Central Nervous System Flashcards
Functions of CNS
basic = sensory + motor (mediated by CNS and PNS, autonomic and somatic) higher = > consciousness, complex and learned motor skills, memory and planning, communication/language
Brain structure
cerebral hemispheres: - grey matter - white matter - basal ganglia - ventricular system brain stem cerebellum
Meninges
membranous coverings of the CNS protective function - important in CSF production > dura mater > arachnoid mater > pia mater
Blood vessels in CNS
cerebral arteries -
- if blood supply to a particular part if the brain is interrupted, the patient will develop symptoms due to the lack of function of the part of the brain supplied by the vessel
cerebral veins -
- venous blood drains eventually to the internal jugular vein
The skull
cannot expand
if the volume of tissue/fluid inside the skull increases the intracranial pressure rises = herniation
herniation is where a part of the brain moves from one part of the skull to the other
Spinal chord
8 cervical nerve pairs 12 thoracic nerve pairs 5 lumbar nerve pairs 5 sacral nerve pairs 1 coccygeal nerve pair
Peripheral NS
spinal and cranial nerves
branches off linking CNS to peripheral sensory receptors and effector organs (muscles and glands)
autonomic and somatic
Name the cells in PNS and CNS
- neurones - the processors
- glial cells - supporting functions
> Schwann cells
> astrocytes
> oligodendrocytes
What area of the brain is the motor cortex?
pre-central gyrus
What area of the brain is the sensory cortex?
post-central gyrus
What and where is Broca’s area in the brain?
frontal lobe, anterior to the pre-motor cortex
predominantly responsible for speech production
What and where is Wernicke’s area in the brain?
temporal lobe, posterior to auditory cortex
responsible for processing speech and comprehension of written and spoken language
Frontal lobe
decision making, emotional reactions, formation of some types of memory, motor cortex, olfactory function, fluent speech
Parietal lobe
sensory cortex, processing of sensory info
Temporal lobe
language functions and auditory cortex, comprehension of written and spoken words, memory
Occipital lobe
visual cortex
Brain stem
conduction of major motor and sensory pathways, cardio-respiratory functions and consciousness, cranial nerve roots
Cerebellum
precise motor control, language attention ??
Spinal chord nerve roots
specific spinal nerves innervate defined motor functions and sensory territories
damage to spinal chord at specific level = loss of function of spinal nerves below that level
What are focal neurological signs?
a set of symptoms or signs in which causation can be localized to an anatomic site in the central nervous system
What is generalised neurological abnormality?
Essentially an alteration in level of consciousness
Frontal lobe focal neurological signs
Parietal lobe focal neurological signs
Temporal lobe focal neurological signs
anosmia (loss of smell), inappropriate emotions, expressive dysphasia, motor impairment
receptive dysphagia, sensory impairment
cortical deafness, receptive dysphagia
Spinal chord lesions
Physical examination helps to identify the level of injury in spinal cord lesions
Signs limited to a single dermatome or nerve root suggest either a focal nerve root injury or injury to a peripheral nerve
Signs affecting several nerve roots below a certain level eg. Complete paralysis of body and legs with maintained head and neck movement is caused by injuries to the cervical spine (usually traumatic)
Diffuse neurological injury
Usually manifest as impairment of consciousness
Most often due to increased intracranial pressure
May occur as a primary process or as a secondary to response to a focal injury
How do we assess consciousness?
A: alert
V: voice
P: pain
U: unresponsive
Cerebrovascular diseases
strokes, TIA, intracerebral haemorrhages
2 main pathological processes:
> hypoxia, ischaemia, infarction due to impaired o2/blood supply
> haemorrhage from CNS vessels
if blood flow is decreased to a portion of the brain, survival of tissue depends on:
- collateral circulation
- duration of ischaemia
- magnitude and rapidity of decrease blood flow
reduced blood flow to the whole brain = global hypofusion = generalised neuronal dysfunction
Stroke
Face (drooping) Arms (may not be able to raise them) Speech (slurred) Time loss of function lasting greater than 24 hours 2 types; - ischaemic - haemorrhagic risk factors: hypertension, DM, heart disease, hyperlipidaemia
Causes of a stroke
hypoxia of the brain due to blockage of blood vessels by an atheroma or embolus
bleed into the brain caused by hypertension or aneurysm
Left MCA territory infarct -
- damage to speech area in L hemisphere = loss of speech (aphasia)
- damage to L visual pathway = loss of vision to R (hemianopia)
- damage to left motor cortex and internal capsule = weakness of R face, arm and leg
Management of strokes
thrombolysis Aspirin, Clopidogrel physiotherapy occupational therapy SALT
Transient ischaemic attack (TIA)
temporary loss of function that resolves itself within 24 hours
“mini strokes”
symptoms similar to stroke but rapid recovery
treatment = anti-platelet therapy eg. Aspirin, Clopidogrel, control BP, lower cholesterol
Causes of haemorrhagic events
hypertension, aneurysm, neoplasia, trauma, drug abuse, iatrogenic
Intracerebral haemorrhage
“haemorrhagic stroke”
headache, with rapid or gradual decrease in consciousness, localises depending on site of bleed
usually arterial
few survive
Subarachnoid haemorrhage
spontaneous, usually catastrophic
‘thunderous’ headache
meningitis like signs
requires neurosurgical input
Subdural haemorrhage
fluctuant conscious levels
often on anti-coagulants
blood between dura and arachnoid
often minor trauma in the elderly
Extradural haemorrhage
post head injury, slowly falling consciousness levels
often with fractured temporal or parietal lobe
typically middle meningeal artery
Dementia
65+ increased risk
memory loss, decreased speed of thought, language, understanding and judgement affected, have difficulty controlling emotions
70% is Alzheimer’s, 15% is vascular dementia (recurrent small strokes), 15 % dementia with Lewy Bodies
assessment:
- TSH (ensure thyroid function is normal)
- CT scan
- vitamin B12, thiamine = alcoholism
Alzheimer’s disease
due to loss of neurones and synapses, and accumulation of AB amyloid
leads to defects of visual-spatial skill, memory loss, decreased cognition and lack of awareness
treatment = multi-disciplinary approach, cholinesterase inhibitors eg Rivastigmine
Epilepsy
a recurrent tendency to spontaneous, intermittent, abnormal electrical activity in part of the brain
manifest as seizures which can take many forms:
- focal twitching, trance-like, convulsions
usually no identifiable cause
management =
- lifestyle changes eg. driving
- drug compliance (can have side effects = teterogenic0
eg. Sodium Valproate, Carbamazepine, Phenytoin, Lamotrigine
Meningitis
diffuse infection
Bacterial: Neisseria meningitidis, Pneumococcus, Meningococcus
Viral
Fungal
presentation: EARLY - headache, cold hands and feet, pyrexial, LATE - neck stiffness, photophobia, non-blanching rash, seizures
Brain abscess
focal infection
leads to focal brain damage
presents with headache, temp seizures
can spread via blood eg. embolus from bacterial endocarditis, IV drug user at risk
can spread directly eg. from an inner ear infection
Parkinson’s disease
movement disorder
sporadic, familial
can be drug induced
clinically: rigidity, bradykinesia (slowness of movement), resting tremor, postural instability
treatment = MDT approach, L-dopa eg. Madopar, anticholinergic drugs eg Orphenadrine, SURGERY
Tumours
benign lesions can cause problems depending on location/mass effects
can effects skull/meninges/brain itself
presentations: headaches, seizures, cognitive/behavioural change, vomiting, altered consciousness
Tumour metastasis
cancer elsewhere in the body can metastasize the brain eg. breast and small cell lung cancer
eg. meningioma’s, astrocytoma’s, pituitary tumours, glioblastoma
Meningioma’s
benign tumour
slow growing
derived from meningothelial cells
Astrocytoma’s
range from grade 1-4, grade 4 being fatal
Pituitary tumours
cause compression symptoms eg. optic nerve can be hormonally active > classified based on hormone production eg. Prolactinoma surgically removed transphenoidally
