Neurolocalisation Flashcards
What are the functions of the forebrain?
- Thinking!!!!
- Behaviour
- Vision, hearing
- Conscious perception of touch, pain, temperature, body position
- Fine motor activity
What are some signs of forebrain lesions?
- Disorientation, confusion, depression
- Contralateral blindness
- Normalish gait, circling, head turn, head pressing
- Decreased postural responses in contralateral limbs
- Seizures!!
- Behavioural changes
What are the functions of the brainstem?
- Basic functions that keep us alive!
- No decision making processes
- Regulatory centres for cardiovascular system and breathing
What are some signs of brainstem lesions?
- Depression, stupor, coma
- Cranial nerve deficits
- Vestibular signs
- Paresis of all or ipsilateral limbs
- Decerebrate rigidity
- Decreased postural responses
- Respiratory or cardiac abnormalities
What are the functions of the cerebellum
- Control motor activity!
- Regulator not initiator!
- Coordinates and smoothes out movement induced by UMN system
- Inhibits the vestibular system
What are some signs of cerebellar lesions
- Normal mentation
- Ipsilateral abnormal menace
- Vestibular signs
- Ataxia, broad stance, hypermetria
- Intention tremors
- Decerebellate rigidity
- Delayed initiation and then often hypermetric postural responses
What are the functions of the vestibular system?
- Maintain balance!
- Maintain position of the eyes, neck, trunk and limbs relative to position and movement of the head at all times
Where are vestibular receptors and nuclei located?
- Receptors in inner ear transmit information to Cn VIII (Peripheral)
- Vestibular nuclei in brainstem under some control from cerebellum (Central)
What are the main signs of vestibular system lesions?
- Head tilt (contralateral in cerebellar lesions)
- Nystagmus
- Ataxia with leaning and falling, less commonly tight circling
- Positional strabismus
- Paradoxical head tilt
How can the lesion causing nystagmus be localised?
- Try and figure out which is the fast phase and which is the slow phase (direction they are going in)
- Lesion on the side of the slower phase
Describe the signs of central vestibular lesions
- Possible paresis
- Possible proprioceptive defects
- CN V-XII may be affected
- Vertical nystagmus
Describe the signs of peripheral vestibular lesions
- No paresis or proprioceptive defects
- Alert mentation
- Cranial nerve VII may be affected
- Horizontal nystagmus
What is a paradoxical head tilt?
Head tilt contralateral to lesion
+ Some signs of cerebellar disease
If reflexes are normal to increased in both the TLs and PLs where is the spinal lesion located?
C1-C5
If the reflexes are reduced in the TLs but normal to increased in the PLs where is the spinal lesion located?
C6-T2
If the reflexes are reduced in the PLs but normal in the TLs where is the spinal lesion located?
L4-S3
If the reflexes are normal in the TLs but normal to increased in the PLs where is the spinal lesion located?
T3-L3
How can the spinal cord be divided into two based on which limbs are affected?
- C1-T2 – all legs affected
* T3-S3 – pelvic limbs affected
What are the 3 severities of spinal lesions to show how they are affected?
- Ataxia
- Paresis
- Paralysis
What is an UMN?
Efferent neuron that originates in the brain and synapses with a LMN, modulating its activity
What is a LMN?
- Efferent neuron connecting CNS with effector organ (muscle or gland)
- Cell body in spinal cord GM or within the nucleus of a CN and its axon becomes the PN
Where are lower motor neurones located for TLS and PLs?
TLs = cervical intumescence ( C6-T2 ) PLs = lumbosacral intumescence (L4-S3)
Describe the path of the reflex
Skin stimulus detected by pain receptors -> sensory neurone -> relay neurone (grey mater) -> motor neurone -> muscle fibres
What are the signs of a C1-C5 spinal lesion?
- Tetra or hemiparesis/plegia
- Normal spinal reflexes in all limbs
- Horner’s syndrome, respiratory difficulties, urinary retention
What are the signs of a C6-T2 spinal lesion?
- Tetra or hemiparesis/plegia; possible
- Reduced spinal reflexes in thoracic limbs
- Reduced muscle tone, muscle atrophy in TLs
- Possibly reduced/absent cutaneous trunci reflex
- Nerve root signature, Horner’s syndrome, respiratory difficulties, urinary retention
What are the signs of a T3-L3 spinal lesion?
- Paraparesis/plegia (normal TLs)
- Normal muscle tone, no muscle atrophy
- Normal spinal reflexes in all limbs
- Possibly reduced/absent cutaneous trunci reflex caudal to the spinal lesion
- Urinary retention
What are the signs of a L4-S3 spinal lesion?
- Paraparesis/plegia; possible monoparesis
- Reduced spinal reflexes in pelvic limbs, reduced anal tone and perineal reflex in more caudal lesions, reduced muscle tone, muscle atrophy in pelvic limbs
- Nerve root signature, reduced tail tone sensation in caudal lesions, urinary retention in more cranial lesions or urinary
- +/- faecal incontinence in caudal lesions
Give some examples of how interpreting spinal lesions can lead to the wrong localisation
- Pain can cause withdrawal to appear reduced
- If lesion very subtle (e.g. just causing spinal pain), may not be severe enough to affect reflex pathway
- Patellar reflex can become reduced in old age
- Spinal shock in acute cases
Describe spinal shock
Flaccid paralysis with loss of spinal reflexes caudal to lesion in acute SCI
Temporary (hours):
- Anal sphincter reflex 15 min
- Patellar reflex between 30 min and 2h
- Flexor withdrawal reflexes up to 12 hours
Neuropathies are caused by?
Peripheral nerve lesions
Describe the main features of neuropathies
- Reduced spinal or cranial nerve reflexes
- Can affect 1 nerve e.g. trigeminal tumour, facial paralysis, radial nerve paralysis
- Can affect a group of nerves e.g. brachial plexus avulsion or tumour
- Can affect most/all nerves (polyneuropathy)
What are some signs of neuropathies affecting groups of nerves?
- Monoparesis/lameness
- Reduced reflexes in affected limb
- Possibly unilateral cut-off cutaneous trunci
- Possibly Horner’s
What are some signs of neuropathies affecting most/all nerves?
- Flaccid paresis, with little movement
- Hallmark is that spinal reflexes are reduced in the front and back limbs as none of the LMNs are working
- Dogs will have a recued palpebral reflex, lost their bark
What are some causes of neuropathies affecting most/all nerves?
- Inflammatory (idiopathic polyradiculoneuritis)
- Metabolic (Diabetes mellitus, hypothyroidism, etc)
- Degenerative (breed specific)
Junctionopathies are lesions occurring at…
The neuromuscular junction:
- Axon terminal
- Synaptic cleft
- Endplate of skeletal muscle
What is a myopathy?
Any disease that affects the muscles that control voluntary movement in the body
What are the signs of myopathies?
- Generalised weakness and/or exercise intolerance – stiff stilted gait; neck ventroflexion
- Usually no proprioceptive deficits (unless extreme weakness)
- Usually normal spinal reflexes (unless significant muscle atrophy)
- Variable muscle tone and bulk
What are 3 causes of generalised myopathies?
- Inherited/degenerative
- Inflammatory/infectious
- Metabolic
VITAMIND is an acronym for neurological causes, what are they?
- Vascular
- Inflammatory, infectious
- Trauma, toxic
- Anomalous
- Metabolic
- Idiopathic
- Neoplasia, nutritional
- Degenerative
What other factors needsto be considered when describing and analysing neuro lesions
- Lateral or symmetrical
- Focal multifocal or diffuse
- Acute, subacute or chronic
- Progressive, static, improving, waxing and waning
- Painful?
A peracute/acute neuro lesions indicates which 3 causes?
- Vascular
- Trauma/toxic
- Idiopathic (vestibular)
A subacute neuro lesions indicates which 2 causes?
- Inflammatory/infectious
- Degenerative (IVDD)
A chronic neuro lesions indicates which possible causes?
- Degenerative
- Neoplastic
- Metabolic/nutritional
- Anomalous
- Inflammatory/infectious
A progressive neuro lesions indicates which 3 possible causes?
- Neoplastic
- Inflammatory/infectious
- Degenerative
A static/improving neuro lesions indicates which 3 possible causes?
- Vascular
- Trauma/toxic
- Idiopathic (vestibular)
A waxing/waning neuro lesions indicates which cause?
Metabolic
A focal and lateralised neuro lesion indicates which causes?
Neoplasia
Vascular
A multifocal neuro lesion indicates which causes?
- Inflammatory/infectious (most likely)
- Neoplasia
- Vascular
- Trauma
A diffuse and symmetrical neuro lesion indicates which causes?
Metabolic
Toxic
