Definition of Incomplete Quadriplegia
Incomplete quadriplegia (also termed incomplete tetraplegia) is a spinal cord injury affecting the cervical spine where there is partial preservation of motor and/or sensory function below the neurological level of injury, including the lowest sacral segments (S4-S5), with impairment affecting all four extremities. 1
Core Diagnostic Criteria
The defining characteristic that distinguishes incomplete from complete injury is the presence of any sensory or motor function in the lowest sacral segments (S4-S5), which may include:
- Voluntary anal contraction
- Deep anal pressure sensation
- Any sensation at the anal mucocutaneous junction
This sacral sparing is the critical determinant of an incomplete injury, regardless of the extent of motor or sensory loss elsewhere 2.
Clinical Presentation Patterns
Incomplete quadriplegia manifests in several distinct patterns, with central cord syndrome (CCS) being the most common, now accounting for approximately 30% of all incomplete tetraplegia cases 3. The hallmark features include:
- Disproportionately greater motor impairment in upper extremities compared to lower extremities (typically ≥10 motor points difference favoring the lower extremities)
- Variable sensory loss below the level of injury
- Bladder dysfunction, usually urinary retention
- Often occurs in older adults following hyperextension injury in the context of cervical spondylosis 1
Other incomplete syndromes include anterior cord syndrome (10% of incomplete tetraplegia) and Brown-Séquard syndrome (3% of incomplete tetraplegia) 3.
Prognostic Implications Based on Sacral Function
The extent of sacral preservation has critical prognostic value 4:
- Motor complete with only unilateral S4-S5 sensation: No lower extremity motor recovery expected
- Motor complete with bilateral S4-S5 sensation: Mean lower extremity motor score improvement to 12.1 points at one year, with functional recovery (≥3/5 strength) possible in some muscles
- Lower extremity motor score ≥10 at one month: 87% achieve community ambulation with assistive devices at one year
Key Clinical Pitfalls
The diagnosis can be made accurately within the first 24 hours of injury in virtually all cases 2. However, clinicians must avoid:
- Confusing transient spinal shock with complete injury—wait for resolution of spinal shock before declaring completeness
- Missing sacral sparing on examination—always test for voluntary anal contraction and perianal sensation
- Overlooking functional improvement potential in patients with bilateral sacral sensation, even when initially motor complete
Functional Determinants
Activities of daily living and mobility in incomplete tetraplegia correlate most significantly with 5:
- Upper extremity function (GRASSP scores)
- Trunk control ability (most often overlooked in rehabilitation planning)
- Lower extremity motor scores
- Balance capacity
Trunk control training should be prioritized in rehabilitation, as it significantly affects both self-care and mobility outcomes independent of limb function.