Incomplete spinal cord syndromes are caused by lesions of the ascending or descending spinal tracts that result from trauma, spinal compression, or occlusion of spinal arteries. Central cord syndrome, anterior cord syndrome, posterior cord syndrome, and are the most common types of incomplete spinal cord syndromes. In contrast to a complete spinal cord injury, lesions only affect part of the cord, and patients present with a dissociated sensory loss. A spine MRI is the diagnostic modality of choice to determine the etiology, level, and extent of the lesion. Treatment depends on the underlying etiology. In some cases, surgery may be necessary to treat the underlying cause and to improve the patient's outcome. Spinal compression is a medical emergency and requires urgent treatment with steroids and decompressive surgery.
Basic neuroanatomy and function
Pyramidal tracts: lateral corticospinal tract and anterior corticospinal tract
- Descending tracts originate in the cerebral cortex and extend to the in the ventral horn of the spinal cord.
- About 90% of pyramidal neurons decussate as they pass through the medulla and descend further as the lateral corticospinal tract.
- The remaining 10% continue as the anterior corticospinal tract and decussate at the segmental level.
- Function: controls motor function
- Posterior column: posterior funiculus consisting of gracile and cuneate fasciculi
- Spinothalamic tract: anterior spinothalamic tract and lateral spinothalamic tract
Overview of incomplete spinal cord syndromes
|Types of incomplete spinal cord syndromes|
|Syndrome||Affected spinal tracts||Etiology ||Clinical features*|
|Central cord syndrome (most common)|| |
|Anterior cord syndrome|
|Posterior cord syndrome|| |
|(hemisection syndrome)|| || || |
*All syndromes present with dissociated sensory loss: a pattern of selective sensory loss (“dissociation of modalities”), which suggests a focal lesion of a single tract within the spinal cord (or brainstem). 
Overview of incomplete spinal cord lesions
|Spinal cord lesions|
|Pathophysiology||Affected spinal tracts||Clinical features|
|Spinal muscular atrophy|
|Amyotrophic lateral sclerosis|
|Multiple sclerosis|| |
|Vitamin B12 deficiency|| |
|Cauda equina syndrome|
|Conus medullaris syndrome|| |
- Definition: injury to the central region of the spinal cord (central corticospinal tracts and decussating fibers of the lateral spinothalamic tract)
- Most common type of incomplete cord syndrome
- Common in the elderly with preexisting degenerative changes in the cervical spine
- Clinical features
- Diagnostics: CT and/or MRI to determine location, cause, and extent of neurological damage
- Treatment: See “ ”.
- Prognosis: relatively good prognosis
- Damage to the anterior two-thirds of the spinal cord, usually as a result of reduced blood flow or occlusion to the anterior spinal artery (ASA) → anterior spinal artery syndrome (∼ 95% of cases) 
- Systemic hypoperfusion (e.g., heart failure)
Iatrogenic (e.g., during aortic surgery, spinal angiography, or spinal anesthesia)
- Aortic repairs may result in lesions of the artery of Adamkiewicz: a thoracic radicular artery (branch of the intercostal vasculature) that supplies the lower two-thirds of the spinal cord
- Mid-thoracic ASA territory is a watershed area because the is the only major vessel that supplies the spinal cord below the spinal level T8/T9. 
- Arteriosclerosis, vasculitis (e.g., associated with diabetes)
- Thrombosis, embolic occlusion
- Aortic dissection, aneurysm
- Severe hypotension (e.g., following hemorrhage)
- Trauma (e.g., penetrating injury, burst fracture, hyperflexion injury with vertebral instability which is common in young athletes) 
- Pathological compression (e.g., tumors, cervical spondylosis)
Acute (within hours)
- Back or chest pain 
- Bilateral loss of temperature and pain sensation below the level of the lesion due to damage of the spinothalamic tracts
- Lower motor neuron deficits (flaccid paralysis) at the level of and below the lesion
- Autonomic dysfunction (bladder, bowel, and sexual dysfunction, orthostatic hypotension)
Late (after days or weeks)
- Continued sensory and autonomic dysfunction
- Upper motor dysfunction (spastic paraparesis or quadriparesis) below the level of the lesion due to damage to the corticospinal tracts
- Lower motor neuron deficits (flaccid paralysis) at the level of the lesion due to damage to the anterior horn
- Spinal MRI (best confirmatory test)
- Treat the underlying condition (if possible)
- See “”.
- 10–15% functional recovery
- If no recovery is evident and progressive after 24 hours, the prognosis is poor.
- Definition: injury of the posterior spinal cord affecting the posterior column (fine touch, vibration, pressure, and proprioception)
- Epidemiology: very rare
- Etiology 
- Clinical features: bilateral loss of vibration, fine touch, and proprioceptive sensation below the lesion 
- Treatment: See “ ”.
- Prognosis: Patients show functional gain with rehabilitation. 
- Definition: hemisection of the spinal cord (often in the cervical cord)
- Loss of all sensations at the level of the lesion
- Loss of proprioception, vibration, and tactile (fine touch) discrimination below the level of the lesion due to an interrupted posterior column
- Segmental flaccid paresis at the level of the lesion due to the affection of lower motor neurons at the level of the lesion
- Spastic paralysis below the level of the lesion
- Ipsilateral Babinski sign due to the affection of upper motor neuron axons in the lateral corticospinal tracts
- In lesions above T1, Horner syndrome occurs due to damage to ipsilateral sympathetic fibers (the oculosympathetic pathway).
- Contralateral: loss of pain, temperature, and non-discriminative touch (crude touch) sensation one or two levels below lesion due to an interrupted spinothalamic tract
- Treatment: See “ ”.
- Prognosis: poor 
Autonomic symptoms are generally absent in Brown-Séquard syndrome because of unilateral involvement of the descending autonomic fibers.