Proportional Recovery Rule Research Articles

Arguments for the biological and predictive relevance of the proportional recovery rule.

The proportional recovery rule (PRR) posits that most stroke survivors can expect to reduce a fixed proportion of their motor impairment. As a statistical model, the PRR explicitly relates change scores to baseline values - an approach that arises in many scientific domains but has the potential to introduce artifacts and flawed conclusions. We describe approaches that can assess associations between baseline and changes from baseline while avoiding artifacts due either to mathematical coupling or to regression to the mean. We also describe methods that can compare different biological models of recovery. Across several real datasets in stroke recovery, we find evidence for non-artifactual associations between baseline and change, and support for the PRR compared to alternative models. We also introduce a statistical perspective that can be used to assess future models. We conclude that the PRR remains a biologically relevant model of stroke recovery.

Personalized neurorehabilitative precision medicine: from data to therapies (MWKNeuroReha) – a multi-centre prospective observational clinical trial to predict long-term outcome of patients with acute motor stroke

BackgroundStroke is one of the most frequent diseases, and half of the stroke survivors are left with permanent impairment. Prediction of individual outcome is still difficult. Many but not all patients with stroke improve by approximately 1.7 times the initial impairment, that has been termed proportional recovery rule. The present study aims at identifying factors predicting motor outcome after stroke more accurately than before, and observe associations of rehabilitation treatment with outcome.MethodsThe study is designed as a multi-centre prospective clinical observational trial. An extensive primary data set of clinical, neuroimaging, electrophysiological, and laboratory data will be collected within 96 h of stroke onset from patients with relevant upper extremity deficit, as indexed by a Fugl-Meyer-Upper Extremity (FM-UE) score ≤ 50. At least 200 patients will be recruited. Clinical scores will include the FM-UE score (range 0–66, unimpaired function is indicated by a score of 66), Action Research Arm Test, modified Rankin Scale, Barthel Index and Stroke-Specific Quality of Life Scale. Follow-up clinical scores and applied types and amount of rehabilitation treatment will be documented in the rehabilitation hospitals. Final follow-up clinical scoring will be performed 90 days after the stroke event. The primary endpoint is the change in FM-UE defined as 90 days FM-UE minus initial FM-UE, divided by initial FM-UE impairment. Changes in the other clinical scores serve as secondary endpoints. Machine learning methods will be employed to analyze the data and predict primary and secondary endpoints based on the primary data set and the different rehabilitation treatments.DiscussionIf successful, outcome and relation to rehabilitation treatment in patients with acute motor stroke will be predictable more reliably than currently possible, leading to personalized neurorehabilitation. An important regulatory aspect of this trial is the first-time implementation of systematic patient data transfer between emergency and rehabilitation hospitals, which are divided institutions in Germany.Trial registrationThis study was registered at ClinicalTrials.gov (NCT04688970) on 30 December 2020.

Revisiting the Proportional Recovery Model in View of the Ceiling Effect of Fugl-Meyer Assessment.

The aim of this study was to verify the validity of the proportional recovery model in view of the ceiling effect of the Fugl-Meyer Assessment. We reviewed the medical records of patients enrolled in the Korean Stroke Cohort for Functioning and Rehabilitation between August 2012 and May 2015. Recovery proportion was defined as the actual change in Fugl-Meyer Assessment score of the upper extremity between 7 days and 6 months poststroke, relative to the initial neurological impairment. We then used logistic regression to identify clinical factors attributable to a ceiling effect of the Fugl-Meyer Assessment score of the upper extremity and propensity score matching to verify the validity of the proportional recovery rule. We screened 10 636 patients and analyzed 849 patients (mean age, 65.4±11.9 years; female, 320 [37.7%]) with first-ever ischemic stroke. We found, through logistic regression analysis, that a one-unit increase in the initial neurological impairment and the age at stroke onset affected the odds ratio (1.0386 and 0.9736, respectively) of achieving the full Fugl-Meyer Assessment score of the upper limb at 6 months poststroke. We also demonstrated, through propensity score matching, that the difference in initial neurological impairment of the upper extremity resulted in discrepancy of the recovery proportion (0.92±0.20 [0–1] versus 0.81±0.31 [0–1], P<0.001). We demonstrated that the ceiling effect of the Fugl-Meyer Assessment score of the upper extremity is pronounced in patients with mild initial motor deficits of the upper extremity and that the recovery proportion varies according to the initial motor deficit of the upper limb using logistic regression analysis and propensity score matching, respectively. These results suggest that the proportional recovery model is not valid.

Inflated Estimates of Proportional Recovery From Stroke: The Dangers of Mathematical Coupling and Compression to Ceiling.

The proportional recovery rule states that most survivors recover a fixed proportion (≈70%) of lost function after stroke. A strong (negative) correlation between the initial score and subsequent change (outcome minus initial; ie, recovery) is interpreted as empirical support for the proportional recovery rule. However, this rule has recently been critiqued, with a central observation being that the correlation of initial scores with change over time is confounded in the situations in which it is typically assessed. This critique has prompted reassessments of patients' behavioral trajectory following stroke in 2 prominent papers. The first of these, by van der Vliet et al presented an impressive modeling of upper limb deficits following stroke, which avoided the confounded correlation of initial scores with change. The second by Kundert et al reassessed the value of the proportional recovery rule, as classically formulated as the correlation between initial scores and change. They argued that while effective prediction of recovery trajectories of individual patients is not supported by the available evidence, group-level inferences about the existence of proportional recovery are reliable. In this article, we respond to the van der Vliet and Kundert papers by distilling the essence of the argument for why the classic assessment of proportional recovery is confounded. In this respect, we reemphasize the role of mathematical coupling and compression to ceiling in the confounded nature of the correlation of initial scores with change. We further argue that this confound will be present for both individual-level and group-level inference. We then focus on the difficulties that can arise from ceiling effects, even when initial scores are not being correlated with change/recovery. We conclude by emphasizing the need for new techniques to analyze recovery after stroke that are not confounded in the ways highlighted here.

Statistical Considerations for Drawing Conclusions About Recovery

Background Numerous studies have found associations when change scores are regressed onto initial impairments in people with stroke (slopes ≈ 0.7). However, there are important statistical considerations that limit the conclusions we can draw about recovery from these studies. Objective To provide an accessible checklist of conceptual and analytical issues on longitudinal measures of stroke recovery. Proportional recovery is an illustrative example, but these considerations apply broadly to studies of change over time. Methods Using a pooled data set of n = 373 Fugl-Meyer Assessment upper extremity scores, we ran simulations to illustrate 3 considerations: (1) how change scores can be problematic in this context; (2) how “nil” and nonzero null-hypothesis significance tests can be used; and (3) how scale boundaries can create the illusion of proportionality, whereas other analytical procedures (eg, post hoc classifications) can augment this problem. Results Our simulations highlight several limitations of common methods for analyzing recovery. We find that uniform recovery leads to similar group-level statistics (regression slopes) and individual-level classifications (into fitters and nonfitters) that have been claimed as evidence for the proportional recovery rule. New analyses, however, also speak to the complexities in variance about the regression slope. Conclusions Our results highlight that one cannot identify whether proportional recovery is true or not based on commonly used methods. We illustrate how these techniques, measurement tools, and post hoc classifications (eg, nonfitters) can create spurious results. Going forward, the field needs to carefully consider the influence of these factors on how we measure, analyze, and conceptualize recovery.

Bringing proportional recovery into proportion: Bayesian modelling of post-stroke motor impairment.

Accurate predictions of motor impairment after stroke are of cardinal importance for the patient, clinician, and healthcare system. More than 10 years ago, the proportional recovery rule was introduced by promising that high-fidelity predictions of recovery following stroke were based only on the initially lost motor function, at least for a specific fraction of patients. However, emerging evidence suggests that this recovery rule is subject to various confounds and may apply less universally than previously assumed. Here, we systematically revisited stroke outcome predictions by applying strategies to avoid confounds and fitting hierarchical Bayesian models. We jointly analysed 385 post-stroke trajectories from six separate studies-one of the largest overall datasets of upper limb motor recovery. We addressed confounding ceiling effects by introducing a subset approach and ensured correct model estimation through synthetic data simulations. Subsequently, we used model comparisons to assess the underlying nature of recovery within our empirical recovery data. The first model comparison, relying on the conventional fraction of patients called 'fitters', pointed to a combination of proportional to lost function and constant recovery. 'Proportional to lost' here describes the original notion of proportionality, indicating greater recovery in case of a more severe initial impairment. This combination explained only 32% of the variance in recovery, which is in stark contrast to previous reports of >80%. When instead analysing the complete spectrum of subjects, 'fitters' and 'non-fitters', a combination of proportional to spared function and constant recovery was favoured, implying a more significant improvement in case of more preserved function. Explained variance was at 53%. Therefore, our quantitative findings suggest that motor recovery post-stroke may exhibit some characteristics of proportionality. However, the variance explained was substantially reduced compared to what has previously been reported. This finding motivates future research moving beyond solely behaviour scores to explain stroke recovery and establish robust and discriminating single-subject predictions.

Predicting Upper Limb Motor Impairment Recovery after Stroke: A Mixture Model.

ObjectiveSpontaneous recovery is an important determinant of upper extremity recovery after stroke and has been described by the 70% proportional recovery rule for the Fugl–Meyer motor upper extremity (FM‐UE) scale. However, this rule is criticized for overestimating the predictability of FM‐UE recovery. Our objectives were to develop a longitudinal mixture model of FM‐UE recovery, identify FM‐UE recovery subgroups, and internally validate the model predictions.MethodsWe developed an exponential recovery function with the following parameters: subgroup assignment probability, proportional recovery coefficient , time constant in weeks , and distribution of the initial FM‐UE scores. We fitted the model to FM‐UE measurements of 412 first‐ever ischemic stroke patients and cross‐validated endpoint predictions and FM‐UE recovery cluster assignment.ResultsThe model distinguished 5 subgroups with different recovery parameters (, , , , , , , , , ). Endpoint FM‐UE was predicted with a median absolute error of 4.8 (interquartile range [IQR] = 1.3–12.8) at 1 week poststroke and 4.2 (IQR = 1.3–9.8) at 2 weeks. Overall accuracy of assignment to the poor (subgroup 1), moderate (subgroups 2 and 3), and good (subgroups 4 and 5) FM‐UE recovery clusters was 0.79 (95% equal‐tailed interval [ETI] = 0.78–0.80) at 1 week poststroke and 0.81 (95% ETI = 0.80–0.82) at 2 weeks.InterpretationFM‐UE recovery reflects different subgroups, each with its own recovery profile. Cross‐validation indicates that FM‐UE endpoints and FM‐UE recovery clusters can be well predicted. Results will contribute to the understanding of upper limb recovery patterns in the first 6 months after stroke. ANN NEUROL 2020;87:383–393 Ann Neurol 2020;87:383–393

What the Proportional Recovery Rule Is (and Is Not): Methodological and Statistical Considerations

In 2008, it was proposed that the magnitude of recovery from nonsevere upper limb motor impairment over the first 3 to 6 months after stroke, measured with the Fugl-Meyer Assessment (FMA), is approximately 0.7 times the initial impairment (“proportional recovery”). In contrast to patients with nonsevere hemiparesis, about 30% of patients with an initial severe paresis do not show such recovery (“nonrecoverers”). Hence it was suggested that the proportional recovery rule (PRR) was a manifestation of a spontaneous mechanism that is present in all patients with mild-to-moderate paresis but only in some with severe paresis. Since the introduction of the PRR, it has subsequently been applied to other motor and nonmotor impairments. This more general investigation of the PRR has led to inconsistencies in its formulation and application, making it difficult to draw conclusions across studies and precipitating some cogent criticism. Here, we conduct a detailed comparison of the different studies reporting proportional recovery and, where appropriate, critique statistical methodology. On balance, we conclude that existing data in aggregate are largely consistent with the PRR as a population-level model for upper limb motor recovery; recent reports of its demise are exaggerated, as these excessively focus on the less conclusive issue of individual subject-level predictions. Moving forward, we suggest that methodological caution and new analytical approaches will be needed to confirm (or refute) a systematic character to spontaneous recovery from motor and other poststroke impairments, which can be captured by a mathematical rule either at the population or at the subject level.

A critical time window for recovery extends beyond one-year post-stroke.

The impact of rehabilitation on post-stroke motor recovery and its dependency on the patient’s chronicity remain unclear. The field has widely accepted the notion of a proportional recovery rule with a “critical window for recovery” within the first 3–6 mo poststroke. This hypothesis justifies the general cessation of physical therapy at chronic stages. However, the limits of this critical window have, so far, been poorly defined. In this analysis, we address this question, and we further explore the temporal structure of motor recovery using individual patient data from a homogeneous sample of 219 individuals with mild to moderate upper-limb hemiparesis. We observed that improvement in body function and structure was possible even at late chronic stages. A bootstrapping analysis revealed a gradient of enhanced sensitivity to treatment that extended beyond 12 mo poststroke. Clinical guidelines for rehabilitation should be revised in the context of this temporal structure.NEW & NOTEWORTHY Previous studies in humans suggest that there is a 3- to 6-mo “critical window” of heightened neuroplasticity poststroke. We analyze the temporal structure of recovery in patients with hemiparesis and uncover a precise gradient of enhanced sensitivity to treatment that expands far beyond the limits of the so-called critical window. These findings highlight the need for providing therapy to patients at the chronic and late chronic stages.

Theta burst stimulation in neglect after stroke: functional outcome and response variability origins.

Spatial neglect is a strong and negative predictor of general functional outcome after stroke, and its therapy remains a challenge. Whereas inhibitory non-invasive brain stimulation over the contralesional, intact hemisphere has generally been shown to ameliorate neglect on a group level, a conspicuous variability of the effects at the individual level is typically observed. We aimed to assess the characteristics and determinants of the effects of inhibitory non-invasive brain stimulation in neglect, identifying which patients would respond to this therapeutic approach and which not. To this end, we prospectively included 60 patients with a subacute right-hemispheric stroke. In 30 patients with spatial neglect, continuous theta burst stimulation (cTBS) was applied over the left posterior parietal cortex in a randomized clinical trial, either in eight or 16 trains, or as sham stimulation. Thirty patients without neglect served as a control group. Neglect severity was measured with a neuropsychological test battery and the Catherine Bergego Scale, at admission to and at discharge from inpatient neurorehabilitation, as well as at 3 months follow-up. General functional outcome was assessed by means of the Functional Independence Measure and the Lucerne ICF-based Multidisciplinary Observation Scale. The impact of clinical and demographic factors was evaluated, and the influence of lesion location and extension was assessed by means of voxel-based lesion-symptom mapping. On a group level, both cTBS protocols (i.e. eight and 16 trains) significantly reduced neglect severity in both the Catherine Bergego Scale and the neuropsychological tests, at discharge and 3 months later. Furthermore, cTBS significantly improved general functional outcome. On an individual level, hierarchical cluster and voxel-based lesion-symptom mapping analyses revealed that the variability in the responses to cTBS is determined by the integrity of interhemispheric connections within the corpus callosum, in particular parieto-parietal connections. In cTBS responders, in whom neglect and general functional outcome were significantly improved, the corpus callosum was intact, whereas this was not the case in cTBS non-responders. Moreover, analyses based on the proportional recovery rule and the Maugeri predictive stroke recovery model showed that the recovery of neglect and of the activities of daily living was accelerated only in cTBS responders. Furthermore, the level of activities of daily living recovery of these neglect patients was brought close to the one of right-hemispheric control patients without neglect. Hence, in neglect patients with intact interhemispheric connectivity, cTBS over the contralesional posterior parietal cortex significantly improves and accelerates neglect recovery and, associated with it, general functional outcome.

Recovery after stroke: not so proportional after all?

The proportional recovery rule asserts that most stroke survivors recover a fixed proportion of lost function. To the extent that this is true, recovery from stroke can be predicted accurately from baseline measures of acute post-stroke impairment alone. Reports that baseline scores explain more than 80%, and sometimes more than 90%, of the variance in the patients' recoveries, are rapidly accumulating. Here, we show that these headline effect sizes are likely inflated. The key effects in this literature are typically expressed as, or reducible to, correlation coefficients between baseline scores and recovery (outcome scores minus baseline scores). Using formal analyses and simulations, we show that these correlations will be extreme when outcomes are significantly less variable than baselines, which they often will be in practice regardless of the real relationship between outcomes and baselines. We show that these effect sizes are likely to be over-optimistic in every empirical study that we found that reported enough information for us to make the judgement, and argue that the same is likely to be true in other studies as well. The implication is that recovery after stroke may not be as proportional as recent studies suggest.

Is There Full or Proportional Somatosensory Recovery in the Upper Limb After Stroke? Investigating Behavioral Outcome and Neural Correlates

Background. Proportional motor recovery in the upper limb has been investigated, indicating about 70% of the potential for recovery of motor impairment within the first months poststroke. Objective. To investigate whether the proportional recovery rule is applicable for upper-limb somatosensory impairment and to study underlying neural correlates of impairment and outcome at 6 months. Methods. A total of 32 patients were evaluated at 4 to 7 days and 6 months using the Erasmus MC modification of the revised Nottingham Sensory Assessment (NSA) for impairment of (1) somatosensory perception (exteroception) and (2) passive somatosensory processing (sharp/blunt discrimination and proprioception); (3) active somatosensory processing was evaluated using the stereognosis component of the NSA. Magnetic resonance imaging scans were obtained within 1 week poststroke, from which lesion load (LL) was calculated for key somatosensory tracts. Results. Somatosensory perception fully recovered within 6 months. Passive and active somatosensory processing showed proportional recovery of 86% (95% CI = 79%-93%) and 69% (95% CI = 49%-89%), respectively. Patients with somatosensory impairment at 4 to 7 days showed significantly greater thalamocortical and insulo-opercular tracts (TCT and IOT) LL (P < .05) in comparison to patients without impairment. Sensorimotor tract disruption at 4 to 7 days did not provide significant contribution above somatosensory processing score at 4 to 7 days when predicting somatosensory processing outcome at 6 months. Conclusions. Our sample of stroke patients assessed early showed full somatosensory perception but proportional passive and active somatosensory processing recovery. Disruption of both the TCT and IOT early after stroke appears to be a factor associated with somatosensory impairment but not outcome.

Abstract WP146: Predictors of Recovery From Acute Aphasia

Introduction: Making accurate predictions about a stroke patient’s language/speech-motor outcome and recovery potential is a challenge. We previously showed that a combined variable of lesion site and size pertinent to relevant white matter language structures, the Arcuate Fasciculus lesion load (AF-LL), correlated highly with measures of speech fluency in chronic aphasic patients (Marchina et al., 2011; Wang et al., 2013). However, studies in motor recovery and other domains have shown that behavioral measures in the acute stroke phase might be equal or better predictors of recovery compared to lesion measures. Whether or not any of these measures follow a proportional recovery rule, has not been established. Hypothesis: To evaluate whether acute aphasia measures (overall WAB score) and/or acute lesion measures (e.g., AF-Lesion Load) predict recovery from aphasia. Methods: Over a period of several years, patients presenting with acute aphasia were evaluated using a bedside version of the Western Aphasia Battery complemented by picture naming tests, automatic speech measures, and custom-made word/phrase spoken and sung test. A total of 100 acute patients were assessed of which 56 followed up at 3 months. Lesion maps drawn on diffusion-weighted images were used to calculate lesion loads of a probabilistic Arcuate Fasciculus (AF) tract derived from matched elderly healthy control subjects. Analyses included correlations between recovery potential and actual recovery and other predictors of 3 months outcome. AF-LL was regressed with the overall WAB score, measures of speech fluency and naming ability (using the Boston Naming Test). Results: The overall bedside WAB score in the acute stroke period was the best predictor of the overall WAB score at 3 months (R2=0.60). This predictor was slightly improved when a measure of speaking-singing dissociation was added to the model. Lesion-load of the AF was also a good predictor of WAB score at 3 months (R2=0.48), but did not improve outcome predictions of the WAB score by itself. Overall acute aphasic patients followed a proportional recovery rule, but only recovered about 56% of what was theoretically possible. Conclusion: Language and Speech-Motor Outcome after stroke can be predicted best by a bedside WAB score.

Is the proportional recovery rule applicable to the lower limb after a first-ever ischemic stroke?

ObjectiveTo investigate (a) the applicability of the proportional recovery rule of spontaneous neurobiological recovery to motor function of the paretic lower extremity (LE); and (b) the presence of fitters and non-fitters of this prognostic rule poststroke. When present, the clinical threshold for fitting nor non-fitting would be determined, as well as within-subject generalizability to the paretic upper extremity (UE).MethodsProspective cohort study in which the Fugl-Meyer Assessment (FMA)-LE and FMA-UE were measured <72 hours and 6 months poststroke. Predicted maximum potential recovery was defined as [FMA-LEmax−FMA-LEinitial = 34 –FMA-LEinitial]. Hierarchical clustering in 202 first-ever ischemic stroke patients distinguished between fitting and not fitting the rule. Descriptive statistics determined whether fitters and non-fitters for LE were the same persons as for UE.Results175 (87%) patients fitted the FMA-LE recovery rule. The observed average improvement of the fitters was ~64% of the predicted maximum potential recovery. In the non-fitter group, the maximum initial FMA-LE score was 13 points. Fifty-one out of 78 patients (~65%) who scored below the identified 14-point threshold at baseline fitted the FMA-LE rule. Non-fitters were more severely affected than fitters. All non-fitters of the FMA-LE rule did also not fit the proportional recovery rule for FMA-UE.ConclusionsProportional recovery seems to be consistent within subjects across LE and UE motor impairment at the hemiplegic side in first-ever ischemic hemispheric stroke subjects. Future studies should investigate prospectively distinguishing between fitters and not-fitters within the subgroup of patients who have initial low FMA-LE scores. Subsequently, patients could be stratified based on fitting or not fitting the recovery rule as this would impact rehabilitation management and trial design.

Does Stroke Rehabilitation Really Matter? Part A: Proportional Stroke Recovery in the Rat

Background. In human upper-limb stroke, initial level of functional impairment or corticospinal tract injury can accurately predict the degree of poststroke recovery, independent of rehabilitation practices. This proportional recovery rule implies that current rehabilitation practices may play little or no role in brain repair, with recovery largely a result of spontaneous biological recovery processes. Objective. The present study sought to determine if similar biomarkers predict recovery of poststroke function in rats, indicating that an endogenous biological recovery process might be preserved across mammalian species. Methods. Using a cohort of 593 male Sprague-Dawley rats, we predicted poststroke change in pellet retrieval in the Montoya staircase-reaching task based on initial impairment alone. Stratification of the sample into “fitters” and “nonfitters” of the proportional recovery rule using hierarchical cluster analysis allowed identification of distinguishing characteristics of these subgroups. Results. Approximately 30% of subjects were identified as fitters of the rule. These rats showed recovery in proportion to their initial level of impairment of 66% (95% CI = 62%-70%). This interval overlaps with those of multiple human clinical trials. A number of variables, including less severe infarct volumes and initial poststroke impairments distinguished fitters of the rule from nonfitters. Conclusions. These findings suggest that proportional recovery is a cross-species phenomenon that can be used to uncover biological mechanisms contributing to stroke recovery.

Does Stroke Rehabilitation Really Matter? Part B: An Algorithm for Prescribing an Effective Intensity of Rehabilitation

Background. The proportional recovery rule suggests that current rehabilitation practices may have limited ability to influence stroke recovery. However, the appropriate intensity of rehabilitation needed to achieve recovery remains unknown. Similarities between rodent and human recovery biomarkers may allow determination of rehabilitation thresholds necessary to activate endogenous biological recovery processes. Objective. We determined the relative influence that clinically relevant biomarkers of stroke recovery exert on functional outcome. These biomarkers were then used to generate an algorithm that prescribes individualized intensities of rehabilitation necessary for recovery of function. Methods. A retrospective cohort of 593 male Sprague-Dawley rats was used to identify biomarkers that best predicted poststroke change in pellet retrieval in the Montoya staircase-reaching task using multiple linear regression. Prospective manipulation of these factors using endothelin-1-induced stroke (n = 49) was used to validate the model. Results. Rehabilitation was necessary to reliably predict recovery across the continuum of stroke severity. As infarct volume and initial impairment increased, more intensive rehabilitation was required to engage recovery. In this model, we prescribed the specific dose of daily rehabilitation required for rats to achieve significant motor recovery using the biomarkers of initial poststroke impairment and infarct volume. Conclusions. Our algorithm demonstrates an individualized approach to stroke rehabilitation, wherein imaging and functional performance measures can be used to develop an optimized rehabilitation paradigm for rats, particularly those with severe impairments. Exploring this approach in human patients could lead to an increase in the proportion of individuals experiencing recovery of lost motor function poststroke.

Proportional Recovery From Lower Limb Motor Impairment After Stroke.

In people with preserved corticospinal tract (CST) function after stroke, upper limb impairment resolves by ≈70% within 3 months. This is known as the proportional recovery rule. Patients without CST function do not fit this rule and have worse upper limb outcomes. This study investigated resolution of motor impairment in the lower limb (LL). Patients with stroke and LL weakness were assessed 3 days and 3 months after stroke with the LL Fugl-Meyer. CST integrity was determined in a subset of patients using transcranial magnetic stimulation to test for LL motor-evoked potentials and magnetic resonance imaging to measure CST lesion load. Linear regression analyses were conducted to predict resolution of motor impairment (ΔFugl-Meyer) including factors initial impairment, motor-evoked potential status, CST lesion load, and LL therapy dose. Thirty-two patients completed 3-month follow-up and recovered 74% (95% confidence interval, 60%-88%) of initial LL motor impairment. Initial impairment was the only significant predictor of resolution of motor impairment. There was no identifiable cluster of patients who did not fit the proportional recovery rule. Measures of CST integrity did not predict proportional LL recovery. LL impairment resolves by ≈70% within 3 months after stroke. The absence of a nonfitter group may be because of differences in the neuroanatomical organization of descending motor tracts to the upper limb and LL. Proportional recovery of the LL is not influenced by therapy dose providing further evidence that it reflects a fundamental biological process.

Generalizability of the Maximum Proportional Recovery Rule to Visuospatial Neglect Early Poststroke

Background and objective. Proportional recovery of upper-extremity motor function and aphasia after stroke may suggest common mechanisms for spontaneous neurobiological recovery. This study aimed to investigate if the proportional recovery rule also applies to visuospatial neglect (VSN) in right-hemispheric first-ever ischemic stroke patients and explored the possible common underlying mechanisms. Methods. Patients with upper-limb paresis and VSN were included. Recovery defined as the change in Letter Cancellation Test (LCT) score at ~8 days and 6 months poststroke. Potential recovery defined as LCTmax-LCTinitial = 20 − LCTinitial. Hierarchical clustering separated fitters and nonfitters of the prediction rule. A cutoff value on LCTmax-LCTinitial was determined. The change in LCT and Fugl-Meyer Assessment Upper Extremity was expressed as a percentage of the total possible score to investigate the communality of proportional recovery. Results. Out of 90 patients, 80 displayed proportional recovery of VSN (ie, “fitters,” 0.97; 95% CI = 0.82-1.12). All patients who did not follow the prediction rule for VSN (ie, ”nonfitters”) had ≥15 missing O’s at baseline and failed to show proportional recovery of the upper limb. Conclusions. This study shows that the proportional recovery rule also applies to patients with VSN poststroke. Patients who fail to show proportional recovery of VSN are the same patients who fail to show proportional recovery of the upper limb. These findings support the idea of common intrahemispheric mechanisms underlying spontaneous neurobiological recovery in the first months poststroke. Future studies should investigate the prognostic clinical and neurobiological markers of these subgroups.

The proportional recovery rule for stroke revisited.

The proportional recovery rule for stroke revisited.