What is the differential diagnosis for paraparesis?

Differential Diagnosis for Paraparesis

The differential diagnosis for paraparesis should be systematically organized by anatomical location and temporal pattern, with compressive myelopathy (tumors, hematomas), inflammatory myelitis, and vascular myelopathies representing the three primary categories requiring urgent differentiation. 1, 2

Categorization by Temporal Pattern

Acute Onset (Hours to Days)

The rapidity of symptom onset is critical for narrowing the differential, as acute presentations suggest vascular or inflammatory causes while gradual progression indicates neoplastic or metabolic etiologies 1.

Vascular Causes:

• Spinal cord ischemia presents with acute onset paraparesis and sensory changes, occurring in 2-6% of thoracic aortic procedures and representing the most feared complication of descending thoracic aortic repairs 1
• Anterior spinal artery syndrome typically presents with painful, subacute (rather than apoplectiform) onset, affecting motor function and pain/temperature sensation while sparing proprioception 2
• Cerebral venous thrombosis involving the sagittal sinus can cause bilateral motor signs including paraparesis 1

Inflammatory/Infectious Causes:

• Acute transverse myelitis (20% of paraparesis cases in one series) presents with bilateral sensory deficit, clearly defined rostral border, and bladder dysfunction 3, 4
• Guillain-Barré syndrome progresses over days to 4 weeks with bilateral paresthesias, weakness, absent/decreased reflexes, elevated CSF protein, and electrodiagnostic evidence of neuropathy 5
• Infectious myelitis from neurotropic viruses or mycoplasma, typically occurring with meningitis or encephalitis 2

Subacute to Chronic Onset (Weeks to Months)

Compressive Myelopathy:

• Spinal tuberculosis is the most common cause of paraparesis (30% in one series), typically presenting with backache (75% of cases) and paresthesias (62.5%) 4
• Primary spinal cord tumors account for 10% of paraparesis cases, with myelography showing block in 58.5% of patients 4
• Epidural abscess or hematoma presents with localized back pain (often deep-seated), fever in only one-third of abscess cases, radiculopathy, and progressive spinal cord syndromes 6

Demyelinating Diseases:

• Multiple sclerosis presents with multifocal paresthesias affecting different body regions at different times, with MRI showing periventricular white matter lesions that are sharply demarcated, round or flame-shaped, and may enhance with gadolinium 5
  • Lesions typically spare U-fibers initially and involve the corpus callosum, distinguishing MS from other white matter diseases 5
  • Partial acute transverse myelopathy in MS shows small lesions in lateral or posterior spinal cord 3
• Neuromyelitis optica (Devic's disease) is now recognized as a distinct entity from MS based on recent immunologic studies 3
• Acute disseminated encephalomyelitis (ADEM) represents acute parainfectious or postvaccinal myelitis and must be distinguished from initial MS episodes due to different prognosis and treatment 3

Systemic/Autoimmune Causes:

• Symptomatic transverse myelitis associated with connective tissue diseases (SLE, Behçet's disease, Sjögren's syndrome) or sarcoidosis 2
• Lyme disease can present with encephalomyelitis showing multifocal white matter involvement, CSF lymphocytic pleocytosis, and positive two-tier serology 5

Metabolic/Hereditary Causes:

• Inborn errors of metabolism causing hereditary spastic paraparesis in adults, which are often treatable and essential to identify 7
• Vitamin B12 deficiency causes subacute combined degeneration with both central (myelopathic) and peripheral (neuropathic) manifestations 5

Anatomical Localization Patterns

The specific pattern of deficits is crucial for localization 2:

Anterior Spinal Cord Syndromes:

• Anterior spinal artery syndrome
• Selective anterior horn involvement
• Centromedullary syndromes 2

Long Pathway Syndromes:

• Isolated posterior column involvement
• Combined pyramidal pathway involvement 2

Brown-Séquard Syndrome:

• Unilateral cord lesion with ipsilateral motor and proprioceptive loss, contralateral pain/temperature loss 2

Critical Diagnostic Approach

Initial Clinical Assessment

Key features to document:

• Temporal pattern: Acute onset suggests vascular/inflammatory; gradual suggests neoplastic/metabolic 1
• Pain involvement: Backache present in 75% of compressive causes 4
• Spasticity: Present in 57.5% of patients (note: acute pathologies initially cause flaccid paraparesis with areflexia/hyporeflexia due to spinal shock) 2, 4
• Sensory level: Sharp sensory level indicates spinal cord injury requiring emergent imaging 5
• Bladder/bowel dysfunction: Suggests cauda equina syndrome or spinal cord compression 5

Imaging Strategy

MRI is the preferred imaging modality for suspected spinal pathology, even though CT may be more accessible out of hours 6. An MRI-based classification system organizes findings into six patterns: extradural, intradural/extramedullary, intramedullary, intramedullary-tract specific, spinal cord atrophy, and normal appearing spinal cord 8.

• CT scan following myelography exactly delineates primary spinal cord tumors and confirms diagnosis in spinal TB, arachnoid cysts, and other compressive myelopathies 4
• MRI with gadolinium demonstrates plaques of demyelination in MS and characterizes inflammatory lesions 5, 4

Laboratory Evaluation

For suspected vascular causes:

• Complete blood count, chemistry panel, prothrombin time, activated partial thromboplastin time 1
• Screening for prothrombotic conditions in suspected cerebral venous thrombosis 1

For inflammatory/infectious causes:

• CSF examination is essential when distinguishing spinal cord infarction from myelitis, as CSF analysis differentiates these conditions 3
• CSF shows elevated protein in Guillain-Barré syndrome and lymphocytic pleocytosis in Lyme neuroborreliosis 5
• Oligoclonal bands support MS diagnosis 3

For metabolic causes:

• Thyroid function, vitamin B12, electrolytes (potassium, magnesium, phosphate, calcium) 5
• Serum ferritin if restless legs syndrome suspected 5

Common Pitfalls to Avoid

Do not delay imaging if delayed recovery after neuraxial block occurs: Policies should accept that prompt investigation will include many women with no pathology found, as this is necessary to identify the rare cases of epidural abscess or hematoma 6.

Distinguish psychogenic paraplegia: This must be considered in the differential, though organic causes must be thoroughly excluded first 2.

Consider cauda equina syndrome: Since acute spinal cord pathologies cause flaccid paraparesis with areflexia (spinal shock), acute polyradiculoneuritis and cauda equina syndrome must be included in the differential 2.

Age-specific considerations: Special care must be taken in patients younger than 10 or older than 59 years, those with progressive onset, and those with atypical presentations 6.