Week 10 - Pathology Of The CNS Flashcards
Name the different lobes of the brain
Frontal, parietal, occipital, temporal
What does the brain consist of?
- cerebral hemispheres (grey matter, white matter, basal ganglia, ventricular system)
- brain stem
- cerebellum
What are the meninges?
- membranous coverings of the central NS
- protective function and important in production of cerebrospinal fluid
-dura mater –> arachnoid mater –> pia mater
Explain the blood supply to the brain
- the cerebral arteries supply a defined territory within the cerebral cortex
- if blood supply to a particular part of the brain is interrupted - symptoms developed due to lack of blood supplied to that part of the brain by that vessel
-circle of Willis - arteries supplying brain
Explain the venous drainage of the brain
Veins covering the brain to ensure venous drainage
What is the skull and what can occur because of it?
- bony box which can’t expand
- if the volume of tissue fluid inside the skull increases, the intracranial pressure rises
- results in herniation where a part of the brain moves from one compartment of the skull to another
What is herniation and what does it present with?
where a part of the brain moves from one compartment of the skull to another
- brain herniation frequently presents with abnormal posturing (characteristic positioning of the limbs indicative of severe brain damage)
- lowered level of consciousness - GCS score of 3-5
- one or both pupils dilated - fail to restrict in response to light
- vomiting can also occur due to compression of the vomiting centre in the medulla oblongata
What is the function of the spinal cord?
-communication of motor and sensory functions between brain and peripheral nervous system
Name the regions of the spine and how many nerve pairs it has
Cervical - 8 nerve pairs
Thoracic - 12 nerve pairs
Lumbar - 5 nerve pairs
Sacrum - 5 nerve pairs
1 coccygeal nerve
What surrounds the spinal cord?
Meninges
What is the basic neuroanatomy of the peripheral nervous system?
- spinal and cranial nerves
- branches of above linking CNS to peripheral sensory receptors and effector organs (muscles and glands)
- autonomic and somatic nervous systems
What are the cells of the nervous systems?
Neurons - the processors
Glial cells - supporting functions
- Schwann cells, astrocytes and oligodendrocytes
Where are the sensory and motor cortex located?
Sensory = post-central gyrus
Motor = pre-central gyrus
Which areas are responsible for speech and language production?
Broca’s area:
- frontal lobe, anterior to pre-motor cortex
- predominantly responsible for speech production
Wernicke’s area:
- temporal lobe, posterior to auditory cortex
- speech processing and comprehension of written and spoken language
What is the frontal lobe responsible for?
- complex executive functions involved in decision making
- emotional reactions
- formation of some types of memory
- motor cortex
- olfactory function
- generation of fluent speech
What is the parietal lobe responsible for?
- sensory cortex
- processing of sensory information
What is the temporal lobe responsible for?
- language functions (auditory cortex and comprehension of written and spoken words)
- memory
What is the occipital lobe responsible for?
-visual cortex
What is the brain stem responsible for?
- conduction of major motor and sensory pathways
- control of cardiorespiratory function
- consciousness
- cranial nerve roots
What is the cerebellum responsible for?
- precise motor control
- ? Others - language, attention (not yet well defined)
What is the basic functional anatomy of spinal cord nerves/roots in the CNS?
Spinal cord nerve roots:
- specific spinal nerves innervate defined motor functions and sensory territories
- damage to spinal cord at a specific level will cause loss of function of spinal nerves below that level
- sensory dermatomes
What is a sensory dermatome?
A dermatome is an area of skin supplied by sensory neurons that arise from a spinal nerve ganglion
-symptoms that follow a dermatome (e.g. Like pain or a rash) may indicate a pathology that involves the related nerve root
What are focal neurological signs?
Set of symptoms or signs in which causation can be localised to an automatic site in the CNS
What is generalised neurological abnormality?
Essentially an alteration in level of consciousness
What focal neurological signs may arise from the frontal lobe?
- anosmia (lack of sense of smell)
- inappropriate emotions
- expressive dysphasia (language disorder marked by deficiency in the generation of speech)
- motor impairment
What focal neurological signs may arise from the parietal lobe?
- receptive dysphasia
- sensory impairment
What focal neurological signs may arise from the temporal lobe?
- cortical deafness
- receptive dysphasia
How are spinal cord lesions examined?
- 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 e.g. complete paralysis of the body and legs with maintained head and neck movement is caused by injuries to the cervical spine
What may a diffuse neurological injury present as?
- usually manifest as impairment of consciousness
- most often due to increased intracranial pressure (ICP)
- may occur as a primary process or as a secondary to response of to a focal injury
What may be the causes of reduced consciousness?
- may be obvious on external examination (e.g. trauma) or easily identified on basic observations (e.g. hypoxia, hypothermia)
- may require additional bedside tests or more clinical history (e.g. hypo/hyperglycaemia, post-ictal state in an epileptic patient)
How is consciousness assessed?
Basic - assess responsiveness
- A = alert
- V = voice
- P = pain
- U = unresponsive
More complex - Glasgow coma scale (GCS)
- best response = 15
- comatose client = 8 or less
- totally unresponsive = 3
What are the functions of the nervous system?
Basic: sensory –> motor
(mediated by central and peripheral NS, autonomic and somatic)
Higher:
(consciousness, complex and learned motor skills, memory and planning, communication and language)
What does cerebrovascular disease incorporate?
- strokes
- TIAs
- intracerebral haemorrhage
What are the 2 main pathological processes in cerebrovascular disease?
- hypoxia, ischaemia and infarction due to impaired blood supply/oxygenation
- haemorrhage from CNS vessels
What does the brain require a constant supply of?
Glucose and oxygen
Why is cerebral blood flow autoregulated?
-maintain adequate perfusion over a wide range of blood pressure and intra-cranial pressure (ICP)
What affects the severity of cerebral vascular disease?
Blood flow reduced to a portion of the brain, tissue survival depends on:
- collateral circulation
- duration of ischaemia
- magnitude and rapidity of flow reduction
-blood flow reduced to the whole brain e.g. global hypoperfusion (e.g. hypotension, cardiac arrest) can result in generalised neuronal dysfunction
What is a TIA and what is its symptoms?
- transient ischaemic attack
- characterised by temporary loss of function that resolves itself within 24 hours
- ‘mini-stroke’
- symptoms similar to that of a full stroke but recovery is rapid
How is a TIA treated?
- 10% chance of having a full stroke within 4 weeks if left untreated
- anti-platelet therapy: aspirin or clopidogrel
- control BP
- lower cholesterol
What is a stroke?
Loss of function lasting greater than 24hrs
2 main types
- ischaemic
- haemorrhagic
What are the risk factors of a stroke?
- hypertension
- diabetes mellitus
- heart disease - ischaemic, AF
- previous TIAs
- hyperlipidaemia
What are the causes of a stroke?
Hypoxia of brain
- blockage of blood vessel by atheroma
- blockage of blood vessel by embolus
Bleed into the brain
- hypertension related
- berry aneurysm
How are strokes managed?
Depending on type
- thrombolysis
- aspirin/clopidogrel
- physio
- occupational health
- SALT
- supportive treatment
What can cause haemorrhagic events?
- hypertension
- vascular malformation
- berry aneurysm
- neoplasia
- trauma
- drug abuse
- iatrogenic (relating to illness caused by medical examination or treatment - e.g. side effects of drugs)
What are the different types of haemorrhage in the brain?
- intracerebral
- subarachnoid
- subdural
- extradural
What is an intracerebral haemorrhage?
- ‘haemorrhagic stroke’
- presents as headache with rapid or gradual decrease in conscious level - localises depending on site of bleed
- usually arterial in origin
- show mass effect
- in 80% cases with hypertension the bleed is ‘capsular haemorrhage’
- few survive
What is a subarachnoid haemorrhage?
- spontaneous
- often catastrophic
- 80% rupture of saccular aneurysms
- thunderclap headache
- ‘meningitis like’ signs
- requires neurosurgical input
What is a subdural haemorrhage?
- fluctuant conscious level
- often on anticoagulants
- bleeding from bridging veins between cortex and venous sinuses
- blood between dura and arachnoid
- often minor trauma in the elderly
What is an extradural haemorrhage?
- post head injury, slowly falling conscious level, possibility with lucid period
- often with fractured temporal of parietal bone
- typically the middle meningeal artery
What is dementia?
- progressive and largely irreversible clinical syndrome with widespread impairment of mental function
- complex needs and high levels of dependency and morbidity
What are the risks/signs of dementia?
- > 65 years old increased risk
- memory loss
- speed of thought
- language
- understanding/judgement
- disinterest in usual activities
- difficulties in controlling emotions
What types of dementia are there and how prevalent is each type?
- Alzheimer’s disease (70%)
- vascular dementia - recurrent small strokes (15%)
- Lewy body dementia (15%)
- along with some rare causes - e.g. Syphilis
If the frontal lobe is affected by dementia, what dysfunction may occur?
- behaviour disorders
- mood
- motivation
- judgement
- planning
- reasoning
- appetite and continence
- disinhibition
If the temporal lobe is affected by dementia, what dysfunction may occur?
Memory dysfunction
If the parietal lobe is affected by dementia, what dysfunction may occur?
Dysphasia - language disorder marked by deficiency in the generation of speech
Dyspraxia - difficulties in activities requiring coordination and movement
If the subcortical area of the brain is affected by dementia, what dysfunction may occur?
-slowness of thought processes
What assessments can be done for people with dementia?
- TSH - ensure thyroid function is normal
- CT scan (not all cases) - to check for intracranial pathology
- vitamin B12, thiamine - alcoholism
What is the cause of Alzheimer’s disease and what does it lead to?
- due to and accumulation of AB amyloid, Tau-neurofibrillary tangles and plaques, and loss of neurones and synapses
- leads to defects of visual-spatial skill (gets lost), memory loss, decreasing cognition, ansognosia (lack of awareness)
How is dementia treated?
- multidisciplinary team
- new treatments include cholinesterase inhibitors e.g. rivastigmine (use closely controlled - NICE)
What is epilepsy?
A recurrent tendency to spontaneous, intermittent, abnormal electrical activity in part of the the brain, manifest as seizures
- seizures can take many forms (focal twitching, trance-like, convulsions)
- usually no identified cause
- for example, can be due to - space occupying lesions, stroke, alcohol withdrawal
How is epilepsy diagnosed?
- good history taking
- exclude structural abnormality
- EEG - electroencephalogram - test that measures and records the electrical activity of your brain
- any triggers e.g. TV?
How is epilepsy managed?
- compliance very important
- depending on seizure type
- have serious side effects (teratogenic)
- examples = sodium valproate (epilim), carbamazepine, phenytoin, lamotragine
What types of infections can occur in the brain?
Diffuse infection
-e.g. Meningitis
Focal infection
-e.g. Abscess
What types of meningitis can you get?
Bacterial
- neisseria meningitidis
- pneumococcus
- meningococcus
Viral
Fungal (rare - HIV etc.)
What is the presentation of meningitis?
Early
- headache
- cold hands and feet
- pyrexial
Late
- neck stiffness
- photophobia
- Kernig’s sign (pain and resistance on passive knee extension with hip fully flexed)
- non-blanching rash
- seizures
What is a brain abscess, how does it spread and what are the effects?
- focal infection
- can lead to focal brain damage or mass effect
- can present with headache, seizures, temperature
- radiologically a ‘ring enhancing lesion’ - differential diagnosis is a glioblastoma
- can spread via blood e.g. Embolus from bacterial endocarditis, IV drug users at risk
- can spread directly e.g. from an infected inner ear
What is Parkinson’s disease?
- movement disorder
- sporadic or familial
- can be drug induced
-associated with the degeneration of the basal ganglia of the brain and a deficiency of the neurotransmitter dopamine
What are the clinical signs of Parkinson’s disease?
- rigidity
- bradykinesis (slowness of movement)
- resting tumour
- postural instability
How is Parkinson’s disease treated?
- multidisciplinary team approach
- L-DOPA e.g. madopar
- anticholinergic drugs e.g. orphenadrine
- drug induce Parkinson’s (e.g. Haloperidol) can be helped by procyclidine
- surgery?
What types of tumours can affect the brain and why?
- benign and malignant
- benign tumours can cause problems depending on location and mass effects
- can affect the skull, the meninges or the brain itself
What are the symptoms/presentation of a brain tumour?
- headaches
- seizures
- cognitive or behavioural change
- vomiting
- altered consciousness
Can metastasis occur in the brain?
Yes
- cancers elsewhere in the body can metastasise in the brain
- must be included when tumours are found on CT and MRI scans - e.g. Breast and small cell lung cancer
What is the most common benign tumour to arise in the brain?
Meningiomas
- benign
- generally well circumscribed, slow growing
- derived from meningothelial cells
- enlarge slowly, don’t often infiltrate the brain and can be often removed surgically
- can be found incidentally on brain imaging scans
What malignant tumours are commonly known to arise in the brain?
Astrocytomas
- range from WHO grade I-IV
- grade I generally good outcome but grade 4 usually fatal
Glioblastoma
Explain about pituitary tumours
- cause compression symptoms (e.g. of the optic nerve)
- can be hormonally active (classified based on hormone produced, e.g. Prolactinoma)
- surgically removed transphenoidally (brain surgery where an endoscope and/or surgical instruments are inserted in to part of the brain by going through the nose and the sphenoid bone)
