Demonstration of striatopallidal iron deposition in chorea-acanthocytosis by susceptibility-weighted imaging

Abstract

Chorea-acanthocytosis (ChAc) is a rare hereditary disorder characterized by involuntary choreiform movements and erythrocytic acanthocytosis [1]. MRI commonly shows a T2-signal increase in the atrophic striatum, which reveals neuronal loss with gliosis on autopsy. Increased brain iron levels are seen in various neurodegenerative diseases [2–5] and can be easily detected by newer MR imaging technologies, such as susceptibility-weighted imaging (SWI) [2, 3]. We attempted to visualize areas of degenerative change according to abnormal iron deposition in ChAc by using SWI. A 35-year-old woman presented with exacerbation of orolingual dyskinesia, dysarthria and cognitive decline during the course of 3 years. There was no family history of similar neurological disorders. Neurological examination revealed orofaciolingual dyskinesia and intermittent choreiform movements of the head and neck. There was involuntary tongue protrusion and self-mutilating behaviour affecting the tongue and lips. Also, her speech was dysarthric. Muscle power and bulk, and sensory function were all intact. She could walk without difficulty. Hyporeflexia was present in the lower limbs. On laboratory examination, the serum creatine kinase (CK) level was elevated at 345 IU/l (normal range 5–217 IU/l). Serum lipids and lipoprotein electrophoresis were normal. There were no abnormal findings in the nerve conduction study, including electromyography, muscle CT and EEG. Cardiomyopathy, cardiac arrhythmia and hepatosplenomegaly were absent. Genetic tests for Huntington’s disease, DRPLA, and spinocerebellar ataxia 1, 2, 3 and 17 were all negative. Peripheral blood smear revealed 20% acanthocytes confirmed by scanning electron microscopy (Fig. 1a). Brain MR imaging (3.0-T MR system, Verio, Siemens, Germany) revealed the bilateral atrophic putamina and head of caudate nuclei with increased signal intensity on T2-weighted (Fig. 1b) and iso-signal intensity on T1-weighted imaging. SWI (TR = 28 ms, TE = 20 ms, flip angle = 20 slice thickness = 2 mm) showed a paramagnetic dark signal in both striata (Fig. 1c), the corresponding area to T2 hyperintensity. Also, dark condensed stripes were observed in the lateral pallidum (arrows, Fig. 1d). Such a paramagnetic signal was not prominent in conventional gradient echo sequences (Fig. 1e). No evidence of calcification or hemorrhage was observed on brain CT (Fig. 1f). Genetic screening for VPS13A gene or Western blot for chorein was not available. The clinical presentation of this patient most likely fits with ChAc. However, correct clinical diagnosis is difficult due to symptom overlap with McLeod syndrome (MLS) [1]. Although neither mutations of the XK gene nor Kell antigen expression was looked for in this patient, the diagnosis of MLS is unlikely based on the lack of J.-H. Lee (&) Department of Neurology, Medical Research Institute, Pusan National University Yangsan Hospital, Beomo-ri, Mulgum-eup, Yangsan-si, Gyeongsangnam-do 626-770, South Korea e-mail: jhlee.neuro@pusan.ac.kr