Muscle Weakness – Distal

Muscle Weakness – Distal: Excerpt from In A Page: Pediatric Signs and Symptoms

Distal weakness is most likely secondary to neuropathy, and is often associated with loss of deep tendon reflexes (DTRs) either with or without sensory abnormalities. In contrast, increased DTRs or extensor plantor responses raise the concern for “central” causes of weakness (stroke, neoplasm, demyelinating disease, etc.).

Differential Diagnosis

• Guillain-Barré syndrome (GBS)
  –Acute, acquired, or monophasic
  –Ascending weakness and parasthesias
• Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)
• Compression neuropathy
  –Trauma
  –Neoplasm (e.g., plexiform neurofibroma in neurofibromatosis type 1)
• Charcot-Marie-Tooth
  –Defect in peripheral myelin protein
  –Causes distal segmental demyelination
  –Manifested by distal muscle atrophy and weakness
• Drug-induced
  –Phenytoin
  –Isoniazid
  –Nitrofurantoin
  –Vincristine
  –Zidovudine
• Spinal muscular atrophy
• Juvenile segmental spinal muscular atrophy
• Miller-Fisher syndrome
  –Clinical triad of ataxia, ophthalmoplegia, and areflexia
• Tick paralysis
• Juvenile amyotrophic lateral sclerosis
• Giant axonal neuropathy
• Vitamin B12 deficiency
• Toxic neuropathy
  –Arsenic
  –Lead
  –Mercury
  –Thallium
  –Glue sniffing
• Uremic neuropathy
• Idiopathic axonal neuropathy
• Hereditary distal myopathy
• Inclusion body myopathy
• Rheumatoid arthritis
• Refsum disease
• Metachromatic leukodystrophy
• Krabbe disease
• Cockayne syndrome
• Conversion reaction
  –Usually fluctuating and unpredictable

Workup and Diagnosis

• History
  –Acute vs chronic, associated sensory findings, associated systemic/neurologic abnormalities
  –Family history (family members may not be affected to same degree)
  –Toxic exposures
• Physical exam
  –Abnormal gait can be the presenting symptom of either proximal or distal leg weakness
  –Stumbling, especially with foot eversion or dorsiflexion
  –Weakness of the hand muscles (e.g., difficulty writing, opening jars, or working with tools)
  –Inspect muscle for atropy, hypertrophy, fasciculations, myotonia, cogwheeling
  –Palpate muscles for tenderness
  –Mirror movements, hypotonia, spasticity/rigidity
  –Assess strength and power with push/pull testing, functional hop in place, knee bends, posture
  –Pronator drift, standing on toes/heels, symmetry
  • Labs
    –Serum CK
    –In neuropathic disorders, CK is usually normal or mildly increased; moderate to severe elevation of CK suggests myopathy
  • Electromyogram/nerve conduction studies
    –Demonstrate the extent, chronicity, and categorization
  • Muscle biopsy
    –Histochemistry, EM, enzymatic/genetic testing

  Treatment

  • Acute demyelinating disorders (GBS, CIDP)
    –Often respond to intravenous gamma-globulin
  • Medication/chemotherapy-induced neuropathies
    –Often improved after cessation of the offending medication
    –Response is time-dependent; may take up to months
  • Toxic exposures
    –Often difficult to detect, unless resulting from acute overdose
  • Metabolic neuropathies are treated supportively
  • Braces often assist with foot drop for both acquired and congenital neuropathies

Book Source Details

• Book Title: In A Page: Pediatric Signs and Symptoms
• Author(s): Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan
• Year of Publication: 2007
• Copyright Details: In A Page: Pediatric Signs and Symptoms, Copyright © 2007 Lippincott Williams & Wilkins.

More About Muscle pain

• Back to disease: Muscle pain: Introduction
• Next Book Extract About Muscle pain: Muscle Weakness – Proximal (In A Page: Pediatric Signs and Symptoms)
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: In A Page: Pediatric Signs and Symptoms Authors: Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 1-4051-0427-9

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