Freezing of the Feet While Seated, but Not While Walking

Freezing of gait (FOG) is defined as paroxysmal episodes where there is an inability to step effectively, despite attempting to do so. Patients describe it as their feet feeling glued to the floor. It is a motor sign typically seen in advanced Parkinson's disease (PD) and atypical parkinsonism. Similar motor blocks may also occur during repetitive hand movements, speech or swallowing.1, 2 Here we describe the unique case of a PD patient who experienced freezing of the feet while simulating walking in the seated position, but not while actually walking. He was a 67-year-old man with onset and PD diagnosis at age 55, who complained of difficulty moving his legs while seated 7 years after onset. At the time of this evaluation, he was prescribed carbidopa-levodopa 10–100 mg, two tablets four times a day. He reported no freezing while walking or turning, nor with his upper extremities, during either ON or OFF state. He had no apparent cognitive impairment or behavioral issues. On examination during an ON state (Video 1), UPDRS part III score of 26, he manifested freezing of his legs in the seated position when asked to lift them or to simulate walking. He was unable to lift either leg unless he used his hand to touch his leg and initiate the movement, similar to an external tactile cue. However, when walking or turning he had no freezing, and no retropulsion. He had mild leg dyskinesia. Freezing in the legs was partially levodopa responsive. During OFF state, he reported worsening severity of freezing of the legs as well as worsening tremor and walking speed. Freezing of legs occurred during both OFF and ON states, which is similar to phenomenon seen with patients with FOG. Generally, patients with FOG find that moving their feet and legs while sitting or performing other activities with their legs is not a problem. A dramatic example of this was a patient with severe FOG who was able to ride a bicycle.3 However, studies have shown that in FOG patients freezing while seated can be induced, for example when exposed to anxiety-provoking virtual scenarios.4 In speculating about what this case tells us about the pathophysiology of freezing, one possibility relates to the role of anticipatory postural adjustments (APAs), simultaneously integrating lateral weight shifting onto the stance leg with the actual forward movement of the swing leg, which are important in FOG generation.5 The fact that APAs are not necessary during cycling is one of the explanations why riding a bicycle is much better preserved for many people with PD. Such APAs would also not be necessary during the repetitive stepping while sitting, nevertheless freezing can still occur suggesting that it was caused by other factors, such as difficulty in inter-limb coordination. In this case, freezing while seated appeared to be at least partially levodopa responsive, and also responded favorably to sensory cues similar to that seen in FOG. This type of seated freezing may be expected to occur in patients who also manifest freezing during walking, but freezing that occurs only while seated (but without FOG) has not been previously reported.4 The occurrence of freezing in the legs without locomotion suggests that freezing phenomenology may be more of a motor control issue rather than specifically a gait-related impairment. (1) Research Project: A. Conception, B. Organization, C. Execution; (2) Statistical Analysis: A. Design, B. Execution, C. Review and Critique; (3) Manuscript Preparation: A. Writing of the First Draft, B. Review and Critique. B.P.: 1B, 1C, 3A. B.R.B.: 1B, 3B. S.A.F.: 1A, 1B, 3B. We would like to thank the patient and his family for their participation. Ethical Compliance Statement: The authors confirm that the approval of an institutional review board was not required for this work. However, written informed consent for video and case publication was obtained, and is included in Supplementary Material. The video of this patient was recorded some years ago. We were unable to locate the original consent form signed by the patient. He has since passed away. We were able to contact his wife, and she recently electronically signed a new consent and this was witnessed by one of our nurses. Written patient consent obtained from patient's spouse authorizing the offline and/or online distribution of video material. The authors confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines. Funding Sources and Conflict of Interest: The authors declare that there are no relevant disclosures to report. 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