Neurosurgery Flashcards
When is spinal decompression surgery indicated?
- Tumour
- IVDD
What are the indications for spinal fusion surgery?
- Instability of the spine: atlanto-axial subluxation, Wobbler (dynamic instability), IVDD
- Fracture
- Conditions where ongoing instability may cause ongoing trauma of the spinal cord
Name the surgical options for spinal decompression
- Dorsal laminectomy
- Hemilaminectomy
- Ventral slot
What is a dorsal laminectomy?
Removal of the roof of vertebra
What is a hemilaminectomy?
Removal of the side of vertebra
What is a ventral slot?
Drill up through bone to access ventral part of spinal cord
Explain the basic principles of spinal decompressive surgery regarding maintenance of spinal integrity
- Depends on intervertebral disc and 2 articular facet joints (sit above spinal cord except on C1 and C2)
- Biomechanically can remove one facet joint without expected clinical consequences
- If damage 2, then may encounter problems of stability as only the disc is holding spine together
what are teh treatment options for spinal fractures?
- Fixation if stability is compromised
- Decompression if compression is the cause of pathology (e.g. bone fragment of dislocation compressing spinal cord)
- Conservative therapy if stable
Explain how spinal stability can be assessed based on vertebral compartments
- Vertebra can be divided into 3 compartments
- Dorsal, middle and ventral
- Instability determined as more than one compartment being compromised
What is included in the dorsal compartment of vertebrae?
Lamina and dorsal ligaments
What is included in the middle compartment of the vertebrae?
- Dorsal longitudinal ligament
- Dorsal annulus
- Dorsal portion of vertebral body
What is included in the ventral compartment of the vertebrae?
- Ventral longitudinal ligament
- Ventral annulus
- Ventral portion of the vertebral body
Describe the conservative therapy for spinal fracture
- Strict cage rest 5-6 weeks, minimise mobilisation of spine
- Other management as appropriate: analgesia, bladder management, prevention of bed sores, motivational therapy, physiotherapy as appropriate
Describe the main concern regarding hemilaminectomies in the cervical spine
- Rarely performed in this area
- Vertebral artery runs in canal through vertebrae C1-6
- ## Drilling through this would be fatal
Describe the advantages of a hemilaminectomy
- Allows lateral approach to the spinal cord
- Allows exposure ventral to the spinal cord
Describe the disadvantages of a hemilaminectomy
- Requires lateralisation i.e. need to know what side lesion is on, if midline then can perform on either side, but not both
- Risk of damage to nerve roots/spinal nerves via intervertebral foramina opening
- Risk of damage to ventral venous plexus
Describe the advantages of a dorsal laminectomy
- Useful for bilateral lesions
- Can be performed anywhere along spine except C1-2
- Relatively easy soft tissue approach
- Avoids ventral venous plexus
Describe the disadvantages of a dorsal laminectomy
- Width of laminectomy limited by the articular facet joints (varies along spine)
- Limited exposure lateral and ventral to the spinal cord
- Deep hole in the thoracic region
- Only good for lesion on top of, or down both sides of the spinal cord
Describe the anatomical basis for a ventral approach to the cervical spinal column
- Through vertebral bodies, centred on the intervertebral disc
- Need to avoid previous surgical sites for recurring IVDD
- Easy access if in neck region
- Drill up through vertebral body to get access to vertebral canal
Describe the advantages of a ventral slot surgery
- Allows access to the ventral aspect of the spinal cana
- Easy approach (if know anatomy) down to the bones
Describe the disadvantages of the ventral slot surgery
- Limited access, visibility
- Only feasible in cervical region
- Significant risk of haemorrhage (may drill through ventral venous plexus)
- Post operative morbidity
Discuss the use of ventral slot surgery in a Doberman
- Common require this surgery
- can be significant risk as high risk of drilling through ventral venous plexus
- BUT Doberman also prone to Von Willebrand’s disease
What are the internal spinal fixation options?
- Orthopaedic procedures e.g. plates
- Pins and methylmethacrylate
What are the external spinal fixation options?
Spinal casting only
Discuss external fixation of the spine using spinal casting
- For relatively stable fractures in good alignment
- Plaster cast immobilises bones enough to allow natural healing of bones
- More simple, more natural vs internal fix.
- U shaped casts, strapped on
- More expensive long term due to nursing requirements
- Difficult to do successfully
- Cervical stabilisation easier than thoracolumbar
What are the main disadvantages of spinal casting?
- High nursing requirement: urination, frequent bandage changes, sores likely to develop under bandage as dog walks
- Sedation for each bandage change
- Risk of tracheal/oesophageal occlusion with cervical casts, post op swelling can then prove fatal
Outline the requirements for post-operative management of a tetraplegic/paretic or paraparetic/plegic patient
- Empty bladder
- Analgesia
- Cage rest
- Physiotherapy
- Food
Discuss the use of physiotherapy post-operatively for spinal treatment
- Which type depends on pathological processing occurring
- E.g. hydrotherapy poor choice for unstable spine
- If stable, want to get limbs moving asap
- Need to ensure dog is able to see/go outside at least once a day
Discuss the anaesthesia for spinal injury patients
- Intrinsically nothing special
- Care re. blood pressure
- Reduction in blood pressure leads to reduced perfusion of the spinal cord and brain, needs to be maintained
- Reduced blood pressure leads to avascular necrosis of the spinal cord which leads to worse outcome and potential absence of recovery
Discuss the use of steorids in spinal injury patients
- Contraindicated in acute cases
- May be useful in chronic cases
Outline the principles of intracranial surgery
- Feasible in some circumstances e.g. large tumour removal
- Will inevitably cause iatrogenic intracranial trauma
- Anaesthesia requires careful control and consideration of ICP
