Indications and Contraindications
Access and Indications
Lumbar puncture. The most common method of CSF collection is lumbar puncture. This is usually performed for the diagnostic purpose of CSF analysis. In recent decades, the development and availability of imaging procedures have meant that CSF analysis is required less frequently. Nevertheless, it is still indicated for the diagnosis or detection of the following conditions:
• Inflammation of the nervous system.
• Neoplasia of the nervous system.
• Disturbances of consciousness of unknown origin.
• Neurodegenerative diseases.
• Old hemorrhages.
Less often, there is a therapeutic indication for lumbar puncture, for:
• Reduction of CSF volume in order to reduce cerebrospinal pressure (e. g., pseudotumor cerebri, normal-pressure hydrocephalus).
• Administration of drugs (e. g., chemotherapeutics, local anesthetics, antispasmodic agents, antibiotics, cortisone, or contrast media).
Suboccipital and cervical puncture. Other puncture sites are the medial cisternal access at the inferior margin of the occiput (suboccipital puncture) and access between the first and second cervical vertebrae (cervical puncture). Since postpuncture complaints are rare, both these methods were widely used in the past. However, these interventions carry a high risk; the medulla oblongata is easily injured, and accidental puncture of the cervical venous plexus or atypically running an artery with an atypical course may cause excessive bleeding. Cerebrospinal puncture at these sites is therefore indicated only when no CSF can be obtained by lumbar puncture (e. g., in the presence of local inflammation or tumors, severe osteochondrosis, or after spinal surgery). In any case, this puncture calls for excellent anatomical knowledge, a great deal of experience, and extreme care.
Ventricular puncture. This is a neurosurgical intervention. It is indicated to release intracranial pressure when basal adhesions (e. g., due to subarachnoid hemorrhage or purulent meningitis) have led to dysfunction of CSF absorption and circulation and, finally, to obstructive hydrocephalus. The ventricular drainage usually remains in place for several days so that CSF may be collected repeatedly for follow-up tests. In addition to ultrasterile handling, it must be remembered that cell debris tends to sediment in the tube system. For this reason, the first 3–4 mL of CSF should be discarded and only the subsequent portion be used for CSF analysis.
Ventricular catheter. A ventricular catheter with a reservoir (Rickham or Ommaya reservoir) facilitates regular intrathecal administration of drugs, usually chemotherapeutic agents. Before the drug is administered, CSF can and should be collected for analysis by puncture of the reservoir. The puncture is easy to carry out using a perfusion cannula with wings (butterfly needle). Under sterile precautions, the cannula is introduced perpendicularly into the reservoir, and about 1 mL of CSF is slowly aspirated with a 5-mL syringe. This first sample, corresponding to the content of the catheter, is discarded, and the CSF that follows it is used for analysis. Ventricular CSF is not representative of the whole CSF compartment; its analysis is therefore suitable for excluding massive irritation and inflammation—but not as the only form of treatment monitoring of meningeal carcinoma.
Absolute contraindications. Elevated intracranial pressure with threatened herniation contraindicates lumbar puncture. If raised intracranial pressure is suspected clinically, cranial computed tomography (CCT) must be performed prior to lumbar puncture. A midline shift beneath the cerebral falx and/or an axial increase in pressure with the loss of suprachiasmatic and perimesencephalic (basilar) cisterns (Gower et al., 1987) are absolute contraindications. Superficial or deep inflammation in the puncture area also contraindicates lumbar puncture.
Fig. 5.1 a, b
a Lumbar puncture needles. Top: Quincke needle (yellow, 20 G × 312). Middle and bottom: Sprotte needle (green, 21 G × 312) and guiding trocar.
b Comparison of needle tips. Left: Sprotte needle with conical tip and lateral opening. Right: Quincke needle with sharply ground tip.
Relative contraindications. Coagulopathy is a relative contraindication. Thrombocyte counts lower than 50 000/μL increase the risk of hemorrhage. Thrombocyte counts below 20 000/μL require platelet substitution therapy prior to puncture. In a patient undergoing anticoagulant therapy with heparin, the heparin treatment must be stopped for 2 hours and the partial thromboplastin time (PTT) must have returned to normal. Heparin treatment may be resumed about 2 hours after puncture. If a patient has had effective oral anticoagulation, the prothrombin time (PT, Quick test) should have returned to at least 50% or the international normalized ratio (INR) should be at least 1.5. Acute situations require administration of prothrombin complex (PPSB).
Materials and Methods
Spinal puncture needles. Two different types of cannula are available in various lengths and diameters for cerebrospinal puncture (Fig. 5.1):
• Quincke needle: The Quincke spinal needle has a slant, sharply ground tip. This facilitates percutaneous passage; the needle can be easily advanced and, thanks to its elastic firmness, is easy to guide accurately. This cannula type is usually to be preferred in patients in whom puncture is difficult for anatomical reasons. Its disadvantage is that the relatively large diameter of the tip damages the dura, and a considerable amount of cerebrospinal fluid may leak from the puncture site once the cannula is removed (see “Postlumbar Puncture Syndrome” below).
• Sprotte needle: A widely used alternative is the flexible Sprotte needle, which, with its conical tip with a lateral opening, causes little trauma to the dura. The drawback is that penetration of the skin requires a sharply ground stylet, which serves as a guide for the puncture needle but does make it more difficult to correct the position of the needle.
Pitfalls in the Use of Quincke Needles
The puncture trauma caused by the Quincke needle can be reduced by turning the needle such that the sharply ground opening faces laterally during introduction. This way, the longitudinally running dural fibers are more pushed apart than cut through, and can rapidly close up again when the needle is removed.
CSF collection tubes. The tubes should be sterile, clean, and noncoated, and also crystal-clear so as not to obstruct the macroscopic assessment. A conical bottom of the tube is best for centrifugation because the cell pellet will collect there and the supernatant can be gently poured or pipetted off. Since the tubes are frequently sent away for analysis, tight closure is essential. Glass tubes are unsuitable, not only because of the risk of breakage but also because cells have an increased tendency to adhere to glass. Polystyrene is inert in this respect; it is also the most suitable material for DNA and RNA analysis and for measuring neurotransmitters and cytokines.
Performing the Lumbar Puncture
Patient education. The patient needs to be thoroughly informed about puncture of the subarachnoid space. For formal legal reasons, this must be done at least 24 hours prior to the procedure, except in cases of emergency. As with every invasive procedure, the patient should give consent in writing, either by signing the informed consent form provided (e. g., Perimed form) or without a form.
Positioning. Lumbar puncture may be performed with the patient sitting or lying down. In any case, it is a good idea to have the position supported by an assistant. It is essential that it is a relaxed position for the patient, with as much ventral flexion and stretching of the lumbar spine (arching of the back) as possible and with the legs flexed.
• In the sitting position, it is advisable for the patient to have both legs resting on a raised support (e. g., a chair), pulling the knees in toward the chest and bending the neck forward while grasping the knees with the arms. A pillow may be pushed beneath the thighs for support.
• In lateral decubitus, the patient is helped by another person to keep torso and legs flexed. When performing lumbar puncture on a patient in this position, the bed should be firm in order to avoid “artificial” scoliosis.
Puncture site. Lumbar puncture is performed between the spinal processes of the fourth and fifth lumbar vertebrae (L 4/L 5), or the third and fourth lumbar vertebrae (L 3/L 4). The L 4/L 5 interspace is easy to locate by palpating the right and left iliac crests and imagining a line between them that cuts the spinal process of vertebra L 4. The puncture site lies below this imaginary line, exactly on the midline.
Puncture between vertebrae L 2 and L 3 must be avoided, because the terminal cone of the spinal cord usually reaches down to vertebra L 2 and the risk of injuring the spinal cord is therefore high.
How to Perform a Lumbar Puncture
Mark the puncture site and thoroughly clean the area with a surgical disinfectant. From now on, it is mandatory that you wear sterile gloves and follow aseptic procedures. Anxious and tense patients may receive local anesthesia: after intradermal injection, infiltrate the deeper tissues with 1–2 mL of 1% or 2% lidocaine solution. After 2–3 minutes, stretch the skin around the puncture site using the thumb and index finger (or index and middle fingers) of the left hand and insert the puncture needle at the marked puncture site in slightly cranial direction. To help you guide the puncture needle securely, it makes sense to rest the arm lightly on an armrest. The depth of penetration varies: it is normally about 3.5–4.5 cm (considerably more in obese or muscular patients, less in children). When the needle penetrates the flaval ligament or the dura, you will feel a springy resistance. Then withdraw the stylet, keep it sterile, and let the CSF drain into the collection tubes. If there is no CSF dripping, reinsert the stylet and advance the needle very slowly. If the CSF still does not flow, pull back the needle toward the skin and then correct its direction. As a last resort, you can repeat the lumbar puncture one vertebra higher (at the L 3/L 4 interspace).
If the CSF drips very slowly, you may carefully turn the needle slightly. To check the needle position, have someone apply abdominal pressure; the drip rate should increase noticeably. If the needle position is correct, use the Queckenstedt test to check for free CSF passage. To do this, carefully press the jugular veins—again, the drip rate should increase noticeably.
If the needle is advanced too far it may damage the ventral venous plexus and there will be blood in the CSF. If the needle touches a nerve root, the patient will feel a sharp pain radiating into the leg (“like an electric shock”). If this happens, the needle must be pulled back immediately and its direction corrected medially.
Once the CSF has been collected, reinsert the stylet (still sterile!) into the puncture needle. Remove the needle, compress the puncture site with a sterile swab, and cover it with a sterile swab.
Postpuncture management. After lumbar puncture, it is sensible to have the patient lie prone for 1–2 hours to compress the puncture site and minimize CSF leakage from it. Although controlled studies have not confirmed that postpuncture bed rest after lumbar puncture has a favorable effect in terms of reducing postpuncture headache, in practice it has proven sensible to have several hours of bed rest and to avoid physical strain for at least 24 hours (Dieterich and Brandt, 1985; Cook et al., 1989).
Pitfalls in Performing a Lumbar Puncture
When collecting the CSF, it is important to ensure that neither the rim nor the lid of the collection tube comes into contact with the gloves, as powder particles from the gloves produce artifacts that would interfere with the interpretation of the cytological preparations.
Bloody CSF. If the CSF has the color of flesh or appears bloody, let it drip into at least three tubes (three-tube method) and compare the intensities of the blood admixed. Decreasing color intensities indicate artificial admixture of blood; the bloody CSF should be centrifuged immediately (200–300 g). A clear supernatant also indicates that the puncture fluid was artificially bloody.
Collecting CSF from the Ventricular Catheter
Today, ventricular CSF is collected almost exclusively by closed drainage systems. During the collection, which is usually by means of a three-way stopcock, it is essential that sterile precautions are carefully observed. The volume of CSF between the tip of the catheter in the ventricle and the collection site outside the ventricle is about 2 mL. Hence, the first 2 mL of CSF drawn should be discarded to ensure accurate analysis of the ventricular CSF. Even after the catheter has been clamped, because of the tendency of cell debris to form sediment within the system it is recommended that 5 mL CSF be drawn and discarded.
Complications of Lumbar Puncture
Puncture may cause the transient manifestation of low cerebrospinal pressure syndromes such as radicular irritation and, more commonly, postlumbar puncture headache.
Postlumbar Puncture Syndrome
Symptoms. Postlumbar puncture syndrome is characterized by headache, often accompanied by further vegetative symptoms such as nausea, hypotension, tachycardia, sweating, and orthostatic dysregulation. The symptoms appear with a latency period of several hours, in 80% of cases within 48 hours. Only in rare cases do symptoms last for more than 5 days. The headache mostly improves or disappears completely when the patient lies down. The headache is most prominent in the back of the neck (Schwarz et al., 1999).
Frequency. The frequency of postlumbar puncture headache reported in the literature varies widely; it is between 5% and 60% for diagnostic lumbar puncture and myelography, and between 1% and 40% for spinal anesthesia.
Etiology. Numerous factors favoring the occurrence of postlumbar puncture syndrome have been discussed in the literature; they include age, sex, body mass index (BMI), needle size (Flaatten et al., 1987; Müller et al., 1994; Hafer et al., 1997), needle diameter, direction of puncture, and bed rest after the puncture.
• Age, sex, and BMI: Patients aged below 60 years tend to suffer more often from postpuncture symptoms, and women are more often affected than men. A low BMI seems to favor the symptoms (Kuntz et al., 1992).
• Puncture hole: The decisive factor is the size of the puncture hole, which is determined by the size of the needle (needles > 22G must only be used for special indications) and by the form of the sharp tip (Fig. 5.1 b). With the Sprotte needle, postpuncture headaches develop in only 6.7% of cases; with the Quincke needle, the figure is 18.9% (Carson and Serpell, 1996; 22 G needles in both cases; n = 7580).
• Bed rest: Bed rest after lumbar puncture does not seem to play an important role. However, this view is based mostly on the comparison of at least 4 hours of bed rest versus resting for 24 hours, so that it seems advisable to recommend several hours spent mostly in bed and to avoid heavy physical activity for 1–2 days.
Pathophysiology. Low cerebrospinal pressure develops when more CSF is lost through the puncture site than can be compensated by production of new CSF. This leakage has been demonstrated by scintigraphy and magnetic resonance imaging (MRI). Low cerebrospinal pressure causes irritation of pain-sensitive intracranial structures (blood vessels, meninges, tentorium, and falx) when in the upright standing position. Cerebral vascular dilatation and reduced venous drainage also seem to play a role (Iqbal et al., 1995; Wang and Schmidt, 1997).
Severe complications after lumbar puncture are extremely rare so long as contraindications are heeded.
Potentially, cerebral and spinal herniation, intracranial and spinal hemorrhage, cranial nerve paresis, and inoculation meningitis may occur.
Herniation. The use of imaging procedures to exclude elevated intracranial pressure has minimized the risk of herniation. Relatively, the risk of herniation is highest in acute bacterial meningitis:
• In 19 out of 445 children (4.3%), cerebral herniation was observed (Rennik et al., 1993). In 5 of these 19 children (26%), CCT was normal. In 12 children, the complication occurred within 12 hours after lumbar puncture.
• The autopsies of 27 out of 40 adults who died of bacterial meningitis (Durand et al., 1993) revealed temporal herniation, with 4 of them also showing cerebellar herniation. In 5 patients, herniation occurred within minutes or a few hours after lumbar puncture. The cerebrospinal pressure was documented in 4 patients and was greater than 50 cmH2O.
Spinal cord compression by a space-occupying mass. If there is an extramedullary space-occupying mass compressing the spinal cord, the release of CSF pressure during lumbar puncture may lead to increased pressure on the spinal cord distal to the compression, or it may damage the cauda equina.
Hemorrhage. In very rare cases, lumbar puncture may lead to subdural hematoma and hygroma even in the absence of clotting disturbances, when dural veins rupture due to low cerebrospinal pressure. A similar mechanism is postulated when there is postpuncture subarachnoid hemorrhage from an incidental basal aneurysm. After traumatic vascular puncture, spinal subdural and epidural hematomas and symptoms of meningeal irritation may develop due to hemorrhages from—usually—lateral venous and arterial vessels.
Inoculation meningitis. Bacterial meningitis due to inoculation during lumbar puncture is extremely rare (0.2%) if meticulous attention is paid to maintaining sterility, thorough disinfection, and avoidance of droplet infection.
Cranial nerve palsies. A similar frequency is reported for cranial nerve palsies, the most common one being sixth (abducens) nerve palsy, but the third, fourth, fifth, seventh, and eighth cranial nerves can also be affected. These effects are caused by low CSF pressure and appear after a latency period of 4–14 days; they usually disappear within 4–6 weeks.
Sensory irritation. If the puncture needle touches a nerve root, the sensory irritation eases off after a short time. However, patients often complain about nonspecific back pain for several days after the lumbar puncture.
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