neuro investigations Flashcards
skull x ray
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
computerised tomography
X-Ray source rotated around patient
Radiation attenuation measured
→ Two-dimensional picture
Map of tissue density: white = most dense, black = least dense
indications for CT brain
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
cerebral angiography
indications
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
MRI
role of MRI
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
T1 vs T2 weighted image
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
other MRI methods STIR FLAIR DWI functional MRI
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.
CI for MRI
ferrous metallic foreign bodies old gunshot shrapnel older types of fracture fixation implanted electrical medical devices cochlear implanted insulin pump pregnant claustrophobia
PET
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
lumbar puncture
role in diagnosis
complications
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
muscle biopsy
Needle or open
Essential in diagnosis of inflammatory myopathies metabolic myopathies
Physiotherapy relevance: treat as a minor muscle injury
EEG
electro-encephalography
recording of cerebral electrical potentials by electrical potentials by electrodes on the scalp
abnormalities reflect general pathological processes not specific diagnosis
uses of EEG
epilepsy states of altered consciousness post traumatic and anoxic coma parasomnias dementias toxic confusional states cerebral infections encephalopathies
electromyography
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
diagnostic EMG
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
