0:00

Up until now,

0:02

with respect to the evaluation of trauma

0:04

and degenerative diseases of the globe,

0:07

we have relied on CT scanning.

0:09

Now you may ask, "Why rely so heavily on CT scanning,

0:13

particularly for diseases that also occur in children?"

0:16

The problem with MRI scanning in globe

0:19

pathology is that the eye moves.

0:22

So it's very hard to have the patient fixate their gaze

0:26

for 3-5 minutes during a typical MRI pulse

0:29

sequence and not have motion artifact obscure subtle

0:33

abnormalities, such as anterior hyphemas

0:37

or small detachments of the globe.

0:40

In this situation,

0:41

we are most concerned with the intracranial extension

0:45

of this patient's retinoblastoma.

0:47

We've seen the CT scan and we saw the calcification.

0:51

Calcification is much better visualized

0:53

on CT rather than MRI.

0:57

This first pulse sequence that's being shown

0:59

is the brain image, a FLAIR scan.

1:03

However, it nicely depicts the difference in the intensity

1:09

of the left globe compared to the right globe.

1:13

The right globe has normal CSF intensity

1:17

in the vitreous.

1:19

However, the left globe is bright in signal intensity

1:23

on this FLAIR scan.

1:28

We note that there are different components

1:31

of the globe signal intensity.

1:34

There is the very high bright signal intensity,

1:37

and then we have some intermediate

1:39

signal intensity tissue.

1:41

And to establish whether or not this represents

1:46

hemorrhage versus tumor will require gadolinium

1:50

enhanced pulse sequences.

1:52

We also note, in this case, that

1:54

there appears to be a mass

1:57

between the internal carotid arteries

2:00

in the suprachoroid

2:02

portion of the internal carotid arteries in the

2:06

suprasellar cistern. To evaluate this mass,

2:10

we would prefer to have coronal images.

2:13

These are the coronal T1-weighted scans

2:16

through the orbits, as well as the brain.

2:21

As we scroll through this,

2:22

we'll initially look at the orbital imaging.

2:25

The orbital imaging demonstrates the absence of a lens

2:30

on the left side, and the enlargement of the globe,

2:36

with mixed signal intensity abnormality.

2:40

Here we have slightly hyperintense

2:43

area of T1-weighted signal.

2:46

Here we have a mild hyperintense area of signal.

2:53

And this should be CSF in signal intensity.

2:57

So, both of these are abnormal.

3:00

But there's different components within the abnormality.

3:03

If we scroll more posteriorly,

3:06

we see that we have marked enlargement of

3:10

the left optic nerve sheath complex.

3:13

The left optic nerve sheath complex

3:18

is enlarged compared with the right, and this will

3:21

extend posteriorly through the optic canal.

3:25

Here we are scrolling posteriorly and we enter

3:29

the optic canal. From the optic canal,

3:32

we have the prechiasmal optic nerve segment.

3:37

On the right, we have the normal optic nerve.

3:43

On the left, you have an enlarged optic nerve.

3:48

We then scroll more posteriorly.

3:54

On this image,

3:55

we see the pituitary gland as the slightly hyperintense

4:00

material between the cavernous carotid arteries.

4:02

The cavernous carotid arteries

4:04

show the signal void of flow.

4:08

However, above the pituitary gland, we find this mass.

4:12

This is the intracranial extension of the retinoblastoma,

4:18

coursing along the optic nerve

4:20

to involve the optic chiasm.

4:23

We can scroll more posteriorly and we arrive at

4:28

the posterior margin of the optic chiasm.

4:33

On this image,

4:34

we see the third ventricle,

4:38

inferior portion, and we see the posterior

4:44

portion of the optic chiasm.

4:47

However, there is a mass which is infiltrating the posterior

4:51

portion of the optic chiasm,

4:52

even to the base of the third ventricle.

4:56

It is now at the point of entering the brain.

5:00

This is better seen on the axial

5:03

scans on T2 weighting.

5:07

When we scroll through this

5:10

sequence,

5:12

we again see the abnormal mass

5:16

in the suprasellar cistern.

5:24

However,

5:25

emanating posteriorly, we can see extension of the tumor

5:33

into the brain substance itself.

5:36

This is depicted as the brighter areas

5:41

on the T2-weighted scan.

5:43

And this tumor can track along the optic pathway into

5:48

the optic radiations of the temporal lobe

5:52

and even to the occipital lobe.

5:55

Let's now look at the post-contrast fats suppressed

6:00

T1-weighted scans.

6:02

In this case,

6:04

one can see the intracranial component of the tumor in

6:08

the suprasellar cistern and extending

6:11

through the optic canal.

6:14

We also see a component that is in the

6:17

cistern anterior to the midbrain.

6:22

These are seen along the surface of the midbrain and in

6:29

the suprasellar cistern, as well as along the

6:34

optic nerve in the orbit.

6:36

Once again,

6:37

it is important to make sure that one scrolls through

6:40

and observes the signal intensity enhancement

6:44

characteristics of the contralateral globe

6:47

to exclude bilateral retinoblastomas,

6:50

which may occur in one third of patients.

6:53

In those patients who have familial retinoblastoma

6:57

and bilateral retinoblastoma,

6:59

one may have what is called the trilateral retinoblastoma.

7:05

In this case, you see a mass in the pineal region.

7:09

The pineal gland is considered the

7:12

"third eye", because you may have pineal blastomas in

7:16

association with bilateral retinoblastomas

7:19

in those patients who have hereditary retinoblastoma.

7:25

This patient does not have that.

7:30

However,

7:33

on the axial post-gadolinium enhanced

7:36

scans, through the pontine region,

7:40

one sees an area of abnormal enhancement.

7:44

This is on the right side,

7:46

and this area of contrast enhancement

7:49

represents subarachnoid seeding

7:53

within the brain of retinoblastoma.

7:57

In this case, along the root entry

8:00

zone of the fifth cranial nerve.

8:04

If one scrolls additionally through this case,

8:09

it sheds light on the abnormality that was identified

8:12

at the surface of the midbrain.

8:15

This area of contrast enhancement is along the

8:20

typical route of the third cranial nerve,

8:25

leaving from the interpeduncular cistern

8:28

and coursing towards the left eye.

8:31

So this patient has subarachnoid seeding along the left

8:36

third cranial nerve as well, as the right fifth cranial nerve,

8:40

and therefore, has a very poor prognosis.