What is the diagnosis and management for a young female presenting with sudden onset bilateral lower limb weakness, power 3/5, and exaggerated knee reflexes, with no other abnormalities?

Acute Transverse Myelitis or Spinal Cord Compression

This presentation of sudden-onset bilateral lower limb weakness with power 3/5 and exaggerated knee reflexes in a young female strongly suggests an upper motor neuron lesion at the spinal cord level, most likely acute transverse myelitis or spinal cord compression, requiring emergency MRI of the entire spine and urgent neurology consultation. 1

Critical Immediate Assessment

This is not Guillain-Barré syndrome despite the bilateral leg weakness, because:

• Hyperreflexia (exaggerated knee reflexes) excludes GBS - GBS characteristically presents with areflexia or hyporeflexia, not hyperreflexia 2, 3, 1, 4
• The sudden onset "at night" suggests a vascular or compressive etiology rather than the ascending pattern typical of GBS 2, 4
• GBS typically develops over days to 4 weeks, not suddenly overnight 1, 4

The exaggerated reflexes indicate upper motor neuron pathology (spinal cord), not peripheral nerve disease. 1

Emergency Diagnostic Approach

Immediate Red Flag Assessment

Examine immediately for these life-threatening features: 1

• Bladder/bowel dysfunction - Ask about urinary retention, incontinence, or constipation
• Sensory level - Check for a sharp demarcation where sensation changes on the trunk
• Saddle anesthesia - Test perineal sensation
• Anal sphincter tone - Perform rectal examination

If any of these are present, this is a surgical emergency requiring MRI within hours. 1

Clinical Examination Priorities

• Check for a sensory level on the trunk - This localizes the spinal cord lesion and indicates cord pathology requiring emergency imaging 1
• Test for clonus and Babinski sign - These confirm upper motor neuron involvement 1
• Assess upper limb strength and reflexes - Normal upper limbs with abnormal lower limbs suggests a thoracic cord lesion 1
• Single breath count - If <19, respiratory muscles may be affected and ICU monitoring is needed 3

Most Likely Diagnoses

1. Acute Transverse Myelitis

• Sudden onset bilateral leg weakness with hyperreflexia is classic 1
• Often preceded by viral illness or occurs spontaneously in young adults
• Can progress rapidly over hours to days
• Requires urgent high-dose corticosteroids

2. Spinal Cord Compression

• Emergency MRI of entire spine is mandatory to exclude compressive lesions 1
• Causes include epidural abscess, hematoma, tumor, or disc herniation 5
• Surgery within 12-72 hours improves outcomes if compression is present 1

3. Anterior Spinal Artery Syndrome

• Sudden onset suggests vascular etiology
• Typically causes motor weakness with preserved posterior column function (vibration/proprioception)
• More common in young females with risk factors (oral contraceptives, hypercoagulable states)

Immediate Management Algorithm

Step 1: Emergency MRI of entire spine with and without contrast 1

• Do not delay imaging - this is time-sensitive
• Look for cord compression, cord signal abnormality, or vascular lesions

Step 2: While awaiting MRI:

• Admit to monitored bed with capability for ICU transfer 3
• Check vital capacity and negative inspiratory force 3
• Establish IV access
• Hold oral contraceptives if patient is taking them 6

Step 3: Laboratory workup:

• Complete blood count, comprehensive metabolic panel
• ESR, CRP (elevated in inflammatory myelitis or abscess)
• Vitamin B12, copper, TSH (reversible causes)
• Consider HIV, syphilis, Lyme serology depending on risk factors

Step 4: Lumbar puncture after MRI excludes mass lesion:

• CSF analysis for cell count, protein, glucose, oligoclonal bands
• CSF cultures and viral PCR panel
• Cytology if malignancy suspected

Step 5: Neurology consultation immediately 1

Treatment Considerations

If Transverse Myelitis Confirmed:

• High-dose IV methylprednisolone 1000 mg daily for 3-5 days (standard practice for acute inflammatory myelitis)
• Consider plasma exchange if no response to steroids
• Screen for underlying autoimmune conditions (NMO-IgG/aquaporin-4 antibodies, MOG antibodies, ANA, anti-dsDNA)

If Cord Compression Found:

• Immediate neurosurgical consultation 1
• High-dose dexamethasone 10 mg IV followed by 4 mg every 6 hours
• Surgery within 12-72 hours if indicated 1

Common Pitfalls to Avoid

• Do not assume GBS based on bilateral leg weakness alone - reflexes are the key distinguishing feature 2, 3, 7
• Do not wait for bladder symptoms to develop - early intervention prevents permanent dysfunction 1
• Do not perform lumbar puncture before imaging - if mass lesion present, LP risks herniation 1
• Do not dismiss the diagnosis if initial symptoms seem mild - cord lesions can progress rapidly over hours 1, 8

Rare cases of GBS with hyperreflexia have been reported but are extremely uncommon 7 - in this clinical context with sudden overnight onset, spinal cord pathology must be excluded first.