Steroid-responsive intracranial germinoma presenting as Holmes' tremor: importance of a tissue diagnosis.

Holmes' tremor (rubral or midbrain outflow tremor) refers to a hyperkinetic movement disorder characterized by mild resting and more severe postural and action tremor often with associated brainstem symptoms, dystonia and cerebellar deficits. This syndrome should prompt lesional evaluation with neuroimaging focused on the dorsal midbrain, cerebellar outflow tracts, and thalamus. Herein we report a 26-year-old previously healthy male who presented with 4 years of progressive horizontal diplopia, right Parinaud syndrome, and appendicular ataxia. Neuroimaging revealed a right dorsal midbrain enhancing lesion which completely resolved with intravenous methylprednisolone prompting a diagnosis of neuroinflammatory syndrome. Subsequent clinical and radiographic evaluations, however, revealed steadily progressive left dorsal midbrain syndrome with an expansile enhancing lesion which culminated 4 years from symptom onset with a right upper extremity low-frequency rest, postural and action tremor, ataxic dysarthria, and mild right dystonia with dysdiadochokinesia. Uncomplicated brainstem biopsy confirmed intracranial germinoma and the patient underwent definitive radiation therapy with dramatic radiographic response and partial clinical improvement. This case, which to our knowledge is only the second report of intracranial germinoma presenting as Holmes' tremor, highlights the critical importance of definitive tissue diagnosis in the evaluation of lesional brainstem pathology presenting as Holmes' tremor. Steroid responsiveness can be seen in non-inflammatory pathology including intracranial germinoma. Prompt evaluation and appropriate treatment are important as Holmes' tremor responds poorly to symptomatic therapies and response to radiation therapy is favorable for germinomas.