2. Skull X-rays• Standard views:
– Lateral
– Postero-anterior
– Towne`s (fronto-occipital)
• Look for:
– Fractures
– Bone erosion: focal( pituitary fossa)
– generalized (Multiple
myeloma)
– Bone hyperostosis: focal
(Meningioma),
generalized (Paget`s disease)
– Abnormal calcification: tumors
(meningioma), aneurysmal wall
– Midline shift of pineal body
– Signs of increased intracranial pressure
– Configuration: platybasia, basilar
impression
3. Computed tomography (CT)
scanning
• A pencil beam of X-ray
traverses the patient's head
and a diametrically opposed
detector measures the extent
of its absorption.
• Determination of absorption
values for multiple small
blocks (voxels)
• Reconstruction of these areas
on a two-dimensional display
(pixels) provides the
characteristic CT scan
appearance
4.
5.
6.
7.
8.
9.
10. Interpretation of the cranial CT
• Ventricular system: size, position, compression
• Width of cortical sulci and sylvian fissure:
• Skull base and vault: hyperostosis, osteolytic lesion,
remodelling, depressed fracture
• Multiple lesions: tumor, abscesses, granuloma,
infarction, trauma
• Abnormal tissue density:
– Midline shift
– Ventricular compression
– Obliteration of the basal cisterns, sulci
– High density( blood, calcification in tumor or AVM or
hamertoma)
– Low (infarction, tumor, abscess, oedema, encephalitis,
resolving hematoma)
– Mixed (tumor, abscess, AVM, contusion, hemorrahgic
infarct)
12. MRI
Magnetic resonance imaging (MRI) is an imaging technique
used primarily in medical settings to produce high quality
images of the soft tissues of the human body.
It is based on the principles of nuclear magnetic resonance
(NMR), a spectroscopic technique to obtain microscopic
chemical and physical information about molecules
MRI has advanced beyond a tomographic imaging
technique to a volume imaging technique
13. • The composition of the human body is primarily
fat and water
• Fat and water have many hydrogen atoms
• 63% of human body is hydrogen atoms
• Hydrogen nuclei have an NMR signal
• MRI uses hydrogen because it has only one
proton and it aligns easily with the MRI magnet.
• The hydrogen atom’s proton, possesses a
property called spin
1.A small magnetic field
2.Will cause the nucleus to produce an NMR
signal
14. • The spinning hydrogen protons act like small ,
weak magnets.
• They align with an external magnetic field (Bø).
• There is a slight excess of protons aligned with
the field. (for 2 million , 9 excess)
~6 million billion/voxel at 1.5T
• The # of protons that align with the field is so
very large that we can pretty much ignore
quantum mechanics and focus on classical
mechanics.
15. • Now if an electromagnetic radio frequency (RF)
pulse is applied at the resonance (Larmor,
precession, wobble) frequency, then the protons
can absorb that energy, and (at the quantum
level) jump to a higher energy state.
• At the macro level, the magnetization vector,
Mø, (6 million billion protons) spirals down
towards the XY plane.
16. • Once the RF transmitter is
turned off three things
happen simultaneously.
1. The absorbed RF energy
is retransmitted (at the
resonance frequency).
2. The excited spins begin
to return to the original Mz
orientation. (T1 recovery to
thermal equilibrium).
3. Initially in phase, the
excited protons begin to
dephase (T2 and T2*
relaxation)
17.
18.
19.
20.
21.
22. FLAIR (T2 with water suppression)
T2 with fat suppression
T1 with contrast
Echoplanar
Proton density
MR spectroscopy (MRS)
Functional MRI (fMRI)
Perfusion MR
MR angiography/venography (see image below)
Diffusion and diffusion tensor MR
Diffusion-weighted imaging (good for small strokes)
Gradient echo (GRE)
Fast imaging employing steady-state acquisition (FIESTA)
23. Advantages
• Can select any plane, e.g. coronal,
sagittal, oblique.
• No ionizing radiation.
• More sensitive to tissue changes, e.g.
demyelination plaques.
• No bone artifacts, e.g. intracanalicular
acoustic neuroma
24. Disadvantages
• Limited slice thickness-3mm.
• Bone imaging limited to display of
marrow.
• Claustrophobia.
• Cannot use with pacemaker or
ferromagnetic implant.
25. MR angiography
• Rapidly flowing
protons can create
different intensities
and by a special
sequence can
demonstrate
vessels, aneurysms,
and AVM
27. Ultrasound
• Extracranial: Doppler, colour
doppler
• Intracranial-transcranial doppler
ultrasound:
– Assessment of intracranial
hemodynamics
– Detection of vasospasm in SAH
28. Angiography
• DSA: subtraction of a
pre-injection film from
the angiogram
eliminates bone
densities and improves
vessel definition
– Phases:
• Arterial
• Capillary
• Venous
Carotid
vertebral
30. Radionuclide imagingRadionuclide imaging
• Single photon emissionSingle photon emission
computed tomographycomputed tomography
(SPECT):(SPECT):
– Uses compounds labelled
with gamma-emitting tracers
(ligands) and a rotating
gamma camera is often used
for detection
– Detection of early ischemia
– Evaluation of patients with
intractable epilepsy of
temporal lobe origin
– Thallium SPECT: differentiate
low from high grade tumors.
32. Lumbar punctureLumbar puncture
• CSF analysis
• CSF drainage and pressure reduction
• Avoid LP:
– If raised intracranial pressure is suspected
– If platelet count is less than 40 000 and
prothrombin time is less than 50% of
control
34. OthersOthers
• EEG
• Evoked potentials:
– Visual
– Auditory
– Somatosensory
• EMG and NCS
• Neuro-otological tests
– auditory system
– vestibular system
35. BAER - brainstem auditory evoked response
• Brainstem auditory evoked response (BAER) is
a test to measure the brain wave activity that
occurs in response to clicks or certain tones.
• The test is done to:
– Help diagnose nervous system problems and hearing loss
(especially in newborns and children)
• Find out how well the nervous system works
– Check hearing ability in people who cannot do other hearing
tests.
– This test may also be performed during surgery to decrease the
risk of injury to the hearing nerve and brain.
36. • Abnormal test results may be a sign of hearing loss,
multiple sclerosis, acoustic neuroma, or stroke.
• Abnormal results may also be due to:
• Brain injury
• Brain malformation
• Brain tumor
• Central pontine myelinolysis
• Speech disorders
•
37.
38. • The waveform represents specific
anatomical points along the auditory
neural pathway: the cochlear nerve and
nuclei (waves I and II), superior olivary
nucleus (wave III), lateral lemniscus (wave
IV), and inferior colliculi (wave V). Delays
of one side relative to the other suggests a
lesion in the 8th cranial nerve between the
ear and brainstem or the brainstem itself.
