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The “Stutter‐Step”: A Peculiar Gait Feature in Advanced Huntington's Disease and Chorea‐Acanthocytosis

2018; Wiley; Volume: 5; Issue: 2 Linguagem: Inglês

10.1002/mdc3.12586

2330-1619

Pichet Termsarasab, Steven J. Frucht,

Mitochondrial Function and Pathology

Huntington's disease (HD) and chorea-acanthocytosis (ChAc) are two of the genetic causes of chorea. Although chorea often dominates the clinical picture, dystonia, parkinsonism, tics, and ataxia can coexist. In both HD and ChAc, chorea diminishes over time, while parkinsonian features gradually emerge and predominate. The gait disorders described in HD are often choreic mixed with dystonia1 and/or parkinsonism. A predominantly cerebellar gait has also occasionally been reported. In ChAc, in addition to chorea and parkinsonism, a peculiar "rubber man gait" may appear due to a sudden lapse of muscle tone in the trunk or legs.2 In this report, we describe a new and peculiar gait disorder in HD and ChAc, which we term the "stutter-step" gait. The video demonstrates four patients with HD (Video S1) and two with ChAc (Video S2). The HD patients (all genetically confirmed) had typical clinical features of HD, including chorea, with variable degrees of cognitive and psychiatric symptoms. Two patients with ChAc also had classic clinical features, including chorea, parkinsonism, dystonia, and evidence of myopathy (Patient 5) and neuropathy (Patient 6). The diagnosis was confirmed in both cases by demonstrating chorein deficiency on western blot analysis. All patients are in early- or mid-stage of the diseases. The stutter-step gait was seen during multiple follow-up visits, when available, over a period up to 3–4 years. Features of the stutter-step include reduced stride length and cadence, hesitation (especially during heel-off terminal stance phase), hyperflexion of the knee during mid-stance phase, and asymmetric weight bearing on the foot during foot-flat or loading response phase. All these features, especially the latter three, give rise to what we propose as the stutter-step. Some features, such as reduced stride length and hesitation may resemble freezing of gait (FOG) or festination buried into this complex gait. However, the overall character of stutter-step appears to be more complex than just FOG or festination. Of note, hyperflexion of the knee may be ipsilateral (for example, Patients 1 and 2) or contralateral to the less-mobile side of the patient (the side with less chorea or more parkinsonism). In addition to the stutter-step, FOG (especially during turns) can be seen in Patient 1. Patient 4 conspicuously demonstrated a wide-based gait and Patient 5 had circumduction of the right leg during the swing phase, possibly due to a coexisting myopathy. Previously published gait analysis in HD demonstrated reduced walking speed, cadence and stride length, as well as increased variability of stepping rates.3-5 In contrast to the stutter-step, one kinematic study in HD patients demonstrated reduced knee flexion during the initial and mid swing phases.6 However, there were remarkable overlaps of the results between HD and control group in this study, as well as right/left discrepancy. Further studies are needed to confirm these findings. Although these features may be part of the stutter-step, they still do not completely paint the entire picture of what we described here. More importantly, the identification of the stutter-step is accomplished by putting all these features together, in motion, rather than considering one individual gait parameter at a time. Designing gait analytic methods that include movement hesitation, the degree of weight bearing on each foot and incorporation of kinematic analysis may provide more insight into the stutter-step. The underlying pathophysiology of the stutter-step is unknown. It is also not known how much the disorder and what part of the stutter-step may stem from voluntary or subconscious attempts by the patient to prevent falling (i.e., being a compensatory component). Further understanding from thorough gait analysis and differentiating primary from compensatory gait features may be useful for designing rehabilitation strategies for fall prevention. (1) Clinical Project: A. Conception; B. Execution; (2) Clinical Assessment and Data: (3) Manuscript Preperation: A. Writing of the First Draft; B. Review and Critique. P.T.: 1B, 2, 3A, 3B S.J.F.: 1A, 1B, 2, 3B Ethical Compliance Statement: We 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 Conflicts of Interest: The authors report no sources of funding and no conflicts of interest. Financial Disclosures for previous 12 months: The authors report no financial disclosures for previous 12 months. Videos accompanying this article are available in the supporting information here. Video S1. This video demonstrates Patients 1-4 with Huntington's disease. A stutter-step characterized by hesitation especially during heel-off in terminal stance phase, hyperflexion of the knee during mid-stance phase, and asymmetric weight bearing on the foot during foot-flat or loading response phase is demonstrated in all patients, in addition to variable degrees of chorea. Each patient also has additional features, for example facial chorea in Patient 1, dystonic retrocollic neck posturing in Patient 3, and prominent wide-based gait in Patient 4. Video S2. This video demonstrates Patients 5 and 6 with chorea-acanthocytosis. A stutter-step as described in Video S1 is again seen. Additional features include circumduction of the left leg, possibly attributed to myopathy and/or dystonia in Patient 5, and a classic rubber man appearance in Patient 6. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. 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