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- 29 juillet
2026
- Front
Neurol
- 2026;17:1824166
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- Scholarpedia
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- Impact of
Parakinesia brachialis oscitans on limb
functional recovery after stroke: a cohort
study
- Wang C, Hu H, Wang R, Xu B, Du J, Su Z,
- Guo S, Wang J, Tian X.
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les articles sur la parakinésie brachiale
oscitante
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articles about parakinesia brachialis
oscitans
Parakinesia brachialis oscitans (PBO),
involuntary elevation of the paralyzed upper
limb during yawning is a rare phenomenon after
ischemic stroke, but its prognostic significance
remains unclear due to limited systematic
studies.
Objective: To compare 3-month motor
recovery between ischemic stroke patients with
PBO, without PBO, and with spontaneously
resolved PBO using a propensity score-matched
design.
Methods: This retrospective cohort
study included 33 patients with PBO identified
in the database as the PBO group, while the
non-PBO group was selected from patients with
acute ischemic stroke between March and June
2024. Two independent neurologists reviewed
medical records according to standardized
criteria to identify PBO (within 7_days of
stroke onset) and collected baseline data from
all patients within 24_h of stroke onset. PSM
(1:2) was used to balance baseline
characteristics (age, sex, vascular risk
factors, stroke location, ASPECTS score,
baseline Lovett score, and FMA score) between
the PBO and non-PBO groups. The primary outcome
was the FMA score at 3_months; the secondary
outcome was the Lovett classification. All
outcome assessors were blinded.
Results: After matching, 26 PBO
patients were matched to 52 non-PBO patients
with balanced baseline characteristics. At
3_months, the PBO group showed significantly
higher FMA scores (mean difference 3.77, 95% CI:
_0.54&endash;6.97; p_=_0.022) and Lovett grades
(p_=_0.018) than the non-PBO group. Among PBO
patients, the PBO disappearance group (n_=_19)
within 1_month achieved higher FMA scores than
the PBO persistence group (n_=_14) (mean
difference 7.11, 95% CI: _13.10&endash;-1.06;
p_=_0.021), whereas Lovett grades did not differ
significantly (p_=_0.111).
- Conclusion: In this
propensity-score-matched cohort study, the
presence of PBO was associated with better
recovery of motor function at 3_months. Early
spontaneous resolution of PBO was associated
with better fine motor outcomes compared to
persistent PBO. These findings, which support
the hypothesis, suggest that PBO may serve as a
potential prognostic indicator warranting
further prospective research.
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- La parakinésie brachiale oscitante
(PBO), c'est-à-dire
l'élévation involontaire du membre
supérieur paralysé lors d'un
bâillement, est un phénomène
rare après un AVC ischémique, mais
sa signification pronostique reste incertaine en
raison du nombre limité d'études
systématiques.
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- Objectif : Comparer la
récupération motrice à 3
mois chez les patients victimes d'un AVC
ischémique présentant une PBO, ne
présentant pas de PBO et chez ceux dont
la PBO s'est résolue spontanément,
à l'aide d'une méthode
d'appariement par score de propension.
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- Méthodes : Cette étude
de cohorte rétrospective a inclus 33
patients présentant une PBO,
identifiés dans la base de données
comme constituant le groupe PBO, tandis que le
groupe non-PBO a été
sélectionné parmi les patients
ayant subi un AVC ischémique aigu entre
mars et juin 2024. Deux neurologues
indépendants ont examiné les
dossiers médicaux selon des
critères standardisés afin
d'identifier les cas de PBO (survenus dans les 7
jours suivant le début de l'AVC) et ont
recueilli les données de base de tous les
patients dans les 24 heures suivant le
début de l'AVC. Un appariement par score
de propension (PSM, rapport 1:2) a
été utilisé pour
équilibrer les caractéristiques de
base (âge, sexe, facteurs de risque
vasculaires, localisation de l'AVC, score
ASPECTS, score de Lovett initial et score FMA)
entre les groupes PBO et non-PBO. Le
critère de jugement principal
était le score FMA à 3 mois ; le
critère de jugement secondaire
était la classification de Lovett. Tous
les évaluateurs des critères de
jugement étaient en aveugle.
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- Résultats : Après
appariement, 26 patients du groupe PBO ont
été appariés à 52
patients du groupe non-PBO présentant des
caractéristiques de base
équilibrées. À 3 mois, le
groupe PBO présentait des scores FMA
(différence moyenne de 3,77, IC à
95 % : _0,54 à 6,97 ; p = 0,022) et des
grades de Lovett (p = 0,018) significativement
plus élevés que le groupe non-PBO.
Parmi les patients sous PBO, le groupe
présentant une disparition de la PBO (n =
19) en moins d'un mois a obtenu des scores FMA
plus élevés que le groupe
présentant une persistance de la PBO (n =
14) (différence moyenne de 7,11, IC
à 95 % : _13,10 à _1,06 ; p =
0,021), tandis que les grades de Lovett ne
présentaient pas de différence
significative (p = 0,111).
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- Conclusion : Dans cette étude
de cohorte appariée par score de
propension, la présence d'un PBO
était associée à une
meilleure récupération de la
fonction motrice à 3 mois. La
résolution spontanée
précoce de la PBO était
associée à de meilleurs
résultats en matière de
motricité fine par rapport à une
PBO persistante. Ces résultats, qui
corroborent l'hypothèse, suggèrent
que la PBO pourrait constituer un indicateur
pronostique potentiel justifiant la poursuite de
recherches prospectives.
-
- Introduction
- Ischemic stroke is the most common disabling
disease in China. With the acceleration of
population aging, its incidence continues to
rise, with over 3 million new cases annually
(1). The resulting loss of working capacity
imposes significant life and economic burdens on
patients and their families. Early
rehabilitation therapy, particularly limb
function rehabilitation, significantly impacts
patients' subsequent quality of life (2). 70 to
80% of patients experience varying degrees of
motor impairment, and 50 to 60% of patients
continue to have functional impairments 6_months
later (3).
- Parakinesia brachialis oscitans (PBO) refers
to the phenomenon where paralyzed limbs exhibit
involuntary movement during yawning, observed
after neurological damage causes loss of
voluntary limb movement. This uncommon
occurrence was first termed PBO by Walusinski et
al. (4). Current research on PBO, both
domestically and internationally, remains
limited to scattered case reports and
mechanistic hypotheses. Systematic, multimodal
explanations of its mechanisms are lacking, and
high-level evidence-based medical evidence
linking PBO to rehabilitation prognosis is
absent (5). Clinically, rehabilitation outcomes
for patients exhibiting PBO appear distinct from
those without this phenomenon. A previous study
indicated that 25% of patients with PBO remained
paralyzed, while the others regained varying
degrees of limb mobility; only 5% regained hand
function (6). The PBO phenomenon may serve as a
clinical biomarker capable of predicting a
patient's potential for functional recovery,
guiding the timing and intensity of
rehabilitation interventions to achieve better
functional outcomes. Against this backdrop, we
conducted a cohort study to investigate whether
the presence of PBO, as well as its persistence
versus resolution within the first month
post-stroke, is associated with differences in
functional recovery (assessed at 3_months) in
patients with ischemic stroke.
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- DISCUSSION
- PBO represents a distinct and often
overlooked clinical manifestation in stroke
patients with hemiplegia, characterized by
involuntary elevation of the paralyzed limb
during yawning (12). Previous studies have
primarily consisted of a small number of case
reports; as shown in Table 5, these reports have
proposed possible pathophysiological mechanisms,
but no studies have specifically examined the
relationship between this phenomenon and
functional outcomes (13&endash;16). Among the 33
patients exhibiting PBO in this study, 31
demonstrated involuntary elevation solely in the
upper limb, while 2 exhibited simultaneous
elevation in both upper and lower limbs. Given
this phenomenon, the study analyzed only upper
limb function using the Lovett classification
and FMA score. The Lovett classification is
frequently used clinically for its intuitive
assessment of limb functional changes. The FMA
score quantifies upper limb motor ability
through various movements, providing more
accurate evaluation of fine motor skills (17).
Yawning is a complex physiological behavior
involving multi-level neural regulation: its
initiation and control primarily rely on the
paraventricular nucleus of the hypothalamus,
which projects signals via oxytocinergic,
cholinergic, and other neuronal groups to the
hippocampus, brainstem (pons, medulla), and even
the spinal cord (18). Pathological or excessive
yawning represents a clinically significant
manifestation following acute stroke. Research
indicates it frequently signals damage to the
brainstem reticular formation or
cortical/subcortical regions (particularly the
insula and caudate nucleus). This demonstrates
direct overlap between the neural pathways
governing yawning and the lesion site in stroke
(19).
- Due to the relatively low incidence of PBO,
this study employed PSM to select patients with
comparable baseline characteristics for
comparison with the PBO cohort, ensuring
research rigor (20). A total of 33 PBO patients
were recorded, matched 1:2 via PSM, resulting in
26 patients (PBO group) matched to 52
corresponding patients (non-PBO group). Further
analysis revealed that at 3_months, the PBO
group demonstrated statistically significant
superiority over the non-PBO group in Lovett
muscle strength grading and FMA scores
(p_<_0.05). In previous case reports, several
neurophysiological hypotheses have been
proposed, including three main hypotheses: the
disinhibition of cortical-to-subcortical motor
pathways, the activation of the extrapyramidal
motor-emotional system, and proprioceptive
feedback transmitted via the
cerebellar-brainstem-spinal cord circuit; all of
these may contribute to the occurrence of
involuntary limb movements during yawning, as
shown in Figure 3 (21&endash;23). However, these
mechanisms were not directly tested in the
present study. Our findings are primarily
interpreted at the clinical association level,
rather than as mechanistic evidence. Regardless
of the hypothesis, the occurrence of PBO
suggests that primitive motor networks at the
brainstem and spinal cord level remain
relatively intact or exhibit heightened
excitability. These networks include the
reticulospinal system and cerebellar-brainstem
connections, and their preservation occurs
despite disruption of the corticospinal tract,
which serves as the primary descending motor
pathway. In this study, patients in the PBO
group demonstrated significantly superior muscle
strength and motor function scores at 3_months
compared to the non-PBO group, suggesting that
PBO may represent an observable clinical sign
associated with the integrity and excitability
of primitive motor pathways. The PBO phenomenon
is compatible with the hypothesis that the
lower-level motor centers in the brainstem and
spinal cord retain functional integration
capabilities and that neural connections to limb
muscles remain partially intact. The ability to
perform the complex coordinated movement of PBO
may indicate that the "alternative pathway" from
the brainstem to the anterior horn cells of the
spinal cord is structurally preserved and
functionally activatable. Compared to non-PBO
patients, those exhibiting PBO possess more
complete "neurological reserve." During the
process of neural reorganization following a
stroke, these preserved and activatable
primitive pathways provide a potential
anatomical and physiological basis for the
recovery of motor function. Rehabilitation
training may be able to leverage these pathways
to compensate for the impaired function of the
corticospinal tract, thereby achieving superior
functional recovery outcomes.
- Literature reports suggest that PBO may be
associated with poor patient outcomes (12). We
classified patients whose PBO resolved within 1
month post-stroke as the disappearance group and
those with persistent PBO as the persistence
group. Statistical analysis of Lovett muscle
strength grades and FMA scores between the two
groups after stroke revealed no statistically
significant difference (p_>_0.05).
Three_months later, the FMA scores in the
disappearance group were significantly higher
than those in the persistence group
(p_<_0.05). There was no statistically
significant difference in Lovett muscle strength
grading between the two groups (p_>_0.05). In
this study, the FMA score focuses more on
evaluating isolated movements, coordination, and
fine motor control, which are highly dependent
on the integrity of the corticospinal tract
(24). The Lovett scale provides a relatively
coarse ordinal estimate of muscle strength,
mainly reflecting the ability to move against
gravity or resistance, and may be less sensitive
to subtle improvements in selective motor
control, coordination, and distal upper-limb
performance (25). Compared to the FMA, the
Lovett scale is less sensitive as a measure of
physical fitness when assessing changes in
athletic ability. The higher FMA scores in the
disappearance group suggest better recovery of
corticospinal tract function. Regarding this
outcome, we venture the hypothesis that the
persistent PBO phenomenon may serve as a
clinical marker of the motor system's failure to
transition successfully from a "lower-level
compensatory mode" to a "higher-level dominant
mode" post-stroke. This may indicate that neural
remodeling has become stuck in an inefficient
plateau phase. The superior function in the
disappearance group likely stems not only from
the "re-inhibition" of lower-level centers
following corticospinal tract recovery but also
from an active, successful "functional
hierarchical transition" process. In the
persistent PBO group, impaired recovery of the
corticospinal tract leaves lower pathways
persistently overactive and "unleashed" due to
lack of higher-level control. This state itself
may hinder corticospinal reorganization through
mechanisms like synaptic competition, creating a
vicious cycle (26). Consequently, functional
recovery remains stalled at a plateau,
preventing further improvement.
- The early disappearance of PBO may indicate
successful remodeling of corticospinal tract
function and the "return" of higher-level motor
control, signaling that the nervous system is
progressing toward a more optimal functional
reorganization. However, at present, these
observations should not be taken as evidence to
modify rehabilitation intensity or timing in
routine clinical practice. Rather, they suggest
that PBO status may be worth evaluating as a
stratification variable in future prospective or
interventional rehabilitation studies.
- In this PSM retrospective cohort, the
presence of PBO after ischemic stroke was
associated with better 3-month motor outcomes,
as reflected by higher Lovett grades and FMA
scores compared with matched patients without
PBO. Among patients with PBO, early
disappearance of the phenomenon within 1_month
was associated with better 3-month FMA
performance than persistent PBO. These findings
suggest that PBO may be a clinically observable
sign associated with short-term motor recovery
trajectory after stroke.
- Several methodological limitations should be
considered. First, this was a retrospective
single-center study, which may limit
generalizability. Second, follow-up was limited
to 3_months, and therefore longer-term recovery
trajectories could not be evaluated. Third,
although all patients received rehabilitation
management, the content, intensity, frequency,
and adherence of rehabilitation interventions
during follow-up were not standardized or
quantitatively captured, which may have
influenced functional outcomes. Fourth, there
were marked baseline differences in functional
severity before matching, and baseline
severity-related variables played an important
role in the PSM process. While this approach
improved comparability, it may also affect the
interpretation of between-group outcome
differences and reduce the representativeness of
the matched sample relative to the source
population.
- Residual confounding cannot be excluded
despite PSM, because matching can only address
measured variables. Unmeasured or incompletely
measured factors, such as detailed lesion
burden, corticospinal tract integrity, acute
treatment characteristics, and rehabilitation
exposure, may still have influenced the observed
associations, particularly given the modest
sample size and limited subgroup numbers. This
is a retrospective observational study
design;the present study relied primarily on
clinical functional scales without complementary
objective biomarkers, such as lesion-specific
imaging analyses, diffusion-based assessment of
corticospinal tract integrity, or
electrophysiological measures. Whether PBO can
be considered a valid prognostic marker requires
larger-scale, multicenter, prospective studies
with longer follow-up periods and multimodal
assessments of the underlying mechanisms. Future
research should aim to employ multimodal
neuroinformation fusion (synchronous acquisition
and analysis of high-resolution MRI,
electroencephalography, surface
electromyography) to quantitatively analyze
PBO-specific neural circuit characteristics.
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