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Lumbar Puncture – Indications and Usage

Posted by Dr. Jack Sacks, Esq.on October 07, 2011

Lumbar puncture is a procedure performed in the lower back area, where a needle is inserted between two vertebrae to remove a sample of cerebrospinal fluid (CSF). The patient flexes his/her back to widen the spaces between the vertebrae so it is easier for the physician to access the region. The back is washed with antiseptic soap or iodine and covered with a sterile sheet. A local anesthetic is used to numb the area and then a thin hollow needle is inserted through the spinal membrane and into the spinal canal. During this portion of the procedure, the patient generally feels pressure. The CSF pressure is measured, a small amount of fluid is removed, and the pressure is measured again. The needle is removed and the site is bandaged. The total procedure takes about 45 minutes.

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Lumbar puncture is used to collect CSF for analysis to help in diagnosing conditions such as subarachnoid hemorrhage (typically caused by ruptured aneurysm or traumatic brain injury), meningitis (inflammation of the membranes around the brain), and cancers of the brain or spinal cord. Lumbar Puncture may also be utilized to inject anesthetic medications, chemotherapeutic drugs, contrast material, or radioactive substances into CSF.

Lumbar Puncture may be used to identify increased or decreased CSF pressure.  Increased CSF pressure can be caused by increased intracranial pressure as is seen with traumatic brain injury, ruptured aneurysm, and sometimes hydrocephalus. On the other hand, decreased CSF pressure can be caused by spinal cord tumor, shock, fainting, or diabetic coma.  Normal CSF appears clear and colorless. When an infection is present, the CSF may look cloudy and be yellow or pink in color. Infection may be suspected if there is an increased level of white blood cells and/or protein. Increased CSF glucose indicates hyperglycemia whereas decreased CSF glucose may reflect hypoglycemia, bacterial or fungal infection, tuberculosis, or meningitis. If tumor cells are detected, the patient may have cancer in the brain, spinal cord, or CSF.  If there are increased gamma globulin levels, the patient may be suffering from multiple sclerosis, neurosyphilis, or Guillan-Barre syndrome. The analysis of the CSF by the lab and the measuring of CSF pressure recorded from the lumbar puncture help in determining a diagnosis in many serious clinical situations.