What is the medical term for the inability to extend the neck due to muscle weakness?

Dropped Head Syndrome: Medical Term for Inability to Extend the Neck Due to Muscle Weakness

The medical term for the inability to extend the neck due to muscle weakness is "Dropped Head Syndrome" (DHS). This condition is characterized by severe weakness of the neck extensor muscles resulting in an inability to lift the head from a flexed position, creating a chin-on-chest deformity 1.

Clinical Presentation and Characteristics

• Definition: Dropped Head Syndrome involves severe weakness of the neck extensor muscles resulting in progressive reducible cervical kyphosis 2
• Appearance: Patients present with the chin resting on or near the chest and inability to extend the neck to a neutral position
• Functional impact: Significant disability with difficulty maintaining horizontal gaze, eating, and performing daily activities

Etiology and Classification

Dropped Head Syndrome can be categorized based on underlying causes:

Neuromuscular Causes (Weakness of Neck Extensors)

• Radiation-induced: Can occur as a delayed complication following high-dose mantle-field radiotherapy for conditions like Hodgkin lymphoma 1
• Neuromuscular disorders:
  • Myasthenia gravis
  • Motor neuron disease/Amyotrophic lateral sclerosis
  • Myositis/inflammatory myopathies
  • Muscular dystrophies 3
  • Congenital myopathies (rare) 1

Increased Tone of Neck Flexors

• Movement disorders: Cervical dystonia 4
• Parkinson's disease

Other Causes

• Structural: Post-traumatic deformity, infection, tumor
• Inflammatory: Ankylosing spondylitis 3
• Idiopathic: Adolescent idiopathic cervical kyphosis 3

Diagnostic Approach

Clinical Assessment

• Evaluate ability to actively extend the neck against gravity
• Assess passive range of motion (to differentiate from fixed deformities)
• Look for "sensory tricks" that may temporarily improve posture (suggestive of dystonia) 5
• Measure isometric neck strength (typically 25-44% lower in affected patients) 6

Investigations

1. Blood tests: To identify inflammatory or metabolic causes
2. Imaging:
   • MRI cervical spine: Most sensitive for detecting ligament injury and soft tissue abnormalities 1
   • Flexion-extension radiographs: May be useful to assess stability and mechanical issues 1
3. Neurophysiological studies: EMG/nerve conduction studies
4. Muscle biopsy: When inflammatory or degenerative muscle disease is suspected

Management Approaches

First-Line Treatment

• Underlying cause treatment: Address any identified primary condition
• Conservative management:
  • Physical therapy to improve range of motion and functional capacity 7
  • Cervical collars for temporary support

Pharmacological Options

• For dystonic causes:
  • Botulinum toxin injections (first-line for cervical dystonia) 7, 5
  • Nerve-stabilizing agents (pregabalin, gabapentin, duloxetine) for pain management 7

Surgical Management

• Indications: Progressive deformity, neurological compromise, or failure of conservative treatment 2
• Approaches:
  • Cervicothoracic arthrodesis (extending to thoracic spine) is more successful (87% success rate) than cervical arthrodesis alone (29% success rate) 2
  • C2 is the most common upper level of fusion (63% of cases) 2

Prognosis and Complications

• Radiation-induced DHS: Generally considered irreversible 1
• Post-surgical complications: Dysphagia and airway-related complications in 75% of patients undergoing anterior surgical approaches 2
• Quality of life: Significant impact on daily activities and social interactions due to inability to maintain horizontal gaze

Clinical Pearls and Pitfalls

• Key distinction: Differentiate between weakness-related dropped head (reducible with passive movement) versus dystonia-related (may have sensory tricks that temporarily improve posture)
• Avoid misdiagnosis: Don't confuse with ankylosing spondylitis or fixed structural deformities
• Surgical consideration: Cervicothoracic fusion (extending to thoracic spine) has significantly better outcomes than cervical fusion alone 2
• Comprehensive approach: Address both the mechanical aspects of head position and the underlying neurological or muscular pathology

Dropped Head Syndrome represents a significant functional disability that warrants thorough evaluation and appropriate management based on the underlying cause to improve quality of life and prevent progression.