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To investigate the clinical significance of upper and lower extremity transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs) in patients with parkinsonism.
Twenty patients (14 men, 6 women; mean age 70.5±9.1 years) suffering from parkinsonism were included in this study. All participants underwent single-pulse TMS session to assess the corticospinal excitability of the upper and lower extremity motor cortex. The resting motor threshold (RMT) was defined as the lowest stimulus intensity able to evoke MEPs of an at least 50 µV peak-to-peak amplitude in 5 of 10 consecutive trials. Five sweeps of MEPs at 120% of the RMT were performed, and the mean amplitude and latency of the MEPs were calculated. Patients were also assessed using the Unified Parkinson's Disease Rating Scale part III (UPDRS-III) and the 5-meter Timed Up and Go (5m-TUG) test.
There was a significant positive correlation between the RMTs of MEPs in the upper and lower extremities (r=0.612, p=0.004) and between the amplitude of MEPs in the upper and lower extremities (r=0.579, p=0.007). The RMT of upper extremity MEPs showed a significant negative relationship with the UPDRS-III score (r=–0.516, p=0.020). In addition, RMTs of lower extremity MEPs exhibited a negative relationship with the UPDRS-III score, but the association was not statistically significant (r=–406, p=0.075).
These results indicated that the RMT of MEPs reflect the severity of motor dysfunction in patients with parkinsonism. MEP is a potential quantitative, electrodiagnostic method to assess motor function in patients with parkinsonism.
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A 69-year-old male patient with previous history of traumatic brain injury 5 months ago was admitted to the Department of Neuropsychiatry because of aggressive behavior and delusional features. After starting on 2 mg of risperidone per day, his delusion, anxiety, and aggressive behavior gradually improved. Two weeks later, he was given 10 mg of donepezil per day for his mild cognitive impairment. After 6 weeks of admission in the Department of Neuropsychiatry, he showed parkinsonian features including difficulty in walking, decreased arm swing during walking, narrowed step width, scooped posture, bradykinesia, tremor, and sleep disorder. To rule out the primary Parkinsonism, dopamine transporter imaging technique [18F]fluoropropyl-carbomethoxy-iodopropyl-nor-β-tropane positron emission tomography-computed tomography (18F]FP(IT PET-CT)) was performed, and dopamine transporter activity was not decreased. We considered that his parkinsonian features were associated with the combination of risperidone and donepezil. Both drugs were stopped and symptoms rapidly disappeared in several days.
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