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Dr. Palmer ants here from memory online. We're talking

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rare diseases today and charcoal Marie

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tooth disease this enigmatic disorder

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that you learned about in medical school, but thought you'd never see. Well, you will

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see it it goes by the abbreviation CMT and

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there are some other synonyms that you have

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heard throughout your medical career hereditary motor and

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sensory neuropathy or hmsn perennial

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muscular atrophy distal hereditary

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motor neuropathy d h

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m n hereditary sensory neuropathy

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or HSN or HSA and

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some debate whether that's included in

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the subset of nomenclature and

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distal spinal muscular atrophy or

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DMS a

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Now this is one of the few disorders that is named after three

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doctors who originally described the

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disease John Martine. Charcoal Pierre Marie

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and Howard Henry tooth Jean Martine

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charcoal is often referred to as the father

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of Neurology and you've heard his name on other

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disorders.

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now in terms of genetics

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the genetic center around the duplication of one major Gene

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and that is pmp22 Gene

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which you received one from each parent by the

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way in cmt1, and it's common subset

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one a

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This is a demolinating autosomal dominant

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disorder, but it accounts for at least 50% of

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all the cases of charcoal

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Marie tooth cmt2 may involve

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more the center of the nerve the the axon

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it's also autosomal dominant cmt4 recessive

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and these are far less common this single

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Gene duplication of PMP 22 accounts

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for at least 50% of the

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cases. However, there are over 100 gene

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mutations associated with

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charcoal Marie to syndrome that have been described CMT.

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Well an autosomal dominant disease, it's

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not just one disease. It has enumerable subtypes and

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each variant has in common involvement of

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the myelin sheath of the peripheral nerves. The disease

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is slowly Progressive and variable and can

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arise without any redo familiar

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history in some cases which makes it

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a bit confusing.

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CMT is the most common neuropathy in

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the lower extremities and the perineal and tibial nerves

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will often be the presenting areas for you.

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And so looking at the lower extremity is

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going to be very important in these individuals the

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symptoms usually present in adolescence. The

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symptoms are variably motor

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and sensory. They can be more towards the

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pure sensory more towards the pure motor and they

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involve the hands and feet.

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The patients may experience foot drop muscle atrophy cramping

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paresthesis nerve pain

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clumsiness sprained ankles falling and

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typically when you look at these patients who have progressed

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to a certain level, you'll see something called a stork

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leg where the upper portion of the leg is nice and plump and

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then it tapers very abruptly for a long

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distance pescavis or a high arch foot pest planets

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a flat foot and then claw hand

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or hammer toe Pearl.

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The longest nerves in the body are affected first. So the

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branches of the sciatic nerve the perineal nerve and the

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tibial nerve are commonly affected. There are

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a couple of other Oddities that I wanted to share with you

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one is known as nhpp. It's

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a hereditary neuropathy with a

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predilection to pressure palsies now unlike

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the other cases are charcoal Marie tooth

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where there is a PMP 22 Gene duplication.

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This one is a gene deletion.

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Which makes it all the more interesting cmt3 formerly

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known as dejareen sotis syndrome,

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some of you have heard this name previously as

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a subset of giant

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cell neuropathy with nerve swelling.

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We no longer use this term dejareen sodas has

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fallen out of favor, and then there are hereditary sensory and

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hereditary motor neuropathies, which some people

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include in charcoal Marie tooth and others divide them

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into disorders unto themselves.

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the diagnosis of CMT involves nerve

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conduction testing biopsy of

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the Cyril nerve DNA testing also not

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shown here assessing the other members

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of the family and sometimes Imaging

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Let's have a look at a real case on Mr. Imaging.

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This is the 35 year old man who presents with weakness

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and clumsiness and also knee pain?

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He's carrying a small anterior knee effusion.

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And what should strike you as you

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look at the stack of artery?

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Vein and nerve is the

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signal of the nerve now normally a nerve

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signal is going to be intermediate and confluent.

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If you have very high resolution,

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then you may see subunits of

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the nerves you might see little dots inside.

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And they should fill that entire space. They should

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be symmetric. They should each be the same

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caliber. None of them should demonstrate any crimping or

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interruption or defects what we

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see in this patient. Let's look

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at the tibial nerve right here is something

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that's a little bit gray on the outside. But rather

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white on the inside, let's blow it

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up. It is a T2 weighted image.

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I mean, where is that confluent solid gray

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signal intensity. That's not gray.

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That's hyperintense in the center. And

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also in the periphery only a thin

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shell of hypo intensity remains and

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just to show you that it's not just one slice. It's

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contiguous. You never ever

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see that confluent beautiful.

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Homogeneous gray signal intensity now this

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nerve up higher this tibial nerve

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up higher when it merges with the perineal nerve will become

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the sciatic nerve and the sciatic nerve innervates the

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hamstrings now, let's demagnify or demystify this

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and look at our semimemembranosis muscle.

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It looks so much different than its Brethren on

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either side. And that's because it's severely a

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trophic as a result of this

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demyelinating peripheral nerve syndrome,

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but we're not done yet. We're going to track our perineal nerve

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which as we go up.

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Doesn't quite meet the tibial nerve, but it's on

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its way. Let's blow this up and make it bigger again.

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And look at our perineal nerve. It's so bright.

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Within that it's almost cystic appearing

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now. Let's work our way down signal signal.

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signal

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signal and the signal persists for quite a

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long distance. And remember this is

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a disorder that likes to affect the longest nerves in the

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body another tip off to the diagnosis. All those

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subtle besides that semi-membranosis atrophy,

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which is weird is this

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In the lateral compartment, you're starting to see a

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component of myo edema, which is

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the precursor of muscular atrophy

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and is a form of nerve injury

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manifest as initial muscle swelling

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and then the muscle becomes a trophic

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small and fat latent.

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So this is one of our cases of charcoal Marie

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tooth. Shall we look at another?

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This 28 year old girl presented with left leg numbness

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extending from the knee down. So more

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of a sensory presentation. Let's look

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at the axial projection. I'll bring out

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my trusty pen.

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And my MRI online yellow right

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there and we've got an artery nice and black with flow

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void in the middle. Then we've got a vein on top

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of that. It's a little bit larger and then

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behind that we have the nerve. So let's take

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my yellow markers off for a minute. And let's look at

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the nerve. It's got numerous components to it.

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What is this component this very bright

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area. I'm going to put an arrow on it right now. So the non

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radiologist viewing this video can see it

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right there that is Cystic to generation of

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the myelin of a nerve and also,

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it's Axon.

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Then we've got another Finding and that is in the perineal nerve.

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Look at the bizarre appearance of

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the perineal nerve in the prior case, even though

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I don't have my gray color to show

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you the nerve should be a fairly homogeneous structure

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and occasionally with high resolution.

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You'll see some of its internal subunits. I

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drew it in yellow, but it's really more gray or

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dark gray. What is this high fat

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like signal intensity that wraps itself around

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the nerve this is this is Schwan

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Schwan cell degeneration. So to speak

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and then we look at the coronal projection now and we

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have an interesting finding that should have been the tip off

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to the diagnosis in the first place. When we hone in

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on the area that the patient describes as being symptomatic which

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was in the outside of the

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leg. We see that the lateral compartment is a

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bit a trophic. It has a little too much fat in it

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and the fat for the non.

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Ideologist again being the high signal intensity

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because this is a fat weighted T1 weighted

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image. Whereas the image on the right is a water

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weighted image. The fat should be dark either dark

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gray or black here. It's dark gray. And what

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do we see in the muscle? We see a muscle that is intensely

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right all the way up and

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down in the lateral compartment. And this is an example of

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myo edema secondary to

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denervation. So this is slightly different

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example from from the former case where you're

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seeing extensive muscular edema and

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slightly different manifestations of nerve cell

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degeneration in one of the variants of Sharko Marie

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tooth.