Diagnostic tests Flashcards
1
Q
What is the single most useful and cost effective test for neuro problems?
A
Neurological examination
2
Q
List some other diagnostic tests used to test neurological function?
A
- Blood test
- Blood Pressure
- Urinalysis
- Faecal analysis
- Imaging
- CSF analysis
- Functional testing
- Biopsy
3
Q
What are some diagnostic challenges in neurology?
A
- CNS is well protected
- Encased in bone (limits imaging modalities and access)
- Elood brain barrier - Lack of functional reserve and poor regenerative capacity limit the use of biopsy techniques due to the possibility of severe, permanent dysfunction
- Combination of specific and non-specific tests
- Diagnosis of exclusion
4
Q
What are the 3 main causes of seizures?
A
- Idiopathic epilepsy
- Structural epilepsy
- Reactive seizures
5
Q
Describe idiopathic epilepsy
A
Genetic or presumed genetic in origin
No inter-ictal neurological signs
6
Q
Describe structural epilepsy
A
- Epileptic seizures which are provoked by intracranial or cerebral pathology
- Concurrent neurological signs usually present
- Inflammatory, neoplastic, traumatic
7
Q
Describe reactive epilepsy
A
- Seizure occurring as a natural response from the normal brain to a transient disturbance in function
- Concurrent neurological signs usually present
- Metabolic or toxic
8
Q
List some DDx for epilepsy (think VITAMIN D)
A
Ischaemic encephalopathy
Meningoencephalitis of unknown origin
Traumatic brain injury, toxicity
Hydrocephalus, congenital abnormality
Hepatic or renal encephalopathy
Idiopathic epilepsy
9
Q
How is idiopathic epilepsy diagnosed?
A
Diagnosis of exclusion
10
Q
Describe the tier 1 confidence interval for investigation of a patient with seizures
A
- 2 or more seizures, 24hrs apart
- Age of onset between 6m and 6y
- Normal inter-ictal examination
- No clinically significant abnormalities on minimum database
- Fasting bile acids +/- NH3
- Family history of IE
11
Q
Describe the tier II confidence interval for investigation of a patient with seizures
A
Unremarkable fasting and post-prandial bile acids
MRI of the brain
CSF analysis
12
Q
Describe the tier III confidence interval for investigation of a patient with seizures
A
Ictal or inter-ictal EEG abnormalities
13
Q
What would you assess on the blood test of a patient with seizures?
A
- Haematology and biochemistry (incl electrolytes, Ca and Glu)
- Liver function testing (Bile acid stimulation test, Ammonia)
- +/- Endocrine function tests (Fructosamine, insulin levels (insulioma)
- +/-Clotting function
14
Q
In which cases is urinalysis useful in neurological patients?
A
- Cerebrovascular accident
- To assess for an underlying cause
- Cushings
- Hyperproteinuria (PLN or hypertension) - Discospondylosis - Identify if UTI is underlying cause of infection
- Paraparesis/ urinary dysfunction - Increased risk of UTI
15
Q
What is the imaging modality of choice for the brain?
A
MRI
16
Q
What are the disadvantages of MRI?
A
Anaesthesia
High cost
Limited availability
Artefacts (metal objects)
17
Q
When is CSF analysis used in neurological patients?
A
Most useful to exclude inflammatory or infectious conditions
- Can also be abnormal in neoplastic or traumatic conditions
18
Q
What are the limitations of CSF analysis?
A
- May not be abnormal due to location (if parenchymal) or nature of the lesion (non-exfoliating)
- Can have non-specific changes
- Cell counts correlate with exfoliation into CSF not severity of disease
19
Q
When is CSF analysis contraindicated?
A
- Increased intracranial pressure - mental status, pupil size and PLR, abnormal postures, vestibular eye movement
- Coagulopathy
- Cervical (cerebellomedullary cistern) collection contraindicated in some conditions (Chiari-like malformation, AA instability, cervical trauma)
20
Q
What equipment is needed to perform CSF analysis?
A
Spinal needle
Collection pots (sterile plain +/-EDTA, extra for culture)
Clippers, scrub, gloves
21
Q
What are the 2 sites of CSF analysis?
A
Cerebellomedullary cistern or lumbar cistern - caudal to lesion
22
Q
What must not be done when collecting CSF?
A
Do not aspirate!
23
Q
What volume of CSF is sampled?
A
Maximum volume - 1ml/5kg
24
Q
Describe the normal features of CSF on analysis
A
- Gross - clear
- Cell count
- RBC 0/μl
- WBC <5/μl - Protein (via Lab spectrophotometer)
- Cervical <30mg/dl
- Lumbar <45mg/dl
25
How does blood contamination affect a CSF sample?
Falsely increases WBC count (1/μl per 500 RBC) and protein (~1mg/dl per 1000 RBC)
26
How is albuminocytological dissociation seen on CSF analysis?
- Increased protein without increased WBC
- Non specific: extradural compression (disc disease), neoplasia, infection, vasculitis, trauma, syringomyelia, degenerative myelopathy
27
What does pleocytosis mean?
The presence of an abnormally large number of lymphocytes in the cerebrospinal fluid.
28
List some causes of a neutrophilic pleocytosis
- Granulomatous meningoencephalomyelitis
- Bacterial meningitis
- Fungal
- FIP
- Post myelography, haemorrhage, neoplasia, trauma
29
List some causes of a mononuclear pleocytosis
- Granulomatous meningoencephalomyelitis
- CNS lymphoma
- Viral
- Bacterial meningitis
30
List some causes of a mixed pleocytosis
- Granulomatous meningoencephalomyelitis
- Non-inflammatory disease e.g. infarct
- Bacterial meningitis
- Protozoal
- Fungal
31
List some causes of an eosinophilic pleocytosis
- Eosinophilic meningoencephalomyelitis
- Parasitic
- Protozoal
- Fungal
32
What is electroencephalography and when is it used?
Assess forebrain activity
Identification of seizure activity
- Ictal = at the time of the seizure
- Inter-ictal = between seizures
33
List the DDx for spinal neurolocalisation
- Ischaemic myelopathy
- Meningomyelitis of unknown origin (MUO), discospondylitis, Toxoplasmosis, Neosporosis, FIP, FeLV, SRMA*
- Fracture and luxation, traumatic disc extrusion
- AA instability
- Chiari-like malformation, vertebral abnormalities
- spinal/ vertebral neoplasia
– Intervertebral disc disease (IVDD) type I and II, cervical stenotic myelopathy (CSM), degenerative lumbosacral stenosis (DLSS), degenerative myelopathy (DM)
34
Describe the use of blood tests for patients with spinal disease
+/- infectious disease testing
Haematology and biochemistry (incl electrolytes, Ca and Glu)
C-reactive protein (CRP) (SRMA)
35
Which agents might affect the spinal cord in dogs?
Neospora caninum
Toxoplasma gondii
Angiostrongylus vasorum (SNAP blood test, Baermann faecal)
36
Which agents might affect the spinal cord in cats?
Toxoplasma gondii
FeLV
FIV
FIP (FCoV)
37
Radiography is most useful for what type of abnormality?
Bony
38
Describe the use of CT for spinal lesions?
Excellent for bony detail
Rapid acquisition of images
Contrast can be used – intra-thecal (myelography) or IV
Useful for
- Trauma patients
- Surgical planning of stabilisation
39
What is the imaging modality of choice for spinal lesions?
MRI
40
Myelography is useful for what types of lesions?
Extradural or bony lesions
41
What must be done before myelography?
CSF analysis
42
How is myelography carried out?
- Inject 0.3ml/kg contrast (Iohexol)
- Lumbar or cervical medullary cistern
- Minimum of 2ml and maximum of 0.45ml/kg
- Keep head elevated
43
When is myelography contraindicated?
- Coagulopathy
- Spinal instability
- Cloudy/turbid CSF (suggestive of inflammatory process)
44
What are the main risks of myelography?
- Seizures
- Neurological deterioration
- Dysrhythmia's
- Respiratory arrest
- Infection
- Chemical myelitis
- Death
45
What are the risks of MRI?
Anaesthesia
Movement/heating of implants
Foreign bodies
46
Describe an extradural finding on myelography
- Axial displacement of 1 or more contrast columns
- Columns often thin or partially disrupted at the site of the lesion
- MOST COMMON
- Ddx – IVD herniation, Vertebral stenosis, Neoplasia
47
Describe an intradural/extramedullary finding on myelography
- Filling defect WITHIN the contrast column
- ‘Golf tee’ sign or widening of subarachnoid space due to a arachnoid diverticulum
- Ddx – Neoplasia (meningioma, peripheral nerve sheath tumour), Arachnoid diverticulum
48
Describe an intramedullary finding on myelography
Divergence of contrast columns
Ddx –Neoplasia, Acute ischaemic myelopathy, Contusion, Haemorrhage, Myelitis
49
In which conditions is CSF analysis indicated?
- Steroid responsive meningitis-arteritis (SRMA)
- Meningomyelitis of unknown origin
- Bacterial myelitis/ meningitis
- Empyema
- Discospondylitis
50
List some DDx for neuromuscular disease
- Polymyositis (immune mediated or infectious), acquired myasthenia gravis, polyradiculoneuritis, Botulism, Tick paralysis, protozoal (Toxo/Neo), Viral (FeLV/ FIV)
- focal trauma, organophosphate, lead, vincristine
- Addisons, Cushings, hypokalaemia, Diabetes, insulinoma
- thymoma, paraneoplastic
- muscular dystrophy, neuroaxonal dystrophy
51
Which blood tests would you want to perform for neuromuscular disease?
- Haematology and biochemistry (incl electrolytes, Ca2+ and glucose)
- T4/TSH
- Fructosamine/ insulin
- ACTH stimulation test
- Immune mediated disease: Specific autoantibodies
52
When is imaging used in neuromuscular disease?
To check for concurrent disease
Radiography
Abdominal ultrasound
CT
53
What is the neostigmine response test and when is it used?
- For Junctionopathies - acquired and some congenital Myasthenia gravis
- IV administration of neostigmine
- Prolongs action of acetylcholine at the NMJ
- Slower onset but longer duration of action compared to edrophonium
54
Describe the use of MRI for neuromuscular disease
Good for assessment of muscle and nerve
Contrast generally required
55
Describe the uses of electrodiagnostics for neuromuscular disease
Identifying denervated muscles
Extent and severity
Treatment monitoring
56
What is motor nerve conduction velocity used for?
- Assess conduction along a nerve – used to investigate suspected peripheral neuropathies
- Stimulate a motor nerve at a minimum of 2 sites and record the evoked electrical activity (CMAP)
57
What is a muscle biopsy used for?
Sample affected muscle (EMG to help identify)
- Area where muscle fibres are orientated in a single direction
- Distant from tendons
58
When a nerve is biopsied how can you minimise defects?
Third to half of the nerve width and ~1cm in length
Keep straight, but not stretched
Fix in formalin
59
Name the hearing test used for deafness
Brainstem Auditory Evoked Response
60
What are the signs of dysautonomia in cats
Cough, vomit/retch, anorexia, third eyelid protrusion, mydriatic unresponsive pupils, dry eye and nose, constipation, incontinence, bradycardia, megaoesophagus
61
What are the signs of dysautonomia in dogs?
Cough, vomit/retch, anorexia, hypersalivation, diarrhoea or constipation. Dry mucous membranes, dry eye and nose, mydriasis or anisocoria, megaoesophagus, bradycardia, decreased anal tone, atonic bladder
62
How is dysautonomia diagnosed?
Mainly based on the constellation of clinical signs seen
Definitive diagnosis requires PME
63
What are the signs of Horners syndrome?
Miosis, ptosis of upper eyelid, protrusion 3rd eyelid, enophthalmus, conjunctival hyperaemia
