In a 41-year-old man living with HIV on lamivudine and tenofovir who developed acute progressive lower-extremity weakness and pin‑prick paresthesias after a motorcycle accident, what urgent diagnostic and initial therapeutic steps should be taken?

Urgent Spinal Cord Compression Must Be Ruled Out Immediately

This patient requires emergent MRI of the entire spine (cervical through lumbar) within hours, not days, to exclude compressive myelopathy or cauda equina syndrome—both neurosurgical emergencies that can result in irreversible paralysis if not addressed urgently. The positive bilateral kidney punch test with pain radiating to the left lower extremity, combined with progressive ascending neurological symptoms (left leg weakness progressing to bilateral foot involvement), raises critical concern for spinal pathology rather than simple peripheral neuropathy.

Critical Diagnostic Priorities

Immediate Workup (Within 24 Hours)

Neuroimaging:

• Emergent MRI spine (complete cervical, thoracic, lumbar) to evaluate for:
  • Spinal cord compression from mass lesions (lymphoma, abscess, tuberculoma)
  • Epidural abscess
  • Transverse myelitis
  • Vacuolar myelopathy
  • Vertebral lesions with cord impingement

The positive kidney punch test is atypical for simple HIV-associated distal symmetric polyneuropathy and suggests possible retroperitoneal or spinal pathology 1.

Laboratory Assessment:

• CD4 count and HIV viral load (urgent—determines risk stratification for opportunistic infections)
• Creatine phosphokinase (CPK) to exclude myopathy or rhabdomyolysis 2, 3
• Complete metabolic panel including creatinine (tenofovir can cause renal toxicity) 4
• Serum lactate (elevated in 81% of HIV-associated neuromuscular weakness syndrome) 2
• Vitamin B12, folate, TSH
• Syphilis serology (RPR/VDRL)
• Hepatitis B surface antigen (patient on lamivudine/tenofovir which treats HBV) 5

If CD4 <200 cells/μL, add:

• Serum cryptococcal antigen
• Toxoplasma IgG
• CMV PCR
• Consider lumbar puncture (after MRI excludes mass effect) for CSF analysis including cell count, protein, glucose, VDRL, cryptococcal antigen, and opportunistic infection workup

Key Clinical Red Flags in This Case

1. Progressive ascending pattern: Started left leg, now bilateral—suggests myelopathy rather than length-dependent peripheral neuropathy
2. Rapid progression (3 weeks): Too fast for typical HIV-associated distal symmetric polyneuropathy
3. Motor > sensory involvement: Difficulty lifting foot, dragging gait—suggests upper motor neuron or nerve root pathology
4. Positive kidney punch test with radiation: Highly unusual for peripheral neuropathy; suggests structural spinal or retroperitoneal pathology
5. Suboptimal ART regimen: Lamivudine + tenofovir alone is incomplete therapy—missing third agent (integrase inhibitor, NNRTI, or protease inhibitor) 6, 7

Differential Diagnosis by Likelihood

High Priority (Life-Threatening)

1. AIDS-related CNS lymphoma with spinal involvement 1

   • Risk highest if CD4 <50 cells/μL
   • Can present as cauda equina syndrome
   • Requires urgent MRI and possible biopsy

2. Spinal epidural abscess

   • Progressive weakness, back pain with radiation
   • Medical emergency requiring surgical decompression

3. Tuberculous spondylitis (Pott's disease)

   • Endemic consideration depending on location
   • Can cause cord compression

Moderate Priority

1. HIV-associated neuromuscular weakness syndrome (HANWS) 2

   • Associated with stavudine exposure (not present here, but can occur with other NRTIs)
   • Hyperlactatemia in 81% of cases
   • Can occur after ART discontinuation or with mitochondrial toxicity
   • Check CPK and lactate urgently

2. Vacuolar myelopathy 8, 9

   • Occurs in advanced HIV (CD4 typically <200)
   • Progressive spastic paraparesis
   • Diagnosis of exclusion after imaging rules out structural lesions
   • Improves with ART initiation

3. Cytomegalovirus (CMV) polyradiculopathy

   • If CD4 <50 cells/μL
   • Ascending flaccid paralysis
   • CSF shows neutrophilic pleocytosis
   • Requires urgent ganciclovir

Lower Priority (But Must Exclude)

1. HIV-associated distal symmetric polyneuropathy 10, 11

   • Most common HIV neuropathy (occurs in 33-67% of patients)
   • Typically length-dependent, distal, symmetrical
   • Does NOT explain: rapid progression, motor predominance, positive kidney punch test, or ascending pattern
   • Treatment: gabapentin first-line (titrate to 2400 mg/day divided doses) 10

2. Guillain-Barré syndrome or CIDP

   • Ascending paralysis
   • Requires nerve conduction studies and CSF analysis

Immediate Therapeutic Steps

1. Complete the ART Regimen Urgently

The current regimen (lamivudine + tenofovir) is incomplete and suboptimal 6, 7. This two-drug combination without a third active agent does not constitute adequate HIV treatment and may lead to virological failure and resistance.

Recommended immediate action:

• Add dolutegravir 50 mg once daily to the existing lamivudine/tenofovir regimen 7
  • This creates the recommended regimen: dolutegravir + tenofovir/lamivudine
  • Dolutegravir has high barrier to resistance
  • Well-tolerated with minimal drug interactions
  • However: If CD4 <200 or concern for CNS opportunistic infection, consider starting boosted darunavir instead until resistance testing returns 7

Critical caveat: Do not delay ART optimization, but if spinal lymphoma is confirmed, coordinate with oncology as some regimens may need modification.

2. Renal Function Monitoring

Tenofovir disoproxil fumarate requires dose adjustment if creatinine clearance <50 mL/min 4:

• CrCl 30-49: dose every 48 hours
• CrCl 10-29: dose every 72-96 hours
• Calculate creatinine clearance immediately
• Monitor for proximal renal tubulopathy (check urine protein, glucose, phosphate)

3. Symptomatic Pain Management (While Awaiting Diagnosis)

If peripheral neuropathic component confirmed:

• Gabapentin: Start 300 mg at bedtime, titrate to 800 mg three times daily (2400 mg/day total) over 1-2 weeks 10
• Topical capsaicin 8% patch: Single 30-minute application can provide relief for 12 weeks 10
• Avoid lamotrigine (not effective for HIV neuropathy) 10

Do NOT start neuropathic pain treatment until structural spinal pathology is excluded—treating symptoms could mask progression of a surgical emergency.

Common Pitfalls to Avoid

1. Assuming this is simple HIV neuropathy: The clinical pattern (rapid progression, motor predominance, positive kidney punch test) is atypical and demands structural imaging first

2. Delaying spinal MRI: This is a potential neurosurgical emergency. Order MRI stat, not routine

3. Continuing incomplete ART regimen: Two-drug NRTI-only therapy is inadequate and risks resistance 6, 7

4. Missing opportunistic infections: If CD4 <200, this patient is at high risk for CNS lymphoma, CMV, toxoplasmosis, and tuberculosis 1

5. Attributing everything to tenofovir toxicity: While tenofovir can cause renal issues and rare myopathy, it does not typically cause acute progressive myelopathy

6. Starting empiric treatment without diagnosis: Resist the urge to start gabapentin or other symptomatic therapy until you have imaging—you may be treating a compressive lesion that needs surgery

Follow-Up Algorithm

If MRI shows mass lesion or cord compression: → Urgent neurosurgery consultation → Consider biopsy if lymphoma suspected → Start dexamethasone if cord edema present → Adjust ART based on final diagnosis

If MRI normal and CD4 <200: → Lumbar puncture for CSF analysis → Consider CMV polyradiculopathy (start ganciclovir empirically if high suspicion) → EMG/nerve conduction studies

If all structural/infectious causes excluded: → Diagnosis: likely vacuolar myelopathy or HIV-associated neuropathy → Optimize ART (add dolutegravir) → Start gabapentin for neuropathic pain → Physical therapy → Monitor for improvement over 3-6 months with viral suppression 10, 8, 9

The key message: This patient needs emergent spinal imaging before anything else. The clinical presentation suggests myelopathy or radiculopathy, not simple peripheral neuropathy, and delay could result in permanent paralysis.