NEURO: Part 3 Flashcards
At what level does the spinal cord finish at
L1
Where does the caudal equine start at
L1 and continues into lumbar vertebra
Where are sensory neurone ganglion found
Dorsal root ganglion
Why is analgesia aimed at sensory neurone cell bodies
Have a higher SA
Take up anaesthetics better
What neurones do Epidural anaesthetics give
Sensory block than motor
At what level is an epidural given
Below L1
Why is an epidural given below L1
Allows us to anaesthetise the lower body but maintains brain function (need to keep breathing lol)
Where is the tube for epidural delivery inserted
BELOW L1 outside the dura mater - local anaesthetic is then put into epidural space
Where will the epidural then diffuse to after delivery
To dorsal root ganglion - will stop cell bodies from functioning so no pain felt
Why do we use a blunt needle when delivering an epidural
Do not want it to go into the CSF
What happens if the epidural ends up in the CSF
Will travel up the spine to the brain - respiratory failure
What is the best way to sample CSF
LUMBAR PUNCTURE
At what vertebral levels is lumbar puncture done
L3/4
L4/5
Why is a sharp needle done for a lumbar puncture
Since we want to penetrate the dura and extract CSF plunger to aspirate
What is the role of Nerve conduction Studies
Looks at peripheral nervous system; motor neurone -> root -> nerve -> NMJ -> muscle
Describe the nerve conduction study in sensory function assessment
- AP triggered by electrical stimulation
2. Potential is recorded using sticky electrodes to measure size of response and its speed
Describe the nerve conduction study seen in motor function assessment
- AP triggered causing ACh to be released at the NMJ
- ACh activates ACh receptors on muscle and causes muscle contraction - visible twitch
- Measure size of response and speed
What damage is indicated in small response of nerve conduction
Axon loss
What damage is indicated in slow response of nerve conduction
Demyelination
Role of Electromyography
EMG detects myopathies (pathology of muscle),
Why is an EMG more accurate than NCS in myopathies
NCS will be normal but EMG won’t be
Describe how EMG works
- Uses needle to detect electrical activity of muscle
2. Records activity of individual motor units
Why would we use EMG to look at big motor units
For nerve/motor neurone pathology
Why would we use EMG to look at small motor units
Muscle pathology - myopathy
Can axonal neuropathies be treated
No
Can demyelinating neuropathy be treated
Yes
When can NCS AND EMG be used
Investigate: Focal nerve entrapment Generalised neuropathy Myopathy Motor Neurone disease
When is Electroencephalography used
When looking at brain pathologies (e..g seizures)
What is EEG
Electrodes are placed in specific locations on the scalp
Patient asked to do various things during recording (close eyes, hyperventilate)
Epilepsy
Describe the anatomical location of the brainstem
Posterior fossa with the cerebellum
What separates the cerebrum from the cerebellum
Tentorium
so cerebrum sometimes called superiortentorium and cerebellum inferiortentorium
What structures does the brainstem have to go through to meet the spinal cord
Tectorial hiatus
Foramen magnum
What parts of the skull does the oculomotor nerve run over
Petrous apex of the temporal bone
Under what condition can we get a CN3 palsy
When the CN3 is fractures or inflamed, CN3 can push against the bone
FIXED DILATED PUPIL
Signs of cerebellar syndrome
Ataxia = loss of full control of body movements (limbs not steady)
Nystagmus = rapid eye movements (Ipsilateral)
Deficit is ON SAME SIDE AS CEREBELLAR LESION
Where is the periaqueductal grey located
Floor of the 4th ventricle
What is the role of the brainstem
- Alertness
- Sleep/Wake
- REM + Non-rem sleep
- Resp centre
- CV centre
How many cerebellar peduncles are there
3
Where are the cavernous sinuses located
- Lateral aspect of the body of the sphenoid bone
Blood supply of the cavernous sinus
Superior and inferior ophthalmic veins
Superior cerebral vein
Dural venous sinus
What structures pass through the cavernous sinus
O TOM CAT
O - Oculomotor nerve T - Trochlear O - Ophthalmic trigeminal M - Maxillary trigeminal C - Carotid (internal) A - Abducens T - Trochlear nerve
On an MRI what colour is bone
BLACK
Criteria for brainstem death
- Pupils do not change
- Cornea reflex
- Caloric vestibular reflex
- Cough reflex
- Gag reflex
- Respirations
- Response to pain
What is the caloric vestibular reflex
Placing cold or warm water into the external auditory canal producing currents in opposite direction:
If water is 44 degrees or above: Both eyes will turn towards the contralateral ear
If water is cold: Eyes will turn to ipsilateral ear
What are the three main examinations done during a head injury
- Glasgow coma scale - measure level of consciousness
- Look at materialising signs: Identify which hemisphere issue is with
- Look at pupils for signs of raised ICP
ALSO MONITOR VITAL SIGNS
Max score you can get in the glasgow coma scale
14
3 categories of Glasgow coma scale
- Motor response
- Verbal response
- Eye opening response
When and why can’t the GCS be used
Within one hour of the event - inaccurate
How do we check for lateralising signs
Check painful stimuli response: Pinch behind the ear and will see what side has issue (R hand may come up but not L)
Thus Right hemisphere issue
What features of the eye are going to indicate increased ICP
- Fixed dilated pupil (CN3 palsy)
2. Papilloedema
How is head injury managed
- IV MANNITOL
- Diazepam
3, Intubation - IF GCS is less than 8 - Neurosurgery
What is MANNITOL
A diuretic - reduces oedema and thus ICP
Why is Diazepam used in head injuries
Stops seizures
Describe the neurosurgeon procedures done for head injuries
- ICP monitor insertion
2. Burrholes or carniectomy to relieve ICP
What is BUrrholes
Small holes made in the skull to reduce pressure
What is Craniectomy
Part of the skull is removed to relief pressure
What check should we always do for people with head injury
Shave the head to check for lacerations as these may result in fatal bleeding
Suture lacerations and then do a CT
Define TIA
A brief episode of neurological dysfunction due to temporary local ischaemia without infarction
Define infarction
Tissue death due to poor oxygen supply
How long does it take for TIA symptoms to resolve
24 hours
What condition do TIAs foreshadow
MI and strokes
In what gender is TIA common in
Black Males
Why are blacks at a greater risk of TIA
Greater genetic risks of hypertension and atherosclerosis predisposition
What is the main cause of a TIA
Atherothromboembolism from carotid artery (internal??)
Cardioembolism from: Mural thrombus post-MI or AF
Valve disease
Prosthetic valve
Hyperviscoity: Olycythaemia, SCA, Raised WCC or myeloma
Hypo perfusion in younger people
What conditions can cause hypo perfusion
Cardiac dysrhythmia
- Postural hypotension
- Decreased flow through atheromatous arteries
Risk factors for TIA
- Age
- Hypertension
- Smoking
- Diabetes
- Heart Disease: Valvular, ischaemic or AF
- Past TIA
- PAD
- Raised PCV
- Polycythaemia Vera
- Combined oral contraceptive pill
- Hyperlipidaemia
- Excess alcohol
- Clotting disorder
- Vasculitis (SLE, giant cell arteritis)
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What is the most common cause of a TIA
Cerebral ischaemia
How long does a TIA last for
5-15 mins (resolves before cell death can occur)
Differential diagnosis of TIA
Same symptoms but if they gradually progress:
Demyelination
Tumour
Migraine
Clinical Presentation of all TIAs
- SUDDEN loss of function, usually lasting for minutes, with complete recovery and NO infarction
Clinical presentation of carotid artery anterior circulation TIA
SUPPLIES frontal and medial part of cerebrum:
- Weak, numb CONTRALATERAL leg and milder arm symptoms
- Hemiparesis: Weakness on entire side of th body
- Hemi sensory disturbances
- Dysphagia (language impairment)
- Amaurosis fugax
What is Amaurosis fugax
- Sudden transient loss of vision in one eye (‘curtains coming down vertically into field of vision)
What causes Amaurosis fugal
- Temporary reduction in retinal and ophthalmic ciliary blood flow = temporary retinal hypoxia
Clinical presentation of Vertebrobasilar artery TIA
- Diplopia (double vision)
- Vertigo
- Vomiting
- Choking and dysarthria (unclear articulation of speech but understandable)
- Ataxia
- Hemisensory loss
- Hemianopia vision loss
- Loss of consciousness
- Transient global amnesia (episode of confusion/amnesia lasting several hours before complete recovery)
- Tetra paresis (muscle weakness affecting all 4 extremities)
Differential diagnosis of a TIA
- STROKE (can’t be distinguished until full recovery)
- Hypoglycaemia (symptoms spread and intensify over few mins with visual scintillations - blinking)
- Migraine aura
- Focal epilepsy
- Intracranial lesion (tumour or subdural haemotoma)
- Syncope due to arrhythmia
- Todd’s paralysis (transient weakness of arm, hand or leg after seizure)
- Retinal or vitreous haemorrhage
- Giant cell arteritis
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Why is Giant cell arteritis mistaken for TIA
- Raised ESR
- Thickening and tenderness of temporal artery
- Monocular, temporary visual impairment
How is TIA diagnosed
- FBC
- Carotid artery doppler ultrasound
- MR/CT angiography
- ECG
- CT or diffusion weighted MRI
- ECHO monitoring
What are we looking for in FBA for TIA
- Polycythaemia
- ESR (raised in vasculitis)
- Hypoglycaemia
- Creatinine, electrolytes
- Cholesterol
Why is a carotid artery doppler ultrasound done
Lok for stenosis/artheroma
Role of MR/CT angiography for TIA
Extent of stenosis
Role of ECG in TIA
Lok for AF or evidence of MI
How is TIA managed
- ABCD2 score risk
- ASPIRIN + DIPYRIDAMOLE
- CLOPIDOGREL in long-term
- Anticoagulant (WARFARIN)
- Simvastatin
- Ramipril or Candesartan
- Improve diet, stop smoking
DO NOT DRIVE FOR AT LEAST 4 week following TIA
What is the ABCD2 score risk assessment
- Age > 60 = 1
- Blood pressure >140/90 = 1
- Clinical features:
Unilateral weakness = 2
Speech disturbance without weakness = 1 - Duration of symptoms:
Symptoms lasting more than 1 hour = 2
Symptoms lasting 10-59 mins = 1 - Diabetes = 1
What does an ABCD2 score of 6 or more mean
- Predicts a stroke and referred to specialist immediately
ALL PATIENTS WITH SUSPECTED TIA should be seen within 7 days
Consequence of a score greater than 4
Specialist referral within 24 hours
What conditions can increase risk of stroke
- AF
- More than 1 TIA in on week
- TIA on anticoagulant
Role of purkyne cells in the cerebellum
- Receive synaptic inputs from the cerebellar nuclei
What neurotransmitter is used by purkinje cells
GABA (they had inhibitory effects)
What are the role of the granular cells
These are thin, unmyelinated axons that transmit into the purkyne layer
What do granule cells use as a neurotransmitter
Glutamate (excitatory effect on purkyne cells)
Where do mossy fibres originate from
Pontine nucleus
Role of mossy fibres
Excitatory synapses with granule cells
Where do climbing fibres originate from
Inferior olivary nucleus on contralateral side of brainstem
Name the four nuclei of the cerebellum
Dentate
Globose
Emboli form
Fastigial
Modalities of the dentate nucleus
Proprioception
nociception
Somatic input
Responsible for execution and planning of fine movement
Describe the direct pathway
Check book
Describe indirect pathway
Check book
What forms the ventral striatum
Olfactory tubercle and Nucleus accumbens
What forms the dorsal striatum
Caudate nucleus
Putamen