Equis ISSN 2398-2977

CSF: collection - ultrasound-guided antlato-occipital

Synonym(s): Ultrasound-guided atlanto-occipital collection of cerebrospinal fluid

Contributor(s): Graham Munroe, Rachael Conwell

Introduction

  • The collection of cerebrospinal fluid (CSF) in horses is a well recognized additional aid in the investigation of neurological disease.
  • It can be collected from the cisternal or the lumbosacral site.
  • Until recently it has been usually obtained via lumbosacral centesis in the standing horse, with or without ultrasound guidance CSF: collection. Limitations include: the need to use a very long needle (15 cm/6 in); the potential for contamination with blood (this may be decreased by using ultrasound-guidance); the potential for an non-representative sample when assessing cranial disease due to the long distance between the sampling point and disease source; and finally, the potential for injury to the clinician, who is close to the hind limbs when carrying out the procedure, if the horse reacts violently.
  • Obtaining a CSF sample more cranially has some advantages; cerebellomedullary, atlanto-occipital and cervical C1/C2 centesis have been described. Cerebellomedullary centesis has been reported in standing horses but is technically difficult. Standing cervical C1/C2 collection was reported in 2012. Atlanto-occipital centesis, with or without ultrasound guidance, had only been reported in patients under general anesthesia Anesthesia: general - overview up until 2014 when it was described in the standing adult horse.
  • The use of general anesthesia is of major concern in ataxic and intracranial lesion patients as there is an increased risk of injury upon recovery, therefore standing collection techniques avoid this risk.
  • Ultrasound guidance has been used to allow the proper placement of contrast medium into the subarachnoid space for myelography and to minimize the risk of needle placement into the subdural space or within the spinal cord.

Uses

  • Collection of CSF samples in standing patients from between the occipital part of the caudal head and the first cervical vertebra (C1).

Advantages

  • Can be used to obtain CSF in standing patients with no reported detrimental effects.
  • Blood contamination is minimized with this technique. This is particularly important where EPM testing is to be undertaken as small amounts of blood contamination can interfere with the test.
  • Rapid technique with increased accuracy of needle placement into the dorsal aspect of the subarachnoid space.
  • Penetration of the spinal cord, nerve roots and vertebral vessels is avoided by the orientation of the needle and the ultrasound guidance.
  • Potentially more representative sample for evaluation of cranial disease.

Disadvantages

  • A sudden drop in CSF pressure created during the withdrawal of CSF can result in tentorial herniation and subsequent convulsions.
  • May be contraindicated if there are clinical signs of brain herniation.
  • Possible risk of trauma to spinal cord if horse lifts head suddenly during the procedure.

Requirements

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Preparation

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Procedure

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Aftercare

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Outcomes

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Prognosis

  • Determined by underlying neurological disease.

Further Reading


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