Ann Rehabil Med.  2017 Aug;41(4):701-704. 10.5535/arm.2017.41.4.701.

Joubert Syndrome Presenting With Normal Pyramidal Decussation: A Case Report

• Kim NS
• Park SH

• KMID: 2389417
• DOI: http://doi.org/10.5535/arm.2017.41.4.701

Abstract

Joubert syndrome (JS) is a rare genetic disorder characterized by a congenital malformation of the hindbrain, and accompanied by axonal decussation abnormalities affecting the corticospinal tract and the superior cerebellar peduncles. To the best of our knowledge, there are no reports of normal pyramidal decussation in JS. Here, we describe the case of an 18-year-old boy presenting midline-crossing corticospinal projections, which were considered normal corticospinal tract trajectories. Diffusion tensor imaging and motor evoked potential study analysis demonstrated the exclusive presence of decussating corticospinal projections in the patient. Based on these results, we suggest that JS might be associated with several, diverse corticospinal motor tract organization patterns.

Keyword

Evoked potentials; Developmental disabilities; Joubert syndrome

MeSH Terms

Adolescent
Axons
Developmental Disabilities
Diffusion Tensor Imaging
Evoked Potentials
Evoked Potentials, Motor
Humans
Male
Pyramidal Tracts*
Rhombencephalon

Figure

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  Fig. 1 Axial T2-weighted (A) and T2-weighted fluid-attenuated inversion recovery (B) brain magnetic resonance imaging scans at the pontomesencephalic junction show the molar tooth sign (arrow). The midsagittal T1-weighted image (C) shows hypoplasia of the cerebellar vermis (arrowhead). Sanger sequencing chromatograms verified c.3557delA and c.4277T>C in the C5orf42 gene (D). The black indicates a guanine, red indicates a thymine, blue indicates a cytosine, and green indicates an adenine.

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  Fig. 2 Axial color-coded map at the level of the pontomesencephalic junction shows the absence of the midline ‘focal red dot’ which is interpreted as the absent decussation of the fiber tracts within the superior cerebellar peduncles (A). The transpontine fiber shows no abnormality at the basis pontis (B, C, D). The red indicates a predominant left-right (x-element), green indicates an anteroposterior (y-element), and blue indicates a superior-inferior (z-element) orientation of the anisotropic component of diffusion within each voxel.

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  Fig. 3 Diffuse tensor imaging at the level of the dentate nuclei shows that the dentate nuclei is abnormally located more laterally (arrowheads).

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  Fig. 4 Recording of the right and left 1st dorsal interossei motor evoked potentials with transcranial magnetic stimulation of left (A) and right (B) cortex shows contralateral responses only, suggesting crossed corticospinal projections from each hemisphere. TMS, transcranial magnetic stimulation.

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