Neurolocalisation

Question 1

If an animal had an abnormal gait/ postural reactions in A4L, where could the lesion be depending on spinal reflex results?

Answer 1

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

Question 2

If an animal had an abnormal gait/ postural reactions in the HLs, where could the lesion be depending on spinal reflex results?

Answer 2

Normal to increased - T3–L3 spinal cord segments
Decreased to absent - L4–S3 spinal cord segments,
peripheral nerve roots/nerves of the pelvic limbs

Question 3

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?

Answer 3

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

Question 4

If an animal had an abnormal gait/ postural reactions in one thoracic limb, where could the lesion be depending on spinal reflex results?

Answer 4

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

Question 5

If an animal had an abnormal gait/ postural reactions in one pelvic limb, where could the lesion be depending on spinal reflex results?

Answer 5

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

Question 6

What is the withdrawl test assessing?

Answer 6

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.

Question 7

What would you expect to see with a peripheral neuropathy?

Answer 7

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

Question 8

What are the main differentials for polyneuropathies in the UK?

Answer 8

Inflammatory/immune-mediated polyneuropathies and polyradiculoneuropathy;
 Degenerative polyneuropathies;
 Idiopathic neuropathies;
 Endocrine neuropathies;
 Paraneoplastic neuropathies;
 Toxic neuropathies

Question 9

What are the most common neuro-toxins?

Answer 9

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

Question 10

What are the most common junctionopathies?

Answer 10

Myasthenia Gravis

Botulism

Question 11

What are myopathies characterised by?

Answer 11

muscle weakness, pain(myalgia), cramp and/or failure to relax (myotonia)

Question 12

What inflammatory myopathies are there?

Answer 12

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

Question 13

What does blindness with normal pupils indicate?

Answer 13

lesion of the forebrain; diencephalon, optic radiation, or occipital cortex

Question 14

What does a weak or absent perineal reflex suggest?

Answer 14

lesion affecting the S1 to S3 spinal segments or pudendal nerve.

Question 15

What are the signs of a forebrain lesion?

Answer 15

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

Question 16

What are signs of brainstem lesions?

Answer 16

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

Question 17

What are signs of cerebellar lesions?

Answer 17

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

Question 18

What are signs of vestibular dysfunction?

Answer 18

 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

Question 19

How do you tell central from peripheral lesions?

Answer 19

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

Question 20

When may you get an ipsilateral head tilt?

Answer 20

 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

Question 21

Compare LMN and UMN

Answer 21

• 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)

Question 22

What can you see on a C1-C5 lesion?

Answer 22

 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

Question 23

What can you see with a C6-T2 lesion?

Answer 23

 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

Question 24

What can you see with a T3-L3 lesion?

Answer 24

 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

Question 25

What can you see with an L4-S2 lesion?

Answer 25

 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

Question 26

When may spinal reflexes point to the wrong lesion?

Answer 26

 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

Question 27

Compare a high spinal lesion and polyneuropathy

Answer 27

Spinal reflexes should be reduced in A4L in a neuropathy, not in a spinal lesion (normal or one half of the body reduced)