Differential Diagnosis for Left-Sided Sciatica in an Early 80s Patient with a History of Breast Cancer

Single Most Likely Diagnosis

• Lumbar Disc Herniation: This is the most common cause of sciatica, especially in older adults. The patient's age and new onset of left-sided sciatica pain make this a likely diagnosis. The fact that they have never been diagnosed with sciatica before suggests a new event such as a herniated disc.

Other Likely Diagnoses

• Lumbar Spinal Stenosis: This condition is common in older adults and can cause sciatica, especially with walking or standing. Given the patient's age, this is a plausible diagnosis.
• Degenerative Spondylolisthesis: This condition, where one vertebra slips forward over the one below it, can cause sciatica and is more common in older adults, particularly women.
• Osteoporotic Compression Fracture: Given the patient's history of breast cancer and use of letrozole (an aromatase inhibitor that can lead to bone loss), an osteoporotic compression fracture could be a cause of the sciatica, especially if there was a recent trauma or even a minor fall.

Do Not Miss Diagnoses

• Spinal Metastasis: Given the patient's history of breast cancer, spinal metastasis is a critical diagnosis not to miss. Breast cancer can metastasize to the spine, causing pain, and sciatica could be a presenting symptom.
• Cauda Equina Syndrome: Although less common, this is a medical emergency that requires immediate attention. It involves compression of the nerves in the lower spine, leading to severe pain, numbness, and potentially bladder and bowel dysfunction.
• Infection (e.g., Discitis or Osteomyelitis): Infections of the spine can cause sciatica and are more serious, requiring prompt diagnosis and treatment.

Rare Diagnoses

• Tarlov Cyst: These are rare, fluid-filled sacs that can compress nerve roots and cause sciatica.
• Arachnoiditis: Inflammation of the membranes surrounding the spinal cord, which can cause sciatica, though it is relatively rare.
• Neurogenic Tumor: Tumors originating from the nerve tissues, such as neurofibromas or schwannomas, can cause sciatica but are less common.

Each of these diagnoses should be considered in the context of the patient's full medical history, physical examination, and potentially, diagnostic imaging such as MRI or CT scans.