Page 4 - Clinical Connections - Autumn 2022

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Page 4 - Clinical Connections - Autumn 2022
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ºÚÁÏÉç RESEARCH    STUDY    VETERINARY SERVICES       ºÚÁÏÉç.AC.UK
             Equine
            PAIN(T) IN THE NECK – CT MYELOGRAPHY

            OF THE CERVICAL SPINE


            Maty Looijen, Equine Resident

                  linical  problems  associated  with   cerebrospinal fluid protects the spinal cord).   compression within the neck.
                  the  cervical  spine  in  horses  are   It is historically used to identify spinal cord   There  are  a  variety  reasons  for
            C common. They involve a wide variety   compression causing ataxia. However, the   compression,   but   cervical   vertebral
            of symptoms, including neurological deficits   myelographic contrast column abnormalities   malformation  is  one  of  the  most  common
            (e.g.  ataxia,  dysmetria,  paresis),  neck   associated  with  the  abnormality  of  the   causes  of  ataxia  in  sport  horses.  It  is
            pain  and  stiffness,  and  gait  abnormalities.   vertebral  canal  can  only  be  accessed   thought to be a developmental abnormality
            Neurological abnormalities most commonly   in  a  single  dorsoventral  orientation  on   caused  by  genetic  predispositions  and
            result  from  spinal  cord  abnormalities  (e.g.   radiographs.         environmental  influences,  such  as  diet,
            infection/inflammatory conditions, neoplasia                            growth rate, workload and trauma
            or compression).                                                          The  pathophysiology  of  the  disease
              Investigation of horses with neck problems                            involves  spinal  cord  compression  due  to
            can involve a neurological and/or lameness                              malformation  and/or  malarticulation  of  the
            examination,  blood  tests,  a  cerebrospinal                           vertebrae,  static  or  dynamic  instability  of
            fluid  tap  or  an  EMG  (electromyography                              the  vertebral  canal,  soft  tissue  or  bony
            –  electronic  muscle  stimulant  test).                                changes  of  the  cervical  vertebral  bodies,
            Radiography and ultrasonography may be                                  their articulations and associated soft tissue
            helpful  tools  in  investigating  the  cervical   Figure 2: Transverse CT image at the level of   structures.
                                                 C4-C5, on the left without myelogram and on
            spine,  however  they  lack  sensitivity  and   the right with myelogram
            specificity.
              Radiographic   examinations   are   Advanced imaging
            commonly performed for the evaluation of   MRI  and  CT  are  much  better  modalities
            potential bone abnormalities and alignment   to  evaluate  and  further  identify  the  cause
            of  the  vertebrae.  If  abnormal  findings  are   of  spinal  cord  compression,  due  to  their
            seen,  a  further  challenge  is  to  distinguish   3D  compilation  of  the  anatomy.  MRI  of
            their clinical significance. This is similar for   the  cervical  spine  in  horses  is  currently
            ultrasonographic  examinations,  which  are   not available, due to the limited size of the   Figure 3: Transverse CT image at the level
            commonly performed to further investigate   magnet. CT, however, has become popular   of C6-C7 showing moderate reduction of the
                                                                                     dorsal contrast column indicating focal spinal
            the soft tissues associated with the cervical   over the last decade. Additionally, the spinal   cord compression
            spine.  The  neck  has  a  complex  anatomy,   cord can be highlighted by CT myelography,
            and  radiography  or  ultrasonography  are   which  now  can  be  investigated  in  a   Furthermore,  we  have  to  distinguish
            not  able  to  visualise  details  of  the  deeper   lateromedial  and  craniocaudal  direction   abnormalities  which  originate  from  either
            structures  (e.g.  the  spinal  cord).  Both   as  well  as  dorsoventral.  By  visualising   degenerative  or  acquired  lesions,  such  as
            modalities therefore often lack the possibility   lesions  accurately,  we  can  improve  our   osteoarthritis,   fractures,   (sub)luxations,
            to establish a final diagnosis.     understanding of cervical spine pathologies,   intervertebral  disc  disease  or  neoplasias.
                                                treat  lesions  more  precisely  and  develop   Osteoarthritis of the articular process joints
                                                new treatments.                     does not necessarily implement compression
                                                  A CT myelography of the neck at the ºÚÁÏÉç   on  the  spinal  cord,  this  depends  on  their
                                                is  performed  under  general  anaesthesia   size  and  shape  in  relation  the  position  of
                                                to  avoid  side  effects  and  improve  image   the spinal cord in the vertebral canal. Lastly,
                                                quality. Contrast medium is injected into the   soft tissue abnormalities commonly found in
                                                subarachnoid space, at the atlanto-occipital   relation to spinal cord compression involve
                                                articulation (figure 1).            synovial  cysts,  epidural  haematomata  or
                                                  It diffuses in the vertebral canal caudally   ligamentum  flavum  thickening  –  all  which
                                                and thereby outlines the spinal cord (figure   we  now  diagnose  with  the  help  of  CT
                                                2). Interpretation is done by our radiologists   myelography.
                                                via  subjective  evaluation  and  objective
                                                measurements,  indicating  compression
              Figure 1: Atlanto-occipital injection of the   of  the  spinal  cord  and/or  the  surrounding
              subarachnoid space performed under general
              anaesthesia, with the horse in the CT  contrast column. In contrast to radiographic
                                                myelography,  CT  myelography  (figure  3)
              Radiographic   myelography   of   the   can  establish  differences  in  height  and
            cervical  spine  is  a  technique  where  an   width  of  the  contrast  column  and  spinal
            extradural  contrast  agent  is  injected   cord. CT myelography helps us to localise     For equine referrals, please call: 01707
            into  the  subarachnoid  space  (where  the   and  definitively  diagnose  of  spinal  cord   666297
                                                                                           Email:
                                                                                         equinehospital@rvc.ac.uk

            4   Autumn 2022
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