61-year-old female with uncontrolled type 2 diabetes mellitus on insulin 70/30 twice daily, hypertension on losartan, hyperlipidemia on atorvastatin, presenting with a 4-month history of left foot dorsum pain radiating to the lateral leg and lower back, worsened by leg elevation, walking and pressure over the left medial malleolus, partially relieved by ibuprofen + acetaminophen (Alaxan) and vitamin B complex (B1, B6, B12), elevated blood pressure (140/90 mmHg), discrete limp on the right side, dragging left foot, pins‑and‑needles on medial malleolus pressure, and full range of motion – what is the most likely diagnosis and recommended next steps?

Diagnosis: Diabetic Lumbosacral Radiculoplexus Neuropathy (DLRPN)

This patient most likely has diabetic lumbosacral radiculoplexus neuropathy (DLRPN), not simple distal symmetric polyneuropathy, based on the asymmetric presentation (left-sided predominance), radiating pain from foot to lower back, acute-on-chronic course over 4 months, and uncontrolled diabetes. 1, 2

Key Diagnostic Features Supporting DLRPN

• The pain pattern—starting in the left foot dorsum and radiating up the lateral leg to the lower back—is characteristic of radiculoplexus involvement rather than typical distal symmetric polyneuropathy, which would be bilateral and symmetric 3, 2
• The asymmetric presentation with left foot dragging and discrete right-sided limp indicates proximal nerve involvement (lumbosacral plexus or nerve roots) rather than pure distal neuropathy 4, 5
• The 4-month duration with episodic worsening fits the natural history of DLRPN, which typically presents subacutely over weeks to months 2
• Uncontrolled type 2 diabetes (on insulin 70/30) is the strongest risk factor for DLRPN, with diabetic patients having 7.91 times higher odds of developing this condition 2

Critical Differential Diagnosis Pitfall

• Do not assume this is lumbar radiculopathy from degenerative disc disease—DLRPN is frequently misdiagnosed as structural spine pathology, leading to unnecessary epidural injections or surgery 5
• The full range of motion and absence of typical radicular signs (no mention of straight leg raise positivity) argue against pure mechanical radiculopathy 5

Immediate Next Steps

1. Confirm Diagnosis with Electrodiagnostic Studies

• Order nerve conduction studies and electromyography (EMG) immediately to demonstrate the characteristic pattern of DLRPN: asymmetric sensorimotor involvement affecting multiple lumbosacral nerve roots and plexus elements 1, 5, 2
• EMG will show active denervation in paraspinal muscles and proximal leg muscles (distinguishing this from pure peripheral neuropathy) and help exclude chronic inflammatory demyelinating polyneuropathy (CIDP) 4, 5

2. Advanced Imaging

• Order MR neurogram of the lumbosacral plexus and pelvis to visualize nerve inflammation and thickening in the sciatic and femoral nerves, which can confirm DLRPN and exclude structural causes 5
• Standard lumbar spine MRI is insufficient—it may show degenerative changes that are red herrings; the MR neurogram specifically images the plexus and proximal nerve roots 5

3. Laboratory Exclusion of Alternative Causes

• Measure vitamin B12 level (metformin can cause deficiency that worsens neuropathy) 1
• Check TSH to exclude hypothyroidism 1
• Obtain serum protein electrophoresis with immunofixation to rule out monoclonal gammopathy 1
• Measure ESR, CRP, and ANA to assess for autoimmune/inflammatory causes 1

Immediate Symptomatic Management

Optimize Neuropathic Pain Control

• Increase pregabalin from the current subtherapeutic 75 mg to 150 mg at bedtime for 1 week, then advance to 150 mg twice daily (morning and bedtime) if tolerated 1
• The therapeutic range for diabetic neuropathy is 300-600 mg/day divided into 2-3 doses; the current 75 mg dose is inadequate 1
• If pregabalin is not tolerated or inadequate at 300 mg/day after 4-6 weeks, switch to duloxetine 60 mg daily (can increase to 120 mg) 1
• Avoid opioids including tramadol—the American Diabetes Association strongly recommends against their use due to addiction risk and lack of long-term efficacy 1

Address Sleep and Mood Disturbances

• Screen for depression and anxiety using validated tools, as over two-thirds of patients with painful diabetic neuropathy have comorbid mood disorders that worsen pain outcomes 6, 1
• Treat sleep disturbance concurrently with pain management, as nocturnal pain exacerbation is characteristic and severely impacts quality of life 3

Disease-Modifying Interventions

Glycemic Optimization (Priority #1)

• The uncontrolled diabetes (on insulin 70/30 BID) is driving neuropathy progression—target HbA1c of 6-7% to slow further nerve damage, though this will not reverse existing injury 1
• Consider endocrinology referral for insulin regimen optimization, as current therapy is clearly inadequate 1
• Avoid extreme glucose fluctuations, as erratic control intensifies neuropathic pain symptoms 1

Cardiovascular Risk Factor Management

• The blood pressure of 140/90 mmHg requires optimization—hypertension is an independent risk factor for diabetic neuropathy with an odds ratio of 1.58 1
• Continue atorvastatin for hyperlipidemia, as dyslipidemia contributes to neuropathy progression in type 2 diabetes 1

Comprehensive Foot Care Protocol

• Perform 10-g monofilament testing immediately to assess for loss of protective sensation, which predicts ulcer and amputation risk 6, 1
• Test vibration perception with 128-Hz tuning fork and assess ankle reflexes 6, 1
• Inspect for foot deformities, callus formation, and pre-ulcerative signs 6
• Refer to podiatry for ongoing preventive care given the high-risk features (neuropathy, uncontrolled diabetes, foot pain) 6, 1
• Educate patient to inspect feet daily, never walk barefoot, and report any skin breaks immediately 6

Consideration of Immunotherapy (If Severe)

• If pain is severe and disabling despite optimized pharmacotherapy, consider a trial of intravenous immunoglobulin (IVIg) or corticosteroids, as DLRPN may have an autoimmune component 4
• This is reserved for patients with severe ongoing pain given significant side effects in diabetic patients 4
• A trial of plasma exchange can identify patients who might respond to immunotherapy 4
• Natural history favors spontaneous improvement over 6-12 months, so aggressive immunotherapy should be reserved for refractory cases 4

Follow-Up Timeline

• Reassess pain using numeric rating scale (0-10) in 2 weeks after pregabalin titration 1
• Review EMG and MR neurogram results within 2-3 weeks to confirm diagnosis 5
• Repeat HbA1c in 3 months to assess glycemic control 1
• Schedule comprehensive foot examination every 3-6 months given high-risk status 1

Prognosis

• DLRPN typically improves spontaneously within 6-12 months, though pain can be severe during the acute phase 4
• Recurrence occurs in approximately 5% of cases (3/62 episodes in one series) 2
• Long-term outcome depends critically on achieving glycemic control to prevent progression of underlying diabetic neuropathy 1