What could be causing tingling and crawling sensations in the lower legs, feet, upper back, and arms, and how should it be diagnosed and managed?

Differential Diagnosis and Management of Widespread Tingling and Crawling Sensations

Your symptoms of tingling and crawling sensations affecting multiple body regions—lower legs, feet, upper back, and arms—most likely represent either peripheral polyneuropathy, restless legs syndrome (RLS) with atypical distribution, or a combination of both, and require systematic evaluation starting with diabetes screening, medication review, and neurological examination.

Initial Diagnostic Priorities

Most Critical Conditions to Rule Out

Diabetic peripheral neuropathy is the single most common identifiable cause of these symptoms and must be evaluated first. 1, 2 The widespread distribution affecting both lower and upper extremities suggests a length-dependent polyneuropathy, though the upper back involvement is atypical. 3

• Immediate laboratory testing should include: fasting glucose, HbA1c, vitamin B12 level, complete metabolic panel, and thyroid function tests 1, 4
• Check serum ferritin if symptoms worsen at rest or in the evening, as values <50 ng/mL suggest iron deficiency-related RLS 3, 4

Medication-Induced Causes

Review all current medications immediately, particularly metformin (≥2g daily), chemotherapy agents, statins, antipsychotics, and antidepressants. 1 Long-term metformin use is a frequently overlooked cause of B12 deficiency leading to peripheral neuropathy with tingling in a stocking-glove distribution. 1

• Antipsychotics and SSRIs can exacerbate or cause RLS symptoms that may spread to the trunk and upper extremities 3, 5

Physical Examination Essentials

Perform focused neurological testing including:

• 10-g monofilament testing (most useful for detecting loss of protective sensation) 4
• 128-Hz tuning fork for vibration perception 3
• Pinprick sensation, temperature sensation, and pressure sensation 3
• Ankle reflexes and assessment of deep tendon reflexes in all extremities 3
• Gait and balance assessment (instability increases fall risk 12-fold in symptomatic older adults) 4

The physical examination is usually unremarkable in primary RLS, but secondary causes such as peripheral neuropathy or radiculopathy may be detected. 3

Distinguishing Between Key Diagnoses

Restless Legs Syndrome with Atypical Distribution

RLS should be strongly considered if you can answer "yes" to these four questions: 3

1. Is there an urge to move the legs accompanied by uncomfortable or unpleasant sensations (described as creepy-crawly, burning, itching)?
2. Do symptoms begin or worsen during rest or inactivity (sitting or lying down)?
3. Are symptoms partially or totally relieved by movement (walking, stretching)?
4. Do symptoms worsen or only occur in the evening or night?

Critical caveat: Although RLS classically affects lower extremities, symptoms can involve upper extremities and even the trunk. 3 The upper back "crawling feeling" you describe fits this atypical but recognized pattern. 5

Peripheral Polyneuropathy

Suspect polyneuropathy if:

• Symptoms are relatively constant throughout the day (not circadian) 3
• Sensory loss is demonstrable on examination 3
• Symptoms follow a length-dependent pattern (feet worse than legs, though your upper extremity involvement complicates this) 1, 2

The differential diagnosis for polyneuropathy includes: 3

• Diabetic neuropathy (most common)
• Alcohol-associated polyneuropathy (prevalence 22-66% among chronic alcohol users) 2
• Vitamin B12 deficiency (especially with metformin use) 1
• Chemotherapy-induced neuropathy (prevalence 30-40% depending on agents) 2
• Cervical and lumbar spine disease with nerve root compression 3

When to Obtain Advanced Testing

Electrodiagnostic studies (EMG/nerve conduction studies) are indicated if: 3

• Initial laboratory workup is unrevealing
• Examination reveals objective weakness or sensory loss
• Symptoms are progressive or severe
• Diagnosis remains uncertain after initial evaluation

MRI of the cervical and/or lumbosacral spine should be considered if: 3

• Symptoms suggest radiculopathy or plexopathy
• There are focal neurologic findings on examination
• Upper back symptoms suggest spinal cord involvement

Note that electrodiagnostic studies may be normal when performed early in the disease course (within 1 week) or in mild disease. 3

Management Algorithm

If Diabetic Neuropathy is Confirmed

Tight glycemic control is the only convincingly proven strategy to prevent or delay progression. 1, 4 This is the primary intervention and takes precedence over symptomatic treatment.

For symptomatic relief of neuropathic pain and sensory symptoms: 3, 1

• First-line: Duloxetine 30mg daily for one week, then increase to 60mg daily (provides 30-50% pain reduction and may improve numbness/tingling) 1
• Alternative agents: Pregabalin, gabapentin, tricyclic antidepressants (amitriptyline), or venlafaxine 3, 1

If RLS is Confirmed

Dopamine receptor agonists are first-line pharmacologic treatment: 3

• Ropinirole: Start 0.25mg orally 1-3 hours before bedtime, increase to 0.5mg after 2-3 days, then 1mg after 7 days; titrate by 0.5mg weekly increments to maximum 4mg 3
• Pramipexole: Start 0.125mg orally 2-3 hours before bedtime, double every 4-7 days to maximum 0.5mg 3

Important warnings about dopamine agonists: 3

• Side effects include nausea, orthostatic hypotension, sleepiness, headache, and compulsive behaviors
• In older patients, particular consideration must be given to drug interactions and orthostasis risk
• These agents cause less augmentation than levodopa-carbidopa

Iron supplementation if ferritin <50 ng/mL is recommended and may be sufficient treatment in some cases. 3

If Metformin-Induced B12 Deficiency

Continue vitamin B12 supplementation at 2500 mcg daily. 1 Monitor B12 levels in all patients on long-term metformin. 1

Common Pitfalls to Avoid

1. Dismissing upper back and arm symptoms as "atypical" for RLS: While less common, RLS can affect these areas and should not exclude the diagnosis 3, 5

2. Failing to check ferritin in suspected RLS: This is a reversible cause that may respond to iron supplementation alone 3

3. Assuming diabetic neuropathy in diabetic patients without excluding other causes: Spinal stenosis causing neurogenic positional pedal neuritis can mimic diabetic neuropathy and is frequently misdiagnosed 6

4. Not recognizing medication-induced causes: Antipsychotics, SSRIs, tricyclic antidepressants, lithium, and dopamine antagonists can all exacerbate or cause these symptoms 3, 5

5. Overlooking spinal pathology: Cervical and lumbar spine disease with nerve root compression must be excluded, especially given your upper back involvement 3

Non-Pharmacologic Interventions

Physical activity has been shown to improve neuropathy symptoms and should be recommended regardless of etiology. 1 Exercise, physiotherapy, and ergotherapy can be beneficial depending on symptoms and functional deficits. 2

If symptoms worsen with spinal position (standing, walking, or lying in bed), consider neurogenic positional pedal neuritis from spinal stenosis—symptoms may improve with spine flexion or walking with wheeled support. 6