Can Radiation Therapy for Head and Neck Cancer Cause Peripheral Neuropathy in the Legs and Balance Problems?
Yes, radiation therapy for head and neck cancer can cause peripheral neuropathy and balance problems, though these are recognized late effects that typically manifest months to years after treatment rather than immediate complications. 1
Understanding the Mechanism and Timeline
Radiation-induced neuropathies develop through increased oxidative stress-mediated apoptosis, neuroinflammation, and altered cellular function in nervous tissues, eventually leading to fibrotic tissue formation and loss of neuronal function. 2 The median time to development of cranial neuropathy is approximately 7.7 years after radiation completion, with a range of 0.6 to 10.6 years. 3
Clinical Presentation and Affected Areas
The neurological complications from head and neck radiation primarily affect cranial nerves and local structures rather than causing distant peripheral neuropathy in the legs. 4 The most commonly affected cranial nerves include:
- CN XII (hypoglossal nerve) - occurring in 7% of 10-year survivors 3
- CN X (vagus nerve) - occurring in 6% of 10-year survivors 3
- CN V (trigeminal nerve) - less common 3
- CN XI (spinal accessory nerve) - less common 3
Important Clinical Distinction
Peripheral neuropathy in the legs from head and neck radiation is extremely unlikely, as radiation effects are localized to the treatment field. 2, 4 If a patient with head and neck cancer develops leg neuropathy and balance problems, alternative etiologies must be investigated:
- Chemotherapy-induced neuropathy - particularly from cisplatin (commonly used concurrently with radiation) or vincristine, which frequently cause distal sensory neuropathy affecting the legs 5
- Paraneoplastic syndromes - remote effects of cancer 5
- Metastatic disease - spinal cord compression or leptomeningeal disease 6
- Concurrent medical conditions - diabetes mellitus, vitamin deficiencies 5
Risk Factors for Radiation-Induced Neuropathy
On multivariable analysis, factors significantly associated with increased risk of cranial neuropathy include:
- Site of primary disease 3
- Post-radiation neck dissection 3
- Concurrent chemotherapy 3
- Higher radiation doses 3
Traditional risk factors may not reliably predict complications in irradiated patients, meaning neurological risks can be underestimated. 1
Clinical Monitoring Requirements
The American Society of Clinical Oncology recommends lifetime monitoring for neurological late effects in all head and neck cancer survivors who received radiation therapy. 1 Specific monitoring should include:
- Assessment for peripheral neuropathy symptoms (numbness, tingling, pain, sensory changes) 1
- Evaluation of balance dysfunction through functional testing 1
- Screening for neurocognitive deficits affecting memory and language 1
- Complete head and neck examination every 1-3 months in year 1, every 2-6 months in year 2, every 4-8 months in years 3-5, and annually thereafter 6, 7
Management Approach
Exercise programs specifically designed to address balance dysfunction and peripheral neuropathy can be beneficial. 1 For radiation-induced cranial neuropathies affecting swallowing (CN X/XII deficits), 8 of 13 patients required permanent gastrostomy tubes, indicating significant functional impact. 3
Critical Pitfall to Avoid
Do not attribute leg neuropathy and balance problems to head and neck radiation without thoroughly investigating other causes, particularly chemotherapy toxicity from cisplatin. 5 The radiation field for head and neck cancer does not extend to the lower extremities, making direct radiation injury to leg nerves anatomically implausible. 2, 4