Ch 27 neurodiagnostics Flashcards
name parts of motor neuron unit
1 - motor neuron
2 - Ventral nerve root
3 - Spinal nerve
4 - Plexus
5 - motor nerve fibre
6 - NMJs
7 - muscle fibre
(A - sensory nerve fibre, B -spinal ganglion, C - Dorsal nerve root)
What are the three categories of clinical signs of neuromuscular disorders?
Generalisaed or localised muscle weakness
Functional manifestations (paresis, weakness, regur, dysphagia etc)
Physical manifectations (atrophy, hypertrophy, skeletal deformities)
Classification of Neuromuscular Dz (4)
- Neuropathies – disorders of neuron, including cell body, axon, Schwann cell, and myelin
- Junctionopathies – disorders of MS transmission
- Myopathies – disorders of muscle fibers
- Neuromyopathies – disorders of both neurons and muscle fibers
What are the principle signs of autonomic neuropathy?
Anisocoria or mydriasis
Decreased tear secretion
Decreased saliva
Bradycardia
Clinical Signs of Neuromuscular Disorders
mypathic, neuropathic syndrome
- LMN signs – muscle weakness – lameness, paresis/paralysis, gait abnormalities, exercise-related weakness, dysphagia, regurgitation, dyspnea, and dysphonia
- Myopathic syndrome - generalized weakness, exercise intolerance, stiff and stilted gait, body/limb tremors,
- Neuropathic syndrome - flaccid paresis/paralysis of innervated structures (e.g., limb/facial muscles, esophagus, larynx, anal sphincter),31 neurogenic muscle atrophy, reduced/absent reflexes and muscle tone, and muscle fasciculations
What is required in a minimum database specific for NMD
CK - skeletal muscle damage
Electrolytes - muscle weakmesss (K, Ca)
Lactate -exercise myopathy
Urinalysis for myoglobinuria
Thyroid screening
Serum ACh-Receptor Antibiodies - myasthenia gravis
How do you interpret CK in regards to NMD?
Large/ >10,000: muscular dystrophies, necrotising myopathies and inflammatory myopathies
Mild-to-mod: inflammatory myopathies and in some degenerative myopathies
Mod-to-marked elevations in anorectic cats
How can you distinguish myoglobinuria from haemoglobinuria?
ammonium sulfate precipitation test
2 main specific tests for NMD?
Electrodiagnostic testing
Muscle and nerve biopsies
What is electromyography?
The detection and characteristion of electrical activity (potentials) recorded from a patients muscles
List the 4 types of normal spontaneous muscle activity which can be seen on electromyography
Insertional activity - stimulated by insertion of the needle
Miniature end-plate potentials - when needle is in close proximity to NMJ
End-plate spikes - a single, normal myofibre depolarises completely
Motor unit action potentials - normal muscle which is not completely at rest
List the three forms of abnormal spontaneous activity seen on electromyography
“Fibs” and “Sharps” - spontaneously firing, hypersensitive, single myofibers as a result of destabilisation of the sarcolemmal membrane
Complex repetitive discharges - polyphasic waves of uniform frequency, configuration and amplituse. Due to spontaneous discharge of a myofiber and its surrounding myofibers in near synchrony.
Myotonic potentials - Waxing and waning frequencies
What are nerve conduction studies?
the recording and analysis of electrical waveforms of biologic origin elicited in response to electrical or physiologic stimuli
What nerves are most suitable for nerve conduction studies?
Fibular, tibial, ulnar and radial
What are some criteria when selecting a muscle for biopsy?
Affected by the disease, but functional
Easily identified, minimal surgical approach with muscle fibres orientated in a single direction
Low morbidity
Previous interpretive experience
(Preferred biopsy sites have been published)
Remote to tendon insertions and aponeuroses
remote to previous arrea of teting (reduce artifact)
What are the commonly chosen muscles for biopsy?
Lateral head of the triceps (distal third)
Vastus lateralis (distal third)
Cranial tibial (proximal third)
Temporalis muscles
suture is placed through the nerve to separate nerve fascicles from the major part of the nerve.
What are the two options for performing a muscle biopsy?
Percutaneous
Open
What muscle biopsy is recommended for congenital myaesthenis gravis?
external intercostal muscle, exhibiting decreased numbers of ACh receptors
What fixative is used for electron microscopy samples?
Glutaraldehyde
criteria when selecting a nerve biopsy
Affected by the disease
Easily biopsies with low morbidity
Has an estabilished normal
Innervates a muscle which is routinely biopsied
Common fibular nerve most common!
What fixatives are used for nerve biopsies?
10% formalin
2.5% glutaraldehyde
Assessment of the cutaneous
trunci muscle reflex in healthy cats:
comparison of results acquired by
clinicians and cat owners
Chyong-Ying Tsai 2022
vs
These findings suggest that elicitation of the CTR in the cat can be unreliable. Further prospective controlled studies are warranted to determine whether continued inclusion of the CTR in feline neurologic examinations is justified. 2020
Conclusions and relevance The overall normal response rate of the CTMR in healthy feline subjects was low when
performed by a clinician, regardless of the method applied. Conversely, a high percentage of normal responses
was obtained by cat owners performing CTMR at home, potentially indicating the impact of stress on the CTMR performance.
Transient depression of pelvic limb reflexes
in dogs with acute focal thoracolumbar myelopathy
Hodshon 2018
Prospective study.
ANIMALS
34 dogs.
based on on MRI or CT images
Nine (5 with compressive IVDH and all 4 with FCE or ANNPE)
of 34 (26%) dogs were classified as affected. Patellar reflexes were depressed in 2 of 9 affected dogs. The median time required for withdrawal reflexes to return to normal was 60 hours (range, 12 to 156 hours).
Value of thoracic and abdominal screening in dogs with neurological signs
Destri 2021
206 dogs
Review of imaging findings in dogs with neurological signs but no thoracic or abdominal signs
2-5% clinically important abnormlities found, unrelated to the CNs dz
Evaluation of the Idexx ProCyte Dx® for analysis of canine cerebrospinal fluid
Romero-Fernandez 2020
good sensitivity (92.6%) and moderate specificity
(67.4%) for total nucleated cell count when compared to the reference standard
differential cell counts
where available, appeared to correlate well with the external laboratory manual differential cell counts,
with a good-to-high agreement in 25 of 26 samples (96.2%).
Clinical Significance: The Idexx ProCyte Dx® analyser performed well
Rapid in-house method of CSF analysis utilising sedimentation direct from the spinal needle
C. Hare 2019
onto slide.
The new method had high sensitivity (89%) and specificity (100%) for the detection of laboratory-defined pleocytosis. Agreement on the type of pleocytosis was good.
Clinical Significance: Clinically useful information can be obtained from CSF samples in a patient-side setting without additional equipment. This technique may be of benefit if little fluid is available or if logistical constraints limit the availability of rapid specialist results.
