Differential Diagnosis for Progressive Right Arm Weakness and Sensory Changes
Single Most Likely Diagnosis
- Radiation-Induced Brachial Plexopathy: This condition is a well-known complication of radiation therapy, especially when the radiation field includes the brachial plexus, as might be the case with radiation to the supraclavicular lymph nodes. The latency period of 7 years after radiation also fits this diagnosis, as radiation-induced brachial plexopathy can occur months to years after the radiation treatment.
Other Likely Diagnoses
- Metastatic Disease Involving the Brachial Plexus: Given the patient's history of cancer (base of tongue and supraclavicular lymph node involvement), there is a possibility of metastatic disease affecting the brachial plexus, leading to the observed symptoms.
- Recurrent Primary Tumor: Although less likely if the patient has been in remission, a recurrent tumor at the base of the tongue or in the supraclavicular area could potentially compress or invade the brachial plexus, causing the symptoms.
Do Not Miss Diagnoses
- Pancoast Tumor: A tumor located at the apex of the lung can compress or invade the brachial plexus, leading to arm weakness and sensory changes, particularly in the distribution of the lower trunk of the brachial plexus (which includes the hand). Although the patient's history does not directly suggest a lung tumor, missing this diagnosis could be catastrophic due to its implications for treatment and prognosis.
- Vascular Causes (e.g., Subclavian Artery Thrombosis or Embolism): While less directly related to the radiation history, vascular events affecting the subclavian artery could lead to arm weakness and sensory changes due to decreased blood flow. This would be a medical emergency requiring prompt intervention.
Rare Diagnoses
- Idiopathic Brachial Plexitis (Neuralgic Amyotrophy): This is an inflammatory condition of the brachial plexus that can cause sudden onset of arm weakness and pain. It is not directly related to the patient's radiation history but could be considered if other causes are ruled out.
- Hereditary Neuropathies (e.g., Charcot-Marie-Tooth Disease): These conditions could potentially cause progressive arm weakness, but they would not typically be associated with a history of radiation therapy or cancer. They are less likely given the patient's specific history and the distribution of symptoms.