II. Signs: Perform complete physical examination

  1. Infant with decreased Muscle tone
  2. Exam distinguishes site of disorder
    1. Upper Motor Neuron Lesion
    2. Lower Motor Neuron Lesion

IV. Differential Diagnosis: Lower Motor Neuron Causes

  1. Brainstem or spine
    1. Spinal muscular atrophy (Anterior Horn Cell Disorder)
    2. Acute Flaccid Paralysis
    3. Infection
      1. Poliomyelitis
      2. Coxsackie Virus
  2. Neuromuscular Junction
    1. Congenital Myasthenia Gravis
    2. Lambert-Eaton Myasthenic Syndrome
    3. Guillain Barre Syndrome
    4. Botulism
  3. Muscle
    1. Muscular Dystrophy
    2. Congenital Myopathy
    3. Inflammatory Myopathy
  4. Other
    1. Tick Paralysis
    2. Benign Congenital Hypotonia

V. Imaging

  1. Head MRI (or consider Head CT if MRI not available)

VI. Diagnostic Studies

VIII. Labs: Test as indicated

  1. Toxicology screen
  2. Serum Ammonia and Venous pH
    1. Serum Amino Acids
    2. Urine Amino Acids and organic acid
  3. Karyotype
  4. TORCH Virus Screening

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