Objective: We describe an unusual case of progressive right-sided hemidystonia with accompanying imaging and video.

Background: Intracranial germinomas most often arise from midline structures, but can occur within the cerebral hemispheres, thalamus, cerebellum, and basal ganglia. The most commoninitial clinical manifestation of BGGs is gradual-onset hemiparesis. Few cases describe dystonia as a presenting symptom.

Method: An 11-year-old male with trisomy 21 presented with one year of progressive, moderate to severe right-sided hemidystonia with right lower facial weakness. Evaluation included MRI with left more than right mineralization of the globus pallidi. DBS was being considered when, approximately 24 months after symptom onset, proximal right arm dystonia was replaced by marked proximal right arm weakness. Repeat MRI was stable, and CT head showed calcium deposition, interpreted as consistent with Down syndrome idiopathic calcification. Five years after onset of initial symptoms, MRI showed the development of a 6 x 4.5 x 6 cm heterogeneous enhancing solid and cystic mass centered within the left basal ganglia and thalamus. Subsequent biopsy confirmed a diagnosis of pure germinoma.

Results: This case illustrates that basal ganglia tissue changes related to early tumor growth can present as dystonia, several years prior to the presence of a mass. Hemidystonia associated with BGG can evolve into weakness of affected body parts.

Conclusion: BGG should be considered during the evaluation of new onset focal, segmental or hemidystonia, especially if symptoms evolve atypically or are associated with weakness, mineralization or atrophy.

Axial T2 FLAIR MRI 36 months after symptom onset.

Axial T2-FLAIR MRI 5 years after symptom onset.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/basal-ganglia-germinoma-bgg-presenting-as-hemidystonia/