neuroophthalmology and imaging modalities

1. NEUROIMAGING AND
ELECTRO-
DIAGNOSTICS
Dr Usama Iqbal

2. NeuroImaging
 Objectives:
 What type of Modality to order
 Interpretation
 CT and MRI findings of common ocular and
Orbital Pathologies

3. CT Scan
 Back to Basics.
 What is CT or Computed Tomography.

4.  It employs X rays which pass through body
and reach a detector , image is reconstructed
using computer.
 Tissue Density is represented by gray Scale.
 White being Maximum Density (Bone) and
Black being Minimal Density (air).

5. Contrast Enhancement
 Iodinoized Contrast medium improve
sensitivity and specificity.
 CI > allergic to I, and CKD.
 Not Indicated in case of Haemorrhage,
Fractures and Localization of FB’s.

6. Indications ( 1st Objective 0f
Class)
 Orbital Trauma ( Bone )
 EOM Evaluation
 Orbital Tumors ( Bony Involvement)
 Orbital Cellulitis
 IntraOrbital Calcifications & IOFB
 Acute haemorrhage
 When MRI in C/I > Ferrous FB.

7. Not Useful
 Optic Nerve Diseases
 Demyelinating Disorders

8. How to Read CT- Scan
Have a Knowledge about Normal
Anatomy.
Fluid filled structures like globe , fat are dark
Dense structures like bone are dense

10.  Lets get Started.

22. MRI
 What is MRI?

23.  MRI employs a powerful magnet , radio waves
and movement of protons inside our body to
produce images.
 Unlike CT it does not subject the patient to
ionizing Radiations.

24. Benefits and DeBenifits
 MRI is used in
 Optic nerve pathology , Optic Nerve Sheath
Lesions. Demyelination and cranial nerve
assessment.
 Sellar Masses, Cavernous Sinus Pathology,
Intracranial Lesions of Visual Pathway.
 • Less useful in trauma. Fractures not well
depicted.

25. Warning
 Caution about MRI
 • MRI should not be done in a patient
suspected of metallic foreign body without
doing CT. if a ferromagnetic particle is present
, it can have missile effect and damage orbital
structures. •
 Should be cautious while doing MRI in patients
with pacemakers , protruding metallic objects,
Cochlear Implants.

26. Basic Sequences
 Weighting Refers to Two Methods of
measuring relaxation time or protons when MF
is switched off.
 One Can see Pathology in Many Colours.
 We call them T1 and T2 weighted images

29. Image Enhancement
 Gadolinium Contrast administered IV, only
visualized on T1 weighted images,
 Fat Suppression Techniques> Useful for
imaging the Orbit.
 STIR sequence , this sequence suppresses fat
to highlight pathology.

31. Other Sequences:
 (Just for Exam Point of view)
 FLAIR: Supresses signals from CSF > useful
for Peri Ventricular Plaques of Demylination.
 FIESTA and CISS: Cranial Nerve Palsies.

32. Normal MRI (Spotting)

36.  Lets move to pathologies.

37. Multiple sclerosis. T1-weighted axial MR
image
showing characteristic periventricular

38. Enhancement techniques. (A) Pre-contrast sagittal T1-weighted image of a
meningioma; (B) post-contrast image showing enhancement of the tumour

42. Angiography
 MRA:
 Non Invasive Method
 to demonstrate abnormalities such as
stenosis,
 dissection, occlusion, arteriovenous
malformations and aneurysms.
 MRV:
 dural sinus occlusion and stenosis.
 it suitable for patients to whom contrast cannot
be given

43. CT Angiography & Venography
 The method of choice in the investigation of
intracranial aneurysms
 CTV is believed to be at least as sensitive as
MRV in the diagnosis of cerebral venous
thrombosis However, contrast is always
required and a significant radiation dose is
delivered.

44. Catheter Angiography
 Until recently, this technique was the first-line
investigation in the diagnosis of intracranial
aneurysms but may now be reserved for cases
where CTA is equivocal or negative

46. ElectroDiagnostics
 Visual (visually) evoked potential
 (VEP) tests record electrical activity of the
visual cortex created by retinal stimulation.
Extracted from EEG.
 Indications:
 monitoring of visual function in babies and the
investigation of optic neuropathy particularly
when associated with demyelination.

47.  Technique.
 The stimulus is either a flash of light (flash
VEP)
 or a black-and-white checkerboard pattern on
a screen that periodically reverses polarity
(pattern VEP)

48.  Latency (delay) and amplitude are assessed.
In optic neuropathy both parameters are
affected, with prolongation of latency and a
decrease in amplitude

49. We did it in 1992

50. 2009

51. 2017

53. We have Proved our self
Already

54. Green for WC 2019 (IA)