Thecal Sac Impingement: Causes | Symptoms

What is the Thecal Sac?

Thecal sac impingement will often lead to painful conditions. The thecal sac is filled with CSF (cerebrospinal fluid), and it covers the spinal cord. Its parts are the inner dura and the outer arachnoid membrane. The thecal sac runs “until the S1 to S3 vertebral levels”. When the spine bends forward (flexes), it “elongates and moves upwards”. Upon spinal extension, it “shortens and moves downwards”. The thecal sac is “wider in females”.

There are times when the thecal sac becomes compressed. This might be a result of tumors, spondylolisthesis, spondylolysis, synovial cysts, spinal canal stenosis, osteophytes, spinal fracture, spinal abscess and hematoma, caudal nerve roots, and epidural lipomatosis. Ankylosing spondylitis and chronic adhesive arachnoiditis can also affect the thecal sac. Symptoms of thecal sac compression include muscle weakness, low back pain, and other clinical signs.¹ The thecal sac is meant to protect and insulate nerve tissues. Sometimes osteophytes or herniated discs impinge upon the thecal sac, like “a finger pushing into a water balloon”. There may not be any damage from this; however, if it is a deep impingement, or if it goes as far as the spinal cord, then symptoms might arise.²

Causes and Symptoms of Thecal Sac Impingement

Severe Central Canal Stenosis

A bulging disc, osteophytes, or osteoarthritis can lead to impingement, or something pressing on another structure. The terminology associated with this problem is thecal sac impingement, or a herniated disc “providing a mass effect”, “compressing”, “displacing”, or “encroaching on the thecal sac”. While many cases have no effects, there are some patients who have their spinal cord impacted. This may lead to, “in the lower lumbar spine, severe central canal stenosis”, or even sciatica.³ Some patients may have issues with the lower lumbar spine, leading to compression of the cauda equina nerve roots. This could lead to those sciatica symptoms. Health professionals can use MRI reports to diagnose a thecal sac impingement.⁴

Lumbar Spinal Stenosis

Lumbar spine anatomy includes the lower back vertebral segments, numbered from L1 to the L5 vertebrae. The lumbosacral spine is where the lower back meets the sacrum.⁵ Middle-aged and older patients can be affected by a condition called lumbar spinal stenosis, which occurs when the cauda equina roots are entrapped. Symptoms include back pain, numbness, weakness, leg fatigue, and even bladder and bowel issues. The nerve root supply to the legs, feet, and genital areas “travels in very close apposition within the thecal sac”. Compression, such as lumbar canal stenosis, could cause “dysfunction in multiple root distributions”, impacting multiple body parts.⁶

Neural foraminal stenosis

The neural foramen (intervertebral foramen) is “an opening between vertebrae through which nerves leave the spine”.⁷ Neural foraminal stenosis is a condition of narrowing, where the foramina is constricted. This can lead to pain, numbness, weakness, and tingling. Lumbar stenosis, foraminal cervical (neck) stenosis, and thoracic (middle back) stenosis are all examples of this type of disorder. Arthritis, trauma, and disc herniation or degeneration can cause neural foraminal stenosis.⁸ Some patients may have a diffuse disc bulge, which can happen, for example, in the cervical region. In this case, the thecal sac may become pinched as well. There may be no pain, or there might be “severe radicular pain”, that travels down the arm to the fingers, as could be the case with a cervical disc bulge, for example.⁹

Treatments

Pain medication cannot cure disc impingements and herniation. Even in cases where they are considered to be effective, medications tend to come with side effects that could worsen the patient’s condition. To treat the impingement, patients can cease the aggravating behavior, engage in stretches and exercises (including yoga and Pilates), chiropractic adjustments, massage therapy, and acupuncture. If conservative measures do not work, some patients may be referred for epidural injections or surgery. Before considering those more extreme measures, it may be helpful to engage in “at least 3 months of therapy” first, such as chiropractic, massage, or acupuncture.¹⁰

Spinal stenosis, the spinal canal narrowing, may lead to muscular or sensory weakness. Cervical spinal stenosis is said to be “dangerous because it involves compression of the spinal cord”. While a bulging disc is considered “part of the normal aging process”, a herniated disc is different. It means that there is a “crack in the…outer layer of cartilage” that “allows some of the softer inner cartilage to protrude out”. Other names for herniated discs are slipped or ruptured discs. Herniated discs are more likely to cause pain.

It could be best to treat patients with ice and heat, perhaps avoiding deep tissue work, at first. Craniosacral therapy, isometrics (instead of range of motion movements), and light traction may also be useful. Patients should also practice proper ergonomics, posture, and lifestyle modifications at home. Since there is generally MRI data, chiropractic and massage treatment can be more successful. Even so, “if any motion or position or technique further aggravates the client’s symptoms, it should be immediately stopped”. Chiropractic treatments that might benefit the patient may include hot and cold therapy, electrical stimulation, ultrasound, and adjustments.¹¹