What is the prevalence of idiopathic neuropathic pain (nerve burning) in the thighs and shoulders without a degenerative cause?

Prevalence of Idiopathic Neuropathic Pain in Thighs and Shoulders

Idiopathic neuropathic pain affecting the thighs and shoulders without degenerative causes is relatively uncommon, with most cases of neuropathic pain having an identifiable etiology in 54-75% of patients. 1

Understanding Idiopathic Neuropathic Pain

Neuropathic pain is characterized by:

• "Cold burning pain" sensation
• Pain disproportionate to any inciting event
• Sensory alterations including numbness, tingling, or burning sensations
• Potential allodynia (pain from normally non-painful stimuli) and hyperalgesia (increased pain sensitivity)

When specifically affecting the thighs and shoulders without degenerative causes, several key considerations emerge:

Clinical Presentation

• Bilateral involvement of non-adjacent areas (thighs and shoulders) suggests a systemic rather than focal process
• Pain may be described as burning, electric, or shooting
• Symptoms may be symmetrical or asymmetrical
• May worsen at night or with certain positions

Differential Diagnosis

1. Plexopathy

   • Brachial plexopathy (shoulders): formed from C5-T1 ventral rami 2
   • Lumbosacral plexopathy (thighs): formed from L1-L4 (lumbar) and L4-S4 (sacral) 2
   • Presents with pain, dysesthesia, or burning/electric sensations in multiple peripheral nerve distributions 2

2. Complex Regional Pain Syndrome (CRPS)

   • Usually follows an injury, often minor
   • Pain described as excruciating and worsened by touch
   • Can spread from initially affected limb to contralateral limb 3
   • Shows minimal placebo response except at very early timepoints 2

3. Peripheral Neuropathy

   • Often presents in a "stocking and glove" distribution 1
   • May be idiopathic in 25-46% of cases 1
   • Can involve proximal numbness in later stages

Prevalence Data

The exact prevalence of truly idiopathic neuropathic pain specifically in the thighs and shoulders is not well-documented in the literature, but we can draw some conclusions from related data:

• Peripheral neuropathy in the general population ranges from 1% to 7%, with higher rates among those older than 50 years 1
• Idiopathic causes account for 25-46% of all peripheral neuropathy cases 1
• Neuropathic pain affects 15-50% of patients with various peripheral neuropathies 4
• Chronic idiopathic axonal polyneuropathy represents a significant subset of idiopathic polyneuropathy cases 5

Diagnostic Approach

When evaluating suspected idiopathic neuropathic pain in the thighs and shoulders:

1. Rule out common identifiable causes:

   • Diabetes mellitus
   • Nerve compression or injury
   • Alcohol use
   • Toxin exposure
   • Hereditary diseases
   • Nutritional deficiencies
   • HIV-associated neuropathy (prevalence 13% to >50%) 2

2. Initial laboratory evaluation:

   • Complete blood count
   • Comprehensive metabolic profile
   • Fasting blood glucose
   • Vitamin B12 levels
   • Thyroid-stimulating hormone levels
   • Serum protein electrophoresis with immunofixation 1

3. Imaging considerations:

   • MRI of the brachial plexus for shoulder symptoms
   • MRI of the lumbosacral plexus for thigh symptoms
   • These should include orthogonal views through the oblique planes of the plexus 2

Clinical Implications

The management of idiopathic neuropathic pain remains challenging:

• First-line treatments typically include gabapentinoids and antidepressants 1
• Many patients remain in pain despite treatment or experience significant side effects 5
• Novel treatments such as palmitoylethanolamide (PEA) have shown promise in small case series 5
• Treatment should focus on pain reduction, functional improvement, and quality of life enhancement

Key Takeaway

While specific prevalence data for idiopathic neuropathic pain affecting both thighs and shoulders is limited, the non-degenerative, idiopathic form represents a minority of neuropathic pain cases. Most patients presenting with these symptoms will have an identifiable cause upon thorough evaluation, making truly idiopathic cases relatively uncommon.