0:01

This was a very valuable teaching case in an

0:05

individual who presented to the emergency room with

0:08

a two-week history of a left-sided Horner syndrome.

0:13

I was reading this case with the fellow,

0:15

and it was a patient that had quite a

0:19

bit of pathology on the flare scan.

0:22

What we noticed was that there were multiple white

0:25

matter lesions that were identified in the

0:28

periventricular and subcortical region in a pattern

0:32

that was suggestive of multiple sclerosis.

0:34

The patient did not have a history

0:37

of multiple sclerosis.

0:39

So as I was going over this case with the fellow,

0:41

I said, well,

0:42

we should be very careful about demyelinating

0:45

plaques near the hypothalamus,

0:47

which might account for the patient's Horner

0:50

syndrome or around the third nerve nucleus.

0:53

And we were going over the anatomy of the third

0:55

nerve nucleus in the periaqueductal region

0:59

and looking for demyelinating plaques.

1:01

And I was waxing poetic about MS and how

1:06

it could cause a Horner syndrome.

1:08

The next study was the cervical spine

1:11

and the cervical spine examination.

1:13

I was again talking about how the neurons that lead

1:19

to Horner syndrome may extend into the cervical

1:22

spinal cord, and in particular,

1:24

you wanted to be careful about the C7-T1

1:28

level. So we looked at the cervical spinal cord.

1:31

We saw that there was a little bit of expansion of

1:33

the spinal cord here at the C7 level and then

1:37

went on to the axial scans looking for demyelinating

1:41

plaques. And as you can see,

1:42

there's some bright signal intensity that occurs in

1:45

the midline of this patient and then off to the

1:48

right side in the lateral aspect of the spinal cord

1:52

and then proceeding down even into

1:55

the lower cervical spine.

1:57

We were looking at the C7-T1 level and wondering

2:01

whether there was a demyelinating plaque at the C7-T1

2:05

level on the left side that could account

2:07

for the patient's Horner syndrome.

2:09

Here's the first rib identifying the C7-T1 level

2:12

on the left side. So I was saying, well,

2:15

we have multiple sclerosis,

2:17

we have demyelinating plaques,

2:19

we have something potentially in the periaqueductal

2:21

region. We have something down to C7-T1 level.

2:24

All of these could cause a Horner syndrome.

2:27

But the patient also had an MRA.

2:30

So on the raw data of the MRA,

2:34

I was commenting to the fellow that we should be

2:37

careful to look for an aneurysm which may occur

2:42

at the posterior communicating artery,

2:44

which might affect the third cranial nerve.

2:47

And we sort of spent a lot of time looking at the

2:51

posterior communicating artery and wondering whether

2:53

there was a little bit of an aplasia here.

2:56

So in the end, we read this out as a new

3:00

diagnosis of multiple sclerosis

3:01

with demyelinating plaques,

3:03

which could potentially explain a Horner syndrome,

3:06

and recommended that they look at the

3:11

different first-order, second-order,

3:12

and third-order neurons for the determination of

3:16

the type of Horner syndrome.

3:18

The next day,

3:19

I got a phone call from the neurologist,

3:22

and he said, "That was very excellent work.

3:25

I'm wondering, however,

3:26

whether this patient had a dissection of the

3:29

internal carotid artery on the left side,

3:32

which might be present on the imaging.

3:36

And as I went back over the case, sure enough,

3:40

here's the internal carotid artery,

3:42

and here is a bright signal intensity wall hematoma

3:46

of a left internal carotid artery dissection as

3:51

a source of the patient's Horner syndrome.

3:53

In fact, what I missed on the MRA,

3:56

and which is clearly obvious now,

3:59

is here you can see the internal carotid artery and

4:03

the bright signal intensity wall hematoma accounting

4:07

for the patient's Horner syndrome.

4:09

So, of the different causes of Horner syndrome,

4:12

we got the demyelination in the periacoductal

4:14

region, we got the demyelination in the C7-T1 level.

4:18

We looked for the aneurysm at the posterior communicating artery,

4:21

but the classic diagnosis is a carotid dissection,

4:24

which we missed. So did an addendum on the report.

4:28

Fortunately,

4:29

the complication of the carotid dissection,

4:31

which is flipping a clot up intracranially

4:35

leading to a stroke, did not happen.

4:38

This patient was placed on the antiplatelet drugs

4:42

Aspirin and Plavix to prevent potential thrombus

4:48

formation and did well in the hospital.

4:51

And my mistake

4:54

did not account for any complication.

4:57

But this is an example, I think,

4:59

of a great case of what is called a satisfaction of

5:03

search error, a cognitive error in interpretation.

5:07

We looked for various pathologies.

5:10

We found various pathologies,

5:12

including the demyelination,

5:15

the new diagnosis of multiple sclerosis,

5:17

and the possible aneurysm, and we gave up.

5:19

At that point,

5:20

instead of continuing to look for additional

5:22

pathology where the carotid artery dissection

5:26

would have been discovered.