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
