What is a perineural cyst
The spinal root is covered by two membranes. Normally there is a narrow gap between them, but with a Tarlov cyst this gap widens into a sac filled with cerebrospinal fluid. The cavity communicates with the subarachnoid space through a narrow channel, so when coughing, straining and in an upright position, the pressure inside the cyst increases. Typical localization is the level of the second and third sacral roots, where cysts are often multiple. The sizes vary from a few millimeters to several centimeters, and only large cysts can thin the bone and irritate the root.
- Filled with cerebrospinal fluid, not tumor tissue
- Contains nerve root fibers in the wall
- Most often sacral localization
- Often several cysts occur at once
- Benign condition, does not degenerate
Causes and risk factors
The exact reason is unknown. Congenital weakness of the root membranes and increased cerebrospinal fluid pressure, which gradually widens the gap between the membranes, are discussed. The role played by previous injuries to the sacrum and coccyx, operations and punctures at the lumbar level, and inflammation of the membranes. Cysts are much more common in women, usually in middle age. Sometimes perineural cysts accompany hereditary connective tissue diseases. It is important to understand: in most people with such a finding, the cyst exists for years and does not grow.
- Congenital feature of the root membranes
- Increased cerebrospinal fluid pressure
- Injury to the sacrum or coccyx
- Past punctures and spinal surgeries
- Inflammation of the spinal cord membranes
- Hereditary connective tissue dysplasias
When does a cyst give symptoms?
Complaints appear in a minority of patients and are associated with pressure of the cyst on the root. Characterized by dull or burning pain in the sacrum and coccyx, which intensifies when sitting and standing, when coughing and straining, and weakens when lying down. The pain may radiate to the buttock, back of the thigh, perineum and rectum. Numbness, tingling, and a crawling sensation are added. With large cysts, pelvic functions are affected: urination becomes more frequent or difficult, constipation appears, and sensitivity in the perineum decreases.
- Pain in the sacrum and coccyx, worse while sitting
- Shoots in the buttock and leg
- Pain and numbness in the perineum
- Frequent or difficult urination
- Constipation, feeling of incomplete emptying
- Decreased sensitivity and weakness in the foot
- Discomfort during sexual intercourse
Diagnostics
The main method is MRI of the lumbosacral spine: the cyst is visible as a round formation with liquid contents at the root. A CT scan shows how thin the sacral bone is and how wide the opening is. If it is necessary to prove that the cyst is associated with the subarachnoid space and is really the cause of complaints, CT myelography is performed. Electroneuromyography helps to assess the condition of the root. An obligatory part of the examination is to exclude other causes of pain, so the doctor examines the spine, hip joints and refers to a urologist or gynecologist.
- MRI of the lumbosacral spine
- MRI of three sections for multiple cysts
- CT scan of the sacrum and coccyx
- CT myelography according to indications
- Electroneuromyography
- Consultation with a urologist or gynecologist to rule out other causes
Treatment and observation
If the cyst is found by chance and there are no complaints, treatment is not required - a control MRI is sufficient when symptoms appear. For moderate pain, they begin with conservative measures: non-steroidal anti-inflammatory and analgesic drugs of central action, physical therapy for the pelvic floor and back muscles, posture correction, and sometimes therapeutic blockades. Surgical treatment is discussed only if there is a clear connection between the symptoms and a large cyst and the ineffectiveness of conservative therapy. They use emptying and strengthening of the cyst wall, fenestration, and plasty of the membranes. The decision is made by the neurosurgeon, since the operation is associated with the risk of damage to the root.
- Asymptomatic cyst - observation only
- Short course non-steroidal anti-inflammatory drugs
- Drugs for the treatment of neuropathic pain as prescribed by a doctor
- Therapeutic exercise and strengthening of the pelvic floor muscles
- Avoid prolonged sitting and straining
- Therapeutic blockades for persistent pain
- Surgery - for a large symptomatic cyst and treatment failure