From the Guidelines
Left upper quadrant paresthesia is most commonly caused by thoracic spine problems, peripheral nerve entrapment syndromes, or systemic conditions such as diabetes mellitus or vitamin B12 deficiency, and a thorough neurological examination and diagnostic tests like MRI or nerve conduction studies are essential for determining the underlying cause. The evaluation of left upper quadrant paresthesia should prioritize identifying potential causes that could impact morbidity, mortality, and quality of life, such as nerve compression or damage affecting the left side of the upper body. Common causes include:
- Thoracic spine problems such as herniated discs, spinal stenosis, or degenerative disc disease that compress nerve roots 1
- Peripheral nerve entrapment syndromes like thoracic outlet syndrome or compression of the lateral cutaneous nerve of the thorax
- Systemic conditions including diabetes mellitus, vitamin B12 deficiency, multiple sclerosis, or stroke affecting sensory pathways
- Shingles (herpes zoster) affecting left thoracic dermatomes often presents with paresthesia before the characteristic rash appears
- Less commonly, paresthesia may result from anxiety or panic disorders, certain medications (particularly chemotherapy agents), toxin exposure, or as a post-surgical complication. The provided evidence on Parkinsonian syndromes and lower extremity peripheral artery disease 1 is not directly relevant to the causes of left upper quadrant paresthesia, and thus, the focus should be on the most common and clinically significant causes. Treatment depends on the specific diagnosis but may include addressing the underlying condition, physical therapy, anti-inflammatory medications, or neuropathic pain medications.
From the Research
Causes of Left Upper Quadrant Paresthesia
- Paresthesias may be caused by central or peripheral nervous system abnormalities 2
- Central nervous system-induced paresthesias are most commonly caused by:
- Ischemia
- Structural or compressive phenomena
- Infection
- Inflammation
- Degenerative conditions
- Peripherally induced paresthesias can be caused by:
- Entrapment syndromes
- Metabolic disturbances
- Trauma
- Inflammation
- Connective tissue diseases
- Toxins
- Hereditary conditions
- Malignancies
- Nutritional deficiencies
- Miscellaneous conditions
- Vitamin B12 deficiency, which can be caused by long-term metformin therapy, can lead to peripheral neuropathy and paresthesia 3, 4, 5, 6
- Metformin blocks the absorption of vitamin B12, leading to a deficiency that can cause or worsen distal symmetrical, autonomic, and cardiac neuropathy in patients with diabetes 3
- Patients on long-term metformin therapy are at a high risk for vitamin B12 deficiency and peripheral neuropathy, and interval screening for peripheral neuropathy is recommended even if vitamin B12 levels appear to be normal 4