cysts was undertaken in the case series and one of the case reports described above. The patient with hydatid cysts demonstrated collapsed cysts and spinal cord decompression on MRI at 4-month follow-up. Conversely, the cysts eventually refilled in the three patients with sacral perineural cysts and all subsequently received operative treatment. For more details, refer to the 'Sources of evidence' section.
2.3.3 The Specialist Advisers did not raise concerns about the efficacy of this rare procedure.
2.4.1 Only one case report, of a patient whose spinal hydatid cysts were aspirated under CT guidance, reported safety outcomes. The patient tolerated the procedure well, with no allergy or anaphylaxis. For more details, refer to the 'Sources of evidence' section.
2.4.2 The Specialist Advisers listed potential adverse events as bleeding, infection, and nerve or spinal cord damage, including paraplegia.