Diagnostic lumbar puncture in adults: animated demonstration
Prepare all the equipment on a sterile trolley surface with an assistant’s help.
Sterile gloves and eye protection; it is now common practice for clinicians to wear face masks while performing a lumbar puncture
Fenestrated sterile drape
Chlorhexidine in alcohol (usually spray or swabstick)
10 mL syringe
25-gauge needle (orange)
23-gauge needle (blue)
1% lidocaine local anaesthetic
Spinal needle (ideally an atraumatic spinal needle)
Introducer needle (may be used if using an atraumatic spinal needle)
Manometer tube with three-way tap
Three clear specimen tubes (or four if you suspect subarachnoid haemorrhage)
One fluoride oxalate blood bottle for glucose (grey-topped)
Raised intracranial pressure: patients may present with:
Reduced level of consciousness
Papilloedema (swelling of the optic disc secondary to raised intracranial pressure).
Performing a lumbar puncture (LP) in a patient with raised intracranial pressure may cause fatal herniation of the brain (coning). Lumbar puncture causes a low pressure shunt to form at the site of the LP where cerebrospinal fluid (CSF) can escape. As the CSF pressure drops in the spinal column, CSF and brain tissue may shift towards the low pressure outlet (the site of the LP) leading to either transtentorial or uncal herniation, and subsequently acute neurological deterioration. Coning can lead to coma and death. Careful selection of patients suitable for lumbar puncture, and the use of computed tomography (CT) scanning of the brain, should minimise the risk of performing an LP. At a minimum, all patients undergoing LP should have fundoscopy to inspect for papilloedema performed prior to the procedure.
Coagulopathy: there is a severe risk of bleeding after lumbar puncture if an uncorrected coagulopathy is present. This includes patients on heparin, warfarin, or other oral anticoagulants, or with clotting defects such as disseminated intravascular coagulation, thrombocytopenia, or haemophilia. When the clotting abnormalities are corrected, a lumbar puncture is no longer contraindicated.
Suspected cauda equina syndrome or central cord compression: cauda equina syndrome can be caused by central disc prolapse, tumour, abscess/tuberculosis, haematoma, or trauma. Symptoms include urinary incontinence or retention (may be painless), faecal incontinence, bilateral leg weakness, and pain. Signs may include bilateral reduced power (lower motor neuron) and sensation, reduced perianal (saddle) sensation, reduced anal tone, and bilateral absent ankle reflexes. It is diagnosed by urgent MRI scan of the spine. Patients with cauda equina syndrome need immediate referral to the orthopaedic team or neurosurgeons for surgery. It is not diagnosed by lumbar puncture.
Allergy to local anaesthetic
Refusal by the patient (if they have the capacity to do so)
Cellulitis/abscess overlying the lumbar spine (risk of introducing infection into the CSF).
Indications for diagnostic lumbar puncture include clinical suspicion of:
Meningitis: bacterial, viral, fungal, or tuberculous infections of the central nervous system (CNS)
Demyelinating diseases (e.g., multiple sclerosis)
Peripheral neuropathies (e.g., acute inflammatory demyelinating polyradiculoneuropathy, the most commonly encountered variant of Guillain-Barré syndrome).
Bleeding: Minor bleeding is common, but the formation of an epidural or spinal haematoma may result in neurological deficits. If this happens, urgently seek a neurosurgical opinion.
Headache: Up to around 35% of patients may experience a headache following an LP. It typically occurs within 48 to 72 hours of the procedure, and may take up to 2 weeks to resolve. Patients describe a constant, dull ache bilaterally that is more frontal than occipital. The most characteristic symptom is positional (orthostatic) exacerbation (i.e., the patient has headache pain when upright but generally no pain when supine). The cause is thought to be continued leakage of CSF from the puncture site, and intracranial hypotension. There is good evidence that using atraumatic needles (also known as pencil-point needles) reduces the incidence of post-dural puncture headaches.   If using a conventional needle, you can help prevent headaches occurring by using the smallest needle that is practical, and by keeping the bevel aligned parallel with the dural fibres. If headache occurs following an LP, manage the patient with simple analgesia, rehydration, and antiemetics if there is associated nausea. For severe or prolonged headaches, ask an anaesthetist about a blood patch, where a small amount of autologous venous blood is injected into the adjacent epidural space to ‘clog up the hole’. An infusion of intravenous caffeine is an option for the treatment of headaches following an LP, but the evidence for this is sparse.
Infection: Adherence to a strict aseptic technique will minimise this risk.
Nerve root pain or paraesthesia: Irritation of nerves or nerve roots by the spinal needle can cause dysaesthesias of the lower extremity. Withdrawing the needle without replacement of the stylet can cause aspiration of a nerve or arachnoid tissue into the epidural space. Replace the stylet before moving the needle to prevent this complication.
Failure to collect CSF (a dry tap): Dry taps generally result from misplacement of the spinal needle, most commonly lateral displacement. This can be corrected by complete withdrawal of the needle, re-evaluation of the patient’s anatomy, and reinsertion in the correct place and at the correct angle. In obese patients the regular spinal needle might be too short, so a longer one may need to be used.
Coning: This serious complication can lead to coma and death. Careful selection of patients suitable for lumbar puncture, and use of CT scanning of the brain, should minimise the risk of performing an LP.
Back pain: A potential complication of LP.
Ensure all sharps are disposed of carefully.
Neurological observations should be performed frequently. A Cochrane systematic review found no benefit in advising routine bed rest for preventing the onset of post-dural puncture headache compared with immediate mobilisation.
Send specimens to the lab with request cards completed and bottles labelled accurately.
Send sample two, the fluoride tube, and the blood sample for biochemistry (protein, glucose, pH). Send samples one and three to microbiology for microscopy, culture, and sensitivity (consider requesting viral culture/polymerase chain reaction). If you suspect a subarachnoid haemorrhage, send the fourth sample in an envelope (to exclude light) to biochemistry for xanthochromia.