The main results of this study demonstrate that initial stroke severity as assessed by NIHSS score and the presence of bihemispheric infarcts are significantly associated with the decision to place a PEG tube in a patient with severe dysphagia due to acute or subacute hemispheric infarction, after controlling and correcting for the possible confounding effects of age, lesion location and time from stroke onset to initial swallowing evaluation. PEG placement also showed a trend toward higher initial stroke lesion volume and the presence of periventricular ischemic lesions in multivariate analysis, although the size of our sample and method of analysis might have been under-powered to detect more modest, but nonetheless significant relationships.
One of the most compelling observations of our analysis is the effect of bihemispheric lesions on PEG placement and thus on the failure of swallowing recovery in the acute-subacute phase after a hemispheric infarction. The presence of bihemispheric infarcts (either acute or chronic ischemic lesions in the contralateral hemisphere) in a stroke patient with severe dysphagia increased the odds of PEG placement by a factor of 4.6 after adjusting for other possible confounding variables. This is consistent with previous investigations showing that swallowing functions are under bihemispheric control and further validates the critical role of the nonlesioned hemisphere in mediating swallowing recovery via compensatory reorganization of its’ swallowing cortex.3,6,15
Our analysis included both acute and chronic lesions in contralesional hemispheres (ie, the cerebral hemisphere with a smaller acute ischemic lesion or a chronic infarct compared with the lesional hemisphere that had the greater lesion burden), and we were unable to determine the differential effects of acute versus chronic lesions in the contralesional hemisphere on swallowing recovery in our sample. Furthermore, given the nature of our study sample, we were unable to explore the influence of lesion location and lesion volume in the contralesional hemisphere.
We also investigated the influence of specific lesion sites on the decision for or against PEG placement. These lesion sites were carefully chosen based on data from the literature on their roles in mediating swallowing functions.1,2,14
Although lesions at these sites can impair deglutition, our results indicate that they had no significant impact on the recovery potential of swallowing functions; only the presence of acute periventricular infarcts showed a trend toward association with PEG placement. However, our method did not account for differences in lesion size and extent at these locations or how involvement of multiple such sites in an individual patient affected the chance of PEG placement. The use of newer, more sophisticated imaging techniques, such as voxel-based symptom lesion mapping and diffusion tractography, might help answer these questions in the future.
Total ischemic stroke volume has been shown to be an important predictor of stroke recovery.18
A recent study found acute stroke volume as assessed by DWI sequences to be a significant variable in predicting outcome in multivariate analysis.19
In hemispheric stroke patients with dysphagia, Daniels et al21
found no significant association between severity of dysphagia and size of the stroke lesion using semiquantitative analysis with head CT scans. We employed more quantitative methods and measured ischemic lesion volumes on DWI sequences of brain MRI images, a more reliable method of detecting cerebral ischemia, in the majority of our subjects. We further adjusted the impact of lesion volume thus obtained for other possible influences in a multivariate analysis. Our results show that, after controlling for the potential confounding effects of age, time from stroke onset, clinical stroke severity based on NIHSS score, and lesion location, stroke lesion volume showed a trend toward association with PEG placement. We dichotomized ischemic lesion volume to improve clinical interpretability in terms of OR; the categories chosen (<100 cc and ≥100 cc) were based on the distribution of infarct volumes in our sample to ensure adequate numbers of patients in the PEG and no-PEG groups. But dichotomizing this continuous variable also might have compromised our statistical power and resulted in a more conservative estimate of the effect of lesion volume on swallowing recovery. A possible solution to this problem might have been to subcategorize age into more groups (eg, 25-cc categories); however, we were constrained by our sample size.
Previous studies of global measures for functional recovery have found that NIHSS score is an important predictor of recovery after stroke after adjusting for other variables.16,22
Our results demonstrate that baseline NIHSS score also provides significant prognostic information about swallowing recovery. Every 2-point increase in NIHSS score more than doubled the odds of PEG placement, indicating that larger and more severe strokes are more likely to result in PEG placement in patients with severe dysphagia. Our analysis, however does not clarify whether this relationship is uniform or varies across different intervals of NIHSS. It is possible that analyzing different components of the NIHSS, such as severity of dysarthria, neglect, and alertness, might have enhanced our model’s predictive ability, but our sample size was not sufficiently large to incorporate all these variables in our analysis. On the other hand, our investigation included important neuroanatomical substrates, disruption of which would likely have produced these clinical deficits. In addition, the presence of significant cognitive impairment might have influenced the decision regarding PEG placement in some of our patients. Our study does not fully address this question, because our patients did not undergo formal neuropsychological evaluation after stroke. Most patients appeared to have an impairment in the oropharyngeal phase, with significant delays and aspiration, although some exhibited pocketing or impulsivity, which might reflect a poststroke cognitive deficit. Regardless, our findings indicate that higher initial NIHSS score, which correlates with cognitive impairment and social functioning after stroke,23
is significantly associated with PEG placement in patients with severe dysphagia after a hemispheric infarct.
Several groups have studied the effect of age on swallowing. Overall deglutition slows with aging, and the elderly have delayed initiation of the laryngeal and pharyngeal events, leading to prolonged food bolus transport time.24–26
These changes in swallowing physiology likely make elderly individuals more susceptible to swallowing impairments and also impair their ability to regain their lost function. Other associated factors, including poor dentition, cognitive impairment, and physical frailty, can contribute as well. In previous stroke recovery studies, age seemed to play an important role in predicting functional recovery, implying a significant influence of aging on the stroke-injured brain’s capacity for compensatory reorganization. In our analysis, we found a trend toward an effect of age on PEG placement in our primary analysis, although this was attenuated once all other variables were included in the model. Similar to the situation with infarct volumes, our method of analyzing this variable might have led us to underestimate its effect in the final model.
As a retrospective analysis of a hospitalized cohort, the present study has some inherent biases and limitations. We have attempted to minimize the impact of these influences by using a systematic method for identifying consecutive ischemic stroke patients with severe dysphagia using ICD-9 and CPT-4 codes; however, it is possible that we were unable to systematically capture all such patients using our approach, which might have inadvertently introduced a selection bias. The other possible source of variability is the methods used to assess the severity of dysphagia and swallowing recovery. The patients in our sample did not undergo a standardized swallowing evaluation using validated clinical swallowing scales, but were identified as having severe dysphagia using systematic clinical swallowing evaluations according to hospital-based protocols. Similarly, recovery of swallowing function was not assessed by repeat standardized swallowing evaluation, although all such patients underwent a repeat swallowing evaluation by the speech pathologist. The use of our endpoint of PEG placement provides a very clinically relevant outcome for assessing swallowing recovery, but makes our analysis less likely to be sensitive for detecting more modest changes in swallowing functions. In addition, the care-givers of these patients might have had varying thresholds for implementing PEG placement, which may have introduced some variability in our results.
Despite these limitations, this multivariate analysis improves our understanding of the influence of important clinical and radiological variables in predicting PEG placement and swallowing recovery during hospitalization from stroke. Identifying these variables is an important step in building predictive models that can capture individual information about a patient and aid in making more educated clinical decisions. In addition, prediction models can be useful in clinical trial design for stratification or severity-adjusted analysis. Our current model exhibits a modest but significant ability to predict PEG placement in severely dysphagic stroke patients with hemispheric infarction. We hope that our findings will spawn larger, prospective studies that are better powered to detect influences of lesion location, lesion size, age, and their interplay.