Lumbar puncture is a procedure in which a needle is inserted through the back to the subarachnoid space in the spinal canal often to collect some cerebrospinal fluid or inject a therapeutic agent. The procedure can be performed under imaging, e.g. fluoroscopy or ultrasound-guided. In many locations, imaging-guided lumbar punctures are increasingly the norm .
- suspected meningitis
- demonstration and relief of raised intracranial pressure e.g. in pseudotumor cerebri
- injection of therapeutic or anesthetic agent
- severe bleeding disorders, extreme thrombocytopenia
- suspected epidural abscess or infections in the line of entry
- deformation/trauma to the lumbar vertebrae
- brain tumor, abscess, or other lesions that cause elevated intracranial pressure
Due to the possibility of brain herniation in patients with elevated intracranial pressure, many clinicians will order a head CT before the procedure. Different medical societies have varying recommendations about this issue, however focal neurological findings or altered level of consciousness should prompt consideration of this complication.
The basic equipment for the procedure should be gathered beforehand and may include needles, specimen bottles and tubes, and manometers. Blind lumbar punctures are usually performed with patients in decubitus position with their knees bent towards their chest. Aseptic technique is mandatory. Local anesthesia can be given. With manual palpation, the performer identifies L3, L4, and L5, then guides a needle through the opening between the vertebra.
Most complications associated with LP are relatively minor such as post LP headache or transient back pain. More serious complications may include seizures or nerve damage. Rarely brain herniation can occur.