title: Topodiagnostic implications of hemiataxia: an MRI-based brainstem mapping analysis.
abstract: The topodiagnostic implications of hemiataxia following lesions of the human brainstem are only incompletely understood. We performed a voxel-based statistical analysis of lesions documented on standardised MRI in 49 prospectively recruited patients with acute hemiataxia due to isolated unilateral brainstem infarction. For statistical analysis individual MRI lesions were normalised and imported in a three-dimensional voxel-based anatomical model of the human brainstem. Statistical analysis revealed hemiataxia to be associated with lesions of three distinct brainstem areas. The strongest correlation referred to ipsilateral rostral and dorsolateral medullary infarcts affecting the inferior cerebellar peduncle, and the dorsal and ventral spinocerebellar tracts. Secondly, lesions of the ventral pontine base resulted in contralateral limb ataxia, especially when ataxia was accompanied by motor hemiparesis. In patients with bilateral hemiataxia, lesions were located in a paramedian region between the upper pons and lower midbrain, involving the decussation of dentato-rubro-thalamic tracts. We conclude that ataxia following brainstem infarction may reflect three different pathophysiological mechanisms. (1) Ipsilateral hemiataxia following dorsolateral medullary infarctions results from a lesion of the dorsal spinocerebellar tract and the inferior cerebellar peduncle conveying afferent information from the ipsilateral arm and leg. (2) Pontine lesions cause contralateral and not bilateral ataxia presumably due to major damage to the descending corticopontine projections and pontine base nuclei, while already crossed pontocerebellar fibres are not completely interrupted. (3) Finally, bilateral ataxia probably reflects a lesion of cerebellar outflow on a central, rostral pontomesencephalic level.
authors: Department of Neurology, Johannes Gutenberg-University Mainz, Langenbeckstr 1, Mainz, Germany. marx@neurologie.klinik.uni-mainz.de
authors: Juergen J
authors: JJ
authors: Marx
authors: Gian D
authors: GD
authors: Iannetti
authors: Frank
authors: F
authors: Thömke
authors: Sabine
authors: S
authors: Fitzek
authors: Francesca
authors: F
authors: Galeotti
authors: Andrea
authors: A
authors: Truini
authors: Peter
authors: P
authors: Stoeter
authors: Marianne
authors: M
authors: Dieterich
authors: Hanns C
authors: HC
authors: Hopf
authors: Giorgio
authors: G
authors: Cruccu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001259:Ataxia / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology*; D002545:Brain Ischemia / Q000150:complications / Q000473:pathology; D001931:Brain Mapping; D001933:Brain Stem / Q000473:pathology*; D002531:Cerebellum / Q000473:pathology; D002544:Cerebral Infarction / Q000150:complications / Q000473:pathology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008526:Medulla Oblongata / Q000473:pathology; D008875:Middle Aged; D010291:Paresis / Q000209:etiology / Q000473:pathology; D011149:Pons / Q000473:pathology; D011446:Prospective Studies; D020824:Spinocerebellar Tracts / Q000473:pathology