The periodic paralyses are muscle channelopathies: hypokalemic periodic paralysis (CACNA1S and SCN4A variants), hyperkalemic periodic paralysis (SCN4A variants), and Andersen-Tawil syndrome (KCNJ2). Both episodic weakness and disabling fixed weakness can occur. Little literature exists on magnetic resonance imaging (MRI) in muscle channelopathies. We undertake muscle MRI across all subsets of periodic paralysis and correlate with clinical features.
A total of 45 participants and eight healthy controls were enrolled and underwent T1-weighted and short-tau-inversion-recovery (STIR) MRI imaging of leg muscles. Muscles were scored using the modified Mercuri Scale.
A total of 17 patients had CACNA1S variants, 16 SCN4A, and 12 KCNJ2. Thirty-one (69%) had weakness, and 9 (20%) required a gait-aid/wheelchair. A total of 78% of patients had intramuscular fat accumulation on MRI. Patients with SCN4A variants were most severely affected. In SCN4A, the anterior thigh and posterior calf were more affected, in contrast to the posterior thigh and posterior calf in KCNJ2. We identified a pattern of peri-tendinous STIR hyperintensity in nine patients. There were moderate correlations between Mercuri, STIR scores, and age. Intramuscular fat accumulation was seen in seven patients with no fixed weakness.
We demonstrate a significant burden of disease in patients with periodic paralyses. MRI intramuscular fat accumulation may be helpful in detecting early muscle involvement, particularly in those without fixed weakness. Longitudinal studies are needed to assess the role of muscle MRI in quantifying disease progression over time and as a potential biomarker in clinical trials.

We report a case of adult-onset, sporadic, hyperkalemic periodic paralysis with primary brainstem musculature symptoms masquerading as recurrent transient ischemic attacks. Unilateral brainstem weakness could be induced with rapid eye blinking, which was followed by lower extremity weakness and cramping. Treatment with acetazolamide and albuterol ameliorated the patient\'s attacks.

This article focuses on the pathogenesis, clinical manifestations, and various treatment modalities for acute hyperkalemia and presents a systematic approach to selecting a treatment strategy. Hyperkalemia, a life-threatening condition caused by extracellular potassium shift or decreased renal potassium excretion, usually presents with non-specific symptoms. Early recognition of moderate to severe hyperkalemia is vital in preventing fatal cardiac arrhythmias and muscle paralysis. Management of hyperkalemia includes the elimination of reversible causes (diet, medications), rapidly acting therapies that shift potassium into cells and block the cardiac membrane effects of hyperkalemia, and measures to facilitate removal of potassium from the body (saline diuresis, oral binding resins, and hemodialysis). Hyperkalemia with potassium level more than 6.5 mEq/L or EKG changes is a medical emergency and should be treated accordingly. Treatment should be started with calcium gluconate to stabilize cardiomyocyte membranes, followed by insulin injection, and b-agonists administration. Hemodialysis remains the most reliable method to remove potassium from the body and should be used in cases refractory to medical treatment. Prompt detection and proper treatment are crucial in preventing lethal outcomes.