1. Indications

Lumbar Puncture (LP) is primarily indicated for the evaluation and diagnosis of patients who present with symptoms consistent with:

Meningitis Meningoencephalitis

Subarachnoid hemorrhage

Other neurologic indications include:

Malignancy Seizures

Metabolic or Degenerative diseases

LP Indications in Neonates (Children less than 1 year of age):

Sepsis evaluation. Febrile children with suspected bacteremia.

Those children too young for accurate clinical evaluation of meningitis.

Apparent febrile seizure.

Mental status change with no identifiable cause.

Additional Uses of LP:

Management of patients with Pseudotumour Cerebri. Administration of intrathecal antibiotic therapy.

Instillation of chemotherapeutic agents.

2. SPECIAL  CASES

1. In suspected cases of Tuberculosis meningitis send CSF for polymerase chain reaction, which is a rapid and sensitive test.

2. Send a CSF Venereal Disease Research Laboratories (VLDR) reagent from patients with a positive serum treponemal test result with possible neurosyphilis or from neonates delivered to mothers with positive results for serum VLDR or rapid protein reaction (either without history of prior treatment or with treatment failure) in order to exclude congenital syphilis.  

3. Computed tomography is indicated before LP in the patient with suspected acute bacterial meningitis who has symptoms suggestive of significantly increased intercranial pressure.

Contraindications

Children with significantly increased signs (evidenced by headache and papilledema) of Intercranial Pressure or a Midline Shift.

 

o Risk of herniation.

 

Severely ill patients with Hemodynamic or Pulmonary Instability, until they are in stable condition and not at risk of herniation.

 

Patients with soft tissue infection over the lumbar spine area.

 

Severe, unresponsive Coagulopathy or severe Thrombocytopenia.

Anatomy

The Bones

The vertebral column contains two curves. Both concave anteriorly, one in the thoracic region and one in the lumbar region. Flexion of the spine rids the column of both these curves and allows you to proceed with the procedure.

During flexion, the inferior articular processes of the top lying vertebra slide upwards. In consequence the inter-laminar foramen enlarges and becomes diamond shaped allowing for an easier puncture.

 

 

 

The Ligaments

As the needle punctures the skin it will need to transverse three ligaments before it can access the spinal canal. The ligaments will be described below in the order that they are encountered by the penetrating needle.

1. Supraspinous Ligament

This is a tough ligament which runs vertically over the apices of the spines of the lumbar and thoracic vertebrae and continues higher up in the cervical region as the ligamentum nuchae.

2. Interspinous Ligament

This ligament is a very thin one and runs between spines of adjacent vertebrae. The ligament attaches along the length of the spinous processes uniting the upper border of the lower one to the lower border of the more cranial one. Anteriorly the ligament blends in with the ligamentum flavum and posteriorly it blends in with the fibers of the supraspinous ligament. It takes the shape of a rectangle. 

3. Ligamentum Flavum

The ligamentum flavum is composed of mainly elastic fibers and is yellow in color, and in name. Flavum is Latin for yellow. It runs from an anterior-inferior surface of a cranial lamina to the posterior-superior surface of the lamina below. Laterally the ligament blends with the capsule of the joint between the articular

processes and then passes over medially where it will meet it's counterpart from the opposite side. Veins will sometimes pass through this ligament and can be punctured accidentally during the lumbar puncture.

a = Ligamentum Flavum

b = Supraspinous Ligament

c = Interspinous ligament

 

 The Foramina

1. Interlaminar foramen - most commonly used for Lumbar Puncture

In the lumbar region at rest, the interlaminar foramen is small and triangular in shape. The sides of the triangle can be thought of as the medial borders of the inferior articular processes of the top lying vertebra. the base of the triangle can be thought of as the top border of the lamina of the lower lying vertebra. (see picture at top of page). The interlaminar foramen can be expanded in area by flexion of the spine.

2. Intervertebral foramen

Where two vertebrae lie, one on top of the other, a foramen forms. The superior notch of the inferior lamina and the inferior notch of the superior lamina form the lower and upper borders of the intervertebral foramen. The boundaries are delineated by the intervertebral disc anteriorly the capsule posteriorly and the pedicles of neighboring vertebrae superiorly and inferiorly.

This foramen is rarely used for the Lumbar Puncture, but can be useful when the traditional puncture site is not practical because of extraordinary circumstances.

 

 

The Meninges and The Spaces

A. Extradural space

 This space lies outside the meninges, between the meninges and the periosteum lining the borders of the vertebral canal. This space extends from the base of the skull to the end of the sacrum and is occupied mostly by small veins, fatty tissues and nerves in transit between the spinal cord and the periphery.

1. Dura mater

The dura mater of the spine, for it has a cranial counterpart, is also known as the theca. The dura mater is the toughest of the three meninges and it ends at the lower limit of the 2nd sacral vertebra. It lies most exteriorly of the three.

A. The Subdural space

This is really only a potential space between the dura and the arachnoid mater. During a lumbar puncture procedure the dura and arachnoid are usually punctured simultaneously since they lie in such close contact.

2. Arachnoid mater

The arachnoid mater, as mentioned above, lies in close union with the dura in the lumbar area. It is the middle of the three meninges and also ends at the 2nd sacral vertebra. It is relatively avascular.

B. The Subarachnoid or Intradural space

This space, the space of interest for the lumbar puncture procedure , lies between the arachnoid and pia meninges and is traversed throughout by fibers joining the meninges called trabeculae as well as the emerging spinal nerves. The spinal cord finishes at the 1st or 2nd Lumbar vertebra and below this the subarachnoid space takes on a circular appearance.  It's diameter is roughly 15mm.   

3. Pia mater

This highly vascular membrane lies closest to the spinal cord. It consists of two layers and gives emerging nerve roots their initial cover.

LP Techniques

1) Lateral Recumbent Position

Patient lies on side in a fetal position. Flex the patient's knees and torso, preventing excessive flexion of the  neck. Maximally flex the spine without compromising the upper airway by having patients legs drawn towards their chest. Patients hands can be placed between their knees and held by an assistant. The assistant's other hand can flex the neck at the appropriate time.

Keep the craniospinal and transverse planes stable.

2) Sitting PositionPlace the infant in a seated position on the edge of the examination table. Place the thighs against the abdomen and flex the trunk. The assistant will stabilize the infant by grasping the patient's right elbow and knee with their left hand and the left elbow and knee with the right hand. The older child should rest elbows on their knees while the assistant stabilizes the position.

Keep the craniospinal and transverse planes stable.

SELECTING AN LP TECHNIQUEUse Lateral Recumbent Position:

for measurement of opening pressure.

 Use Sitting Position:

patients with pulmonary disorders. young infants: prevents hyperflexion of the neck that can precipitate

respiratory distress.

IN EITHER CASE MAINTAIN PROPER ALIGNMENT AND ADEQUATELY RESTRAIN THE PATIENT.In the critically ill or unstable patient, pre-oxygenate at Flo2 = 1.0 at 5L/min via face mask for 3 minutes to prevent hypoxemia during procedure.

Equipment

Prepackaged LP trays contain all necessary equipment except povidone-iodine and sterile gloves

OR ELSE USE

Commercial trays. Spinal needle - 22 gauge:

AGE Length of needle

Less than 1 year 3.75 cm (1.5 inch)

1 year to middle childhood 6.25cm (2.5 inch)

Older children to adolescents 8.75 cm (3.5 inch)

Povidone-iodine solution.

1% Lidocaine and 25 gauge needle for local anesthesia.

Sterile 4 x 4 gauze.

3-4 sterile specimen tubes.

For viral cultures: an additional tube as well as a cup of ice in which to place the specimen before the lab culture.

CSF manometers and 3 way stopcock.

Proceedure :1. Choose Preferred LP technique.

2. Locate The Puncture Site

The spinal cord ends at the L1 and L2 vertebral bodies. The desired sites for lumbar puncture are the interspaces between the posterior elements of L3 and L4 or L4 and L5. You can locate these spaces by palpating the iliac crest. Follow an imaginary line from the iliac crest to the spine. the interspace encountered is L4-L5.. Use it or the interspace cranial to it.

Diagram Key

- The orange lines represent the levels of the lumbar vertebra.

- The spotted line is the imaginary line between the iliac crests that delineates the location in the midline of the inter-vertebral space.

 

After locating the site of intended puncture, mark it by indentation of the skin with a fingernail.

3. Use Sterile Technique

Use sterile technique for the LP. Cleanse the skin with povidine-iodine solution after donning sterile gloves. Using sponges, begin at the intended puncture site and sponge in widening circles until an area of 10 cm in diameter has been cleansed. Drape the child beneath their flank and over the back with the spine accessible to view.

4. Apply Local Anesthetic

Local anesthetic should be used in children older than 1 year of age. Anesthetize the site by injecting 1% lidocaine intradermally to raise wheal, then advance the needle into the desired interspace injecting anesthetic, being careful not to inject it into a blood vessel or the spinal canal.

5. Prepare The Spinal Needle

1. Check the spinal needle to ensure that the stylet is firmly in position, to prevent implantation of epidermoid tissue: have the stylet in place before advancing the needle.

2. Support the needle between your index fingers and stabilize the hub of the needle with your thumbs.

3. Grasp the spinal needle firmly with the bevel facing up toward the ceiling, making the bevel parallel to the direction of the fibers of the ligamentum flavum. The ligamentum flavum runs from vertebra to vertebra in a cranial to caudal orientation.

6. Puncture

1. With the needle perpendicular to the vertical plane but with the bevel pointed slightly cephalad, advance through the skin.

2. Advance slowly into the deeper structures until you detect a slight resistance on penetration of the spinous ligaments. The resistance continues until the needle penetrates the dura, at which time you will typically feel a "pop" sensation caused by the change in resistance. The pop indicates that you are in the subarachnoid space.

3. Remove the stylet.

4. Check for flow of spinal fluid.

5. If there is no CSF, rotate the spinal needle a few millimeters forward, then recheck. Repeat.

6. If the needle meets resistance, withdraw the needle with the stylet in place and reattempt the procedure. Verify that the puncture site is in the correct location. If it is, attempt a paramedian approach just a few millimeters lateral to the midline.

1. Obtaining Spinal Fluid Samples

1. Collect a total of 2 mL of CSF in the premature or full-term neonate. In older children 3 to 6 mL can be safely removed.

2. Note the character of the CSF and, if bloody fluid flows originally, observe the fluid for clearing with subsequent collection.

3. If the fluid does not clear this may indicate the presence of a subarachnoid hemorrhage.

4. After collecting CSF fluid obtain a closing pressure reading as previously indicated.

5. Replace the stylet and remove the needle.

6. Place a bandage over the site and encourage the patient, if able, to lie prone for 3-4 hours to prevent leakage.

2. CSF Analysis Send CSF for analysis of:

Cell count and differential. Protein and glucose determinations.

Gram stain.

Routine culture.

To prevent misinterpretation caused by RBC contamination, send the last tube collected for cell count evaluation.Obtain a peripheral serum glucose level immediately before the LP to determine the CSF serum ratio of glucose.

Complications

Local pain or backache. Post-tap headaches.

Vomiting.

Paralysis (low risk)

Epidermoid tumors.

Subarachnoid epidermal cyst.

Epidural hematomas.

Subdural or subarachnoid hemorrhage.

Spinal cord bleeding.

Acute neurologic or respiratory deterioration.

Hypoxemia or apnea

Cerebral herniation.

Introduction of infection with resultant bacterial meningitis, epidural abscess, diskitis or osteomyelitis. (low risk)

Ocular muscle palsy. (transient)