TECHNIQUE

Cerebrospinal Fluid Tap in Rabbits (Disease Investigation & Management - Treatment and Care)

Summary Information
Type of technique Health & Management / Disease Investigation & Management / Techniques:
Synonyms and Keywords CSF fluid tap
Description
Atlanto-occipital (Cisterna magna) approach

This is the best site for CSF tap. (B601.2.w2, B602.14.w14, J29.16.w7)

  • The CSF is collected from the cisterna magna (B602.14.w14, J29.16.w7) (foramen magnum) (P113.2005.w2)
  • This site can also be used for myelography. (J29.16.w7)

Procedure:

  • Anaesthetise the rabbit
    • General anaesthesia (NOT sedation) is essential for this procedure. (B601.2.w2, B602.14.w14, J213.2.w3)
    • Placement of an endotracheal tube will minimise the risk of airway obstruction during positioning for the procedure. (B601.2.w2, J213.2.w3)
      • However, there is a risk of the endotracheal tube kinking and cutting off the airway during positioning. (V.w65)
  • Place in lateral recumbency and flex the head towards the chest (B601.2.w2, B602.14.w14, J213.2.w3, P113.2005.w2)
    • Be careful not to obstruct the airway. (B601.2.w2, J213.2.w3)
    • Flex the head to no more than 90 degrees to the neck. (J29.16.w7)
  • Clip and aseptically prepare the site on the nape of the neck
    • From the third cervical vertebra cranially to the occipital protuberance and extending laterally past the margins of the atlas. (B601.2.w2, B602.14.w14)
  • Locate the landmarks for needle placement
    1. The occipital protuberance (B602.14.w14)
      • (A point 2 mm caudal to the occipital protuberance). (B601.2.w2, J213.2.w3)
    2. The cranial margins of the wings of the atlas. (B601.2.w2, B602.14.w14, J213.2.w3)

    The needle needs to be inserted approximately midway between these two points. (B601.2.w2, B602.14.w14, J213.2.w3)

    • Or halfway between the occipital protruberance and the craniodorsal tip of the dorsal spine of C2 (the axis), which is just cranial to the cranial margins of the wings of the atlas (C1). (J29.16.w7)
  • Insert the spinal needle midline at 90 degrees to the vertebral column (B601.2.w2)
    • Use a 22 gauge, 38 mm (1.5 inch) spinal needle. (B601.2.w2, J213.2.w3) 
      • 1.5 to 3.5 inch spinal needle (B602.14.w14)
      • The stylet is left in place. (B601.2.w2)
      • The stylet is often not needed because of the relatively small size of many rabbits. (B602.14.w14)
    • 25 gauge 5/8 inch needle. (P113.2005.w2)
    • 23-gauge, 1.25 inch hypodermic needle. (J29.16.w7)
    • Do not have a syringe attached: movement can cause meningeal laceration. (P113.2005.w2)
  • Slowly advance the needle
    • Advance only one to two millimetres at a time directed towards the nose of the rabbit. (B601.2.w2, B602.14.w14, J213.2.w3)
    • When the needle penetrates the dura and the subarachnoid membranes, a slight "pop" will be felt. (B601.2.w2, J213.2.w3)
      • Appearance of CSF at the hub of the needle confirms correct placement. Loss of resistance may or may not be felt as the needle penetrates into the subarachnoid space. (J29.16.w7)
    • If the needle hits bone: redirect the needle cranially or caudally. If it is not possible to redirect the needle then remove it and reassess the anatomical landmarks. (B601.2.w2)
  • Confirm correct placement by removing the stylet and checking for CSF in the hub (B601.2.w2)
    • If measuring the intracranial pressure: attach a manometer. (B601.2.w2, J213.2.w3)
    • If collecting a sample of CSF:
      • Let the fluid drip from the needle into a sterile container; this can take a bit of time especially in small rabbits. (B601.2.w2, J213.2.w3)
        • Preferably into a plastic container, since leucocytes adhere to glass. (J213.2.w3)
        • A red-top collection tube (no anticoagulant) or a tube coated with EDTA may be used. (J29.16.w7)
      • NEVER use a syringe to apply negative pressure to collect the sample. (B601.2.w2, J213.2.w3)
        • Very slow very gentle aspiration may be carried out using a 1 mL syringe and collecting at no faster than 1 mL per 30 seconds. (J29.16.w7)
      • Up to 0.5 mL (up to 1.0 mL in giant breeds) may be collected). (J29.16.w7)
  • Analyse the CSF immediately
    • The fluid should ideally be analysed within thirty to sixty minutes. (B601.2.w2)
    • Refrigerate the sample if immediate analysis is not possible, to reduce degradation of cells in the sample. (J213.2.w3)
Lumbar approach

This is the best site for injection of contrast agent for myelography, but only a few drops of CSF can be collected from this site. (J29.16.w7)

Procedure:

  • Anaesthetise the rabbit
    • General anaesthesia (NOT sedation) is essential for this procedure. (B601.2.w2, B602.14.w14)
  • Clip and aseptically prepare the site over the lumbar vertebrae cranial to the pelvis (B601.2.w2, J29.16.w7)
  • Place in lateral recumbency with the trunk flexed (B601.2.w2)
    • Foam cushions can be placed beneath the lumbar region and between the limbs to achieve true lateral positioning. (B601.2.w2)
    • OR place the rabbit in sternal recumbency. (J29.16.w7)
  • Insert the needle
    • Use a 38 mm (one and a half inch) 22 gauge spinal needle. (B601.2.w2) or a 23-gauge 1.25 inch hypodermic needle. (J29.16.w7)
      • The epidural space is 0.75 - 2.5 cm beneath the skin. (J213.2.w3)
    • Insert "at the cranial edge of the dorsal spinous process of vertebra L6 at a 45-degree angle, with the needle point directed cranially". (B601.2.w2)
    • Insert just cranial to L6, nearly perpendicular to the spine. (J29.16.w7)
  • Slowly pass the needle in a smooth manner (B601.2.w2)
    • A sample can be collected from the dorsal subarachnoid space; however, it is usually necessary to continue through the spinal cord and into the ventral subarachnoid (note: the tail and pelvic limbs may twitch as the spinal cord is penetrated). (B601.2.w2, J29.16.w7)
  • Remove the stylet and check for CSF in the hub (B601.2.w2)
  • Let the fluid drip from the needle into a sterile container
    • This can take a bit of time especially in small rabbits. (B601.2.w2)
    • NEVER use a syringe to apply negative pressure to collect the sample. (B601.2.w2)
  • Analyse the CSF immediately
    • The fluid should ideally be analysed within thirty to sixty minutes. (B601.2.w2)
Appropriate Use (?)
  • Collection of cerebrospinal fluid. (B601.2.w2)
    • This can be useful for the differential diagnosis of neurological disease. (B600.3.w3, B602.14.w14)
    • Culture may be useful for diagnosis of listeriosis. (J213.2.w3)
    • Cytological and biochemical analysis can be carried out. (J29.16.w7)
  • Measurement of intracranial pressure. (B601.2.w2)
  • Myelography. (B601.2.w2, J29.16.w7) See: Imaging in Lagomorph Diagnosis and Treatment
Lumbar approach
  • This is the best site for injection of contrast agent for myelography. (J29.16.w7)
  • This site can also be used for collection of small amounts of CSF. (J29.16.w7)
Atlanto-occipital (Cisterna magna) approach 
  • This is the best site for collection of CSF. (B601.2.w2, B602.14.w14)
  • This site can also be used for myelography. (J29.16.w7)
Notes
  • Spinal needles have a shorter bevel than normal hypodermic needles, therefore extradural leakage is less likely when a spinal needle is used. However, because of the stylet, there is the need for repeated stabilisation of the needle and removal of the stylet to check for CSF appearing. (J29.16.w7)
  • Appropriate restraint
    • General anaesthesia (NOT sedation) is essential for this procedure. (B601.2.w2, B602.14.w14)
  • Sterile equipment
    • The needle must remain sterile; only handle it at the hub.
    • Wear sterile gloves.
  • Disposal of used needles
    • The used spinal needle needs to be disposed of in a sharps container.
Complications/ Limitations / Risk
General complications / risks of cerebrospinal fluid tap
  • Meningeal laceration.(P113.2005.w2)
    • The risk is reduced by not attaching a syringe to the needle. (P113.2005.w2)
  • Cerebral or cerebellar herniation (B601.2.w2, J29.16.w7)
    • This risk is increased if these is increased intracranial pressure (ICP). In cats, increased ICP has been noted with ketamine anaesthesia. Although there is no data suggesting increased ICP in rabbits anaesthetised with ketamine, it may be preferable not to use this agent in anaesthetics where this technique is to be performed. (J29.16.w7)
  • Central nervous system haemorrhage (B601.2.w2)
  • Seizure: can occur post-myelography. Control with diazepam and provide supportive care. (J29.16.w7)
  • Brainstem trauma (B601.2.w2)
  • Spinal cord trauma (B601.2.w2)
  • NEVER use a syringe to apply negative pressure to collect the sample; let the fluid drip from the needle into a sterile container. This can take a bit of time especially in small rabbits. (B601.2.w2)
    • A syringe can be used to take fluid from the needle hub a drop at a time - not applying suction through the needle. (P113.2005.w2)
  • The sample may be contaminated with peripheral blood if small blood vessels are ruptured during the collection procedure. (J213.2.w3, J495.32.w3)
  • The cerebrospinal fluid (CSF) should ideally be analysed within thirty to sixty minutes of collection. (B601.2.w2)
    • Refrigerate the sample if immediate analysis is not possible, to reduce degradation of cells in the sample. (J213.2.w3)
Lumbar approach
  • Only a few drops of CSF can be collected from this site. (J29.16.w7)
Atlanto-occipital (Cisterna magna) approach 
  • Obstruction of the airway
    • There is a risk of obstructing the airway of the rabbit when the head is flexed towards the chest during the procedure. Placement of an endotracheal tube will minimise this risk but care must be taken to ensure a patent airway. (B601.2.w2)
  • Contacting bone during the insertion of the spinal needle
    • If this occurs then redirect the needle cranially or caudally. If it is not possible to redirect the needle then remove it and reassess the anatomical landmarks. (B601.2.w2)
Equipment / Chemicals required and Suppliers
  • A 22 gauge, 38 mm (1.5 inch) spinal needle. (B601.2.w2)
    • 1.5 to 3.5 inch spinal needle (B602.14.w14)
    • 25 gauge 5/8 inch needle. (P113.2005.w2)
    • 23 gauge (0.6 mm) 1.25 inch (30 mm) needle. (J29.16.w7)
  • Sterile gloves
  • Sterile plastic container for the collection of the CSF. (J213.2.w3)
    • A red-top collection tube (no anticoagulant) or a tube coated with EDTA (ethylenediamine tatraacetic acid) may be used. (J29.16.w7)
Expertise level / Ease of Use This procedure should be carried out by an experienced veterinarian.
Cost / Availability
  • Cost of the equipment is relatively inexpensive.
  • Cost of analysis of CSF sample.
Legal and Ethical Considerations In some countries there may be legislation restricting the use of this type of technique to licensed veterinarians. For example in the UK: "The Veterinary Surgeons Act 1966 (Section 19) provides, subject to a number of exceptions, that only registered members of the Royal College of Veterinary Surgeons may practice veterinary surgery." (see: LCofC1 - RCVS Guide to Professional Conduct 2000 - Treatment of Animals by Non-Veterinary Surgeons).).
Author Nikki Fox BVSc MRCVS (V.w103)
Referee Debra Bourne MA VetMB PhD MRCVS (V.w5); John Chitty BVetMed CertZooMed MRCVS (V.w65); Frances Harcourt-Brown BVSc FRCVS (V.w140)
References B600.3.w3, B601.2.w2, B602.14.w14, B611.3.w3, J29.16.w7, J213.2.w3, P113.2005.w2

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