neuro investigations Flashcards

1
Q

skull x ray

A
plain radiographs provide info on bone joint and soft tissue 
preliminary investigation
AP
lateral 
PA
indication: head trauma 
ascertain linear skull fractures 
limited use in detecting depressed or comminuted fractures
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2
Q

computerised tomography

A

X-Ray source rotated around patient
Radiation attenuation measured
→ Two-dimensional picture

Map of tissue density: white = most dense, black = least dense

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3
Q

indications for CT brain

A

Most efficient method of triage for acute trauma
Advantages:
Fast
Accurate at detecting acute haemorrhage (within first 4 hours)
Excellent for assessing facial and skull fractures especially depressed and comminuted skull fractures
Can visualise bleeding including extradural haematomas (EDHs), subdural haematomas (SDHs), actively bleeding parenchymal haemorrhages, brain herniation, mid-line shift

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4
Q

cerebral angiography

indications

A

local anaesthetic catheter into femoral artery with help of guide wire up to carotid
films taken
subtraction of pre injection film from angiogram improves vessel definition

disorders of cerebrovascular circulation 
aneurysm 
arterio-venous malformation 
TIA 
cranial arteritis 
vascular tumour
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5
Q

MRI

role of MRI

A

clearer than CT
no radiation Magnetic field forces hydrogen protons in the body to orient to that field
Radio-frequency current is pulsed through patient, stimulating protons to spin out of equilibrium
Current is switched off and MRI detects energy released when protons re-align with magnetic field
Time taken and energy released depends on nature of tissue
MRI is like a map of proton energy within tissues of the body
MRI distinguishes the molecular composition of tissues, especially fat and water

It is more sensitive in detecting soft tissue abnormalities compared to CT or X-Ray

It is also able to evaluate changes in tissue composition over time, providing a window into the acuity of a disease

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6
Q

T1 vs T2 weighted image

A
water is DARK on T1  and BRIGHT on T2
Look for water (in the
brain, this will be the  CSF)
T1-weighted scans
provide better contrast  between gray and  white matter
T2-weighted scans are
better for oedema

T1 - fat is white
T2 WATER and FAT are white

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7
Q
other MRI methods 
STIR 
FLAIR 
DWI 
functional MRI
A

STIR = short tau inversion recovery
Highly water-sensitive, good for imaging spinal inflammation
FLAIR = fluid-attenuated inversion recovery
Suppresses the signal from free fluid (CSF), highlights pathology in the brain
DWI = diffusion-weighted imaging
Useful for indicating cell death, especially infarct

Contrast agents:
Gadolinium contrast – reduces time for protons to reorient, better at highlighting brain tumours (“gadolinium enhancement”)

Functional MRI (fMRI) correlates the brain’s changing blood flow requirements with changes in neural activity and translates them into differences in the MRI signal, particularly on T2-weighted images. fMRI is increasingly being used to map neural activity in the brain or spinal cord.

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8
Q

CI for MRI

A
ferrous metallic foreign bodies 
old gunshot shrapnel older types of fracture fixation 
implanted electrical medical devices 
cochlear implanted 
insulin pump
pregnant 
claustrophobia
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9
Q

PET

A

position emission tomography
nuclear medicine imagine
radiation introduced into body using a radio tracer
accumulates in organs to be measured and gives off a small amount of energy
energy is then detected and presented as an image
PET scans indicates body function including O2 flow, O2 uptake and glucose consumption
clinical uses : epilepsy, Alzheimers disease, cancer

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10
Q

lumbar puncture
role in diagnosis
complications

A

Purpose
To obtain CSF for analysis

Position
Side lying, Knees to chest
Needle into L4-L5 interspace
3 samples

Precautions
Raised CSF
Tentorial herniation-coning

Meningitis: microbiology
Encephalitis: cell count (erythrocytes)
Metastatic tumour: cell count (white cells)
Polyradiculitis or Guillain Barre Syndrome: protein content
Multiple Sclerosis: IgG synthesis = oligoclonal bands

Contraindications:
Raised intra-cranial pressure (ICP)
Coagulation disorder
Vertebral deformity

Complications  Headache (10%)  Radicular pain (10%)
Tonsillar herniation (extremely rare)

Usually bed rest few hours post LP
Avoid moderate to vigorous physical activity for 24 hours

Occasionally heat / electrotherapy indicated for pain post LP

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11
Q

muscle biopsy

A

Needle or open
Essential in diagnosis of inflammatory myopathies metabolic myopathies
Physiotherapy relevance: treat as a minor muscle injury

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12
Q

EEG

A

electro-encephalography
recording of cerebral electrical potentials by electrical potentials by electrodes on the scalp
abnormalities reflect general pathological processes not specific diagnosis

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13
Q

uses of EEG

A
epilepsy 
states of altered consciousness 
post traumatic and anoxic coma 
parasomnias 
dementias 
toxic confusional states 
cerebral infections 
encephalopathies
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14
Q

electromyography

A

Recording of electrical activity within a muscle
In this lecture, we are referring to EMG as part of
electrodiagnostics (EMG + NCS)
Other EMG: Kinesiological EMG can be surface or fine wire, used by physiotherapists to observe timing and activation of muscles during movement (e.g. Biopac)
Diagnostic EMG involves insertion of needles into muscle to record and observe motor unit action potentials

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15
Q

diagnostic EMG

A

concentric needle is inserted into muscle
potential difference amplified and recorded
normal muscle at rest is electrically silent
diagnostic
localise site of lesion
prediction of recovery

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16
Q

abnormalities on EMG

A

spontaneous activity on rest
fasciculation fibrillation
abnormalities of motor unit potential - amplitude rise time, duration, phases, stability

abnormalities of recruitments
interference pattern

17
Q

nerve conduction studies

A

peripheral nerve stimulated
time from stimulus –> response is calculated

conduction velocity = distance between two sites divided by time taken

18
Q

factors affecting NCS

A
age body temp 
pathology 
delay occurs with nerve entrapment 
demyelinating polyneuropathy 
multifocal motor neuropathy 

repeated stimulation: myasthenia graves

19
Q

evoked responses

A

= evoked potentials
measures electrical activity of brain in response to stimulation of specific sensory nerve pathways
VEPs - visual used in diagnosis of MS
SSEPS - somatosensory - monitoring during surgery

20
Q

electronystagmography

A

Electrical measurement of nystagmus (abnormal beating of the eyes)