Spinal tap test for MS diagnosis

A spinal tap, or lumbar puncture, for multiple sclerosis (MS) is a diagnostic procedure that lets a clinical team evaluate the fluid surrounding the brain and spinal cord, known as cerebrospinal fluid (CSF). For an MS diagnosis, this procedure provides vital clues to help determine whether a patient has the condition.

An MRI is often the first test a person with suspected MS undergoes to help clinical teams identify lesions on the brain or spinal cord.

If teams find lesions suspected to be due to MS, they may request a spinal tap to look for specific proteins in the CSF. These proteins indicate an immune response affecting the protective coverings of certain nerve fibers in the central nervous system. A spinal tap also helps rule out other conditions and provides important information supporting an MS diagnosis, although it does not provide the complete clinical picture.

What is a spinal tap?

A spinal tap is one of several tests used to diagnose MS. A neurologist, or a specialist in brain and nervous system disorders, collects a small sample of CSF from the lower back using a thin needle.

The procedure takes place in a hospital or clinic setting. If a sample shows abnormal protein levels or inflammatory cells, it may indicate MS.

In people with MS, damage to the protective coverings of nerve fibers, known as myelin sheaths, releases certain proteins into the CSF. These include kappa-free light chains and oligoclonal bands. High overall protein levels are also typically present in the CSF of individuals with MS.

If a neurologist finds these proteins in the CSF but not in the blood, MS is a possible diagnosis. However, around 5% to 10% of people with MS do not show CSF anomalies, and other diseases can cause a similar abnormal immune response.

Besides MS, clinicians use this test to confirm other conditions affecting the brain and central nervous system, such as:

• meningitis
• Guillain-Barré syndrome
• brain and spinal cord cancers
• brain bleeds
• dementia
• encephalitis (brain tissue inflammation)
• leukemia
• myelitis (spinal cord inflammation)

Preparing for and getting a spinal tap

In many cases, a neurologist can diagnose MS using an MRI scan alone, making diagnosing MS with a spinal tap unnecessary. However, if an MRI of the brain and nervous system lesions does not provide enough evidence of MS, the neurologist may refer the patient for a spinal tap.

Pretest screening and preparation

Before the procedure, healthcare team members perform a physical exam and review health history to ensure safety and prevent complications:

• Imaging and laboratory tests: Care teams may recommend a CT scan, an MRI, or blood tests in advance to evaluate the lumbar region and check for lesions.
• Medication adjustments: Patients taking blood thinners, such as aspirin or warfarin, may need to adjust their schedule under medical supervision.
• Transportation: For outpatient procedures, patients must arrange for transportation home, as driving is unsafe immediately afterward.

Lumbar puncture procedure steps

A spinal tap is usually a quick procedure lasting 15 to 30 minutes, with the needle remaining in place for only a few minutes. Local anesthesia minimizes pain at the puncture site, though patients remain awake and may feel some pressure.

The primary lumbar puncture procedure steps include:

1. Positioning: The patient lies on their side with knees pulled toward the chest, or sits and leans forward. Remaining still is essential.
2. Cleaning and numbing: The neurologist cleans the skin and applies a local anesthetic to the lower back. While this may cause a slight burning sensation during the procedure, patients will not feel pain, though they may feel some pressure.
3. Needle insertion: The neurologist inserts a thin, hollow needle between two vertebrae — typically between the third and fourth lumbar vertebrae — into the subarachnoid space between the spinal cord and the membrane covering the cord, known as the meninges. Fluoroscopy X-rays may guide the needle.
4. Measuring pressure and collecting fluid: The neurologist measures spinal fluid pressure, withdraws a sample, then removes the needle and applies a bandage.

What to do after the procedure

Following the spinal tap, care teams instruct patients on recovery protocols:

• Rest: Lying flat on the back or side for at least one to several hours
• Driving: Avoiding driving or operating heavy machinery for 24 hours
• Activity: Avoiding strenuous activities and exercise for 24 to 48 hours
• Hydration: Drinking plenty of fluids
• Work: Returning to work after being cleared by the healthcare team

Results are typically available within two to three days, though specialized tests may take longer.

MS spinal tap side effects

Spinal tap tests are generally safe, though some individuals undergoing an MS spinal tap may develop side effects or complications.

What is a spinal headache?

A common side effect is a spinal headache, developing in 10% to 40% of patients. This occurs when fluid leaks into nearby tissues, usually starting several hours to two days after the test and lasting from a few hours to more than a week.

Headaches typically worsen while standing or sitting and may be accompanied by nausea, vomiting, or dizziness. Management strategies include:

• resting in bed while lying flat
• increasing fluid intake
• taking over-the-counter pain relievers
• receiving intravenous fluids or caffeine
• undergoing an epidural blood patch if symptoms persist

Other side effects

Additional potential side effects include:

• back pain or discomfort: Tenderness in the lower back that may radiate down the legs
• bleeding: Minor bleeding near the insertion site or, rarely, in the epidural space
• brainstem herniation: An extremely rare complication where a tumor or lesion takes up space in the brain and increases pressure in the skull, compressing the brainstem. Pre-procedure imaging screens for this risk.

Spinal tap and MS diagnosis

After CSF collection, laboratory testing evaluates immune cells, antibodies, and proteins that signal an abnormal immune response within the central nervous system. These findings demonstrate that the immune system is attacking healthy cells.

Spinal tap results indicating MS may include:

• the presence of oligoclonal bands in the CSF
• elevated levels of immunoglobulin G antibodies
• other myelin breakdown proteins in the CSF
• other markers that may help rule out other conditions

Because other diseases cause similar protein elevations, diagnosing MS requires multiple evaluations before confirming a diagnosis. Primary diagnostic tests alongside MRI and spinal taps include:

• optical coherence tomography: Evaluates retina thickness and nerve fiber damage caused by optic nerve inflammation
• evoked potential tests: Measure the speed of electrical signals along nerve pathways
• blood tests: Rule out conditions with similar symptoms and identify specific biomarkers
• neuropsychological testing: Assesses memory, language, mood, personality, and cognition to establish a baseline and track changes over time

Patients can speak with their healthcare team about any further testing needed based on their spinal tap results.

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