Neuroimaging Flashcards
What are the aims of imaging in neurological cases?
- Narrow down, confirm, rule-out differential diagnoses
- Surgical planning
- Staging
- Prognosis
- Co-morbidities
- Extra-neurological causes
- Treatment response
When does imaging come in as a part of the investigation of neurological disease?
- Clinical examination
- Neurological examination
- Neurolocalisation & problem list
- Initial list of differential diagnoses
- THEN Diagnostic test, including imaging - imaging cannot replace any of the previous steps
List 3 neurological conditions that would have expected imaging changes allowing you to confirm a diagnosis
- Paraparesis
- Change in mentation (neoplasia)
- Post traumatic signs (fractures)
Describe the use of radiography for neurological cases
- Associated with bone lesions (fractures, luxation, discospondylitis, tumours?, otitis media)
- Rule out of bone-associated lesions
- Limited value for intracranial conditions
- Limited value for spinal “soft tissue” conditions unless myelography
When is aural radiography indicated?
Chronic otitis
Peripheral vestibular syndrome
Facial nerve paralysis
Horner’s syndrome
-> Middle ear disease
What is better than radiography for aural imaging?
CT
Which radiographic projections are useful for aural imaging?
- Lateral (but superimposition of bullae)
- Open mouth rostrocaudal (might be difficult in brachycephalic dogs)
- Allows identification of L or R bullae
- Oblique views
Describe the use of radiography for spinal imaging and how to get the best image
- Lateral and ventrodorsal (spine closer to the plate) radiographs to identify location correctly
- Importance of straight positioning (use pads under neck and lumbar region)
- Exposure in expiratory pause (to prevent motion artefacts)
- In multiple sections to avoid geometric distortion
- Centre on region of interest
Describe ‘horses heads’ seen on radiography
Intervertebral foramina (lumbar) = window into the vertebral canal
Which dog breed is most commonly known for their mineralised intervertebral discs?
Dachshund
What are the 5 radiographic signs?
- Shape (Think about symmetry)
- Margination (Are the cortical margins intact?)
- Opacity (Radiolucent or sclerotic?)
- Location (Alignment with adjacent vertebrae – luxation)
- Number (Monostotic, polyostotic = one bone or multiple bones)
Describe the main features of Atlanto-axial subluxation
- Congenital malformation of the dens or excessive laxity of the ligaments
- Toy breeds
- Less common after trauma
Describe the normal angulation and abnormal angulation seen in Atlanto-axial subluxation
- Marked angulation between atlas and axis is abnormal
- The dorsal margin of the vertebral canal of the axis and atlas should form a continuous straight line
- The angle becomes much more acute in subluxation
Describe fractures of the vertebrae
- Traumatic versus pathological
- Traumatic fracture often also subluxated
- Pathological fracture often compression fractures - additionally lysis or periosteal reaction
What is discospondylitis?
Infection of an intervertebral disc and osteomyelitis of adjacent endplates
- Changes to the disc not visible
- Changes to the endplates after ~3 weeks
- Often lumbosacral junction
What are the 4 main features of discospondylitis?
- Irregular endplates: lysis
- Periosteal reaction (new bone)
- Sclerosis next to lysis
- Soft tissue swelling ventrally
Myelography allows you to assess?
For soft tissue lesions within the vertebral canal
Determine location, shape, size
Soft tissue lesions in the vertical canal can be in which 3 locations?
Extradural
Intradural – extramedullary
Intramedullary
How is myelography performed?
- Injection of iodinated positive contrast medium into subarachnoid space
- Followed by orthogonal radiographs
- Outlines surface of spinal cord
- Not a Day 1 competence
- Potentially severe complications!
- Interpretation can be challenging
When is CT indicated as an imaging modality?
Suspected bone lesion
- Trauma
- Abnormal anatomy
Otitis media
Large intracranial tumours?
Peripheral nerve tumours?
Concurrent disease
When is MRI indicated as an imaging modality?
- Most things BUT not bone
- Brain and spinal cord parenchymal lesions
- Seizures
- Intervertebral disc extrusions
- Muscular lesion
List the main features of MRI
- No ionising radiation
- VERY strong magnetic fields!
- Safety is great concern
- Strict rules for access and what can enter the room
- Fatal accidents possible
- MRI physics are complex
- Excellent soft tissue resolution
- Different “sequences” and contrast medium (gadolinium) can highlight differences between tissues
- Radiological signs still used for lesion characterisation (“signal intensity” instead of “opacity”)
Compare degenerative disease and discospondylitis
- Degenerative intervertebral disc disease is common
- Usually asymptomatic
- But can precede disc herniation or predispose for infections
- If severe differentiation can be difficult (use other modalities)
- Degenerative disc disease has smooth end plates unlike discospondylitis
What is Spondylosis deformans
Typical bridging or spur-like new bone arising from the ventral aspect of the endplates
Not clinically significant (until proven otherwise)
Very rare
