Hemiparkinsonism as a complication of an Ommaya reservoir. Case report. The authors describe the case of a 28-year-old woman who developed the following symptoms in her right hand: a lasting resting tremor, transient focal rigidity, and paresthesia. These deficits occurred following treatment with intrathecal methotrexate via an Ommaya reservoir which was placed too deeply, resulting in trauma to the contralateral mesencephalon. 