Does anyone know anything about spinal muscular atrophy type 4?

[Kitchener]

Hello Everyone

I'm back on the forum after a few months off while being treated for multifocal motor neuropathy (MMN). Just to briefly recap my history on this forum I was diagnosed with MND in March 2011 and subsequently referred to a second neurologist who was unconvinced by the original diagnosis. She took the view that while I could very well have MND, I might instead have MMN and I have been on IVIg treatment since last May. My health thankfully has been good throughout, and I have only experienced weakness and atrophy in one hand (the right) over the past nine months (although this has been slowly progressive). I can still run, cycle, swim and function normally. However, I think my neuro has become a little uncertain of the MMN diagnosis because my hand is getting worse, not better (despite the fact the rest of me is fine). Yesterday she brought up the possibility that I might have late onset (Type 4) spinal muscular atrophy (SMA). For reference I am in my early 40's and have been experiencing symptoms (fasciculations, progressive weakness right hand only) for 14 months. I understand SMA is a genetic condition, and my neuro has sent me to the pathology lab to get a genetic test done to check for damage/deletion of the SMN1 gene. As this forum contains a vast font of knowledge on all things neurological, I wonder if anyone knows anything about SMA and specifically:

(i) how accurate is the genetic test?
(ii) what are the range of prognoses for Type4 SMA?

Many thanks for your help!

 

[kashmiri]

Hi @Kitchener,

Sorry to hear about your condition. As to your questions,

1. Genetic testing for SMA is very reliable and is conclusive of disease.
2. Symptom spectre in SMA type 4 ranges from light mobility impairment (problems with walking) to complete loss of mobility combined with wasting of other muscles (most commonly proximal muscles of hands). Moscles on both sides are equally affected. Other complications so common in "lower" SMA types (esp. respiratory problems) are extremely rare in SMA 4.
It might be interesting to have a genetic testing done towards the number of SMN2 gene copies as this can give some clues about the course of disease (the higher the SMN2 copy number, the less severe the symptoms are likely to be); however, this testing is not normally available commercially and few labs do it.

I recently updated and expanded the Wikipedia article on SMA, you might like to have a look there.

Wish you good luck!

 

[Kitchener]

Hi Kashmiri

I really appreciate the feedback. The hands sound like me, the legs don't. However, if the test is reliable I will know one way or the other in the next few weeks.

As an aside, I'm a little surprised that spinal muscular atrophy (SMA) doesn't crop up more often on the "Do I have ALS?" board. The initial presentation of symptoms appears very similar to ALS, and I suspect that because the condition involves loss of motor neurons the EMG of a person presenting with SMA would be very hard to distinguish from one with ALS (Wright, please correct me if I'm wrong there). True it is very uncommon, but so is ALS and the incidence rates in the general population would be of the same order of magnitude. That said it's taken my neuro nearly a year to realise this may be a possibility for me. I'm very interested in other people's thoughts on this subject.

Many thanks

Kitchener

 

[Bliz]

In SMA IV there is no bulbar involvement and the progression is usually (not always) pretty slow so its often called "benign". From what I know, there is no upper motor neuron involvement so together with absence of bulbar signs and speed of progression these are clues that can differentiate it against ALS.

 

[Kitchener]

Thanks Bliz

I agree that lack of UMN involvement can differentiate SMA from ALS. I am thinking though that someone presenting with SMA IV would get a "dirty" EMG, very similar to ALS (and close enough that some neuros who aren't hyper-specialised might miss the difference). I will caveat the last sentence by deferring to anyone on this forum who knows more about EMGs than me, and can share a view on it. What I am getting at is that I believe that anyone who gets a "dirty" EMG but doesn't have obvious UMN symptoms should discuss getting a genetic test for SMA IV with their physician.

 

[laurel]

Kitchener how much IVIG do you receive and how often? Over on the GBS/CIDP forum there has been lots of discussion about how many neurologists don't prescribe the right dose and not often enough. Unfortunately that forum is shut down right now while they update it--as a member posted a very good video during which the top neurologists discussed the importance of frequency in prescribing IVIG. Lots of members were getting it every 4-6 weeks and were deteriorating before their next treatment. I'll try to see if I can turn up that discussion by searching on the internet. I know my husband gets 100 Grams every 3 weeks and that just marginally maintains him. If he is a day or two late his loses strength and grip in his hand. I'll search and let you know what I turn up. I think the same principles apply with MMN.
Laurel

 

[Kitchener]

Hi Laurel

I get 60 grams of IVIg every two weeks, so pretty close to your husband. For reference my weight is 78 kgs. Over the past 9 months of treatment I have retained my health and still go running, cycling etc. I have had some meodest deterioration of my right hand - my grip os OK but weaker (can still carry shopping bags), I have trouble with the fine motor things like turning a key or writing. Otherwise I'm fine. I'm fine over the course of the two week interval in IVIg, except that the infusion seems to stimulate my fasciculations over the first week and then this calms down over the second week. I think that there are three separate conclusions that can be drawn from all of this:

1. The IVIg is working as it has stabilised my condition (MMN) with only modest further deterioration of the right hand
2. The IVIg is not really working because the right hand is still deteriorating
3. The IVIg is merely having a placebo effect as I have some other condition, not MMN

You can take your pick, as clearly my neuro can't tell between the three, so why should we be able to - this is why she is now getting me tested for SMA.

I hope this helps and nice to be in touch again

Kitchener

 

[HelenL]

I also was interested in learning about SMA, as I have nearly no UMN signs, but evidently it's evident on my EMGs.... not sure how they differ on those, but I'm still considered to have ALS. Thanks for opening this thread, I'm still interested in this as well.

 

[Kitchener]

Hi Helen

I had a chance to speak to a good friend of mine, who is a research scientist specalising in genetics. He was of the same view as kashmiri ie. the genetic test would very accurately determine whether I had SMA or not. Have you had the test?

Thanks

Kitchener

PS if there is anyone on the board that can offer an opinion on my theory that the EMGs of a patient presenting with ALS and one presenting with SMA IV would be very similar, I would be very grateful..

 

[momofsixkids60]

Kitchener,

There is a "snippet" of an article in the recent (jan-mar) edition of the QUEST magazine. I believe it's page 18 or 20. I believe you can read it online, mine is the "paper form". If for some reason you are unable to access it, feel free to contact me and will send it to you.

Kimberly

 

[momofsixkids60]

Darn, moderation

 

[HelenL]

No I haven't had the SMA genetic test, though I'll ask at the clinic next time I go... have to say it's definitely a long shot, but I do have a slower version of ALS as far as I can tell. Not that I have anything to judge it by first hand.

 

[bryant123martha]

I was diagnosed with SMA and when the testing came back it was negative. I attended the international conference for SMA and it was very informative. I was able to speak to the SMA researchers and they were very helpful. Apparently as long as the SMA genetic testing you have done has the sequencing it is extremely accurate. If not it will not show if you have mutated or deleted genes and it could look normal when it is not. I only presented with Lower motor neuron signs and my EMG looked like SMA but my test was negative so the specialist said I couldn't have it. I went to the MDA clinic where I started showing with Upper Motor neuron signs only 3 month ago. He did another EMG and said it does look like SMA but it can't be with the Genetic testing and now I am presenting with upper motor neuron signs. Both agree I had PMA but it could be turning into Traditional ALS.

 

[Kitchener]

Hi Helen

I had the same converstation as Martha with my friend the geneticist. If the test is done with DNA sequencing then it is very accurate. I think that there is another test that can done without sequencing which is not so clear cut. I also think SMA is a long shot for me, but as far as I'm concerned so is all of this. At least the right test is definitive, and it will rule SMA in or out (unlike so much of the poking and prodding in this area). Martha I'm sorry to hear that UMN has come into the picture for you, which in itself would rule out SMA. I wish you all the very best in the journey ahead.

Kitchener

 

[hEsmeralda]

I have a friend who has quite similar situation but she is getting better now, and I hope you will be better !