Hyponatremia Associated with Unilateral Hand Weakness and Numbness: A Case Report
A 62-year old previously healthy man, a machinist, presented with 3 months history of worsening right hand weakness and numbness with difficulty operating machinery at work. Patient also described numbness in his right axilla and right scapular region from last 1 year. The numbness progressed along the posterior aspect of his arm and forearm. It later involved the right hand with flexion deformity of the right hand and fingers. He reported anorexia, fatigability, unintentional weight loss of about 20 Ibs over 3 months and mild chronic cough with no history of fever, night sweats, hemoptysis or dyspnea. He denied neck pain, headaches, or dizziness. Patient also denied trauma to the neck or head. He had 40 pack-year smoking history but denied alcohol use. On examination, he had normal vital signs with no orthostatic changes and a BMI of 17. He appeared older than his stated age. He was conscious, cooperative, oriented to time, place and a person. He reported his mood as “desperate” because he had recently misplaced his glasses. His speech was slow, halting, and soft. His grip strength in right hand was 4/5 with atrophy of the interossei muscles and flexion deformity was noticed at the distal interphalengeal joints (DIP). Sensation to pinprick was reduced along the right C7, C8, and T1 dermatomes. Otherwise the reminder of physical examination was unremarkable. Laboratory investigation showed WBC of 13100cells/mm3 with monocyte of 20%. The biochemical profile showed serum sodium of 121 mmol/L (reference range 136-145 mmol/L), serum osmolality of 254 mOsmol/kg (reference range 270-300 mOsmol/kg), and urine osmolality of 451 mOmol/kg and urinary sodium concentration of 69 mmol/L. Potassium, urea, creatinine, corrected calcium, and liver function test were all within normal. The chest X-ray showed right apical pleural-based density suggestive of a soft tissue mass lesion []. CT scan chest was performed and showed large right apical mass suspicious for primary neoplasm (Pancoast tumor) with apparent chest wall invasion, mediastinal and right hilar adenopathy, and a separate left lung metastatic nodule [Figures and ]. MRI of the chest revealed large right apical superior sulcus pulmonary mass likely primary bronchogenic carcinoma with extensive local spread of disease was most prominent posteriorly involving and surrounding the proximal first and second ribs, spinous transverse processes, adjacent soft tissues and involving the right brachial plexus nerve roots exiting the upper thoracic spine [Figures and ]. CT guided core biopsy of the right apex mass was performed and histopathology showed a poorly differentiated non-small cell lung carcinoma (NSCLC), adenocarcinoma is favored [Figures and ]. Immunohistochemical staining showed cytokeratin 7 was positive, other staining such as the cytokeratin 20, TTF-1, and p63 markers were negative. Brain and abdomen computed tomography screening and bone scan showed no distant metastases could be demonstrated and tumor/node/metastasis staging (T3N2M1a) was stage IV.[] The biochemical profile was consistent with SIADH, a paraneoplastic syndrome secondary to NSCLC. Patient was treated with fluid restriction. On discharge, he was planned for out-patient palliative chemoradiation. After two courses of MIC chemotherapy (mitomycin, ifosfamide and cisplatin) three times weekly, his hyponatremia improved (sodium 131 mmol/L). Patient also reported partial improvement in his right hand weakness and had less fatigue. Patient refused further chemoradiation and opted for hospice based management. He later died few months later.