What Are Some Initial Evaluations for Suspected Congenital Muscle Diseases?

Patient Presentation
A term male infant was transferred from an outside hospital at 8 hours of life to a regional children’s hospital because of poor tone, poor feeding and an elevated creatinine kinase. He was born to a G1P1 mother with appropriate prenatal care. He had been started on antibiotics after blood and urine were obtained. A lumbar puncture was attempted but no fluid was obtained. The family history was negative for any known congenital or neurological problems.

The pertinent physical exam showed normal vital signs, weight of 3.560 kg (50%), head circumference of 34.5 cm (25%), and length of 52 cm (50-75%). Ballard score was consistent with 38 week gestation. He appeared floppy with arms and legs lying more to the side, and he would have poor respiratory effort intermittently. Respiratory pressure support was being provided to the infant. Anterior fontanelle was soft and flat. There were no obvious facial or other dysmorphic features. Skin showed congenital dermal melanocytosis on the sacrum. His heart, lung, abdomen and genitourinary examinations were normal. Neurologically he had poor tone and muscle weakness in the upper and lower extremities. He appeared to respond appropriately to sounds and lights and would look briefly at the examiner. His suck was poor but his gag reflex was intact. He would attempt to do appropriate newborn reflexes but they were poorly performed due to hypotonia and weakness.

The diagnosis of a newborn infant with poor tone and muscle weakness was made. The patient’s clinical course showed that he had some improvement in his physical examination over the next couple of days but still continued with hypotonia and weakness. The respiratory support continued but was slowly weaning. His creatinine kinase also continued to be elevated while other laboratory testing was normal including cultures at day 3. Magnetic resonance imaging of the brain was normal. The neurologist started to discuss additional potential evaluations and their timing with the neonatologists and family.

Discussion
Usually congenital myopathies (CM, e.g. nemaline, core, centronuclear myopathies, etc.) and congenital muscular dystrophy (CMD, e.g. LAMA2-related, collage VI-related, alpha-dystroglycan-related muscular dystrophy, etc.) have been diagnosed based on physical examination and histopathology. Traditionally CMs are due to problems with the muscle contractile apparatus and structures that assist excitation-contraction coupling. CMD are due to problems with the extracellular matrix, muscle membrane and sarcolemmal membrane. Differentiating between CM and CMD have become more blurred as genetic testing and additional research and testing becomes available, and these entities have more overlap in these evaluations. Evaluation, diagnosis and management requires a multidisciplinary team to care for the infant and educate and support their family.

Infants with both CM and CMD usually present with hypotonia and muscle weakness which can cause early feeding problems and possibly respiratory problems. Physical examination findings can be subtle and can change with time. Suspicion of a muscle disease is important for starting the evaluation process and including specialists especially neurologists. Causes of muscle weakness with and without hypotonia can be found here, and hypotonia in infants can be reviewed here.

Learning Point
As with many evaluations, non-muscle related problems need to be considered and ruled in or out. For example, hypothyroidism, hypocalcemia and hypomagnesemia can cause hypotonia, and infection can present in many ways. Botulism is not very common but presents with hypotonia and muscle weakness. Having a suspicion for a muscle disease begins the evaluative process with inexpensive, easily available testing such as creatinine kinase and neuroimaging.

Creatinine kinase (CK) is found in muscles but also in the brain and heart. CK elevation usually indicates some type of muscle injury such as overexertion or rhabdomyolysis and generally returns to normal within 24-48 hours. Causes of rhabdomyolysis can be reviewed here. Newly born infants can have normal CK elevation but again they decline to normal after about 4 days. Persistent CK elevations in newborns is usually abnormal but is not specific for a particular muscle disease. Some muscle diseases may also have normal CK levels. If the CK remains elevated then neuroimaging is often the next step.

Neuroimaging, usually with a brain MRI, assists in determining if there are structural abnormalities and/or ventriculomegaly, or other problems such as changes associated with hypoxic-ischemic encephalopathy. Specific structural changes and no ventriculomegaly may lead to considering CMD or other specific genetic testing for the structural abnormality seen. Normal study or ventriculomegaly may lead to more testing by nerve conduction testing or electromyelography. Neurological evaluation is usually needed to gather and interpret data including potential nerve conduction testing, electromyelography, muscle biopsy and genetic testing. Each of these evaluations have advantages and disadvantages and may not be 100% diagnostic. Therefore a neurologist leading this evaluation is important given the costs, invasiveness and the difficulties there can be with test interpretation.

Questions for Further Discussion
1. What temperature should food be cooked to prevent botulism? A review can be found here
2. What specialists might an infant with a muscle disease need to have services from?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Muscle Disorders and Neuromuscular Disorders.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Mary P, Servais L, Vialle R. Neuromuscular diseases: Diagnosis and management. Orthop Traumatol Surg Res. 2018;104(1S):S89-S95. doi:10.1016/j.otsr.2017.04.019

Butterfield RJ. Congenital Muscular Dystrophy and Congenital Myopathy. Continuum (Minneap Minn). 2019;25(6):1640-1661. doi:10.1212/CON.0000000000000792

Harmelink M. Differentiating Congenital Myopathy from Congenital Muscular Dystrophy. Clinics in Perinatology. 2020;47(1):197-209. doi:10.1016/j.clp.2019.10.005

Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa

How Much Should a Newborn Eat?

Patient Presentation
A 4-day-old female came to clinic for her first visit. Her mother complained that she was a very spitty baby but wasn’t taking enough of her bottle feedings. The mother said she was told to give her 2-3 ounces of formula every 2-3 hours but she wasn’t taking all of it. “She’s only taking about 1.5 ounces and even then she seems to throw up with a lot of the feedings,” her mother said. “My mom says she needs to eat more too, but she just spits up,” complained the mother. The pediatrician noted that the mother kept trying to feed the infant when the baby clearly turned her head away from the bottle and didn’t want it placed back into her mouth. The past medical history showed a term infant born to a G1P1 mother without complications.

The pertinent physical exam showed a healthy appearing female with a weight of 3.873 kg which was decreased 2.1% from birthweight. Transcutaneous bilirubin was 6.8 mg/dL.
Her physical examination was normal except for mild jaundice around the face and upper trunk. During the examination, she had some effortless spit up of formula that did not bother her.

The diagnosis of a healthy, but being overfed infant was made. The pediatrician talked with the mother to help set expectations of how much the newborn would eat now and over the next couple of weeks and longer term. She also pointed out to the mother that the baby refusing the bottle was a cue to stop feeding the baby. “I think if you decrease the amount but keep feeding her fairly often she will be just fine and also won’t spit up as much,” counseled the pediatrician.

The patient’s clinical course at the next visit showed her to be above birth weight and gaining about 22 grams/day. The mother complained that she still had some spitting up, “but its a lot better. My mother still doesn’t believe you and thinks she needs to eat more. I just keep telling her that her grandbaby is okay,” her mother remarked.

Discussion
A serving size and a portion are not the same thing. A serving size is a specific measured amount of food. This is cited on the product label or readily available resources such as cookbooks or the Internet (an example can be found here.) A portion is the amount chosen to be served or eaten by a person. They can be the same but may not be the same. For example, 4 ounces of cereal is a common serving size, but an adult may often eat more than this as their portion.

Children especially need appropriate portion sizes to match their age and body size. A good general rule for any age is a portion is the size of the person’s fist or palm of their hand. For example a 1-3 year probably would only need about 1/3-1/2 of a slice of bread but a 7-10 year old would need about 1 slice. Daily, the American Academy of Pediatrics recommends children should still get:

  • Meat = 2-3 servings
  • Dairy = 2-3 servings
  • Fruit = 2-3 servings
  • Vegetables = 2-3 servings
  • Grains = 6-11 servings

When having a meal, most people consume a few portions. This is usually not the total potential size of their stomach which leads to stretching and being uncomfortable and possibly even emesis.

Learning Point
Newborn infants on day of life 1 have unique needs as they are transitioning to extrauterine life. Importantly in those first few hours newborn infants must maintain glycemic control as hypoglycemia can cause organ damage. Infants who are stressed in some manner (e.g. presumed infection, respiratory distress, etc.) or who are known to have a higher risk of hypoglycemia (e.g. infant of a diabetic mother, large for gestational age infants, etc.) are monitored for hypoglycemia. Infants who have not fed for a long time or who have changes in mentation may also be tested for hypoglycemia. Glycemic control is usually achieved through the balance of glucose stores in the newborn’s body and oral intake through breast or bottle feeding. If an infant has true hypoglycemia, then intervention with oral or intravenous glucose may also be necessary.

How much does a newborn need to take or can even take given the size of their stomach? The stomach itself is also transitioning to extrauterine life. At birth, a small stomach size is expected and only needed.
The size of a newborn’s stomach is about:

  • DOL 1 5-7 ml, large marble
  • DOL 3 22-27 ml, ping-pong ball
  • DOL 10 60-81 ml, extra large chicken egg

Each infant will follow their own needs. On the first day of life the newborn cannot take much volume and needs to learn to feed through more frequent feedings, obtaining the small amount of colostrum that the mother begins to make highlighting the symbiotic relationship between the infant and mother. Over the next couple of days the stomach will expand, but a small amount of breastmilk or formula is still all that can fit into the stomach and small amounts frequently given should continue. Newborns often feed every 1-2 hours or so. Newborn infants over the next two weeks of life have their stomachs expand more so that 1-2 ounces in a feeding (when measured) are appropriate. Feeding at this time also often stretches the interval between feedings to 1-3 hours or so. It is important to follow the infant’s cues regarding feeding though as each infant is unique. When an infant is sated they usually slow down the rate of feeding, take longer pauses between sucking and will turn away from the breast or bottle. If the breast or bottle is re-offered they usually are uninterested. They often will be tired after feeding and fall asleep as well. When an infant is hungry, they will turn their head trying to find a nipple to feed, they may suck on their hands and often will cry to vocalize their hunger.

Overfeeding infants can easily occur with bottle fed infants. The food is easier to transfer from the bottle to infant and the infant cannot move away from the bottle as easily as they can from the breast. Therefore additional fluid may be transferred to the infant even if they are sated. It is not uncommon that parents will also complain that the infant is also spitting up too. The additional cost of formula can be an issue for many families as well. Animal studies and human studies have found that infants who are overfed, even at day 1, are at risk for overweight and obesity in early childhood. One study of formula fed infants in the Women, Infants and Children Special Supplemental Nutrition program (i.e. WIC) found that 37% of formula fed infants < 6 months old were potentially overfed consuming an additional 26 calories/day. This is an additional ~4800 calories over 6 months for these infants.

Questions for Further Discussion
1. How do you counsel parents of newborns to feed their infants?
2. Do family meals prevent obesity? A review can be found here
3. Do picky eaters really exist? A review can be found here

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for this topic: Infant and Newborn Nutrition

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Portions and Serving Sizes – HealthyChildren.org. Accessed October 12, 2021. https://www.healthychildren.org/English/healthy-living/nutrition/Pages/Portions-and-Serving-Sizes.aspx

Bergman NJ. Neonatal stomach volume and physiology suggest feeding at 1-h intervals. Acta Paediatr. 2013;102(8):773-777. doi:10.1111/apa.12291

Watchmaker B, Boyd B, Dugas LR. Newborn feeding recommendations and practices increase the risk of development of overweight and obesity. BMC Pediatr. 2020;20:104. doi:10.1186/s12887-020-1982-9

Anderson CE, Martinez CE, Ventura AK, Whaley SE. Potential overfeeding among formula fed Special Supplemental Nutrition Program for Women, Infants and Children participants and associated factors. Pediatr Obes. 2020;15(12):e12687. doi:10.1111/ijpo.12687

Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa

Mid-Winter Break

PediatricEducation.org is taking a mid-winter break. The next case will be published in the new year on January 10th. Look for a special announcement too. In the meantime, please take a look at the different Archives and Curriculum Maps listed at the top of the page.

We wish you a Happy New Year,
Donna D’Alessandro and Michael D’Alessandro, curators.

How Much Weight Should be Used in Strength Training?

Patient Presentation
In the middle of a busy clinic, the triage nurse said she had a telephone call from a mother who wanted to know about her 15-year-old male and how much weight he should be lifting for his weight training. The pediatrician smiled and said, “That’s a small question with a big answer. It really depends on many things and there isn’t a specific amount I can tell you. It depends on his puberty status, why is he doing the training, who is supervising, and many other questions.” The nurse said she would convey this to the mother, and had already noticed that he had his health maintenance examination appointment scheduled for the following week. “I think that we can discuss this issue at that appointment, but he should use reasonable care if there are weight lifting questions before then or they can try to move the appointment earlier,” he counseled.

Discussion
The benefits of strength training includes improved performance, injury prevention and rehabilitation, improved cardiovascular fitness, improved bone mineral density, improved blood lipid profiles and mental health. The most common risk is injury and most of these “…occur on home equipment with unsafe behavior and unsupervised settings.” Children with a variety of health problems should be evaluated first including hypertension, congenital heart disease, previous use of cardiotoxic medication, seizures, obesity, and Marfan syndrome. Other counseling issues regarding strength training include discussing with the child, teen and family the possibility of eating disorders, distorted body image, and the use of anabolic steroids and other substances.

The American Academy of Pediatrics (AAP) recommends not to begin strength training until at least 7-8 years or when balance and postural controls skills have matured to adult levels which is around this age. There are other general pragmatic considerations too. The child should be able to listen, wait, understand and follow the instructions of an adult. They should have some body sense and control over their body so they can perform the exercise properly, and make the necessary adjustments when they are not doing it properly. Children should be enjoying the activity and not feel coerced to initiating or continuing the activity. These are sensible considerations for any sport. Children and adolescents should perform more repetitions of the exercise using a low amount of weight (i.e. increased weight with fewer repetitions is not recommended). Explosive, rapid lifting of weight is not recommended. Similarly there are no specific ages when an adolescent can begin power training, body-building, or maximal lifts, but many experts including the AAP recommend after the adolescent is skeletally mature to mitigate the risks to the bones, tendons, ligaments and muscles themselves.

Children and teens should have supervision so they can learn to perform the exercises properly initially, receive feedback and have ongoing monitoring so that they continue to perform the exercises properly. Supervision also about numbers of repetitions and weights for workouts can also be devised and monitored. Children and adolescents also do not always use the best judgement and adult supervision can help to ensure safety in the weight room.

Learning Point
As with many things in life, slow and steady strength training can pay dividends. Improvements in strength can be found in properly structured programs of at least 8 weeks duration occurring at least 1-3 times/week. Strength training more than 4x/week does not add to strength and may lead to overuse injuries. Gain in strength, power and muscle size are lost after ~6 weeks of discontinued resistance training.

A 2020 narrative review recommended the following specifics regarding strength training:

  • Prepubertal (pre-peak height velocity)
    • Training focus is on learning the proper movements and techniques
    • General strength training is recommended with emphasis on functional movements
    • 1-3 sets of 8-10 repetitions per training session
  • During puberty (at peak height velocity)
    • Training focus continues on the foundation movements and techniques but also with increases in load and intensity
    • Strength development with increases in training intensity
    • 2-3 sets of 6-8 repetitions, load is 70-80% of maximum strength for 1 repetition (other authors use 60-80% of maximum strength, another author says 8-15 repetitions)
  • Post puberty (post peak height velocity)
    • Training focus continues on function movements, high-intensity loading and increase in intensity
    • High intensity resistance training with traditional and weightlifting movements
    • 3-4 sets x 1-6 repetitions at 70-100% of maximum strength

Questions for Further Discussion
1. When a youth wants to “bulk up” for sports, how much weight gain is advised? A review can be found here
2. What qualifications are required for an adult to supervise youth strength training in your local schools?
3. How do you diagnose hypermobility? A review can be found here

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Exercise for Children and Sport Fitness.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Council on Sports Medicine and Fitness. Strength Training by Children and Adolescents. PEDIATRICS. 2008;121(4):835-840. doi:10.1542/peds.2007-3790

Behringer M, Vom Heede A, Yue Z, Mester J. Effects of resistance training in children and adolescents: a meta-analysis. Pediatrics. 2010;126(5):e1199-1210. doi:10.1542/peds.2010-0445

Lesinski M, Prieske O, Granacher U. Effects and dose-response relationships of resistance training on physical performance in youth athletes: a systematic review and meta-analysis. Br J Sports Med. 2016;50(13):781-795. doi:10.1136/bjsports-2015-095497

Zwolski C, Quatman-Yates C, Paterno MV. Resistance Training in Youth: Laying the Foundation for Injury Prevention and Physical Literacy. Sports Health. 2017;9(5):436-443. doi:10.1177/1941738117704153

McQuilliam SJ, Clark DR, Erskine RM, Brownlee TE. Free-Weight Resistance Training in Youth Athletes: A Narrative Review. Sports Med. 2020;50(9):1567-1580. doi:10.1007/s40279-020-01307-7

Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa