What is the most likely diagnosis and recommended diagnostic and therapeutic plan for a patient with chronic back‑pressure sensation, bowel and bladder dysfunction, autonomic signs (dry mouth, polyuria, tachycardia, night sweats) and new neuropathic leg sensations?

Most Likely Diagnosis: Guillain-Barré Syndrome (GBS) or Severe Autonomic Polyneuropathy

This patient requires immediate hospitalization with ICU-level monitoring capability due to the constellation of bowel/bladder dysfunction, autonomic instability (dry mouth, polyuria, tachycardia, night sweats), and progressive neuropathic symptoms—this presentation suggests Guillain-Barré syndrome or a severe acute-on-chronic polyneuropathy with life-threatening autonomic involvement.

Diagnostic Workup

Immediate Priority Testing

Urgent neurology consultation is mandatory 1. The diagnostic evaluation must include:

• MRI of spine with and without contrast to rule out compressive lesions (tumor, abscess, hematoma) and evaluate for nerve root enhancement/thickening 1

• Lumbar puncture: CSF analysis typically shows elevated protein and often elevated WBCs in immune-mediated neuropathies. Send cytology given the severity 1

• Serum antiganglioside antibody tests for GBS and variants (anti-GQ1b for Miller Fisher variant) 1

• Electrodiagnostic studies (EMG/NCS) to characterize the polyneuropathy pattern 1

Secondary Workup for Reversible Causes

Screen for treatable etiologies 1:

• Diabetic screen (glucose, HbA1c)
• B12, folate levels
• TSH
• HIV testing
• Serum protein electrophoresis (for paraproteinemic neuropathy)
• Vasculitic and autoimmune screening

Autonomic Function Assessment

Cardiovascular autonomic testing should include 2:

• Heart rate variability with deep breathing
• Orthostatic vital signs (looking for >20 mmHg systolic or >10 mmHg diastolic drop without appropriate heart rate increase)
• Resting tachycardia assessment

Urodynamic studies to evaluate bladder dysfunction 2. The combination of bladder dysfunction with autonomic signs significantly increases likelihood of small fiber polyneuropathy 3.

Therapeutic Plan

Immediate Management (If GBS Suspected)

Admit to inpatient unit with rapid ICU transfer capability 1. This is non-negotiable given risk of respiratory compromise.

Initiate immunotherapy immediately 1:

• IVIG 0.4 g/kg/day for 5 days (total dose 2 g/kg) OR
• Plasmapheresis for 5 days PLUS
• Concurrent corticosteroids: methylprednisolone 2-4 mg/kg/day

While corticosteroids aren't standard for idiopathic GBS, they are reasonable in immune-mediated forms 1.

Critical Monitoring

• Frequent neurochecks (at least every 4 hours initially) 1
• Pulmonary function monitoring (forced vital capacity every 4-6 hours) to detect impending respiratory failure 1
• Continuous cardiac monitoring for autonomic instability 1

Symptomatic Management

For neuropathic pain 2:

• First-line: Gabapentin (300-1200 mg TID) or pregabalin (100 mg TID)
• Alternative: Duloxetine (60-120 mg daily)
• Avoid opioids including tramadol due to adverse event risk 2

For constipation/ileus 1:

• Aggressive bowel regimen
• Consider prokinetic agents if gastroparesis present

For bladder dysfunction 2:

• Intermittent catheterization if significant post-void residual
• Avoid medications worsening autonomic function

Medications to AVOID

Do not use 1:

• β-blockers
• IV magnesium
• Fluoroquinolones
• Aminoglycosides
• Macrolides

These can worsen neuromuscular transmission and autonomic dysfunction.

Alternative Diagnosis: Diabetic Autonomic Neuropathy

If diabetes is confirmed and GBS ruled out, the presentation fits severe diabetic autonomic neuropathy with peripheral neuropathy 4, 2.

Management Approach

Optimize glucose control aggressively 2:

• Target near-normal glycemia to slow (not reverse) progression
• This is the only disease-modifying intervention available

Optimize cardiovascular risk factors 2:

• Blood pressure control
• Lipid management
• Weight optimization

Symptomatic treatment as above for neuropathic pain and autonomic symptoms 2.

Critical Clinical Pearls

The "back-pressure sensation" is concerning and may represent:

• Spinal cord compression (hence urgent MRI)
• Severe constipation from autonomic dysfunction
• Bladder distension from neurogenic bladder

The combination of bowel AND bladder dysfunction with autonomic signs is a red flag 3, 5. This suggests either:

1. Severe acute polyneuropathy (GBS)
2. Spinal cord/cauda equina pathology
3. Severe small fiber polyneuropathy with autonomic involvement

Do not wait for complete workup to initiate treatment if GBS suspected—respiratory failure can develop rapidly and is the primary cause of mortality 1.

Autonomic dysfunction in polyneuropathy carries independent mortality risk, particularly cardiovascular autonomic neuropathy 6. This patient requires aggressive monitoring regardless of final diagnosis.