07/04/2026
"Why can bradykinesia improve with dopamine treatment while freezing of gait persists or even worsens in Parkinsonism❓"
✏️ The basal ganglia do not work alone.
They function as a control system together with the cerebral cortex, and they have 𝘁𝘄𝗼 𝗸𝗲𝘆 𝗿𝗼𝗹𝗲𝘀 in motor control.
✔️ 𝗙𝗶𝗿𝘀𝘁, the striatum helps 𝘀𝗲𝗹𝗲𝗰𝘁 𝘄𝗵𝗶𝗰𝗵 𝗺𝗼𝘁𝗼𝗿 𝗽𝗿𝗼𝗴𝗿𝗮𝗺 𝘁𝗼 𝗲𝘅𝗲𝗰𝘂𝘁𝗲.
At any moment, the cortex may send multiple possible motor plans. The striatum decides which one should be chosen.
✔️ 𝗦𝗲𝗰𝗼𝗻𝗱, the dopaminergic system—particularly the pars compacta—acts like a 𝗴𝗹𝗼𝗯𝗮𝗹 𝗯𝗿𝗮𝗸𝗲 𝘀𝘆𝘀𝘁𝗲𝗺.
Motor actions are normally inhibited, and dopamine allows the brake to be selectively released for the chosen action.
☝🏻 With this framework, an important clinical observation becomes clearer:
➤ Some patients have 𝘀𝗲𝘃𝗲𝗿𝗲 𝗯𝗿𝗮𝗱𝘆𝗸𝗶𝗻𝗲𝘀𝗶𝗮 𝘄𝗶𝘁𝗵 𝗹𝗶𝘁𝘁𝗹𝗲 𝗼𝗿 𝗻𝗼 𝗳𝗿𝗲𝗲𝘇𝗶𝗻𝗴 𝗼𝗳 𝗴𝗮𝗶𝘁 (𝗙𝗢𝗚).
➤ Others have 𝗽𝗿𝗼𝗺𝗶𝗻𝗲𝗻𝘁 𝗙𝗢𝗚 𝘄𝗶𝘁𝗵 𝗺𝗶𝗻𝗶𝗺𝗮𝗹 𝗯𝗿𝗮𝗱𝘆𝗸𝗶𝗻𝗲𝘀𝗶𝗮.
These are not simply different severities of the same problem.
👉🏻 A current explanation is that:
➤ 𝗦𝘁𝗿𝗶𝗮𝘁𝗮𝗹 𝘀𝗲𝗹𝗲𝗰𝘁𝗶𝗼𝗻 𝗽𝗿𝗼𝗯𝗹𝗲𝗺𝘀 contribute more to freezing, especially when 𝗺𝘂𝗹𝘁𝗶𝗽𝗹𝗲 𝗮𝗰𝘁𝗶𝗼𝗻𝘀 𝗮𝗽𝗽𝗲𝗮𝗿 𝘀𝘂𝗶𝘁𝗮𝗯𝗹𝗲—for example, during turning, approaching doors, or navigating complex environments.
➤ In contrast, when 𝗼𝗻𝗹𝘆 𝗼𝗻𝗲 𝗮𝗰𝘁𝗶𝗼𝗻 𝗰𝗹𝗲𝗮𝗿𝗹𝘆 𝗳𝗶𝘁𝘀 𝘁𝗵𝗲 𝘀𝗶𝘁𝘂𝗮𝘁𝗶𝗼𝗻, especially for 𝗼𝘃𝗲𝗿𝗹𝗲𝗮𝗿𝗻𝗲𝗱 𝗺𝗼𝘁𝗼𝗿 𝘀𝗸𝗶𝗹𝗹𝘀, the cortex does not present competing options. The striatum does not need to choose, and movement can start smoothly.
👈🏻 On the other hand, in more typical dopaminergic Parkinsonism, patients can still select the correct motor program, but 𝗱𝗼𝗽𝗮𝗺𝗶𝗻𝗲 𝗰𝗲𝗹𝗹 𝗹𝗼𝘀𝘀 𝗽𝗿𝗲𝘃𝗲𝗻𝘁𝘀 𝗲𝗳𝗳𝗶𝗰𝗶𝗲𝗻𝘁 𝗯𝗿𝗮𝗸𝗲 𝗿𝗲𝗹𝗲𝗮𝘀𝗲, leading to slowness and reduced movement amplitude—classic bradykinesia.
‼️ This distinction matters clinically.
➤ 𝗗𝗼𝗽𝗮𝗺𝗶𝗻𝗲𝗿𝗴𝗶𝗰 𝗺𝗲𝗱𝗶𝗰𝗮𝘁𝗶𝗼𝗻 primarily helps with bradykinesia.
➤ 𝗩𝗶𝘀𝘂𝗮𝗹, 𝗮𝘂𝗱𝗶𝘁𝗼𝗿𝘆, 𝗼𝗿 𝘁𝗮𝗰𝘁𝗶𝗹𝗲 𝗰𝘂𝗲𝘀—such as laser lines—can help freezing by triggering 𝘀𝗲𝗺𝗶-𝗮𝘂𝘁𝗼𝗺𝗮𝘁𝗶𝗰, 𝗿𝗲𝗮𝗰𝘁𝗶𝘃𝗲 𝗺𝗼𝘃𝗲𝗺𝗲𝗻𝘁, bypassing the need for internal action selection.
✒️ Body-weight-supported treadmill training and gait robotics also help some patients.
The precise mechanism is still unclear, but my clinical interpretation is that improved gait skill, balance capacity, and confidence reduce excessive conscious control. This allows walking to become 𝗺𝗼𝗿𝗲 𝗮𝘂𝘁𝗼𝗺𝗮𝘁𝗶𝗰, which in turn reduces freezing.
✒️ Freezing of gait is not simply “worse Parkinson’s.”
It reflects a 𝗱𝗶𝗳𝗳𝗲𝗿𝗲𝗻𝘁 𝗰𝗼𝗻𝘁𝗿𝗼𝗹 𝗳𝗮𝗶𝗹𝘂𝗿𝗲, and understanding this distinction helps us choose better strategies.
