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ARTICLES: Feza Deymeer, Piraye Serdaroglu, Yesim Parman, and Mehves Poda Natural history of SMA IIIb: Muscle strength decreases in a predictable sequence and magnitude Neurology 2008; 71: 644-649 [Abstract] [Full text] [PDF]

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Natural history of SMA IIIb: Muscle strength decreases in a predictable sequence and magnitude

Sanne Piepers, W-Ludo van der Pol, Frans Brugman, John H.J. Wokke, Leonard H. van den Berg   (5 December 2008)

Reply from the authors

Feza Deymeer, Piraye Serdaroglu, Yesim Parman, Mehves Poda   (5 December 2008)

Natural history of SMA IIIb: Muscle strength decreases in a predictable sequence and magnitude 5 December 2008
Sanne Piepers, Department of Neurology, UMC Utrecht, PB 85500, 3508 GA Utrecht, The Netherlands PB 85500, 3508 GA Utrecht, The Netherlands, W-Ludo van der Pol, Frans Brugman, John H.J. Wokke, Leonard H. van den Berg Send Correspondence to journal: Re: Natural history of SMA IIIb: Muscle strength decreases in a predictable sequence and magnitude S.Piepers-2{at}umcutrecht.nl Sanne Piepers, et al.	We read the article by Deymeer et al. with interest. The authors document onset of weakness and describe progression of weakness in ten patients with spinal muscular atrophy (SMA) type IIIb. [1] We recently published the natural history data of 12 patients with late onset SMA types IIIb and IV. We could not detect deterioration of muscle strength or functional outcome during a mean follow-up of 2.5 years. According to Deymeer et al., this is too short to detect a decline in muscle strength. [2] Manual muscle testing (MMT) sum scores in our patients were lowest in muscle groups innervated by upper lumbar segments (hip flexors and adductors), which confirms their findings. We were intrigued by how the muscle weakness developed in their patients so we analyzed MMT sumscores of individual muscle groups in our patients. MMT sumscores were lowest in hipflexors (iliopsoas), followed by quadriceps femoris yet strength in hip abductors, hip extensors and hamstrings was relatively preserved. Strength of hipflexors was decreased in eight patients and strength of thigh adductors decreased in five. In the arms, MMT sumscores were lowest in deltoids and triceps and the onset of weakness often coincided. Weakness of deltoids preceded weakness of triceps in one patient. Gluteal muscle groups were spared. Our data seem to corroborate most of the findings of Deymeer et al., with the exception of onset and predominance of weakness in thigh adductors and triceps muscles. The data generally support a segmental pattern of weakness of muscle groups in the legs. Alternatively, muscle dysfunction may be an additional cause of weakness in patients with SMA. [3] References 1. Deymeer F, Serdaroglu P, Parman Y, Poda M. Natural history of SMA IIIb. Muscle strength decreases in a predictable sequence and magnitude. Neurology 2008;71:644-649. 2. Piepers S, van den Berg LH, Brugman F, et al. A natural history study of late onset spinal muscular atrophy types 3b and 4. J Neurol 2008; Jun 30 [Epub ahead of print] 3. Vrbova G. Spinal muscular atrophy: motoneurone or muscle disease? Neuromuscul Disord 2008;18:81-82. Disclosure: The authors report no disclosures.
Reply from the authors 5 December 2008
Feza Deymeer, Dept. of Neurology, Istanbul Medical Faculty, Istanbul University Capa 34390, Istanbul, Turkey, Piraye Serdaroglu, Yesim Parman, Mehves Poda Send Correspondence to journal: Re: Reply from the authors deymeer{at}istanbul.edu.tr Feza Deymeer, et al.	We are pleased that Piepers et al. agreed with most of our findings. The data which conflicted with ours included the thigh adductors and the triceps/deltoid muscles. We tested the thigh adductors against gravity by having the patient lie on her or his side with legs extended and had her or him lift the lower leg up off the floor. We have almost never seen an SMAIII patient with the ability to raise the leg off the floor in the lateral decubitus position. However, some patients are able to use the iliopsoas muscle against gravity very early. This is why we concluded that adductors must have been affected before iliopsoas. Triceps muscles are difficult to grade and it is not surprising that different examiners have conflicting results when there is mild weakness. In most of our patients with a long duration of disease, triceps seemed to be more affected than deltoid. If they were inspected after resistance was no longer possible, patients made a rotating movement when extending the forearm against gravity, implying the use of other muscles. There was a clockwise movement on the right and an anti-clockwise movement on the left. Finally, it was not possible to fully extend the forearm against gravity. We found that most of the patients had reduced strength of MRC 2-3/5 at 15 years whereas the deltoids were still MRC 4/5. We compared the proximal muscles by needle EMG. [4] The electromyographic differences between muscles were more striking in the lower compared to the upper extremities. In comparing adductors (adductor longus) with abductors (gluteus medius) in the patients with short disease duration (≤ 10 years), the interference pattern was always severely reduced in the adductors and better in the abductors. Although there was early, severe reduction in the interference pattern in the strong muscles of the upper extremities, triceps muscles were the worst when a difference was observed. Reviewing our deltoid results, the interference pattern was mild to moderately reduced in the deltoids (similar to biceps) versus severe reduction in the triceps in all but one of the five patients who had EMGs in the first 4 years of the disease. One patient already had severe reduction in the deltoid. With longer disease duration, the differences disappeared, more definitively after 10 years. Thus, our conclusion that triceps must have been affected before deltoid muscles was based on both early and late clinical examinations as well as our early EMG findings. Reference 4.Deymeer F, Serdaroglu P, Poda M, Gulsen-Parman Y, Ozcelik T, Ozdemir C. Segmental distribution of muscle weakness in SMA III: implications for deterioration in muscle strength with time. Neuromuscul Disord 1997; 7:521-528. Disclosure: The authors report no disclosures.