Diabetes Mellitus

Classification

Pathophysiology

• Type 1: Autoimmune destruction of islet β-cells → no insulin synthesis or secretion → absolute dependence on exogenous insulin.
• Type 2: Peripheral insulin resistance (especially in muscle, liver, and fat) combined with progressive β-cell dysfunction → relative insulin deficiency. Often driven by obesity, physical inactivity, and genetic predisposition.

Diagnosis

Management

1. Lifestyle Modifications

• Weight reduction (especially in T2DM)
• Regular aerobic exercise
• Medical nutrition therapy (carbohydrate monitoring, reduced saturated fat)

2. Glucose-Lowering Pharmacotherapy

1. Metformin — first-line; reduces hepatic glucose output
2. GLP-1 receptor agonists (e.g., semaglutide, liraglutide) — weight loss, CV benefit
3. SGLT-2 inhibitors (e.g., empagliflozin, dapagliflozin) — renal/CV protection
4. DPP-4 inhibitors (e.g., sitagliptin) — weight-neutral
5. Sulfonylureas (e.g., glipizide) — inexpensive; hypoglycemia risk
6. Insulin — when oral agents insufficient

• Basal-bolus insulin regimen (e.g., insulin glargine + rapid-acting analogs)
• Continuous glucose monitoring (CGM) + insulin pump (CSII) for eligible patients

3. Cardiovascular & Metabolic Risk Reduction

• Blood pressure target: typically < 130/80 mmHg
• Statin therapy for most adults with diabetes
• Antiplatelet therapy in select high-risk patients

4. Glycemic Targets

• HbA1c < 7% for most non-pregnant adults
• Less stringent (< 8%) for elderly, limited life expectancy, or hypoglycemia-prone patients

Complications

Microvascular

Macrovascular

• Coronary artery disease, stroke, and peripheral artery disease — 2–4× higher risk than general population
• Atherosclerosis accelerated by hyperglycemia, dyslipidemia, and hypertension

Acute

• Diabetic ketoacidosis (DKA) — primarily T1DM; high anion gap metabolic acidosis, hyperglycemia, ketonemia
• Hyperosmolar hyperglycemic state (HHS) — primarily T2DM; extreme hyperglycemia (>600 mg/dL), minimal ketosis
• Hypoglycemia — most common acute complication of treatment

Monitoring

• HbA1c: every 3 months until at goal, then every 6 months
• Self-monitoring of blood glucose (SMBG) or CGM
• Annual: urine albumin-to-creatinine ratio, eGFR, lipid panel, foot exam, eye exam
• Blood pressure at every visit

Special Populations

• Pregnancy: tight glycemic control critical; insulin preferred (metformin/glyburide used in some guidelines for GDM)
• Elderly: hypoglycemia avoidance prioritized; simpler regimens preferred
• CKD: dose-adjust or avoid certain agents (e.g., metformin contraindicated with eGFR < 30)

Back Pain with Tingling Sensation to the Legs — Differential Diagnosis

Structured Differential Diagnosis

1. Lumbar Disc Herniation / Radiculopathy (Most Common)

• Mechanism: Herniated nucleus pulposus compresses a nerve root, most often at L4-L5 or L5-S1.
• Presentation: Sharp/shooting back pain radiating down the leg in a dermatomal pattern; tingling, numbness, or weakness in the corresponding territory. "Sciatica" refers specifically to posteriorly-radiating leg pain in an L5/S1 distribution.
• Key finding: Positive straight leg raise (SLR) test.
• Prognosis: Generally favorable — two-thirds of herniated discs show spontaneous regression on imaging over 6 months (Harrison's Principles of Internal Medicine, 21st ed., p. 622).

2. Lumbar Spinal Stenosis

• Mechanism: Narrowing of the spinal canal (due to osteophytes, ligamentum flavum hypertrophy, facet joint enlargement) compresses the thecal sac and nerve roots.
• Presentation: Bilateral leg pain, tingling, and weakness — classically neurogenic claudication (symptoms worsen with walking/standing and improve with sitting/forward flexion).
• Demographics: Most common cause of spinal surgery in patients over 65 years (Epidural Interventions in the Management of Chronic Spinal Pain, p. 33).
• Imaging: MRI shows reduced dural sac cross-sectional area; CT shows bony canal narrowing.

Pre-op (top row): T2-weighted sagittal MRI (A) shows posterior disc protrusion at L4-5; axial MRI (B) shows thecal sac compression; axial CT (C) confirms bony canal narrowing. Post-op (bottom row): successful neural decompression confirmed on MRI and CT.

3. Cauda Equina Syndrome (Surgical Emergency)

• Mechanism: Massive central disc herniation or other mass compresses the cauda equina nerve roots below L1-L2.
• Presentation: Bilateral leg weakness/tingling, saddle anesthesia (perianal numbness), urinary retention or incontinence, and fecal incontinence.
• Action: Requires urgent MRI and emergent surgical decompression. Do not miss.

4. Piriformis Syndrome

• Mechanism: Spasm or hypertrophy of the piriformis muscle compresses the sciatic nerve in the gluteal region.
• Presentation: Buttock pain with radiation down the posterior leg mimicking disc-related sciatica; no true spinal pathology on MRI.
• Key finding: Pain reproduced by the FAIR test (flexion, adduction, internal rotation of the hip).

5. Spondylolisthesis

• Mechanism: Anterior displacement of one vertebral body over another (commonly L4 over L5), causing nerve root or canal compression.
• Presentation: Low back pain, leg tingling/radiculopathy, and sometimes neurogenic claudication.
• Imaging: Plain X-ray (lateral view) shows "step-off" deformity; MRI for neural involvement.

6. Foraminal Stenosis

• Mechanism: Narrowing of the intervertebral foramen (due to osteophytes or disc degeneration) compresses the exiting nerve root.
• Presentation: Unilateral dermatomal pain and paresthesia; often indistinguishable clinically from disc herniation.

7. Peripheral Neuropathy (e.g., Diabetic)

• Mechanism: Systemic nerve damage (metabolic, toxic, autoimmune).
• Presentation: Bilateral, symmetric tingling/burning in a stocking distribution; associated with back pain if there is concomitant spinal pathology. Note: in diabetic patients, both radiculopathy and peripheral neuropathy may coexist.
• Distinguishing feature: No single dermatomal pattern; no positive SLR; nerve conduction studies abnormal.

8. Vascular Claudication

• Mechanism: Peripheral artery disease (PAD) causing ischemia to the legs.
• Presentation: Leg pain/cramping with exertion; tingling possible; improves with rest (not with positional change as in neurogenic claudication).
• Key finding: Reduced or absent peripheral pulses; ankle-brachial index (ABI) < 0.9.

9. Spinal Tumors (Primary or Metastatic)

• Mechanism: Epidural or intradural mass compresses neural structures.
• Red flags: Pain worse at night/at rest, unexplained weight loss, history of malignancy, age > 50.
• Imaging: MRI with contrast is the gold standard.

10. Vertebral Fracture (Osteoporotic or Traumatic)

• Mechanism: Compression fracture (particularly in osteoporotic elderly patients) may cause retropulsion of bone fragments into the canal.
• Presentation: Acute severe back pain after minimal trauma; neurological signs if the canal is compromised.

11. Epidural Abscess or Discitis/Osteomyelitis (Infection)

• Red flags: Fever, IV drug use, recent spinal procedure, immunocompromised state.
• Presentation: Progressive back pain + neurological deficit; constitutional symptoms.
• Emergency: Requires urgent MRI and often surgical drainage + antibiotics.

Comparison Table

Red Flags Requiring Urgent Workup

• Cauda equina symptoms (saddle anesthesia, bladder/bowel dysfunction) → emergent MRI
• Fever + back pain → rule out epidural abscess
• History of cancer → rule out metastasis
• Progressive neurological deficit
• Pain unrelenting at rest or at night

Diagnostic Approach

1. History: Onset, radiation pattern, aggravating/relieving factors, bowel/bladder function, systemic symptoms
2. Neurological exam: Motor strength, sensation, reflexes, SLR, gait
3. Imaging:
   • MRI lumbar spine — preferred for soft tissue, disc, and neural structures
   • X-ray — for fracture, alignment, spondylolisthesis
   • CT — bony detail when MRI is unavailable
4. Ancillary: EMG/NCS (to differentiate radiculopathy from peripheral neuropathy); ABI (if vascular claudication suspected); ESR/CRP, blood cultures (if infection/tumor suspected)