What are the etiologies of paraplegia?

Etiologies of Paraplegia

Paraplegia results from spinal cord lesions at or below the T2 level, with the most common causes being degenerative disease (spondylotic myelopathy), vascular disorders (spinal cord ischemia, aortic pathology), inflammatory/demyelinating conditions (multiple sclerosis, transverse myelitis), infections (tuberculosis, schistosomiasis), and trauma. 1, 2

Anatomical Localization Principle

• Paraplegia specifically results from thoracic or lumbar spinal cord lesions (T1 and below), sparing upper extremity function because cervical segments remain intact 2
• Lesions above T2 produce tetraplegia/quadriplegia, affecting all four limbs 2
• The level of spinal cord injury determines the distribution of motor and sensory deficits 3

Major Etiological Categories

Degenerative Disease (Most Common Chronic Cause)

• Spondylotic myelopathy is the most common cause of extrinsic spinal cord compression leading to chronic/progressive paraplegia 1, 4
• Contributing factors include disc herniations, spinal degenerative changes, vertebral body degeneration, and ossification of the posterior longitudinal ligament 5, 4
• Intramedullary cord signal changes on MRI represent important prognostic factors for neurosurgical outcomes 5, 1

Vascular Etiologies

Spinal Cord Ischemia:

• Results from atheromatous disease, aortic surgery complications, systemic hypotension, or sickle cell disease 1, 4
• Typically affects watershed zones in the mid-thoracic cord or areas supplied by the artery of Adamkiewicz 6
• Diffusion-weighted MRI shows signal alteration earlier than T2-weighted images in acute ischemic injury 5, 4

Aortic Pathology:

• Thoracic aortic dissection causes acute paraplegia from spinal cord malperfusion in 1-3% of cases 1
• Thoracoabdominal aortic aneurysm can cause chronic vertebral erosion and spinal cord compression, with 12.5% presenting with neurologic impairment including paraplegia 1
• Paraplegia occurs in 2-4% of descending thoracic aortic repairs and 3-10% of thoracoabdominal repairs 5

Vascular Malformations:

• Spinal dural arteriovenous fistulae cause cord edema through venous hypertension 5, 2, 4
• Epidural hematoma can cause acute compression 5, 2

Inflammatory and Demyelinating Diseases

• Multiple sclerosis affects the spinal cord in 80-90% of patients, most commonly the cervical cord, but can cause paraplegia when thoracic segments are involved 5, 2
• Transverse myelitis presents as acute myelopathy and is a medical emergency 5, 2
• Neuromyelitis optica characteristically causes longitudinally extensive spinal cord lesions 5, 2
• Acute disseminated encephalomyelitis involves the spinal cord in approximately 25% of cases 5
• Systemic inflammatory conditions including neurosarcoidosis, systemic lupus erythematosus, Sjögren syndrome, and Behçet disease 5, 2

Infectious Causes

• Schistosomiasis (particularly S. mansoni and S. haematobium) causes myelitis and gradual onset paraplegia, especially in Africa 1
• Tuberculosis (Pott disease) causes vertebral destruction and spinal cord compression 1
• Neurosyphilis can affect the spinal cord 5, 2
• Epidural abscess causes acute compression requiring emergency intervention 2

Neoplastic Causes

• Metastatic disease is a common cause of acute nontraumatic spinal cord syndrome 5
• Primary spinal cord tumors and lymphoma 5, 2
• Paraneoplastic syndromes 5
• Extradural and intradural extramedullary tumors cause extrinsic compression 4

Traumatic Causes

• Traffic accidents, falls, and violence are the most common causes of traumatic spinal cord injury 3
• Worldwide incidence is 4-9 new cases per 100,000 people per year 3
• The proportion of patients with tetraplegia and paraplegia is currently equal 3

Iatrogenic Causes

• Procedures close to the spinal cord (laminectomy, vertebrotomy, spondylodesis, epidural anesthesia) carry risk of mechanical spinal cord damage 6
• Vascular surgery complications, particularly aortic cross-clamping causing ischemic damage 6
• Radiomyelopathy from radiation therapy 6
• Angiography complications 6

Nutritional and Metabolic

• Vitamin B12 deficiency causes subacute combined degeneration 5
• Copper deficiency myelopathy 5

Special Syndromes

Hepatic Myelopathy:

• Presents as paraplegia with progressive spasticity and weakness of lower limbs, with severe motor abnormalities exceeding mental dysfunction 5, 1
• Related to marked, long-standing portocaval shunting 5, 1
• Characterized by hyper-reflexia and relatively mild mental alterations 5
• Unresponsive to standard ammonia-lowering therapy but may reverse with liver transplantation 5

Diagnostic Approach

• MRI of the spine without and with IV contrast is the modality of choice for evaluating all causes of paraplegia 5, 2
• Imaging should be tailored to the suspected level based on clinical examination 5, 2
• Contrast enhancement helps identify inflammatory lesions, tumors, infections, and vascular malformations 5, 2, 4
• CT is insufficient for evaluating spinal cord pathology except for bony abnormalities 5
• MRA should be considered when spinal cord ischemia or vascular malformation is suspected 5, 2

Critical Pitfalls

• Any previous spinal cord damage increases the risk of paraplegic complications from subsequent procedures 6
• Intramedullary cord signal changes do not always correlate with clinical symptom severity 4
• Asterixis and other motor signs are not pathognomonic of any single etiology 5
• Complete paraplegia at presentation has poor prognosis, with three-quarters remaining complete, while patients with initially preserved motor function show substantial recovery 3