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Muscle Weakness in Children
Aka: Muscle Weakness in Children, Motor Delay in Children, Pediatric Neuromuscular Disorder, Congenital Neuromuscular Disorder, Gross Motor Delay, Motor Developmental Delay
- See Also
- Developmental Milestone
- Developmental Coordination Disorder (Clumsiness in Children)
- Muscular Dystrophy
- Epidemiology
- Neuromuscular disorders are rare compared to other Developmental Disorders
- Neuromuscular disorders occur in early childhood in only 1 in 1000
- Contrast with Learning Disorders (1 in 15), Autism (1 in 88), Cerebral Palsy (1 in 303)
- Precautions
- Early diagnosis is preferred
- Improved outcomes
- Improved access to services and reduction in Caregiver stress
- Prompts Genetic Counseling
- Screening
- See Developmental Milestone
- See Developmental Evaluation
- Using standardized tests is critical to avoid missing cases
- Bright Futures Forms
- http://brightfutures.aap.org/tool_and_resource_kit.html
- CDC Muscular Dystrophy
- http://www.cdc.gov/ncbddd/musculardystrophy/
- History
- Birth history
- Perinatal Trauma
- Newborn disorders or signs
- Family History
- Weakness
- Developmental Delay
- Exam
- See Developmental Evaluation
- See Gross Motor Milestone
- See Developmental Red Flags
- Assess Muscle tone (increased of decreased)
- Scarf sign
- Popliteal angle measurement
- Infants age 4-6 months
- Assess for head lag with Pull-to-sit
- Initiate early intervention if not meeting milestones
- Head lag persists at 4 months or older
- Reassess at one month after intervention, and if not meeting Gross Motor Milestones
- Obtain Creatinine phosphokinase (CPK)
- Refer to pediatric neurology
- Infants age 6-9 months
- Assess for ability to achieve and maintain sitting position
- Obtain Creatinine phosphokinase (CPK) and initiate early intervention if not meeting milestones
- Not sitting independently by 7 months
- Not getting into a sitting position by 9 months
- Reassess at one month after intervention, and if not meeting Gross Motor Milestones
- Refer to pediatric neurology
- Children >12 months
- Assess gait and rise to standing
- Initiate early intervention or physical therapy if not meeting milestones
- Not walking by age 15 months
- Not standing from supine without support by 18 months
- Reassess at 18 months of age and if not meeting Gross Motor Milestones (or regression)
- Obtain Creatinine phosphokinase (CPK)
- Refer to pediatric neurology
- Other assessments or concerns at 18-24 months of age (and later) to prompt CPK and referral
- Walking or Running difficulties
- Frequent falling
- Difficulty standing from supine
- Unable to stand when pulled upward
- Hands braced on knee for support when standing (Gowers Maneuver)
- Symptoms
- Muscle cramps
- Signs: General
- Gross Motor Delay
- Delayed crawling or walking
- Decreased Muscle Strength
- Decreased neck strength and ability to hold head upright (head lag)
- Decreased Muscle tone (floppiness)
- Frequent falls
- Other findings variably present
- Fine motor delay
- Cognitive delay
- Incoordination (see Clumsiness in Children)
- Signs: Distinguishing central from peripheral cause
- Central Nervous System cause (e.g. Cerebral Palsy)
- Typically fixed deficits, with signs in neonatal period
- Increased Deep Tendon Reflexes and Clonus
- Spastic gait
- Variable Muscle tone
- Toe Walking (as with peripheral causes)
- Peripheral Nervous System or neuromuscular cause (anterior horn of spinal cord, nerve, Muscle)
- Typically progressive worsening (often with regression from milestones)
- Altered chest appearance may be present (bell-shaped)
- Weak, blunted facial expressions
- High arched Palate
- Tongue fasciculations (esp. spinal muscular atrophy)
- Decreased Muscle tone
- Decreased or absent Deep Tendon Reflexes
- Hyperlordotic, Waddling Gait
- Toe Walking (as with central causes)
- Differential Diagnosis
- Central cause (e.g. Cerebral Palsy)
- Neuromuscular disorder (e.g. Muscular Dystrophy)
- Hypothyroidism
- Congenital Heart Disease
- Nutritional deficiency
- Labs: Indicated in low to normal Muscle tone
- Creatinine Phospokinase (see CPK below)
- Thyroid Stimulating Hormone
- Liver Function Tests
- Serum Aspartate Aminotransferase increased (from Muscle breakdown)
- Serum Alanine Aminotransferasencreased (from Muscle breakdown)
- Labs: Serum Creatinine Phosphokinase (CPK)
- Normal CPK (24 to 180 U/L)
- Primary Central Nervous System Disorder
- Normal CPK does not exclude Muscular Dystrophy
- Mildly increased CPK (180 to 3000 U/L)
- Neuromuscular Causes
- Spinal muscular atrophy
- Neuropathy
- Congenital Myopathy
- Other causes
- See Serum Creatinine Phosphokinase (CPK)
- Recent Immunizations
- Muscle Trauma
- Viral Infection
- Plan if in this range
- Repeat in 2-3 weeks
- Refer to pediatric neurology if still increased (esp. more than three times normal)
- Grossly increased CPK (3000 to 50,000 U/L)
- Causes
- Duchenne Muscular Dystrophy
- Becker Muscular Dystrophy
- Plan if in this range
- Repeat in 1 week
- Refer to pediatric neurology if still in same range
- Repeat in 2-3 weeks if <3000 U/L on recheck to exclude muscle Trauma cause
- Severely increased CPK (>50,000 U/L)
- Admit for Acute Rhabdomyolysis
- References
- National Task Force for the early identification of childhood neuromuscular disorders
- http://www.childmuscleweakness.org/index.php/clinical-evaluation
- Imaging
- Not typically indicated in isolated weakness
- Indications for MRI brain imaging: Suspected Central Nervous System cause
- Increased Muscle tone
- Suspected Cerebral Palsy
- Microencephaly
- Macroencephaly
- Neurocognitive delay or regression
- Evaluation: Gross Motor Delay
- Acutely ill patients (e.g. Muscle pain, Dark Urine, respiratory distress or CPK>50,000)
- Hospitalization
- Central cause suspected (e.g. Cerebral Palsy)
- Refer to pediatric neurology
- Refer to early intervention
- Consider imaging (consider discussing with pediatric neurology)
- Peripheral Cause evaluation
- See Developmental Evaluation
- Perform history as above
- Perform exam as above to direct initial approach
- Refer to early intervention if indicated
- Refer to pediatric neurology if indicated
- Obtain CPK if indicated
- Interpret and manage as described above
- Resources
- Neuromuscular Disorder videos (ChildMuscleWeakness.org)
- http://www.childmuscleweakness.org/index.php/videos
- National Task Force for the early identification of childhood neuromuscular disorders
- http://www.childmuscleweakness.org/index.php/clinical-evaluation
- References
- Lurio (2015) Am Fam Physician 91(1): 38-44 [PubMed]