Neuro Flashcards
What is cerebral blood volume?
the amount of blood in the cranial vault (~10% of total intracranial volume)
What is the Circle of Willis?
the series of interconnected vessels that ensure continual blood supply to the brain - collateral circulation. Fed via internal carotid arteries and vertebral arteries.
What is the Monroe-Kellie Doctrine?
The sum of volumes of the brain tissue, CSF and intracranial blood volume is constant.
- if there is an increase in blood, there will be a decrease in CSF
- increase in brain mass = decrease in blood and/or CSF
- increase CSF = decreased blood
What is intracranial pressure (ICP)?
- the combined pressure of brain tissue, blood and CSF within the cranial vault
- normally between 5 - 15mmHg
- measured by placing a catheter in the lateral ventricle
What is the Cushing’s triad?
The three classic signs of increased intracranial pressure
- increased pulse pressure
- irregular breathing
- decreased pulse
What is cerebral perfusion pressure (CPP)?
Blood pressure gradient across the brain
- determines if neurons receive blood or not
- CPP = MAP-ICP
- normal range = mmHg
Cycle of ICP/CPP
insult contributes to increase ICP, decreases cerebral blood flow, decreases CPP, decreased blood flow to affected area of brain, causes ischaemia, leads to infarction of brain tissue, results in swelling, manifests in cerebral oedema, exacerbates/perpetuates the cycle
types of brain herniation
- Cingulate Herniation – -cingulate gyrus compressed under falx cerebri
- Central Herniation – downward displacement of brain structures
- Uncal or Lateral Herniation – lateral mass displaces cerebral tissue centrally
- Infratentorial Herniation – increased pressure in infratentorial compartment. Herniation may be upwards or downwards
Clinical management of increased ICP
- Mannitol
- CSF drainage
- respiratory support
- analgesics, sedatives, paralytics
- blood pressure management
- seizure prophylaxis
- hypothermia
- decompressive craniectomy
- positioning
- environmental considerations
Define consciousness
a state of awareness of oneself and the environment and responding to that environment
define arousal
individual’s state of awareness. impacted by the reticular activating system (RAS)
define post coma unresponsiveness (previously known as persistent vegetative state)
complete lack of responses that suggest a cognitive component, preservation of sleep-wake cycles and cardiorespiratory function, partial or complete preservation of hypothalamic and brainstem autonomic functions.
define locked in syndrome
syndrome indicative of damage to the brainstem without damage to the cerebrum. No abnormality in level of arousal or consciousness.
Glasgow Coma Scale Eyes assessment readings
4- spontaneously
3- to speech
2- to pain
1- no response
Glasgow Coma Scale best motor response assessment readings
6- obeys commands 5- localises pain 4- flexion withdrawal 3- abnormal flexion 2- abnormal extension 1- no response
Glasgow Coma Scale best verbal response assessment readings
5- oriented 4- confused 3- inappropriate words 2- incomprehensible sounds 1- no response
terms used to describe level of consciousness
- full consciousness (GCS 15)
- confusion (GCS 13-14)
- disorientation (GCS 13-14)
- drowsy (GCS 13-14)
- stupor (GCS 8-10)
- semicomatose (6 - 7)
- coma (GCS 4 - 6) - decorticate or decerebrate posturing
- deep coma (GCS 3)
Altered breathing types
- Cheyne-Stokes breathing
- Central neurogenic hyperventilation
- apneustic breathing
- cluster breathing
- ataxic breathing
diagnostic testing for altered cognitive function
- Blood Glucose
- Serum electrolytes
- Serum osmolality
- Arterial Blood Gas
- Liver Function Tests
- Toxicology screening
Cranial nerves
Cerebral hemisphere - I olfactory - II optic Midbrain - III oculomotor - IV trochlear Pons - V trigeminal - Vi abducens - VII facial - VIII acoustic Medulla - IX glossopharyngeal - X vagus - XI hypglossal - XII spinal accessory
types of seizures
- generalised tonic/clonic (Grand Mal)
- partial complex seizure
- absence seizures (petit mal)
- myoclonic seizure
details of generalised tonic/clonic seizure
Characterised by an aura, sudden loss of consciousness and motor control
Tonic – spasm, increased muscle tone, stiffening
Clonic – muscular contractions, rapid synchronous jerking
details of a partial complex seizure
Alterations in consciousness, unusual stereotyped movement, changes in temperament, confusions, feelings of unreality.
details of an absence seizure (petit mal)
Temporary lapses of consciousness that last a few seconds
details of myoclonic seizures
Bilaterally symmetrical muscle jerks
what is the characteristics of the ideal antiepileptic (anticonvulsant)
- Highly effective but with a low incidence of toxicity
- Effective against more than one type of seizure and for mixed seizures
- Long acting and non-sedating
- Inexpensive
- Does not result in the development of tolerance
What are the main types of antiepilectic medications?
- Drugs that enhance GABA inhibition (eg Clonazepam, phenobarbitone, topiramate)
- Drugs that inhibit sodium channel function (eg. Phenytoin, carbamazepine, sodium valproate)
- Drugs inhibiting calcium channel function
drugs for treating generalised seizures
- Hydantoins (Phenytoin)
- Stabilises nerve membrane throughout CNS by influencing ionic channels in cell membrane, decreases excitability
- Decreasing conduction through nerve pathways it reduces tonic-clonic, muscular and emotional responses to stimulation
- Barbiturates (phenobarbitone)
- Inhibit impulse conduction in the ascending reticular activating system, depresses the cerebral cortex, alter cerebellar function and depress motor nerve output
- Reduce tonic-clonic, muscular and emotional responses to stimulation.
- Benzodiazepines (Clonazepam, diazepam)
Drugs for treating partial seizures
- Carbamazepine, Lamotrigine, Gabapentin and Topiramate
Directly – by altering sodium and calcium channels
Indirectly – by increasing activity of GABA and thereby decreasing excessive activity
Carbamazepine – ability to inhibit polysynaptic responses and to block sodium channels to prevent formation of repetitive action potentials
Gabapentin – inhibits polysynaptic responses and blocks stimulus increases in certain situations.
Lamotrigine – inhibit voltage sensitive sodium and calcium channels, stabilise nerve membranes and modulate release of excitatory neurotransmitters
Indications for phenytoin
Indications – control of tonic-clonic and psychomotor seizures, prevention of seizures during neurosurgery, control of status epilepticus
adverse effects of phenytoin
Adverse Effects – nystagmus, ataxia, dysarthria, slurred speech, mental confusion, dizziness, fatigue, tremor, headache, dermatitis, nausea, Stevens-Johnson syndrome, gingival hyperplasia, liver damage, haematopoietic complications, sometimes fatal.
Phenytoin routes, timings, metabolisation
Route – oral or IV
Onset of action – slow (oral), 1-2 hours (IV)
Duration of action – 6-12 hours (oral), 12-24 hours (IV)
Half Life – 6 to 24 hours
Metabolised in the liver, excreted in the urine
Indications for carbamazepine
Treatment of partial disorders, including partial seizures with complex patterns, tonic-clonic seizures, mixed seizures, trigeminal neuralgia
adverse effects of carbamazepine
drowsiness, ataxia, dizziness, N&V, CV complications, hepatitis, haematological disorders, Stevens-Johnson syndrome
carbamezapine route, timings and metabolisation
Route – Immediate release and slow release oral
Onset of Action – Slow
Half Life – 25-65 hours
Metabolised in the liver, excreted in the urine and faeces
Two main forms of stroke
- heamorrhagic
- ischaemic
what is cerebrovascular disease (CVD)?
- CVD is a general term encompassing different conditions
- One condition can be a predisposing factor towards developing another condition underlying pathology:
- Atherosclerosis - Fat deposits on arterial walls narrow blood vessels reducing cerebral blood supply
- Cerebral Haemorrhage
- Subarachnoid
- Haemorrhage
- Vascular Lesions
- Weakening of Blood Vessels
- Aneurism
- Stroke
- Ischaemic
- Haemorrhagic
- Transient Ischaemic Attack (TIA)
What is a stroke
- Involves sudden interruption in the blood supply to the brain
- Brain cells die due to lack of oxygen following disruption of blood supply leading cause of morbidity and mortality.
- Australia’s 3rd largest medical killer after cancer and heart disease colloquially used to be known as “brain attack”.
- Slurred speech
- Facial droop
- Arm drop/downward drift
Stroke outcomes are influenced by:
- Duration of ischaemia
- Magnitude of loss of flow
- Rapidity of development
- Collateral supply
Most common causes of stroke
1 - Thrombus formation in an area narrowed by vascular disease
2 - Embolus formation from the thrombus (or debris from the atheroma)
3 - A haemorrhage in the cerebrum (cerebral haemorrhage) as a result of both vascular disease and hypertension, or by a congenital aneurysm.
Definition of ischaemic stroke?
- sudden blockage or occlusion of cerebrovascular blood flow.
- Caused by thrombosis or emboli of large or small blood vessels of the brain
- Most common variety of stroke
- 3 major categories of ischaemic stroke
- thrombotic
- embolic
- thrombo-embolic
Definition of thrombus?
- aggregation of blood factors (clot or plaque) causing vascular occlusion.
- most common cause of Ischaemic stroke
- typically occurs when flow in a blood vessel in the brain is obstructed by atherosclerotic plaques
- usually occurs in:
- large vessels of the brain
- older people
- often associated with:
- atherosclerotic heart diseases or
- peripheral artery disease
- not associated with activity and can occur at rest
Definition of embolic ischaemic stroke?
- Cardiogenic embolic stroke
- Movement of the blood clot from the heart to the brain
- Blocks small blood vessels
- Usually originate from thrombus in the left heart
Definition of thrombo-embolic ischaemic stroke?
- Occurs following dislodgement of a clot from an atherosclerotic plaque in the carotid arteries
- Lodges in a downstream blood vessel & blocks blood flow
- Rx and prevention = Carotid endarterectomy, carotid stents
What is a carotid endarterectomy?
- Surgical excision of atheromatous segments of the endothelium and tunica media of the carotid artery.
- Results in smooth tissue lining and facilitating blood flow through the vessel reducing risk of stroke.
What is a transient ischaemic attack (TIA)?
- also termed “mini stroke”
- temporary disturbance in cerebral blood flow
- Focal or localised
- usually reverse before infarction occurs
- causes include:
- Atherosclerosis
- emboli
- may provide a warning of impending stroke.
Definition of a haemorrhagic stroke?
- Is the most frequently fatal stroke
- Rupture of blood vessel results in:
- Oedema
- Compression & increased ICP
- Spasms of adjacent blood vessels
- Leading to worsening oedema and possible eventual brain death
- Two major types:
1. Intracerebral haemorrhage
2. Subarachnoid haemorrhage
What is an intracerebral haemorrhage (ICH)?
- Occurs when a blood vessel bursts within the brain
- Sudden build-up in pressure causes damage to brain cells
- Usually large single bleeds and often catastrophic
- most common cause of spontaneous ICH is hypertension
- Results in micro-aneurysms at bifurcation of arterioles
- Persistently raised blood pressure damages small vessel walls
- Other Causes:
- Brain tumours
- Aneurysms
- AV Malformations
- Angiomas
- AV fistulae
What is a sub-arachnoid haemorrhage?
- Occurs when a blood vessel bursts immediately outside the brain
- Subarachnoid space suddenly fills with blood & pressure increases
- Symptoms include:
- Neck or sudden severe back pain
- Nausea
- Intense migraine-like headache
- Weakness
- Most common cause are cerebral aneurysms of arteries at the base of the brain.
- One-third of patients who suffer an SAH will survive with good recovery; one-third will survive with a disability; and one-third will die.
- Treatment focuses on stopping the bleeding, restoring normal blood flow, relieving the pressure on the brain, and preventing vasospasm.
- When RBCs breakdown and form a clot, they trigger the release of prostaglandins which result in vasospasm, leading to reduced arterial blood supply and ischaemia leading to secondary stroke!
- The greatest risk of vasospasm is 5-10 days after a bleed.
- Prevented with drug called nimodipine – given IV initially then orally.
What is an aneurysm?
- Focal dilation of arteries occurring in about 5% of people.
- r/t:
- Hypertension
- Arteriosclerosis
- Genetic factors i.e.:
+ Inherited connective tissue disorders
+ Autosomal dominant PCKD
+ Ehlers-Danlos syndrome
- Most occur along middle or anterior communicating arteries of the Circle of Willis.
What are arteriovenous malformations?
- Also known as AVMs
- Present as tangled, dilated blood vessels in which arteries flow directly into veins.
- AVMs occur most often at the junction of cerebral arteries:
- Fronto-parietal region
- Frontal lobe
- Lateral cerebellum
- Occipital lobe
- Within the dura
