A 62‐year‐old male mechanic presented with a 3‐month history of worsening right hand numbness and weakness with difficulty operating machinery at work. He reported anorexia, unintentional weight loss of about 20 pounds over 3 months, and mild chronic cough with no fever, night sweats, hemoptysis, or dyspnea. He denied neck pain, headaches, or dizziness. His vitals were normal with a BMI of 17. His grip strength in right hand was 4/5 with atrophy of the interossei muscles). Sensation to pinprick was reduced along the right C7, C8, and T1 dermatomes. The reminder of physical examination was unremarkable. Initial blood work was normal except serum sodium of 121 mmol/L right shoulder and chest x‐ray showed right apical pleural based density suggestive of a soft‐tissue mass lesion. CT scan and MRI of the chest showed large right apical superior sulcus pulmonary mass (Pancoast tumor) likely primary bronchogenic carcinoma with extensive spread to proximal right first and second ribs, right brachial plexus nerve roots, with left lung metastatic nodule. Histopathology of the CT‐guided core biopsy showed a poorly differentiated non–small cell lung carcinoma (NSCLC) in favor of adenocarcinoma. After full body imaging, tumor was staged IV (T3N2M1a). Further workup for hyponatremia showed serum osmolality of 254 mOsmol/kg, urine osmolality of 451 mOsmol/kg, and urinary sodium concentration of 69 mmol/L Thyroid function test, liver function test and cosyntropin stimulation test were all within normal. These results were consistent with SIADH, a paraneoplastic syndrome secondary to non–small cell lung cancer. His initial treatment consisted of pain control and fluid restriction. At the 4‐month follow‐up, the patient's hyponatremia resolved, and he reported partial improvement in his right‐hand weakness. He resumed his follow‐up in the oncology clinic.
Tumor‐associated SIADH in majority of the cases is caused by small cell lung cancer (SCLC). Non–small cell lung cancer (NSCLC) is shown to be responsible for an exceedingly small proportion of paraneoplastic SIADH with few cases reported in the literature. The optimal therapy for SIADH is to treat the underlying malignant disease which may improve this paraneoplastic condition. Although SIADH is rare in NSCLC, careful history and early workup for hyponatremia in patient with weight loss and brachial plexopathy helps early detection and prevent progression of cancer.
The key clinical feature in this case is making the diagnosis of apical lung cancer (Pancoast tumor) in a patient with brachial plexopathy and to recognize the association between syndrome of inappropriate secretion of antidiuretic hormone (SIADH) as a paraneoplastic syndrome and non–small cell lung cancer. Early recognition and appropriate applied management may significantly improve symptoms and prevent complications of hyponatremia, which may enhance quality of life in patients with SIADH.
To cite this abstract:Shaheen K, Alrayies A, Baibars M, Alraies M. Hyponatremia Associated with Unilateral Hand Weakness and Numbness. Abstract published at Hospital Medicine 2013, May 16-19, National Harbor, Md. Abstract 394. Journal of Hospital Medicine. 2013; 8 (suppl 2). https://www.shmabstracts.com/abstract/hyponatremia-associated-with-unilateral-hand-weakness-and-numbness/. Accessed April 5, 2020.