When people ask about what J “has”, I say “a severe neuromuscular disease.” I don’t mean to be vague, but it’s complicated. This is my attempt to make it simple.
The Big Picture
I can’t walk, but I can talk.
— Julianna, age 4
Julianna resembles a 5 year old with ALS (Lou Gehrig’s disease). She has progressive, profound weakness, but her cognition is unaffected.
The Disease: Charcot-Marie-Tooth
Julianna’s disease has a PR problem. With apologies to Drs. Charcot, Marie and Tooth, the name is awful. No one knows what it means, it’s cumbersome to spell and it suggests a dental issue. And the acronym? Try googling “CMT” – you have to get to the third page before you get something other than country music.
This is CMT in a nutshell.
- Charcot-Marie-Tooth is named after 3 neurologists who first described the disease in the 1880’s.
- It is a hereditary neuropathy.
- Neuropathy means that there is a problem with the peripheral nerves.
- What are peripheral nerves? Your brain and spinal cord make up the central nervous system. Everything outside of this is the peripheral nervous system. Nerve roots come out of the spinal cord (when those get squished, they cause a “pinched nerve” in the neck or back.). The nerve roots branch and branch and branch. They go all the way to the toes and the fingertips. These are the peripheral nerves.
- Problems with the peripheral nerves can cause sensory changes (i.e., numbness, tingling, pain) or weakness – or both.
- There are over 70 identified forms of CMT, and new ones are being discovered every year. This is because a lot of different genes code for our peripheral nerves.
- CMT can be diagnosed with a blood test – sometimes. Commercial gene testing exists for a few dozen types. Research labs are working on identifying rare or new types.
- Treatment for CMT is supportive – meaning, you treat the symptoms but cannot cure or stop the disease.
- CMT can be funny. Sometimes it is really mild in one generation, and really severe in another. Which brings us to…
This is Steve’s foot. I always thought that his feet were funny looking.
Steve has high arches, which is a sign of peripheral neuropathy. Steve is active and athletic, so I had no reason to suspect a problem until we started searching for J’s diagnosis.
One afternoon when J was almost 18 months, I decided to check Steve’s reflexes. His arm and knee reflexes were normal. I checked the ankles, and they were – not there. This was definitely not normal. Decreased or absent deep tendon reflexes are another sign of peripheral neuropathy.
I think that this was the moment I knew. For months, I had been thinking of things that would cause J’s symptoms. CMT was on the short list, but there was no known family history.
A few days later, I brought Steve into my office and did a quick nerve conduction study (NCS). This is not the most fun test : electrodes are placed on the legs and arms, and some pretty big shocks are delivered. It measures the speed and size (amplitude) of nerve conduction.
In the legs, nerve impulses should travel at least 40 m/s. Steve’s nerve conduction in the legs was not recordable.
In the arms, nerve impulses should travel at least 50 m/s. Steve’s nerve conduction velocities were in the 20’s.
If there was any doubt before, it was gone at that moment. Steve had CMT. Julianna must have it too.
Things came together pretty quickly after that. I took Julianna to a pediatric neurologist. Her NCS showed velocities of about 10 m/s in the arms. She and Steve had genetic testing done for the most common mutations that cause CMT – it was negative.
As mentioned, commercial gene testing only identifies the most common types of CMT. Shortly after Julianna turned two, we visited Dr. Michael Shy, a CMT expert, in Iowa. His team helps find new and rare cases. They suspect that Steve passed on a gene mutation that causes very mild disease. Julianna probably has a second mutation that makes her disease severe.
For the last three years, researchers around the world have been trying to figure out what gene mutation(s) have caused Julianna’s disease. They have some ideas, but nothing definite. Like I said, it’s complicated.