Marc-Andre Weber MD, Presenter: Research Grant, Bayer AG Research Grant, Guerbet SA Research Grant, Bracco Group Research Grant, Siemens AG Speakers Bureau, Merck & Co, Inc

Armin Nagel DiplPhys, Abstract Co-Author: Nothing to Disclose

Anja Marschar, Abstract Co-Author: Nothing to Disclose

Karin Jurkat-Rott PhD, Abstract Co-Author: Nothing to Disclose

Maya B. Mueller-Wolf MD, Abstract Co-Author: Nothing to Disclose

Hans-Ulrich Kauczor MD, Abstract Co-Author: Research Grant, Boehringer Ingelheim GmbH Research Grant, Siemens AG Research Grant, Bayer AG Speakers Bureau, Boehringer Ingelheim GmbH Speakers Bureau, Siemens AG Speakers Bureau, Novartis AG

Frank Lehmann-Horn PhD, Abstract Co-Author: Nothing to Disclose

Patients with periodic paralysis experience episodic weakness spells with intervals of normal muscle function caused by altered muscle membrane potential due to changes in ion conductivities, such as nonselective cation leaks in hypokalemic periodic paralysis and Kir2.1 mutations of the myocellular potassium (K+) channel in Andersen-Tawil syndrome. The objective was to assess whether altered sodium (Na+) and chloride (Cl-) homeostasis can be visualized in these periodic paralyses using ultrahigh field MRI.

Institutional review board approval and informed consent of all participants were obtained. Twelve 23Na-MR (TR/TE=160/0.35) und ten 35Cl-MR examinations (TR/TE=40/0.6) of both lower legs were performed on a 7-Tesla system in genetically confirmed hypokalemic periodic paralysis (Cav1.1-R1239H mutation, n=5; Cav1.1-R528H mutation, n=5) and Andersen-Tawil syndrome (n=2); median age, 47 years. Data from previous examinations of four healthy volunteers (median age, 45 years) were taken as reference. Additionally, each patient received 3-Tesla proton MR imaging on the same day using T1-weighted, STIR and DIXON sequences. Muscle edema was assessed on STIR images, fatty degeneration on T1-weighted images and the muscular fat fraction was quantified using DIXON. Na+ and Cl- were quantified in the soleus muscle using three phantoms containing 10, 20, and 30 mM NaCl solution as reference.

Median muscular 23Na concentration in mmol/l was higher in Cav1.1-R1239H (34.7, p=0.008), Cav1.1-R528H (29.8, p=0.001), and Kir2.1 mutation (24.2, p<0.001) than in healthy volunteers (17). Median muscular 35Cl concentration in mmol/l was higher in Cav1.1-R1239H (27.7, p=0.002) and Cav1.1-R528H (25.1, p=0.003) but not in Kir2.1 mutation (14.6, p=0.073) than in volunteers (11). Compared with volunteers, Cav1.1-R1239H and Cav1.1-R528H showed muscular edema (p=0.027, p=0.018) but only Cav1.1-R1239H had fatty muscle degeneration (p=0.036) with a fat fraction of 0.26 vs. 0.08 both in Cav1.1-R528H and Kir2.1 mutations.

Using 7-Tesla MRI changes of Na+ and Cl- homeostasis can be visualized in periodic paralyses, most pronounced in the severe phenotype Cav1.1-R1239H with up to daily paralytic episodes.

7-Tesla 23Na and 35Cl MRI can monitor myocellular ion homeostasis non-invasively and may help in testing of pathogenesis, estimating prognosis, and monitoring of treatment in periodic paralyses.

Weber, M, Nagel, A, Marschar, A, Jurkat-Rott, K, Mueller-Wolf, M, Kauczor, H, Lehmann-Horn, F, 7-Tesla Chlorine and Sodium MR Imaging Detects Mutation Dependent Alterations in Muscular Sodium and Chloride Concentrations in Muscular Periodic Paralyses.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14013667.html