0:00

This is an MRI of the brain in a seven

0:03

month-old child with seizures.

0:05

And in the supratentorial brain,

0:07

we can actually see some abnormalities

0:08

in expansile areas of subcortical TT prolongation,

0:12

and possibly some subependymal nodules

0:16

along the lateral margin of the

0:17

body of the lateral ventricles,

0:19

which are suggestive of tuberous sclerosis complex.

0:23

But if we go to the posterior fossa,

0:26

we can actually see what looks like fullness

0:29

at the level of the foramen magnum.

0:31

On the sagittal image,

0:32

we can identify the basion and the opisthion.

0:37

Drawing a line between them

0:39

approximates the plane of the foramen magnum,

0:41

and we can measure that there's

0:43

approximately 9 mm of cerebellar tonsillar extent

0:47

caudal to the level of the foramen magnum.

0:51

This patient had tuberous sclerosis complex.

0:54

They had no symptoms that we were aware of

0:57

related to a Chiari I malformation.

0:59

So, they were followed closely because we knew

1:02

that they were going to get detailed neurologic

1:05

follow-up and detailed imaging follow-up.

1:08

Well,

1:09

a few years later,

1:11

if we look,

1:13

there's actually no longer any cerebellar

1:15

tonsillar ectopia.

1:16

And why is that?

1:18

Well,

1:20

one proposed mechanism

1:23

of a Chiari Type I malformation

1:26

is that you have normal

1:28

developmental growth of the cerebellum,

1:32

but the posterior fossa is

1:35

smaller than it should be.

1:38

And because the posterior fossa

1:41

or the container is too small,

1:43

the cerebellar tonsils or the cerebellum just

1:47

conforms to the container it has available,

1:49

and the cerebellar tonsils start to grow

1:52

caudally and extend caudally where the volume

1:56

of the cerebellum may be normal.

1:58

It's just it has to contort

2:00

to fit its container.

2:02

But remember,

2:04

this first started when this

2:06

child was seven months old.

2:08

We know the brain grows after seven months

2:11

of age, but we know the skull grows.

2:14

So, this is an entity I've seen several times

2:17

where you have a Chiari Type I malformation at

2:20

a young age that was asymptomatic,

2:23

and when followed, ends up normalizing.