NEUROLOGICAL PRINCIPLES Flashcards
Signs of UMN lesions
Weakness - extensors weaker than flexors in the arms, flexors weaker than extensors in legs
Hyper-reflexia + positive Babinski sign
Spasticity
Slight or absent muscle wasting
No fasciculations
Signs of LMN lesions?
Marked atrophy
Fasciculations
Reduced tone
Weakness/decreased power
Hyporeflexia + Absent plantar response
Ascending spinal tracts?
Dorsal column medial lemniscal
Posterior spinocerebellar
Anterior spinocerebellar
Spinal-olivary
Anterior and lateral spinothalamic
Descending spinal tracts?
Anterior and lateral corticospinal
Medial and lateral reticulospinal
Rubrospinal
Vestibulospinal
Tectospinal
Function of dorsal column pathway?
Fine touch, proprioception and vibration
Function of anterior spinothalamic tract?
Crude touch and pressure
Function of lateral spinothalamic tract?
Pain and temperature
Types of spinocerebellar tracts?
Dorsal spinocerebellar tract.
Ventral spinocerebellar tract.
Posterior external arcuate fibers.
Rostral spinocerebellar tract.
Posterior spinocerebellar tract function?
Proprioceptive information from lower limb and trunk
Anterior spinocerebellar tract function?
Proprioception from the lower limbs
Cuneocerebellar tract function?
Proprioceptive infromation from the upper limbs
Which ascending pathways are conscious?
Dorsal column
Spinothalamic
Which ascending pathways are unconscious?
Spinocerebellar
Spinotectal
Spinoreticular
Spinal-olivary
Function of spinotectal pathway?
enables us to orient our eyes and move our head toward the relevant stimulus
Function of spino-olivary pathway?
Proprioceptive information from muscles and tendons
Function of spinoreticular tract?
To increase our level of arousal in response to pain or temperature
Neuronal pathway of dorsal column medial lemniscal tract?
First order neuron - peripheral axons recieve signal inputs from skin and enter the Fasciculis gracilis (if <T6) or fasciculis cuneatus (if T6 or above). They synapse in the nucleus gracilis or nucleus cuneatus in the medulla respectively
Second order neuron - axons from nucleus gracilis and nucleus cuneatus decussate within the medulla and then travel up the contralateral medial lemniscus to the thalamus
Third order neuron - axons from the thalamus go through the internal capsule and terminate in the primary somatosensory cortex of the post central gyrus
Neuronal pathway of the spinothalamic tract?
First order neurones - arise from the sensory receptors in the periphery, enter the spinal cord via dorsal grey horn. They ascend 1-2 vertebral levels and then synapse at the substantia gelatinosa in the tip of the dorsal horn
Second order neurones - these fibres decussate and now form 2 distinct tracts the anterior and lateral spinothalamic tract. These run alongside each other and travel superiorly within the spinal cord, synapsing in the thalamus
Third order neurones - they ascend from the ventral posterolateral nucleus of the thalamus, travel through the internal capsule and terminate at the sensory cortex
What are the 2 main groups of descending (motor) spinal tracts?
Pyramidal and extrapyramidal
What are pyramidal spinal tracts?
Tracts that originate in the cerebral cortex carrying motor fibres to the spinal cord and brainstem
Responsible for voluntary control of the musculature of the body and face
They travel through the pyramids
What are extrapyramidal tracts?
Spinal tracts that originate in the brainstem, carrying motor fibres to the spinal cord
Responsible for the involuntary and automatic control of all musculature e.g. tone and balance
Dont travel through pyramids
How many neurones are typically involved in descending spinal tracts?
2 - UMN and LMN
What are the 2 pyramidal spinal tracts?
Corticospinal tracts and corticobulbar tracts
Function of corticospinal tracts?
Voluntary motor control of the body and limbs
Structure of the corticospinal tracts?
Cerebral cortex receives input from primary motor cortex, premotor cortex, supplementary motor area and some input from somatosensory area
Neurones converge and descend through the internal capsule
They then pass through thr midbrain, pons and enter the medulla
In the caudal part of the medulla the tract divides into the lateral and anterior corticospinal tract
80% - Fibres within the lateral corticospinal tract decussate an then descend into the spinal cord, terminating in the ventral horn at all segmental levels. From the ventral horn, LMN go on to supply the muscles of the body
20% - Fibres within the anterior corticospinal tract remain ipsilateral, descending into the spinal cord. They decussate and terminate in the ventral horn of the cervical and upper thoracic segmental levels
Anterior vs lateral corticospinal tract functions?
Anterior - movement of muscles of trunk, neck and shoulders
Lateral - movement of muscles in limbs
Corticobulbar tracts function?
Innervates muscles of the face, head and neck
Structure of corticobulbar tract?
Primary motor cortex receives a range of inputs and these fibres converge and pass through the internal capsule to the brainstem
Neurones terminate on the motor nuclei of CN where they synapse with LMN which carry the motor signals to the muscles of the face and neck
Does the corticobulbar tract supply unilateral or bilateral innervation to motor neurones?
Bilateral
Except for:
CN VII
CN XII
Both only provide contralateral innervation
Which extrapyramidal tracts decussate and therefore provide contralateral innervation?
Rubrospinal and tectospinal
Function of vestibulospinal tracts?
Vestibular nuclei receptive input from organs of balance and tracts convey this information to the spinal cord, where it remains ipsilateral
Fibres control balance and posture by innervating anti-gravity muscles via LMN
What are anti-gravity muscles?
Flexors of arms
Extensors of legs
2 reticulospinal tracts?
Medial and lateral
Where does the medial reticulospinal tract rise from and what is its function?
Arises from the pins
Facilitates voluntary movements and increases muscle tone
Where does the lateral reticulospinal tract rise from and what is its function?
Arises from the medulla
Inhibits voluntary movements and reduces muscle tone
Where does the Rubrospinal tract rise from and what is its function?
Originates from the red nucleus in the midbrain
Thought to play a role in the fine control of hand movements
(Remember with rubrix cube)
Where does the tectospinal tract rise from and what is its function?
Arises in superior colliculus of the midbrain which receives input from optic nerves
Coordinates movements of the head in relation to vision stimuli
Does the dorsal spinocerebellar tract decussate?
No
Does the anterior spinocerebellar tract decussate?
Yes twice so it remains ipsilateral
Signs of UMN lesion?
Flexion of UL and extension of LL
Hypertonia - clasp knife spasticity
Pyramidal weakness
Brisk reflexes
Scissor or hemiplegic gait
What is pyramidal weakness?
What causes it?
Weakness that preferentially spares the antigravity muscles e.g. weakness of upper limb extensors and lower limb flexors
Caused by UMN lesions
What is clasp knife spasticity?
This is an initial resistance when attempting passive movement of the extremities, followed by a rapid decrease in resistance
Commonly due to UMN lesions
What is scissoring gait?
Aka diplegic gait
Knees and thighs pressed together or crossing each other whilst walking. In an attempt to overcome this adduction, the pt circumducts both legs during the swing phase
Cased by spasticity in the hip adductors
Associated with UMN lesions
Bilateral!
What is hemiplegic gait?
gait in which the leg is held stiffly and abducted with each step and swung around to the ground in front, forming a semicircle
Caused by UMN lesions
Unilateral!
If a patient has all four limbs affected, where in the spinal cord is the lesion likely?
Cervical region
If a patient has only the lower limbs affected, where in the spinal cord is the lesion likely?
In the thoracic region
If a patient has respiratory diffiuclties, where in the spinal cord is a lesion likely?
Above C3
Causes of spinal cord lesions?
MS
Neuromyelitis optica
Infections
Subacute combined degeneration of the cord
Spinal ischaemia e.g. stroke
Intrinsic neoplasm
Hereditary spastic paraparesis
Fracture
Prolapse disc
Haematoma
Osteomyelitis or discitis
Abscess
Metastatic disease
Myeloma
Which cranial nerves are not considered peripheral nerves?
CN I and CN II
These are considered extensions of CNS
What gait is commonly seen in LMN lesions?
High stepping or foot-drop gait
Symptoms and signs of cerebellar disorders
DANISH:
Dysdiadochokinesia, dysmetria, ‘drunk’ appearance
Ataxia
Nystagmus
Intention tremor
Slurred speech
Hypotonia and hyporeflexia
Causes of cerebellar syndrome?
Friedreich’s ataxia, ataxic telangiectasia
neoplastic: cerebellar haemangioma
stroke
alcohol
multiple sclerosis
hypothyroidism
drugs: phenytoin, lead poisoning
paraneoplastic e.g. secondary to lung cancer
Functions of the frontal lobe?
Intellectual function e.g. planning, problem solving, decision making, judgement
Praxis (the ability to perform skilled or learned movements)
Inhibition
Bladder continence
Saccadic eye movements (quick simultaneous movements of both eyes that shifts the centre of gaze from 1 part of the visual field to another)
Motor function
Expression of language (Brocas area)
Functions of the temporal lobe?
Encoding of memories
Processing auditory, visual, olfactory and language sensory input
Functions of the parietal lobe?
The major sensory processing hub for the brain
Recieve and process sensory input e.g. touch, pressure, heat, pain, smell, sight
Functions of the occipital lobe?
Major visual processing region
Functions of the cerebellum?
Coordinates gait
Maintains posture
Controls muscle tone ans voluntary muscle activity
Basically it receives information from the sensory systems and regulates control of movements
Where are primary motor neurones situated?
In the primary motor cortex which is in the pre central gyrus
This is Brodmann area 4
Describe how the neurones are situated topographically in the motor cortex?
They form the motor homonculus
Face and mouth are near the Sylvian fissure
Arm and hand are at the mid portion of the primary motor cortex
The trunk is near the apex of the brain
Leg and foot areas are in the part of the primary cortex that dips into the longitudinal fissure
Describe where in the brainstem the cranial nerves are?
Midbrain - III and IV
Pons - V, VI, VII, VIII
Medulla - IX, X, XI and XII
Function of the substantia nigra in the brainstem?
Dopamine production
Function of the red nucleus in the brainstem?
Involved in limb control and motor coordination
E.g. in a vertebrate without a significant corticospinal tract, gait is mainly controlled by the red nucleus - less useful in primates
E.g. crawling of babies is controlled by this
What is Weber syndrome?
Midbrain stroke syndrome
A form of stroke that affects the medial portion of the midbrain - mainly caused by occlusion of a branch of the posterior cerebral artery
What is wallenberg’s syndrome?
Lateral medullary syndrome
Stroke in the lateral portion of medulla.
Caused by occlusion of posterior inferior cerebellar artery
Brainstem functions?
Site of origin of CN nuclei 3 to 12
Dopamine production
Coordination of movement
Respiratory centre
Cardiac centre
Reticular activating system
Conduit for white matter tracts - motor, sensory, coordination, eye movements
What are the 3 anatomical lobes of the cerebellum?
Anterior lobe
Posterior lobe
Flocculonodular lobe
What are the 3 functional divisions of the cerebellum?
Cerebrocerebellum
Spinocerebellum
Vestibulocerebellum
Function of the cerebrocerebellum?
Involved in planning movements and motor learning - receives inputs from cerebral cortex and pontine nuclei and sends outputs to thalamus and red nucleus
Regulates coordination of muscle activation and is important in visually guided movements
Function of the spinocerebellum?
Regulates body movements by allowing for error correction
Maintenance of tone
Function of the vestibulocerebellum?
Controls balance and ocular reflexes
Receives inputs from the vestibular system and sends outputs back to the vestibular nuclei
If a limb weakness is fatigable where is the likely pathology occuring?
Neuromuscular junction
What is autonomic dysreflexia?
A clinical syndrome that occurs in pt who have a spinal cord injury at or above T6
Afferent signals most commonly triggered by faecal impaction or urinary retention cause a sympathetic spinal reflex via thoracolumbar outflow. This results in an unbalances physiological response characterised by extreme hypertension, flushing & sweating above the level of the spinal cord lesion, agitation, bradycardia
In untreated cases severe consequences of extreme hypertension can occur e.g. haemorrhagic stroke
What is Hoffman test?
When doctor flicks the fingernail of the middle finger down and the thumb will flex = indicates UMN lesion and is likely cervical
What does past pointing in finger-nose coordination test tell you?
Pt has dysmetria - sign of cerebellar damage
What spinal level is the biceps brachii reflex?
C5 and C6
What spinal level is the triceps brachii reflex?
C6, C7, C8
What spinal level is the brachioradialis reflex?
C5, C6, C7
What spinal level is the quadriceps femoris reflex?
L2, L3, L4
What spinal level is the Achilles tendon reflex?
S1, S2
