Lumbar puncture (Lumbar Puncture) is a common diagnostic medical procedure primarily used to extract cerebrospinal fluid (CSF) for laboratory analysis. This procedure involves puncturing the lumbar intervertebral space to obtain fluid samples for evaluating central nervous system diseases, such as meningitis, brain tumors, or multiple sclerosis. It can also be used for therapeutic purposes, such as injecting chemotherapy drugs or reducing intracranial pressure.
This procedure must be performed by a professional physician in a sterile environment and typically takes 15 to 30 minutes. Patients are required to remain in a lateral decubitus or sitting position, with local anesthesia at the puncture site to minimize discomfort. Its clinical value lies in directly obtaining biomarkers related to the lesion, providing crucial evidence for diagnosing various diseases.
Lumbar puncture is an invasive diagnostic procedure that involves inserting a needle through the dura mater of the lumbar spine to directly access the subarachnoid space to obtain cerebrospinal fluid. The collected fluid can be analyzed for bacteria, viruses, cancer cells, or biochemical markers, aiding in the diagnosis of infections, hemorrhages, or metabolic abnormalities. Additionally, measuring the opening pressure during the procedure helps assess changes in intracranial pressure.
The physiological mechanism relies on the dynamic balance of the cerebrospinal fluid circulation system. Fluid loss after puncture may temporarily decrease intracranial pressure, which is utilized in treating specific conditions, such as alleviating symptoms caused by cerebrospinal fluid blockage. However, strict control of the technique is necessary to avoid complications.
It is also applicable for chemotherapy drug infusion (e.g., acute lymphoblastic leukemia) or metabolic disease diagnosis (e.g., hyponatremia). In cases suspected of subarachnoid hemorrhage, CSF analysis can confirm the source and timing of bleeding.
Patients need to lie on their side with their waist bent or lean forward in a sitting position. The puncture site is usually chosen at the 3rd-4th or 4th-5th lumbar intervertebral space. After local anesthesia, a puncture needle penetrates the dura mater, and once venous pressure and cerebrospinal fluid pressure are balanced, collection begins. The total volume usually ranges from 10-20 cc, divided into samples according to examination requirements.
Continuous monitoring of blood pressure and vital signs is necessary during the procedure. When used therapeutically, drugs may be injected, with doses precisely calculated based on body weight and condition. After the operation, patients should lie flat for 2 hours to prevent cerebrospinal fluid leak headaches.
Open pressure measurement is an objective indicator that cannot be replaced by other tests when assessing intracranial pressure abnormalities. For certain hematologic cancers, this procedure is a key pathway for direct drug action on the central nervous system.
Immediate risks: Post-puncture headache (incidence approximately 10-30%), possibly accompanied by neck stiffness and positional aggravation
Older adults or patients with coagulation abnormalities require strict assessment of bleeding risk. Patients with intracranial tumors should undergo imaging confirmation of indications beforehand to avoid inducing brain herniation.
Absolute contraindications:
Relative contraindications include uncontrolled epilepsy or inability to cooperate with positioning. Preoperative assessment should include coagulation function, MRI/CT imaging, and informed consent.
Use of anticoagulants (e.g., warfarin) or platelet inhibitors requires reversal or discontinuation beforehand. Regarding antibiotic therapy, if bacterial meningitis is suspected, the procedure should be performed before antibiotics to preserve microbiological accuracy. Interactions with steroid therapy should be noted, as they may affect cerebrospinal fluid cell counts; inform the physician of all medications being used.
In diagnosing meningitis, CSF bacterial culture sensitivity exceeds 90%, especially when performed within 48 hours of onset. For multiple sclerosis, oligoclonal antibody testing can improve diagnostic accuracy to 85-95%. Therapeutically, intrathecal chemotherapy allows direct drug action on the central nervous system, increasing complete remission rates in leukemia patients to 60-70%. Intracranial pressure measurement in traumatic brain injury patients has a diagnostic consistency of 92%.
Non-invasive options include:
However, these methods cannot replace direct CSF analysis. When lumbar puncture cannot be performed, alternatives include epidural drainage or ventriculoscopy, though with lower accuracy and informational value.
What preparations are needed before a lumbar puncture?
Patients should inform their doctor in advance about current medications or supplements, especially anticoagulants (e.g., aspirin). Fasting for 4-6 hours prior to the procedure is generally recommended, but adequate hydration is allowed. The doctor may request blood tests or imaging to assess spinal structure suitability. Patients should change into surgical gowns and remove metal objects to ensure safety during the procedure.
What are the causes and prevention methods for post-lumbar puncture headache?
Headaches are often caused by cerebrospinal fluid leakage during the procedure, with an incidence of about 10-30%. Prevention includes lying flat for 2-4 hours post-procedure to reduce CSF loss and maintaining adequate hydration. If headaches persist, the physician may perform an "autologous blood patch," injecting a small amount of the patient’s blood into the leak site to promote tissue repair.
How soon can daily activities resume after the procedure? What are the precautions?
It is generally recommended to avoid heavy lifting or bending for 24 hours after the procedure, and to delay hair washing for 2-3 days. When showering, sponge baths are preferred, avoiding contact of the wound with dirty water to prevent infection. Mild back pain or dizziness usually resolve within a few days. Immediate medical attention is necessary if symptoms such as leg weakness, severe headache, or fever occur.
Why are repeated lumbar punctures sometimes necessary?
If the initial examination does not yield sufficient CSF or results are inconclusive (e.g., multiple cultures for tuberculous meningitis), repeat procedures may be required. Additionally, some therapeutic interventions (e.g., chemotherapy injections) may need multiple sessions, with the necessity determined by the physician based on the condition.
How long does it take to get results from a lumbar puncture? How are abnormal indicators interpreted?
Routine tests (such as pressure measurement and bacterial culture) typically require 1-3 working days, while specialized tests may take up to a week. Elevated protein levels may indicate multiple sclerosis, while abnormal white blood cell counts may reflect infection or autoimmune diseases. Final diagnosis should be based on clinical symptoms and other test results, with detailed explanation provided by the physician regarding the significance of the data.
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