What could cause left thoracic paresthesia radiating to the abdomen that worsens at night, and how should it be evaluated and managed?

Left Thoracic Paresthesia Radiating to Abdomen with Nocturnal Worsening

This presentation most likely represents thoracic radiculopathy, which requires urgent evaluation with MRI of the thoracic spine to exclude compressive lesions, followed by consideration of metabolic causes if imaging is unrevealing. 1

Initial Diagnostic Approach

The combination of unilateral thoracic paresthesia radiating in a dermatomal pattern to the abdomen with nocturnal worsening is highly suggestive of thoracic radiculopathy, though this diagnosis is frequently overlooked in clinical practice. 1 The key distinguishing features to assess include:

• Dermatomal distribution: Thoracic radiculopathy typically follows a band-like pattern from the back wrapping around to the anterior abdomen, consistent with nerve root involvement. 1, 2
• Nocturnal worsening: This pattern can occur with nerve compression that worsens with recumbent positioning or with metabolic neuropathies. 3
• Quality of sensation: "Pins and needles" (paresthesia) suggests small fiber involvement within nociceptive pathways, characteristic of peripheral nerve pathology. 4

Critical Red Flags to Exclude Immediately

Before proceeding with routine workup, you must actively exclude life-threatening conditions:

Aortic pathology: Although less likely with pure sensory symptoms, sudden-onset severe pain radiating from back to abdomen in patients with risk factors (connective tissue disorders, hypertension, family history) requires immediate consideration of thoracic aortic dissection. 3 Look specifically for:

• Abrupt or instantaneous pain onset (not gradual paresthesia)
• Pulse deficits or blood pressure differentials >20 mmHg between limbs
• Associated chest pain, syncope, or focal neurologic deficits 3

Spinal cord compression: Progressive symptoms, bilateral involvement, motor weakness, bowel/bladder dysfunction, or gait disturbance mandate emergent imaging. 1

Recommended Diagnostic Workup

First-line imaging: MRI of the thoracic spine with and without contrast is the diagnostic study of choice. 1 This will identify:

• Disc herniation (degenerative disc disease is a frequent cause of thoracic radiculopathy)
• Vertebral compression fractures
• Spinal tumors or metastases
• Inflammatory lesions

Electrodiagnostic studies: EMG and nerve conduction studies are useful adjunctive tools to confirm radiculopathy and localize the level of involvement. 1

Laboratory evaluation if imaging is unrevealing:

• Hemoglobin A1c and fasting glucose (diabetes mellitus frequently causes thoracic radiculopathy) 1
• Vitamin B12 level (deficiency can cause paresthesias) 5
• Complete blood count and metabolic panel
• Consider serum protein electrophoresis if monoclonal gammopathy suspected 5

Management Strategy

Conservative management is appropriate for most cases without red flags:

• Treat underlying metabolic causes (optimize diabetes control, replace vitamin B12) 1
• Physical therapy and postural modifications
• Neuropathic pain medications (gabapentin, pregabalin, or tricyclic antidepressants) for symptomatic relief 4

Surgical intervention is reserved for:

• Progressive myelopathy with neurologic compromise 1
• Severe refractory pain despite conservative measures
• Structural lesions requiring decompression

Corticosteroids may be considered for acute inflammatory radiculopathy, with evidence showing resolution of post-procedural thoracic radiculopathy with steroid tapers. 2

Common Pitfalls

• Missing the diagnosis entirely: Thoracic radiculopathy is uncommon and frequently overlooked, leading to delayed diagnosis and inappropriate treatment. 1
• Attributing symptoms to more common conditions: Abdominal paresthesias may be misattributed to gastrointestinal pathology rather than neurologic causes. 4
• Inadequate imaging: Standard lumbar or cervical spine imaging will miss thoracic pathology—specifically request thoracic spine MRI. 1
• Overlooking diabetic radiculopathy: Diabetes is a frequent cause of thoracic radiculopathy and should be screened in all patients. 1

Alternative Diagnoses to Consider

If thoracic spine imaging and metabolic workup are unrevealing:

• Intercostal neuralgia from prior trauma, herpes zoster, or post-surgical changes
• Peripheral neuropathy with atypical distribution (though typically bilateral and distal) 4, 5
• Restless legs syndrome if symptoms involve urge to move and are relieved by movement, though this typically affects lower extremities bilaterally 3