First-Onset Hypokalemic Periodic Paralysis Following Surgery for Myxopapillary Ependymoma.

BACKGROUND: Hypokalemic periodic paralysis is a rare skeletal muscle channelopathy characterized by intermittent episodes of acute flaccid paralysis with associated hypokalemia. We present here the case of a first-onset hypokalemic periodic paralysis triggered by lumbar spinal surgery for tumor resection. CASE DESCRIPTION: A 37-year-old male without any known prior medical conditions presented with a first-onset attack of hypokalemic paralysis 1.5 days after lumbar spinal surgery for myxopapillary ependymoma. Initially, the patient presented paraparesis mimicking a spinal cord compression, and while en route for imaging there was an abrupt onset of flaccid paralysis with significant respiratory distress. The emergency blood tests revealed extreme hypokalemia with a serum potassium of 1.42 mm/L. The patient was transferred to the intensive care unit, intubated, sedated, and administered intravenous reperfusion with an infusion dose of 20 mEq/hour potassium in a solution of 5% mannitol. Following reperfusion, the patient recovered completely in 12 hours. Renal potassium hyperexcretion and hyperthyroidism were excluded by laboratory tests. The diagnosis was confirmed by genetic tests showing mutation of the CACNA1S gene. CONCLUSIONS: To the best of our knowledge, this is the first described case with the first onset triggered by a neurosurgical intervention and the second case following any kind of surgery. Neurosurgeons should consider hypokalemic periodic paralysis when encountering a rapidly evolving tetraparesis, even in an apparently healthy patient.

Hypokalemic periodic paralysis induced by thymic hyperplasia and relieved by thymectomy.

IMPORTANCE: Hypokalemic periodic paralysis is a muscle channelopathy based on mutations or predisposing variants or secondary to potassium wasting. In contrast to myasthenia gravis, an association with thymic hyperplasia has not yet been reported, to our knowledge. OBSERVATIONS: We report a male patient in his mid-20s with progressive episodes of flaccid muscle weakness, associated low serum potassium levels, and a pathologic decrement in the long exercise test. Because the familial inheritance in the family was initially unknown, thorough diagnostic tests were performed including contrast-enhanced computed tomography scan, which displayed a mass in the anterior mediastinum. The test results for autoantibodies against myasthenia gravis (acetylcholine receptor, muscle-specific tyrosine kinase, and low-density lipoprotein receptor-related protein 4) and other end plate channelopathies were negative, and test results for hypokalemia-inducing hormones (thyroid, corticotropin, and cortisol) were negative. Surgery identified a thymus of 13 × 8 × 3 cm(3). Histologic analysis was consistent with thymic hyperplasia of the follicular subtype and immunohistologic analysis showed cytokeratin 5/6 in hyperplastic epithelial cells. A 2-year follow-up revealed the postoperative absence of weakness episodes. As in 30% of familial cases, molecular genetics testing failed to identify a mutation in periodic paralysis genes. CONCLUSIONS AND RELEVANCE: Thymic hyperplasia can clinically manifest susceptibility to hypokalemic periodic paralysis. For patients with late onset or increasing weakness episodes, we recommend imaging to assess for thymic enlargement and thymectomy at thymic hyperplasia.

Surgical treatment for thyrotoxic hypokalemic periodic paralysis: case report.

Thyrotoxic hypokalemic periodic paralysis (THPP) is a rare, potentially life-threatening endocrine emergency. It is characterized by recurrent muscle weakness and hypokalemia. Because many THPP patients do not have obvious symptoms and signs of hyperthyroidism, misdiagnosis may occur. The published studies revealed that definitive therapy for THPP is control of hyperthyroidism by medical therapy, radioactive iodine or surgery, but the long-term post-operative follow-up result was not observed. We reported two cases of medically refractory THPP with recurrent paralysis of extremities and hypokalemia, and both were combined with thyroid nodules. Both patients were treated with total thyroidectomy; the pathology revealed that one is Graves' disease with thyroid papillary carcinoma, and the other is adenomatous goiter with papillary hyperplasia. No episode of periodic paralysis was noted and laboratory evaluation revealed normal potassium level during the post-operative follow up. Our experience suggests that total thyroidectomy by experienced surgeon is an appropriate and definite treatment for medically refractory THPP, especially in cases combined with thyroid nodules.