Neurolocalisation Flashcards
If an animal had an abnormal gait/ postural reactions in A4L, where could the lesion be depending on spinal reflex results?
Normal to increased in all 4 limbs - Brainstem or C1–C5 spinal cord segments
Decreased to absent in all 4 limbs - Generalised polyneuropathy/ junctionopathy/myopathy
Decreased to absent in thoracic limbs; normal to increased in pelvic limbs - C6–T2 spinal cord segments
If an animal had an abnormal gait/ postural reactions in the HLs, where could the lesion be depending on spinal reflex results?
Normal to increased - T3–L3 spinal cord segments
Decreased to absent - L4–S3 spinal cord segments,
peripheral nerve roots/nerves of the pelvic limbs
If an animal had an abnormal gait/ postural reactions in the thoracic and pelvic limbs on the same side of the body, where could the lesion be depending on spinal reflex results?
Normal to increased in thoracic and pelvic limbs - Ipsilateral brainstem or C1–C5 spinal cord segments
Decreased to absent in thoracic limbs; normal to increased in pelvic limbs - Ipsilateral C6–T2 spinal cord
segments
If an animal had an abnormal gait/ postural reactions in one thoracic limb, where could the lesion be depending on spinal reflex results?
Normal to increased - Ipsilateral brainstem or C1–C5 spinal cord segments
Decreased to absent Ipsilateral C6–T2 spinal cord segments, or the nerve roots, brachial plexus or peripheral nerves affecting that limb
If an animal had an abnormal gait/ postural reactions in one pelvic limb, where could the lesion be depending on spinal reflex results?
Normal to increased - Ipsilateral T3–L3 spinal cord
segments
Decreased to absent Ipsilateral L4–S3 spinal cord
segments, or the nerve roots or peripheral nerves affecting that limb
What is the withdrawl test assessing?
In the thoracic limb, the withdrawal reflex evaluates the integrity of the C6–T2 spinal cord segments (and associated nerve roots), brachial plexus, peripheral nerves (radial, axillary, musculocutaneous, median and ulnar) and the muscles innervated. In the pelvic limb, this reflex evaluates the integrity of the L4–S1 spinal cord segments (and associated nerve roots), the femoral and sciatic nerves, and the muscles innervated.
What would you expect to see with a peripheral neuropathy?
flaccid paresis/paralysis of one or more limbs, decreased limb muscle tone, rapid appendicular muscle atrophy (usually within 10 to 14 days of the onset of signs) and decreased spinal reflexes in all limbs
What are the main differentials for polyneuropathies in the UK?
Inflammatory/immune-mediated polyneuropathies and polyradiculoneuropathy; Degenerative polyneuropathies; Idiopathic neuropathies; Endocrine neuropathies; Paraneoplastic neuropathies; Toxic neuropathies
What are the most common neuro-toxins?
thallium, lead, mercury, organo-phosphates, hexacarbons and a number of other heavy metals. Algal neurotoxins may also be occasionally implicated in dogs exposed to large blooms of blue-green algae
What are the most common junctionopathies?
Myasthenia Gravis
Botulism
What are myopathies characterised by?
muscle weakness, pain(myalgia), cramp and/or failure to relax (myotonia)
What inflammatory myopathies are there?
infection with T gondii, N caninum, Leptospira icterohaemorrhagiae and Clostri-dium species, idiopathic polymyositis
inflammatory myopathy as part of a generalised diseaseprocess, such as systemic lupus erythematosus, dermato-myositis or as a pre-neoplastic myopathy
What does blindness with normal pupils indicate?
lesion of the forebrain; diencephalon, optic radiation, or occipital cortex
What does a weak or absent perineal reflex suggest?
lesion affecting the S1 to S3 spinal segments or pudendal nerve.
What are the signs of a forebrain lesion?
altered mental status (disorientation, depression)
contralateral blindness (decreased menace response with normal PLR)
normal gait
circling (usually ipsilateral), head turn, head pressing, pacing
↓postural responses in contralateral limbs
SEIZURES,
behavioural changes, hemi-neglect syndrome
What are signs of brainstem lesions?
depression, stupor, coma cranial nerve deficits (III – XII) paresis of all or ipsilateral limbs possible vestibular signs possibly decerebrate rigidity ↓postural responses in ipsilateral or all limbs respiratory or cardiac abnormalities
What are signs of cerebellar lesions?
normal mentation
ipsilateral menace response deficit with normal vision
possibly vestibular signs
possibly decerebellate rigidity
intention tremors
truncal ataxia, broad-based stance, hypermetria
delayed initiation and then often hypermetric postural responses
What are signs of vestibular dysfunction?
ipsilateral head tilt
nystagmus (horizontal, rotatory or vertical) - described by direction of the fast phase - lesion on the side of the slower phase…
ataxia with leaning and falling, less commonly tight circling
positional strabismus
How do you tell central from peripheral lesions?
Central - possible proprioceptive deficits, CN V-XII can be affected, nystagmus can be verticle, horizontal or rotary and may change direction, possible paresis, Horner’s is rare, possible decrease in mentation
Peripheral - no proprioceptive issues or paresis, only facial nerve can be affected, horizontal or rotary nystagmus, Horner’s possible, no mentation changes
When may you get an ipsilateral head tilt?
flocculonodular lobe or caudal cerebellar peduncle lesion (both cerebellar)
head tilt contralateral to lesion
+ some signs of cerebellar disease
cerebellum inhibits ipsilateral vestibular nuclei → desinhibition:
inhibition of ipsilateral extensors
facilitation of contralateral extensors
Compare LMN and UMN
- UMN - efferent neuron that originates in brain and synapses with a LMN, modulating its activity
- LMN - efferent neuron connecting CNS with effector organ (muscle or gland)
- LMNs for the TLs are in the cervical intumescence (C6-T2) for the PLs are in the lumbosacral intumescence (L4-S3)
What can you see on a C1-C5 lesion?
tetra or hemiparesis/plegia
deficits in all 4 limbs or ipsilateral ones
normal spinal reflexes
normal muscle tone, no muscle atrophy
possible Horner’s syndrome; respiratory difficulties; urinary retention
What can you see with a C6-T2 lesion?
tetra or hemiparesis/plegia; possible thoracic monoparesis
deficits in all 4 limbs, ipsilateral ones or just 1 thoracic
reduced muscle tone, muscle atrophy
reduced spinal reflexes in thoracic limbs
possibly reduced/absent cutaneous trunci reflex
possible nerve root signature; possible Horner’s syndrome; respiratory difficulties; urinary retention
What can you see with a T3-L3 lesion?
paraparesis/plegia (normal thoracic limbs)
deficits in pelvic limbs
normal muscle tone, no muscle atrophy
normal spinal reflexes
reduced/absent cutaneous trunci reflex caudal to lesion
possible urinary retention
What can you see with an L4-S2 lesion?
paraparesis/plegia; possible pelvic monoparesis
deficits in all pelvic limbs or just 1 pelvic
reduced muscle tone, muscle atrophy in pelvic limbs
reduced spinal reflexes in pelvic limbs, reduced anal tone and perineal reflex in more caudal lesions
possible nerve root signature; possible tail tone sensation in more caudal lesions; possible urinary retention in more cranial lesions or urinary +/- faecal incontinence in more caudal lesions
When may spinal reflexes point to the wrong lesion?
pain can cause withdrawal to appear reduced (as
it is painful to flex limb and animals with stop half way)
if lesion very subtle (e.g. just causing spinal pain), will not affect the reflex pathway
spinal shock in acute cases
the patellar reflex can become reduced in old age
Compare a high spinal lesion and polyneuropathy
Spinal reflexes should be reduced in A4L in a neuropathy, not in a spinal lesion (normal or one half of the body reduced)
