The “crab sign”: an imaging feature of spinocerebellar ataxia type 48

S. Cocozza, G. Pontillo, G. De Michele, T. Perillo, E. Guerriero, L. Ugga, E. Salvatore, D. Galatolo, V. Riso, F. Saccà, M. Quarantelli, A. Brunetti

Research output: Contribution to journalArticlepeer-review


Purpose: A new form of autosomal dominant hereditary spinocerebellar ataxia (SCA) has been recently described (SCA48), and here we investigate its conventional MRI findings to identify the presence of a possible imaging feature of this condition. Methods: In this retrospective observational study, we evaluated conventional MRI scans from 10 SCA48 patients (M/F = 5/5; 44.7 ± 7.8 years). For all subjects, atrophy of both supratentorial and infratentorial compartments were recorded, as well as the presence of possible T2-weighted imaging (T2WI) signal alterations. Results: In SCA48 patients, no meaningful supratentorial changes were found, both in terms of volume loss or MRI signal changes. Atrophy of the cerebellum was present in all cases, involving both the vermis and the hemispheres, but particularly affecting the postero-lateral portions of the cerebellar hemispheres. In all patients, with the exception of only one subject (90.0% of the cases), a T2WI hyperintensity of both dentate nuclei was found. The association of such signal alteration with the pattern of cerebellar atrophy resembled the appearance of a crab (“crab sign”). Conclusion: Our findings suggest that SCA48 patients are characterized by cerebellar atrophy, mainly involving the postero-lateral hemisphere areas, along with a T2WI hyperintensity of dentate nuclei. We propose that the association of such signal change, along with the atrophy of the lateral portion of the cerebellar hemispheres, resembled the appearance of a crab, and therefore, we propose the “crab sign” as a neuroradiological sign present in SCA48 patients. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
Original languageEnglish
Pages (from-to)1095-1103
Number of pages9
Issue number9
Publication statusPublished - 2020


  • Cerebellum
  • Dentate nucleus
  • MRI
  • SCA48
  • adult
  • anxiety disorder
  • Article
  • ataxia
  • ataxic gait
  • autosomal dominant inheritance
  • bradykinesia
  • brain atrophy
  • brain scintiscanning
  • case report
  • cerebellar ataxia
  • cerebellum
  • cerebellum atrophy
  • cerebellum vermis
  • cervical dystonia
  • chorea
  • clinical article
  • cognitive defect
  • dentate nucleus
  • depression
  • dizziness
  • dysarthria
  • dysmetria
  • dysphagia
  • female
  • gait disorder
  • hemisphere
  • human
  • insomnia
  • involuntary movement
  • male
  • mental disease
  • mental health care
  • middle aged
  • mild cognitive impairment
  • neuroimaging
  • neurologic examination
  • neuropsychological test
  • nuclear magnetic resonance imaging
  • nystagmus
  • observational study
  • priority journal
  • retrospective study
  • saccadic eye movement
  • spinocerebellar ataxia type 48
  • spinocerebellar degeneration
  • tendon reflex
  • tonic clonic seizure
  • tremor
  • unsteadiness
  • unsteady gait
  • urine incontinence


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